WO2025141412A1 - Multi-bed fischer-tropsch catalyst process for co2 conversion - Google Patents

Abstract

The present disclosure relates generally to a process for preparing hydrocarbons. The process includes providing an iron FT feed stream comprising carbon dioxide and hydrogen; in an iron FT reaction zone, contacting the iron FT feed stream with an iron-based FT catalyst under conditions sufficient to form an iron FT product stream comprising C5+ hydrocarbons and carbon monoxide; providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the iron FT product stream; and in a downstream cobalt FT reaction zone, contacting the downstream cobalt FT feed stream with a downstream cobalt-based FT catalyst under conditions sufficient to form a downstream cobalt FT product stream comprising C5+ hydrocarbons.

Description

MULTI-BED FISCHER-TROPSCH CATALYST PROCESS FOR CO₂ CONVERSION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority U.S. provisional application number 63/616,393, filed December 29, 2023 and European Patent application number 24166567.8, filed March 26, 2024, each of which is incorporated by reference herein in its entirety.

1 Field

[0001] The present disclosure relates generally to processes for the Fischer-Tropsch synthesis of hydrocarbons from carbon dioxide.

2. Technical Background

[0002] The conversion of synthesis gas (i.e. , a mixture of carbon monoxide and hydrogen, also known as syngas) into hydrocarbons by the Fischer-Tropsch process has been known for decades, but has historically lagged in performance compared to other hydrocarbon synthesis techniques. The growing importance of alternative energy sources has resulted in renewed interest in the Fischer-Tropsch (FT) process as it allows a direct and environmentally-acceptable route to high-quality fuels and feedstock chemicals.

[0003] FT processes are known for producing linear hydrocarbons, as well as oxygenates, that can be useful in fuels and can also serve as valuable feedstock chemicals. The hydrocarbon fuel derived from FT processes is typically better able to meet increasingly stringent environmental regulations compared to conventional refinery-produced fuels, as FT-derived fuels typically have lower contents of sulfur, nitrogen, and aromatic compounds, which contribute to the emission of potent pollutants such as SO2, NO_X, and particulates. Olefins and alcohols and other oxygenates obtained may also be used as reagents in other processes, such as in the synthesis of lubricants.

[0004] Currently, cobalt-based catalysts are the primary type of catalysts used in FT processes; they generally yield linear paraffins as primary products. Iron-based catalyst materials are also known, and can be lower in cost compared to cobalt-based catalyst materials. Iron-catalysed FT typically produces as part of the hydrocarbon product a significant amount of long-chain oxygenates and long-chain a-olefins, which in many cases are desirable products. However, in contrast to cobalt, iron-based catalysts generally exhibit high water gas shift (WGS) activity. The water gas shift reaction competes with the Fischer-Tropsch process by converting CO and H2O to CO2 and hydrogen, as shown below:

The so-called “reverse water-gas shift,” i.e., conversion of CO2 to CO tends to be favored at higher temperatures. Iron-based FT processes can thus use CO2 as a feedstock, as they can catalyze a reverse water-gas shift to form CO from CO2, then catalyze the Fischer- Tropsch conversion of CO to hydrocarbons and oxygenates.

[0005] However, it remains a challenge in iron-based FT process to provide improved CO2 conversion towards C5+ hydrocarbons. As such, there is a need to provide improved iron-based FT processes.

SUMMARY

[0006] In one aspect, the present disclosure provides a process for preparing hydrocarbons. The process includes providing an iron FT feed stream comprising carbon dioxide and hydrogen; in an iron FT reaction zone, contacting the iron feed stream with an iron-based FT catalyst under conditions sufficient to form an iron FT product stream comprising C5+ hydrocarbons (i.e. , including one or more of C5+ alkanes, C5+ olefins, and C5+ oxygenated hydrocarbons) and carbon monoxide; providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the iron FT product stream; and in a downstream cobalt FT reaction zone, contacting the downstream cobalt FT feed stream with a downstream cobalt-based FT catalyst under conditions sufficient to form a downstream cobalt FT product stream comprising C5+ products.

[0007] In particular embodiments as described herein, the process further includes separating the iron FT product stream to provide a water-rich iron FT product stream and a water-poor iron FT product stream; and providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the water-poor iron FT product stream.

BRIEF DESCRIPTION OF THE FIGURES

[0008] The accompanying drawings are included to provide a further understanding of the methods of the disclosure, and are incorporated in and constitute a part of this specification. The drawings are not necessarily to scale, and sizes of various elements may be distorted for clarity. The drawings illustrate one or more embodiment(s) of the disclosure and together with the description serve to explain the principles and operation of the disclosure.

[0009] FIG. 1 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein. [0010] FIG. 2 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

[0011] FIG. 3 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

[0012] FIG. 4 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

[0013] FIG. 5 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

[0014] FIG. 6 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

[0015] FIG. 7 is a schematic view of an embodiment of a process for performing a Fischer-Tropsch process as described herein.

DETAILED DESCRIPTION

[0016] The present disclosure is concerned with iron-based FT processes for converting CO2 to hydrocarbons.

[0017] The present inventors have noted that the overall conversion of CO2 to hydrocarbons in iron-based FT processes can be limited by the WGS equilibrium, i.e., in-situ formed CO and H2O can react back to a certain extent to CO2 and H2, limiting the CO2 conversion to a lower level. This is exacerbated by the fact that there is H₂O produced by the Fischer-Tropsch reaction, shown below:

CO + 2 H₂ -> [-CH2-] + H₂O

This water can push the water-gas shift equilibrium toward CO2, i.e., in the “forward” direction, thus limiting the amount of CO available for conversion to products. Accordingly, while the high water-gas shift activity of iron-based catalysts can be helpful to convert CO2 to CO for use in Fischer-Tropsch synthesis, the latter reaction makes water, which can cause CO to shift back to CO2 . This can provide for an overall limit on the conversion of feedstock carbon to C5+ hydrocarbons, which are the generally-desired FT products.

[0018] Thus, the present inventors note that one of the challenges associated with using CO2 in the feed stream of iron-FT processes is to ameliorate the problem of lower-than- desired overall conversion of CO2 into C5+ products. Here, the present inventors have determined that the reverse water-gas shift/water-gas shift activity of iron-based FT catalysts can be used to provide better C5+ conversion in FT processes. To do so, the present inventors have determined that the combination of an iron-based catalyst with a closely- coupled downstream cobalt-based catalyst can provided to increased overall CO2 conversion. This scheme allows the iron FT stage to be operated in manner that provides a good compromise between CO2 conversion and C5+ selectivity without regarding coproduced CO as an undesired by-product. This is because the closely-coupled cobalt FT stage can provide high conversion of CO from the iron FT stage; cobalt FT catalysts have low water-gas shift activity, and so the water produced in the cobalt FT stage does not cause substantial water-gas shift of CO to CO2.

[0019] In one aspect, the present disclosure provide a process for preparing hydrocarbons from carbon dioxide. The process includes providing an iron Fischer-Tropsch (FT) feed stream comprising carbon dioxide and hydrogen; in an iron FT reaction zone, contacting the iron feed stream with an iron-based FT catalyst under conditions sufficient to form an iron FT product stream comprising C5+ hydrocarbons and carbon monoxide; providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the iron FT product stream; and in a downstream cobalt FT reaction zone, contacting the downstream cobalt FT feed stream with a downstream cobalt-based FT catalyst under conditions sufficient to form a downstream cobalt FT product stream comprising C5+ hydrocarbons. An example of such a process is shown schematically in FIG. 1. In FIG. 1 , the process 100 includes providing an iron FT feed stream 111 comprising carbon dioxide and hydrogen, here, to an iron FT reaction zone, e.g., a reactor 110. An iron-based FT catalyst 113 is contacted with the iron FT feed stream 111 under conditions sufficient to form an iron FT product stream 112 comprising C5+ hydrocarbons and carbon monoxide. The process of this aspect of the disclosure also provides a downstream cobalt FT feed stream comprising carbon monoxide (at least a portion of which is from the iron FT product stream) and contacts the downstream cobalt FT feed stream with a downstream cobalt based FT catalyst to form a downstream cobalt FT product stream. In the process 100 of FIG. 1, at least a portion of carbon monoxide of the iron FT product stream 112 is included in cobalt FT feed stream 121 , which is contacted with the cobalt-based FT catalyst 123, here, in a cobalt FT reaction zone (e.g., a reactor 120). This provides a downstream cobalt FT product stream 122, which includes C5+ hydrocarbons.

[0020] As used herein, a “feed stream” is used to mean the total material input to a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single inlet or multiple inlets. Similarly, a “product stream” is used to mean the total material output from a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single reactor outlet or multiple reactor outlets. For example, hydrogen and carbon dioxide of the iron FT feed stream can be provided to the iron-based FT catalyst in a single physical stream (e.g., in a single pipe to reactor 110), or in multiple physical streams (e.g., separate inlets for carbon dioxide and H₂, or one inlet for fresh carbon dioxide and H₂ and another for recycled carbon dioxide and/or H₂). Similarly, a “product stream” is used to mean the total material output from a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single outlet or multiple outlets.

[0021] As used herein, the term “hydrocarbons” is used as a term to describe FT synthesis products. It includes not only alkanes and olefins, but also the oxygenated hydrocarbons (e.g., alcohols) that are often present to some extent in FT product streams.

[0022] As described above, the iron FT feed stream contains both H₂ and CO₂ (e.g., provided to a reaction zone in a single physical stream or multiple physical streams). In various embodiments as otherwise described herein, the molar ratio of H₂ to CO₂ in the iron FT feed stream is at least 0.1 :1, e.g., at least 0.5:1. In some embodiments, the molar ratio of H₂ to CO₂ in the iron FT feed stream is at least 0.9:1 , e.g., at least 1:1 or at least 1.5:1. In some embodiments, the molar ratio of H₂ to CO₂ in the iron FT feed stream is no more than 20:1, e.g., no more than 15:1 or no more than 10:1. For example, in some embodiments, the molar ratio of H₂ to CO₂ in the iron FT feed stream is in the range of 1:1 to 6:1 , e.g., in the range of 1.5:1 to 3:1. The person of ordinary skill in the art will provide a desired ratio of H₂:CO₂ in the iron FT feed stream, based on the disclosure herein, that provides a desirable conversion and selectivity; excess H₂ can, if consistent with a desirable conversion and selectivity, be provided to flow through the system and provide an iron FT product stream with a desirable ratio of H₂ to CO for the downstream cobalt FT process.

[0023] Other gases may also be included in the iron FT feed stream. For example, in some embodiments, the iron FT feed stream further comprises CO. The person of ordinary skill in the art will provide a desired ratio of hydrogen to carbon monoxide and carbon dioxide (i.e. , oxides of carbon), based on the disclosure herein, that provides a desirable conversion and selectivity. As discussed above, iron-based FT catalysts are known to be highly active for the WGS/rWGS reaction. The present inventors hypothesize that including CO in the iron FT feed stream can provide a compromise between the rWGS reaction and the FT reaction to provide the desired hydrocarbons.

[0024] The amounts of various feed components can be selected to provide a desirable balance of CO₂ conversion and C5+ selectivity, The present inventors note that while hydrogen is necessary for the reverse water-gas shift reaction that forms CO for Fischer- Tropsch synthesis, higher ratios of hydrogen to oxides of carbon can provide for relatively shorter chain hydrocarbons, thus decreasing selectivity for the highly desirable C5+ hydrocarbons. Accordingly, in various embodiments as otherwise described herein, the iron FT feed stream has a ratio of hydrogen to oxides of carbon in the range of 1 :1 to 6:1, e.g., 1.5:1 to 3:1. In various embodiments as otherwise described herein, the iron FT feed stream has a ratio of hydrogen to oxides of carbon in the range of 1:1 to 3:1. Moreover, in various embodiments, proportions in the feed stream of H₂, CO and CO₂ are selected such that the molar ratio H₂/(2CO + 3CO₂) is in excess of 0.5; the present inventors have found that this can help to ensure a positive conversion of CO₂. The molar ratio CO₂/(CO+CO₂) is desirably at least 0.33, e.g., at least 0.4, or at least 0.45, or at least 0.5; this, too, can help to ensure positive conversion of CO.

[0025] In some embodiments of the disclosure as otherwise described herein, the iron FT feed stream further comprises one or more inert gases. For example, in some embodiments, the iron FT feed stream further comprises nitrogen and/or methane. For example, it can be desirable to perform the iron FT process step in the presence of a significant amount of inerts (i.e. , components that are not H₂ or CO₂). For example, in various embodiments, the iron FT feed stream includes up to 80 mol% of one or more inerts, e.g., in the range of 3-80 mol%, or 5-80 mol%, or 10-80 mol%, or 15-80 mol%, or 30-80 mol% of one or more inerts. In various embodiments, the iron FT feed stream includes up to 70 mol% inerts, up to 60 mol% inerts, or up to 50 mol% inerts, e.g., 3-70 mol%, or 5-70 mol%, or 10-70 mol%, or 15-70 mol%, or 30-70 mol%, or 3-60 mol%, or 5-60 mol%, or 10-60 mol%, or 15-60 mol%, or 30-60 mol%, or 3-50 mol%, or 5-50 mol%, or 10-50 mol%, or 15-50 mol%, or 30-50 mol% inerts. In various embodiments, the iron FT feed stream includes up to 80% of one or more inerts selected from methane and nitrogen, e.g., up to 70 mol%, up to 60 mol%, or up to 50 mol%, or 15-70 mol%, or 30-70 mol%, or 15-60 mol%, or 30-60 mol%, or 15-50 mol%, or 30-50 mol%.

[0026] It can be desirable to reduce the amount of water present in the iron FT feed stream to control the WGS/rWGS activity of the iron-based catalyst. Accordingly, in various embodiments as otherwise described herein, the iron FT feed stream has a water content of no more than 10 mol%, e.g., or no more than 2 mol%, or no more than 0.5 mol%. Maintaining a low amount of water can have additional benefits, such as improving catalyst stability.

[0027] As described above, the iron-based FT catalyst described herein have both rWGS and FT activity. As such, the process described herein provides high CO₂ conversion. As used herein, a “conversion” is a molar fraction of a relevant component feed that is converted to products (be it to desirable products or undesirable species). In various embodiments of the present disclosure as described herein, the iron FT reaction zone has a CO₂ conversion of at least 5%, e.g., at least 10%, or at least 20%. In various embodiments of the present disclosure as described herein, the iron FT reaction zone has a CO2 conversion of no more than 60%, e.g., no more than 55%, or no more than 50%. For example, in some embodiments, the iron FT reaction zone has a CO2 conversion of no more than 45%, e.g., no more than 40%. For example, in various embodiments as otherwise described herein, the CO2 conversion is in the range of 5-60%, e.g., 5-55%, or 5-50%, or 5- 45%, or 5-40%, or 10-60%, or 10-55%, or 10-50%, or 10-45%, or 10-40%, or 15-60%, or 15- 55%, or 15-50%, or 15-45%, or 15-40%, or 20-60%, or 20-55%, or 20-50%, or 20-45%, or 20-40%. The person of ordinary skill in the art will, based on the disclosure herein, operate at a degree of conversion that provides a desirable product distribution. Notably, under conditions where there is significant selectivity for CO, e.g., under lower H2/CO2 ratios, lower temperature ranges and higher GHSV values, CO2 conversion is generally modest. This is acceptable, as CO will be substantially reacted in the subsequent cobalt FT stage, and CO2 can pass through the subsequent cobalt FT stage and be recycled to be converted in a subsequent pass.

[0028] The process as described herein includes contacting an iron-based FT catalyst with the iron FT feed stream to perform an FT reaction. Notably, the present inventors have determined that the iron-based FT catalysts, under the conditions described herein, can provide desirably high C5+ selectivities. As used herein, selectivity is the molar fraction of converted material that is converted to a particular product. The Fischer-Tropsch process is typically used to make C5+ hydrocarbons, for example, unsubstituted C5+ hydrocarbons (e.g., alkanes and alkenes) and oxygenated C5+ hydrocarbons (e.g., C5+ alcohols, aldehydes, ketones, carboxylic acids). For example, in various embodiments as described herein, the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with a C5+ selectivity (i.e., for all C5+ species) of at least 40%, e.g., at least 50%, or at least 60%. For example, in some embodiments, the selectivity for C5+ alkanes is at least 40%, e.g., at least 50%, or at least 60%. In some embodiments, the contacting of the iron-based FT catalyst with the iron FT feed stream to provide the product stream is performed with a C2-4 selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. In some embodiments, the contacting of the iron-based FT catalyst with the iron FT feed stream to provide the iron FT product stream is performed with a methane selectivity of no more than 20%, e.g., no more than 15%, or no more than 10%, or no more than 5%. In some embodiments, the contacting of the iron-based FT catalyst with the feed stream to provide the iron FT product stream is performed with a C2-8 oxygenate selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. In some embodiments, the contacting of the iron-based FT catalyst with the iron FT feed stream to provide the product stream is performed with a C2-8 oxygenate selectivity of no more than 15%, e.g., no more than 10%, or no more than 5%.

[0029] In conventional iron FT processes, CO production due to rWGS activity of the iron-based catalyst is considered an unwanted by-product. Here, however, the present inventors have found that any CO produced can be provided to a downstream cobalt FT reaction zone for further processing. Thus, in some embodiments as described herein, the iron-based FT catalysts under the conditions described herein may have some selectivity for CO, i.e. , significant amounts of CO can be output in the iron FT product stream. For example, in some embodiments as described herein, the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity of at least 10%. For example, in some embodiments as described in, the contacting in the iron FT reaction zone is conducted with an overall CO selectivity of at least 15% or at least 20%. In some embodiments as disclosure as described herein, the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity of no more than 80%, e.g., no more than 60%, or no more than 50%, or no more than 40%. In various embodiments, the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity in the range of 10-80%, e.g., 15-80%, or 20-80%, or 10-60%, or 15-60%, or 20-60%, or 10-50%, or 15-50%, or 20-50%, or 10-40%, or 15-40%, or 20-40%.

[0030] One of the main challenges of using CO2 in the feed stream of the FT process is to convert the CO2 to CO at economical and energy-efficient conditions. Conventional rWGS reactions used to active CO2 often require high temperatures and pressures, leading to a more energy intensive and expensive process. Advantageously, the iron FT processes described herein can be performed at temperatures that are lower than temperatures used in many conventional reverse water-gas shift processes. As such, in some embodiments, contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted at a temperature in the in the range of 200-500°C. For example, in various embodiments, the contacting is conducted at an iron FT temperature in the range of 200-450 °C, e.g., 200-400 °C, or 200-350 °C, or 200-300 °C, or 225-500 °C, or 225-450 °C, or 225-400 °C, of 225-350 °C, or 225-300 °C, or 250-500 °C, or 250-450 °C, or 250-400 °C, or 250-350 °C, or 250-300 °C, or 260-500 °C, or 260-450 °C, or 260-400 °C, or 260-350 °C. In various embodiments, the contacting is conducted at an iron FT temperature in the range of 180-280 °C, e.g., 180-260 °C, or 180-240 °C, or 180-220 °C, or 200-280 °C, or 200-260 °C, or 200-240 °C, or 220-280 °C, or 220-260 °C. The present inventors have noted that operation at these temperatures can provide for lower energy demand, as well as for facile integration with a subsequent cobalt-based Fischer-Tropsch process step. At lower temperatures, relatively longer chain hydrocarbon products can be formed. While there may be lower conversion of CO2 at lower temperatures, unreacted CO2 can be recycled, and the lower conversion can be acceptable in view of the desirability of longer-chain hydrocarbon products.

[0031] Additionally, the iron FT processes described herein can be performed at a variety of pressures, as would be appreciated by the person of ordinary skill in the art. In some embodiments of the present disclosure, the contacting the iron FT feed stream with an iron-based FT catalyst is conducted at a pressure of at least 1 barg, e.g., at least 5 barg, or at least 10 barg. In various embodiments of the present disclosure, the contacting is conducted at an iron FT pressure in the range of 1 to 100 barg. For example, the contacting is conducted at an iron FT pressure in the range of 1 to 80 barg, or 1 to 70 barg, or 1 to 60 barg, 5 to 100 barg, 5 to 80 barg, 5 to 70 barg, 5 to 60 bag, or 10 to 100 barg, 10 to 80 barg, or 10 to 70 barg, 10 to 60 barg.

[0032] The iron FT processes described herein can be performed at a variety of GHSV (gas hourly space velocity), as would be appreciated by the person of ordinary skill in the art. As such, the GHSV for performing the iron FT process in the iron FT reaction zone is not particularly limited. For example, in some embodiments of the present disclosure, the contacting the iron FT feed stream with an iron FT-based catalyst is conducted at an iron FT GHSV up to 100,000 IT¹, e.g., up to 75,000 IT¹, or up to 50,000 IT¹. In various embodiments, the contacting is conducted at an iron FT GHSV in the range of 1,000 to 100,000 IT¹, or 1,000 to 75,000 h’¹, or 1 ,000 to 50,000 h’¹, or 2,000 to 100,000 IT¹, or 2,000 to 75,000 IT¹, or 2,000 to 0,000 IT¹, or 5,000 to 100,000 IT¹, or 5,000 to 75,000 IT¹, or 5,000 to 50,000 IT¹. In various embodiments of the present disclose, the contacting is conducted at an iron FT GHSV up to 4,000 IT¹, e.g., up to 4,000 IT¹, or up to 20,000 IT¹. In various embodiments of the present disclose, the contacting is conducted at an iron FT GHSV in the range of 1,000 to 40,000 IT¹, or 1,000 to 30,000 IT¹, or 1 ,000 to 20,000 IT¹, or 2,000 to 40,000 IT¹, or 2,000 to 40,000 IT¹, or 2,000 to 30,000 IT¹, or 5,000 to 40,000 IT¹, or 5,000 to 30,000 IT¹, or 5,000 to 30,000 IT¹, or 10,000 to 40,000 IT¹, or 10,000 to 30,000 IT¹, or 10,000 to 20,000 IT¹. The present inventors note that the CO selectivity and C5+ selectivity of the iron FT process can depend in part on the GHSV at which the process is performed, with higher CO selectivities and lower C5+ selectivities typically resulting from higher GHSV values. The person of ordinary skill in the art would be able to determine a desired CO selectivity and C5+ productivity for a given iron FT process and select an appropriate GHSV for the iron FT process, appreciating that the full range of space velocities described above may not be available for a given iron FT process. [0033] As described above, iron-based FT catalysts often have both rWGS and FT activity, and as such, the iron-based FT catalyst is not particularly limited. For example, in some embodiments as described herein, the iron-based FT catalyst includes at least 10 wt% iron (e.g., at least 15 wt%, at least 20 wt%, or at least 25 wt%), on an elemental basis. In various embodiments as described herein, the iron-based FT catalyst includes at least 30 wt% iron, e.g., at least 35 wt%, or at least 40 wt% iron, on an elemental basis. In some embodiments as described herein, the iron-based FT catalyst is an alkali-promoted ironbased FT catalyst. For example, in some embodiments as described herein, the iron-based FT catalyst includes at least 1 wt% (e.g., at least 2 wt%, or at least 3 wt%) alkali metal, on an elemental basis. In some embodiments as described herein, the alkali metal is one or more of sodium, potassium, rubidium, and cesium. In some embodiments as describe herein, the iron-based FT catalyst further comprises copper.

[0034] The iron-based FT catalysts suitable for use in the process as described herein can be a variety of forms and are not particularly limited. For example, the iron-based FT catalyst may be a supported or unsupported catalyst. While the form of the catalyst is not particularly limited, in various desirable embodiments, the iron-based FT catalyst is a supported catalyst, wherein the support comprises at least one of titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, silicon oxide and zinc oxide. For example, in various embodiments, the support comprises at least one or aluminum oxide and silicon oxide.

[0035] The person of ordinary skill in the art will appreciate that the iron-based FT catalysts of the disclosure can be provided in many forms, depending especially on the particular form of the reactor system in which they are to be used, e.g., in a fixed bed or as a fluidized bed. The supports of the iron-based FT catalysts can be provided themselves as discrete bodies of material, e.g., as porous particles, pellets or shaped extrudates, with the metals provided thereon to provide the iron-based FT catalyst. However, in other embodiments, an iron-based FT catalyst of the disclosure can itself be formed as a layer on an underlying substrate. The underlying substrate is not particularly limited. It can be formed of, e.g., a metal or metal oxide, and can itself be provided in a number of forms, such as particles, pellets, shaped extrudates, or monoliths. The person of ordinary skill in the art will select an appropriate iron-based FT catalyst for the particular reactor system.

[0036] Conventionally, iron-containing catalyst materials are prepared for use as active catalysts by treating them in situ with a reducing gas such as hydrogen, under conditions sufficient to convert a substantial amount of the iron oxides of the calcined catalyst material to metallic iron. Then, when exposed to Fischer-Tropsch reaction conditions, a substantial part of this iron is converted to carbide. It is thus not conventionally necessary to provide a separate carbiding treatment; rather, the carbiding is a natural result of reaction conditions. Accordingly, in various embodiments, the iron-based FT catalyst is activated by contact with H₂ and oxides of carbon (e.g., CO and CO₂).

[0037] The carbiding can be performed in any convenient manner. For example, in various embodiments, the carbiding includes a reduction step, in which the catalyst material is treated with a reducing gas stream (e.g., containing hydrogen) for a time and at a temperature sufficient to provide at least 50 atom% of the catalyst in metallic form. Without intending to be bound by theory, the inventors understand this step to reduce oxidic iron species to metallic iron species, so that they can be more easily carbided in a subsequent treatment with a carbiding gas. Upon treatment with the reducing gas stream, a portion of the iron components present in the FT catalyst as described herein react to form metallic iron (Fe°).

[0038] In various embodiments, the treatment with the reducing gas stream is performed in the substantial absence of carbon monoxide. For example, in various embodiments, the reducing gas stream comprises no more than 1 vol% carbon monoxide, e.g., no more than 0.5 vol%, or no more than 0.1 vol%, or no more than 0.05 vol%, or no more than 0.01 vol% carbon monoxide. In some embodiments as described herein, the reducing gas stream further comprises an inert gas. For example, in some embodiments, the inert gas is nitrogen. In some embodiments as described herein, the hydrogen and inert gas are present in the reducing gas stream in a ratio of at least 1 :1.

[0039] In various embodiments, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 250-650 °C. For example, in various embodiments as described herein, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 250-600 °C, or 250-550 °C, or 250-500 °C. In various embodiments as described herein, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 300-650 °C, e.g., 300-600 °C, or 300-550 °C, or 300-500 °C. In various embodiments as described herein, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 350-650 °C, e.g., 350- 600 °C, or 350-550 °C, or 350-500 °C.

[0040] As described above, treating the catalyst material with the reducing gas stream is conducted for a time sufficient to provide at least 50 atom% of the iron of the catalyst material in metallic form. In various embodiments, treating the catalyst material with the reducing gas stream is conducted for at least 12 hours, e.g., at least 14 hours. For example, in various embodiments as described herein, treating the catalyst material with the reducing gas stream is conducted for a time in the range of 12 to 30 hours, e.g., in the range of 12 to 24 hours, or 14 to 30 hours, or 14 to 24 hours.

[0041] The person of ordinary skill in the art will be able to determine appropriate reducing conditions to provide a catalyst material with at least 50 atom% iron in reduced form. In various embodiments, the treatment with the reducing gas stream is performed to provide a catalyst material in which at least 60 atom% of the iron is in reduced form, e.g., at least 70 atom%. In various embodiments, the treatment with the reducing gas stream is performed to provide a catalyst material in which at least 80 atom% of the iron is in reduced form, e.g., at least 85 atom%. The proportion of iron in reduced form is measured by XRD.

[0042] The carbiding can include treating the catalyst material with a carbiding gas stream comprising carbon monoxide, at a temperature of at least 180 °C for a time sufficient to provide at least 50 atom% of the iron of the catalyst material in carbided form. This can be performed, e.g., after a treatment with a reducing gas as described above.

[0043] In various embodiments of the present disclosure as otherwise described herein, the reducing gas/carbiding gas comprises at least a portion of H₂ and CO (if present) from the iron FT feed stream. For example, in some embodiments, the process further comprises separating at least a portion of H₂ and at least a portion of CO of the iron FT feed stream and contacting it with the iron-based Fischer-Tropsch catalyst to activate the iron-based Fischer-Tropsch catalyst. In the process 200 shown schematically in FIG. 2, at least a portion of H₂ and CO stream 225A is separated from the iron FT feed stream 211 and contacted with the iron-based FT catalyst 213 to activate it. However, separate carbiding processes are not necessary, as the iron-based FT catalyst material can be carbided under the iron FT reaction conditions, especially when treated first with a reducing gas as described above.

[0044] It can be desirable to have a substantial fraction of the iron of the carbided Fischer-Tropsch catalyst material in carbide form, as it is carbide forms that are of highest catalytic activity. For example, in various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, at least 50 atom% of the iron is in a carbide form, e.g., at least 55 atom%, or at least 60 atom%. In various embodiments of the carbided Fischer- Tropsch catalyst materials of the disclosure, in the range of 50-95 atom% of the iron is in a carbide form, e.g., in the range of 50-90%, or 50-85%, or 50-80%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 55-95 atom% of the iron is in a carbide form, e.g., in the range of 55-90%, or 55-85%, or 55-80%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 60-95 atom% of the iron is in a carbide form, e.g., in the range of 60-90%, or 60-85%, or 60-80%. The amount of iron that is in the form of carbide is determined by Mbssbauer spectroscopy, and as such is expressed as an atomic fraction of iron in the form of carbide of the total iron species visible to Mbssbauer spectroscopy.

[0045] The present inventors note that, while oxidic iron is not a highly active catalyst for Fischer-Tropsch synthesis, it can catalyze water-gas shift reactions. In cases where the feed to the FT synthesis includes a high proportion of CO2, the present inventors have determined that water-gas shift activity can be highly desirable to convert that CO2 to CO for use in the Fischer-Tropsch synthesis. Accordingly, the present inventors have determined that some oxidic iron in the carbided Fischer-Tropsch catalyst material can be beneficial. Accordingly, in various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, at least 5 atom% of the iron is in an oxide phase, e.g., at least 10 atom%, or at least 15 atom%, or at least 20 atom%. However, the present inventors also note that oxidic iron forms are generally not active catalysts for Fischer-Tropsch synthesis. Accordingly, in various embodiments, it can be desirable to limit the amount of oxidic iron in the carbided Fischer-Tropsch catalyst material. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 5-50 atom% of the iron is in an oxide phase, e.g., 5-45 atom%, or 5-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 10-50 atom% of the iron is in an oxide phase, e.g., 10-45 atom%, or 10-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 15-50 atom% of the iron is in an oxide phase, e.g., 15-45 atom%, or 15-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 20-50 atom% of the iron is in an oxide phase, e.g., 20-45 atom%, or 20-40 atom%. The amount of iron that is in the form of oxide is determined by Mbssbauer spectroscopy, and as such is expressed as an atomic fraction of iron in the form of oxide of the total iron species visible to Mbssbauer spectroscopy. The person of ordinary skill in the art can, based on the disclosure herein, select carbiding conditions to provide a desired degree of oxidic iron in the carbided Fischer-Tropsch catalyst materials of the disclosure.

[0046] In various embodiments, at least 30 atom% of the oxidic iron of the carbided Fischer-Tropsch catalyst material is in the form of FesC . The present inventors note that this partially-reduced oxide has especially good activity as a reverse water-gas shift catalyst. In various embodiments, at least 40 atom% of the oxidic iron of the carbided Fischer- Tropsch catalyst material is in the form of FesC , e.g., at least 50 atom%. In various embodiments, at least 60 atom% of the oxidic iron of the carbided Fischer-Tropsch catalyst material is in the form of FesC , e.g., at least 70 atom%. The person of ordinary skill in the art can select carbiding conditions, particularly with respect to conditions under which the material is reduced, to provide a desired amount of Fe₃C>4. The amount of oxidic iron present as of Fe₃C>4 is determined using Mdssbauer spectroscopy.

[0047] One of the advantages of using an iron-based FT catalyst with rWGS activity is that CO produced can not only undergo Fischer-Tropsch synthesis in the iron FT stage, it can also be passed to the downstream cobalt FT reaction zone. As described above, the downstream cobalt FT feed stream comprises at least a portion of the carbon monoxide of the iron FT product stream. For example, in some embodiments as described herein, the downstream cobalt FT feed stream comprises at least 50%, at least 60%, at least 70%, or at least 80%, of the carbon monoxide of the iron FT product stream. In some embodiments as described herein, the downstream cobalt FT feed stream comprises substantially all of the carbon monoxide of the iron FT product stream. However, in various embodiments, CO can be provided to the downstream cobalt FT feed stream from other sources. For example, in various embodiments, CO is provided to the cobalt FT feed stream from a CO source other than the iron FT product stream. In FIG. 4, a stream of CO 426a from some other source is included in the downstream cobalt FT feed stream 421. The person of ordinary skill in the art will appreciate that CO can be provided from a variety of sources, e.g., gasification, reforming, or electrochemical CO2 reduction. Moreover, as described in more detail below, CO can be recycled to the cobalt FT feed stream from the cobalt FT product stream.

[0048] The iron FT product stream comprises C5+ hydrocarbons and carbon monoxide. In various embodiments as described herein, the iron FT product stream may further comprises water. In some embodiments as described herein, at least a portion of the iron FT product stream (e.g., C5+ hydrocarbons, CO, and water) is provided to the downstream cobalt FT feed stream. For example, in various embodiments as described herein, at least 50 mol%, e.g., at least 60 mol%, at least 70 mol%, or at least 80 mol%, or the iron FT product stream is provided to the downstream cobalt FT feed stream. In some embodiments as described herein, substantially all of the iron FT product stream is provided to the downstream cobalt FT feed stream.

[0049] As described above, in some embodiments as described herein, the iron FT product stream further comprises water. In some embodiments, at least a portion of the water present in the iron FT product stream is provided to the downstream cobalt FT feed stream. For example, in various embodiments as described herein, at least 50%, at least 60%, at least 70%, or at least 80% or the water present in the iron FT product stream is provided to the downstream cobalt FT feed stream. In some embodiments as described herein, substantially all of the water present in the iron FT product stream is provided to the downstream cobalt FT feed stream. [0050] In an alternative embodiment, the process further comprises separating the iron FT product stream to provide a water-rich iron FT product stream and a water-poor iron FT product, wherein at least a portion (e.g., all of) the water-poor iron FT product stream is provided to the downstream cobalt FT feed stream. For example, in some embodiments, at least a portion (e.g., all of) the carbon monoxide of the water-poor iron FT product stream is provided to the downstream cobalt FT feed stream. An example of such a process is shown schematically in FIG. 2. In FIG. 2, the process 200 includes process for preparing hydrocarbons by providing an iron FT feed stream 211 comprising carbon dioxide and hydrogen, here, to an iron FT reaction zone, e.g., a reactor 210. An iron-based FT catalyst 213, as described herein, is contacted with the iron FT feed stream 211 under conditions sufficient to form an iron FT product stream 212 comprising C5+ hydrocarbons and carbon monoxide. The iron FT product stream 212 is then separating in a water separation zone 216 to provide a water rich iron FT product stream 217A and a water-poor iron FT product stream lean 217B, wherein at least a portion of (e.g., all of) the water-poor iron FT product stream 217B is provided to the downstream cobalt FT feed stream 221. The person of ordinary skill in the art will appreciate that a variety of processes can be used to remove water from the iron FT product stream. For example, the iron FT product stream can be contacted with a water scavenger to remove water therefrom. For example, a molecular sieve guard bed can be used to remove water from the iron FT product stream; water can be recovered from the molecular sieves of the guard bed, e.g., by heating and vacuum. In other embodiments, a knockout vessel can be used. However, use of a knockout vessel can in some cases cool the iron FT product stream enough so that it is desirably reheated for introduction to the cobalt FT process step. In FIG. 2, the process 200, iron FT reactor 210, iron FT feed stream 211 , iron FT product stream 212, iron-based FT catalyst 213, cobalt FT reactor 220, cobalt FT feed stream 221, cobalt FT product stream 222 and cobalt FT catalyst 223 are generally as described herein. Accordingly, in various embodiments as otherwise described herein, the portion of the iron FT product stream that is included in the cobalt FT feed stream has a water content of no more than 10 mol%, e.g., or no more than 2 mol%, or no more than 0.5 mol%.

[0051] As described above, the iron FT product stream also includes C5+ hydrocarbons. As would be understood by the person of ordinary skill in the art, the C5+ hydrocarbons and any water present in the iron FT product stream can be conveniently condensed. In some embodiments of the process as described herein, these substances can be separated from the iron FT product stream via condensation. For example, in some embodiments as described herein, the process further comprises separating the iron FT product stream to provide a condensate-rich iron FT product stream enriched in water and C5+ hydrocarbons and a condensate-poor iron FT product stream lean in water and C5+ hydrocarbons, wherein at least a portion of (e.g., all of) the condensate-poor iron FT product stream is provided to the downstream cobalt FT feed stream. An example of such a process is shown schematically in FIG. 4. In FIG. 4, the process 400 includes process for preparing hydrocarbons by providing an iron FT feed stream 411 comprising carbon dioxide and hydrogen, here, to an iron FT reaction zone, e.g., a reactor 410. An iron-based FT catalyst 413, as described herein, is contacted with the iron FT feed stream 411 under conditions sufficient to form an iron FT product stream 412 comprising C5+ hydrocarbons and carbon monoxide. The iron FT product stream 412 is then separating in a condensate separation zone 416 to provide an iron FT product stream enriched in water and C5+ hydrocarbons 417A and a condensate-poor iron FT product stream lean in water and C5+ hydrocarbons 417B, wherein at least a portion of (e.g., all of) the condensate-poor iron FT product stream 417B is provided to the downstream cobalt FT feed stream 421.

[0052] The person of ordinary skill in the art would appreciate that, based on the processes as described herein, the iron FT product stream may include H₂, CO, and CO₂ and other components in various amounts. Components of the iron FT product stream may be separated and used for various purposes in the integrated process.

[0053] For example, in various embodiments of the present disclosure as described herein, the process further comprises separating the iron FT product stream to recycle at least a portion (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) of one or more components of the iron FT product stream to the iron FT feed stream. For example, when the iron FT product stream includes CO2, the process can include recycling at least a portion (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) of the CO2 of the iron FT product stream to the iron FT feed stream. The iron FT product stream may also include H₂; in some embodiments, the process further includes recycling at least a portion of H₂ of the iron FT product stream (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) to the iron FT feed stream.

[0054] Such recycling is shown in the process 200 of FIG. 2. Here, the process 200 includes separating from the iron FT product stream 212 at least a portion of CO2 (stream 215) to recycle to the iron FT feed stream 211 . Similarly, the process 200 includes separating from the iron FT product stream 212 at least a portion of H₂ (stream 214) to recycle to the iron FT feed stream 211. While stream 215 is depicted as entering reactor 210 through a different inlet than the rest of the iron FT feed stream 211 , it is considered to be part of the iron FT feed stream, as it is part of the material input to the process step. [0055] As noted above, the downstream cobalt feed stream includes H₂. Notably, the iron FT product stream will often include H₂, e.g., unreacted from the iron FT feed stream. In various embodiments, the downstream cobalt FT feed stream includes at least a portion of the H₂ of the iron FT product stream. For example, in various embodiments as otherwise described herein, at least 25% of the H₂ of the iron FT product stream, e.g., at least 50% of the H₂, at least 75% of the H₂, or at least 90% of the H₂ of the iron FT product stream is included in the downstream cobalt FT feed stream. Of course, some of the H₂ of the iron FT product stream can be used for other purposes, e.g., catalyst activation as described herein.

[0056] In some embodiments, substantially all of the H₂ of the downstream cobalt FT feed stream comes from the iron FT product stream. In fact, the person of ordinary skill in the art can provide more H₂ than necessary for the iron FT reaction in the iron FT feed stream, to provide excess H₂ in the iron FT product stream that can then provide a desired amount of H₂ to the downstream cobalt FT feed stream for the Fischer-T ropsch process step. However, in other embodiments, H₂ can be provided to the downstream cobalt FT feed stream from other sources. For example, in various embodiments, H₂ is provided to the downstream cobalt FT feed stream from a H₂ source other than the iron FT product stream. In FIG. 4, a stream of H₂ 426b from some other source is included in the cobalt FT feed stream 421 . The person of ordinary skill in the art will appreciate that H₂ can be provided from a variety of sources, e.g., gasification, reforming, or H₂O electrolysis. Moreover, as described in more detail below, H₂ can be recycled to the downstream cobalt FT feed stream from the downstream cobalt FT product stream.

[0057] It can be desirable to perform the downstream cobalt FT process step in the presence of a significant level of inerts. One such inert, CO₂, can come from the iron FT process, e.g., via the iron FT product stream. Accordingly, in various embodiments as otherwise described herein, the downstream cobalt FT feed stream includes at least a portion of CO₂ of the iron FT product stream. For example, in various embodiments, at least 10% of the CO₂ of the iron FT product stream, e.g., at least 25% of the CO₂, at least 50% of the CO₂, at least 75% of the CO₂, or at least 90% of the CO₂ of the iron FT product stream is included in the downstream cobalt FT feed stream. Accordingly, in various embodiments as otherwise described herein, the portion of the iron FT product stream that is included in the downstream cobalt FT feed stream has a CO₂ content in the range of 10-95 mol% CO₂, e.g., 10-90 mol%, or 10-85 mol%, or 10-80 mol%, or 10-75 mol%, or 10-70 mol%, or 20-95 mol%, or 20-90 mol%, or 20-85 mol%, or 20-80 mol%, or 20-75 mol%, or 20-70 mol%, or 30-95 mol%, or 30-90 mol%, or 30-85 mol%, or 30-80 mol%, or 30-75 mol%, or 30-70 mol% CO₂. Of course, in other embodiments, the downstream cobalt FT feed stream may not include any substantial amount of CO₂ of the iron FT product stream. Accordingly, in various embodiments, the downstream cobalt FT feed stream does not include a substantial amount of CO2 of the iron FT product stream. While it can be desirable generally to recycle CO2 to the iron FT feed stream for use in the iron FT reaction, as described in more detail below, unreacted CO2 can be recycled from the downstream cobalt FT product stream to the iron FT feed stream.

[0058] But it can additionally or alternatively be desirable to include additional inert content to the downstream cobalt FT feed stream, be it CO2 or other inerts such as nitrogen and methane. For example, in various embodiments, one or more inerts (e.g., CO2, nitrogen and/or methane) are provided to the cobalt FT feed stream from a source other than the iron FT product stream. For example, in various embodiments, the downstream cobalt FT feed stream includes up to 80 mol% of one or more inerts, e.g., in the range of 3-80 mol%, or 5- 80 mol%, or 10-80 mol%, or 15-80 mol%, or 30-80 mol% of one or more inerts. In various embodiments, the downstream cobalt FT feed stream includes up to 70 mol% inerts, up to 60 mol% inerts, or up to 50 mol% inerts, e.g., 3-70 mol%, or 5-70 mol%, or 10-70 mol%, or 15-70 mol%, or 30-70 mol%, or 3-60 mol%, or 5-60 mol%, or 10-60 mol%, or 15-60 mol%, or 30-60 mol%, or 3-50 mol%, or 5-50 mol%, or 10-50 mol%, or 15-50 mol%, or 30-50 mol% inerts. In various embodiments, the downstream cobalt FT feed stream includes up to 80% of one or more inerts selected from CO2, methane and nitrogen, e.g., up to 70 mol%, up to 60 mol%, or up to 50 mol%, or 15-70 mol%, or 30-70 mol%, or 15-60 mol%, or 30-60 mol%, or 15-50 mol%, or 30-50 mol%. In various embodiments, the downstream cobalt FT feed stream includes up to 80 mol% of CO2, e.g., up to 70 mol%, up to 60 mol%, or up to 50 mol%, or 15-70 mol%, or 30-70 mol%, or 15-60 mol%, or 30-60 mol%, or 15-50 mol%, or 30- 50 mol%. In FIG. 4, a stream of inert(s) 426c from some other source is included in the cobalt FT feed stream 421. The person of ordinary skill in the art will appreciate that inerts can be provided from a variety of sources. Moreover, as described in more detail below, inerts can be recycled to the cobalt FT feed stream from the cobalt FT product stream.

[0059] The person of ordinary skill in the art can tune the portion of the iron FT product stream that is included in the downstream cobalt FT feed stream to provide a desirable H2:CO ratio. For example in various embodiments, the portion of the iron FT product stream that is included in the downstream cobalt FT feed stream has a H2:CO ratio in the range of 0.5:1 to 10:1, e.g., in the range of 1 :1 to 2.5:1. Of course, whatever the H2:CO ratio of the portion of the iron FT product stream that is included in the downstream cobalt FT feed stream, the person of ordinary skill in the art can add H2 or CO as described above as necessary to provide the desired ratio overall in the downstream cobalt FT feed stream. This can be advantageous, particularly when the preceding iron FT process has low CO selectivity such that the portion of the iron FT product stream that is included in the downstream cobalt FT feed stream is lean in CO (e.g.., H₂:CO is greater than 2:1). The person of ordinary skill in the art can determine an addition rate to co-feed a H₂-deficient syngas stream (e.g., H₂:CO is in the range of 0.5:1 to 1.5:1) to the downstream cobalt FT feed stream such that the downstream cobalt FT feed ends up with a desirable H₂:CO ratio (e.g., in the range of 1.5:1 to 3:1 , or 1.5:1 to 2.5:1). This process is shown in process 400 of FIG. 4, wherein CO feed stream 426A and H₂ feed stream 426B can supply a H₂-deficient syngas stream to downstream cobalt FT feed stream 421 to adjust the ratio of H₂:CO.

[0060] As described above, the downstream cobalt FT feed stream contains both H₂ and CO and the downstream cobalt FT feed stream includes all feeds to the downstream cobalt FT reactor zone, regardless of whether the downstream cobalt FT feed stream is provided as a mixture of feeds or as feeds provided individually to a reaction zone. In various embodiments of the present disclosure as described herein, the downstream cobalt FT feed stream has a H₂:CO ratio in the range of 0.5:1 to 6:1. In some embodiments, the downstream cobalt FT feed stream has a H₂:CO ratio in the range of 1 :1 to 3:1 , or 1 :1 to 2.5:1 . In some embodiments, the downstream cobalt FT feed stream has a H₂:CO ratio of at least 1.4:1. For example, in some embodiments, the downstream cobalt FT feed stream has a H₂:CO ratio in the range of 1.4:1 to 3:1 , or 1.4:1 to 2:1. The person of ordinary skill in the art will provide a desired ratio of H₂:CO in the downstream cobalt FT feed stream, based on the disclosure herein that provides a desirable conversion and selectivity in the Fischer- T ropsch process.

[0061] It can be desirable to reduce the amount of water that is conducted to the downstream cobalt FT process step as having water present for the downstream cobalt FT process step can decrease the activity of the cobalt-based FT catalyst. Accordingly, in various embodiments as otherwise described herein, the portion of the iron FT product stream that is included in the cobalt FT feed stream has a water content of no more than 10 mol%, e.g., or no more than 2 mol%, or no more than 0.5 mol%. Maintaining a low amount of water can have additional benefits, such as improving catalyst stability.

[0062] The downstream cobalt Fischer-Tropsch process is typically used to make C5+ hydrocarbons, for example, unsubstituted C5+ hydrocarbons (e.g., alkanes and alkenes) and oxygenated C5+ hydrocarbons (e.g., C5+ alcohols, aldehydes, ketones, carboxylic acids). In some embodiments as described herein, the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a C5+ selectivity (i.e. , from CO₂ input) of at least 65%, e.g., at least 70%, or at least 75%. In various embodiments of the disclosure as described herein, the contacting the downstream cobalt FT feed stream with the downstream cobalt FT catalyst in the cobalt FT reaction zone is conducted with a C5+ selectivity (i.e., for all C5+ species) of at least 75%, e.g., at least 80%, or at least 85%. For example, in some embodiments, the selectivity for C5+ alkanes is at least 75%, e.g., at least 80%, or at least 85%. In some embodiments, the selectivity for C5+ alkanes and C5+ alcohols is at least 75%, e.g., at least 80%, or at least 85%. In some embodiments as described herein, the contacting of the downstream cobalt FT feed stream with the downstream cobaltbased FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a Cg+ selectivity (i.e., from CO2 input) of at least 50%, e.g., at least 55%, or at least 60%.

[0063] As described above, the process includes contacting a downstream cobalt FT feed stream with a cobalt-based FT catalyst. The person of ordinary skill in the art will select appropriate reaction conditions (e.g., temperature and pressure) in conjunction with the particular feed and catalyst used to provide desired Fischer-Tropsch processes. In some embodiments of the disclosure as described herein, the downstream cobalt FT temperature is in the range of 150-280 °C. For example, in various embodiments, the downstream cobalt FT temperature is in the range of 150-260 °C, or 150-240 °C, or 150-230°C, or 150-220°C, or 175-280 °C, or 175-260 °C, or 175-240°C, or 175-230°C, or 195-280 °C, or 195-260 °C, or 195-250 °C, or 195-240 °C, or 195-230 °C. In some particular embodiments, the downstream cobalt FT temperature is in the range of 150-250 °C, e.g., 195-230 °C. The present inventors note that the downstream cobalt FT feed stream may be lean in CO (i.e., H2:CO is greater than 2:1), especially if the preceding iron FT process has low CO selectivity. In such situations, it can be advantageous to lower the operating temperature of the downstream cobalt FT process to maximize C5+ selectivity of the process. For example, in some particular embodiments, the downstream cobalt FT temperature is in the range of 150-250 °C, e.g., 195-230 °C.

[0064] Notably, in many embodiments, the iron FT temperature and the downstream cobalt FT temperature can be relatively close to one another. The present inventors have noted that the iron-based FT catalysts and processes described herein can provide suitable activity of CO2 even at relatively low temperatures. Accordingly, the iron FT product stream can be provided with a temperature that is suitable for, or at least close to suitable for, the downstream cobalt-based FT reaction step. This can desirably provide for increased process integration. For example, in various embodiments, the iron FT temperature is within 100 °C of the downstream cobalt FT temperature, e.g., within 50 °C of the downstream cobalt FT temperature, or within 25 °C of the downstream cobalt FT temperature.

[0065] In some embodiments of the disclosure as described herein, the contacting the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst is conducted at a pressure of at least 1 barg, e.g., at least 5 barg, or at least 10 barg. In some embodiments of the disclosure as described herein, the contacting is conducted at a downstream cobalt FT pressure in the range of 10-60 barg. For example, in various embodiments, the downstream cobalt FT pressure is in the range of 10-50 barg, 20-50 barg, or 25-50 barg, or 10-40 barg, or 20-40 barg, or 25-40 barg or 10-35 barg, or 20-35 barg, or 25-35 barg. In some embodiments, the downstream cobalt FT pressure is in the range of 20-50 barg.

[0066] The downstream cobalt FT processes described herein can be performed at a variety of GHSV (gas hourly space velocity) values, as would be appreciated by the person of ordinary skill in the art. As such, the GHSV for contacting the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst is not particularly limited. For example, in some embodiments of the present disclosure, the contacting is conducted at a downstream cobalt FT GHSV in the range of 1,000 to 2,000,000 IT¹. In various embodiments, the contacting is conducted at a downstream cobalt FT GHSV in the range of 1,000 to 1 ,200,000 IT¹, or 1,000 to 500,000 IT¹, or 1,000 to 100,000 IT¹, or 5,000 to 1,200,000 IT¹, or 5,000 to 500,000 IT¹, or 5,000 to 100,000 IT¹, or 10,000 to 1,200,000 IT¹, or 10,000 to 500,000 h’¹, or 10,000 to 100,000 IT¹. In various embodiments of the present disclosure, the contacting is conducted at a downstream cobalt FT GHSV in the range of 1,000 to 50,000 IT¹, or 2,000 to 50,000 IT¹, or 5,000 to 50,000 IT¹, or 10, 000 to 50,000, or

1,000 to 40,000 IT¹, or 2,000 to 40,000 IT¹, or 5,000 to 40,000 IT¹, or 10, 000 to 40,000 IT¹, or

1,000 to 30,000 IT¹, or 2,000 to 30,000 IT¹, or 5,000 to 30,000 IT¹, or 10,000 to 30,000 IT¹.

The person of ordinary skill in the art will appreciate that the full range of space velocities described above may not be available for a given cobalt FT process.

[0067] The processes as described herein include contacting a downstream cobalt FT catalyst with the downstream cobalt FT feed stream as described herein. The cobalt FT catalyst for use in the processes as described herein is not particularly limited.

[0068] For example, in some embodiments of the present disclosure as described herein, the downstream cobalt FT catalyst comprises cobalt in an amount in the range of 5- 25 wt%, calculated as Co(0). “Calculated as Co(0)” and analogous terms mean that the weight of cobalt atoms/ions themselves are used in the calculation, and not the total amount of any compound or polynuclear ion in which those cobalt atoms/ions might be bound. For example, in various embodiments, the downstream cobalt FT catalyst comprises cobalt in an amount in the range of 7-25 wt%, or 10-25 wt%, or 5-20 wt%, or 7-20 wt%, or 10-20 wt%, calculated as Co(0). As the person of ordinary skill in the art will appreciate, cobalt-based catalysts are often provided to the reaction zone in the form of cobalt oxide on a support; the cobalt can be reductively activated (e.g., with H2) in situ to provide an active catalyst species with a significant concentration of Co(0). [0069] In various embodiments of the disclosure as described herein, the downstream cobalt FT catalyst further includes manganese. For example, in various embodiments, the downstream cobalt FT catalyst includes manganese in an amount up to 15 wt%, e.g., up to 12 wt%, or up to 10 wt%, or up to 7 wt%, calculated as Mn(0). In certain such embodiments, a catalyst material includes manganese in an amount in the range of 0.1-15 wt%, e.g., 0.1- 10 wt%, or 0.1-5 wt%, 0.5-15 wt%, or 0.5-10 wt%, or 0.5-5 wt%, or calculated as Mn(0). Of course, in other embodiments substantially no manganese is present (e.g., less than 0.1 wt% or less than 0.5 wt% manganese is present).

[0070] The downstream cobalt-based FT catalysts suitable for use in the process as described herein can be a variety of forms and are not particularly limited. For example, the downstream cobalt-based FT catalyst may be a supported or unsupported catalyst. While the form of the catalyst is not particularly limited, in various desirable embodiments, the downstream cobalt-based FT catalyst is a supported catalyst, wherein the support comprises at least one of titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, silicon oxide and zinc oxide. For example, in various embodiments, the support comprises at least one or titanium oxide, aluminum oxide, and silicon oxide. In some embodiments of the present disclosure as described herein, the support is a titanium dioxide support.

[0071] The person of ordinary skill in the art will appreciate that the downstream cobaltbased FT catalysts of the disclosure can be provided in many forms, depending especially on the particular form of the reactor system in which they are to be used, e.g., in a fixed bed or as a fluidized bed. The supports of the downstream cobalt-based FT catalysts can be provided themselves as discrete bodies of material, e.g., as porous particles, pellets or shaped extrudates, with the metals provided thereon to provide the downstream cobaltbased FT catalyst. However, in other embodiments, a downstream cobalt-based FT catalyst of the disclosure can itself be formed as a layer on an underlying substrate. The underlying substrate is not particularly limited. It can be formed of, e.g., a metal or metal oxide, and can itself be provided in a number of forms, such as particles, pellets, shaped extrudates, or monoliths. The person of ordinary skill in the art will select an appropriate downstream cobalt-based FT catalyst for the particular reactor system.

[0072] Cobalt-based FT catalysts are typically activated before use, e.g., to provide cobalt(O) species on a cobalt-based catalyst. Such activation can be performed prior to contacting the cobalt=based FT catalyst with the downstream cobalt FT feed stream.

[0073] For example, in some embodiments, the cobalt FT catalyst is activated by contact with a reducing gas. For example, hydrogen can be an especially suitable gas for activating cobalt FT catalyst, e.g., when the activation is a reduction to metal(O) species, e.g., as for many cobalt-based catalysts. In various embodiments of the present disclosure as otherwise described herein, the reducing gas comprises at least a portion of hydrogen from the iron FT product stream. For example, in some embodiments, the process further comprises separating at least a portion of hydrogen of the iron FT product stream and contacting it with the cobalt FT catalyst to activate the catalyst. In the process 200 shown schematically in FIG. 2, at least a portion of hydrogen stream 225B is separated from the iron FT product stream 212 and contacted with the cobalt FT catalyst 223 to activate it. In other embodiments, H2 present in the downstream cobalt FT feed stream can be used to activate the catalyst. This process is shown schematically in FIG. 4, where at least a portion of hydrogen stream 425 is separated from the cobalt FT feed stream 421 and contacted with the cobalt FT catalyst 423 to activate it. As would be understood by the person of ordinary skill in the art, activation temperatures can vary depending on the catalyst used. As such, the person of ordinary skill in the art would be able to select an appropriate temperature for activating the catalyst, e.g., in the range of 200-400 °C.

[0074] Additional components may be in present in the downstream cobalt FT product stream. For example, in some embodiments, the downstream cobalt FT product stream includes water, which is another product of the Fischer-Tropsch reaction. Also present can be one or more light hydrocarbons (i.e., C1-C4) as a side product. CO and/or H2 can be present, e.g., unreacted from the downstream cobalt FT feed stream. CO2 or other inerts as described herein can also be present. Such components of the downstream cobalt FT product stream can be separated and/or recycled in various manners. In some embodiments as described herein, the process further includes in a downstream separation zone, separating the downstream cobalt FT product stream to provide a light product stream rich in hydrogen, carbon monoxide, carbon dioxide and C1-C4 hydrocarbons; and a heavy product stream rich in C5+ hydrocarbons.

[0075] As described above, the light product stream also comprises light hydrocarbons, i.e., C1-C4 hydrocarbons and the light product stream may be further separated to provide a light hydrocarbon product stream. Light hydrocarbons, while often not a desired portion of a Fischer-Tropsch product to be used as a fuel or a lubricant, can themselves be useful for a number of purposes. Accordingly, in various embodiments, the process further includes separating at least a portion of C1-C4 hydrocarbons from the light product stream to provide a light hydrocarbon stream. For example, in the process 300 of FIG. 3, at least a portion of the C1-C4 hydrocarbon from the light product stream 336 are separated to provide a light hydrocarbon stream 338. The light hydrocarbon stream can, for example, be recycled to the iron FT feed stream or the cobalt FT feed stream. In the process 300 of FIG. 3, light hydrocarbons can be provided as part of the recycle stream 336, which becomes part of the iron FT feed stream 311. In the process 400 of FIG. 4, light hydrocarbons are recycled via recycle stream 436 to downstream cobalt FT feed stream 421.

[0076] The other components of the light product stream, e.g., hydrogen, carbon monoxide, and carbon dioxide may be used in other feeds of the process as described herein. As such, in some embodiments as described herein, at least a portion of hydrogen, carbon monoxide and carbon dioxide of the light product stream is included in the iron FT feed stream and/or the downstream cobalt FT feed stream. For example, it can be desirable to recycle hydrogen from the light product stream, for example, to the iron FT feed stream. For example, in the process of FIG. 3, at least a portion of H2 of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the iron FT feed stream 311 via recycle stream 336. In various embodiments, the process includes recycling at least a portion of H₂ of the light product stream to the downstream cobalt FT feed stream. For example, in the process of FIG. 4, at least a portion of H₂ of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the downstream cobalt FT feed stream 421 via recycle stream 436. In various embodiments, at least 25%, e.g., at least 50% of H₂ of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In various embodiments, at least 75%, e.g., at least 90% of H₂ of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream.

[0077] In some cases, e.g., when H₂ is provided to the downstream cobalt FT feed stream from an H₂ source other than the iron FT product stream, H₂ from the light product stream can make up most of the H₂ of the iron FT feed stream, e.g., at least 90%, at least 95%, or at least 98% of the H₂ of the iron FT feed stream. This is shown, e.g., in FIG. 5. Here, the primary H₂ input to the process is through stream 540, which becomes part of the downstream cobalt FT feed stream 521. H₂ of the light product stream is included in recycle stream 536, which becomes part of iron FT feed stream 511.

[0078] Similarly, it can be desirable to recycle CO of the light product stream, for example, to the iron FT feed stream and/or the downstream cobalt FT feed stream. For example, it can be desirable to recycle carbon monoxide from the light product stream, for example, to the iron FT feed stream. For example, in the process of FIG. 3, at least a portion of carbon monoxide of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the iron FT feed stream 311 via recycle stream 336. In various embodiments, the process includes recycling at least a portion of carbon monoxide of the light product stream to the cobalt FT feed stream. For example, in the process of FIG. 4, at least a portion of carbon monoxide of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the downstream cobalt FT feed stream 421 via recycle stream 436. In various embodiments, at least 25%, e.g., at least 50% of carbon monoxide of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In various embodiments, at least 75%, e.g., at least 90% of carbon monoxide of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream.

[0079] As with hydrogen and carbon monoxide, it can be desirable to recycle carbon dioxide of the light product stream, for example, to the iron FT feed stream and/or the cobalt FT feed stream. Since CO2 is the primary carbon source for the iron FT step, it can be especially desirable to recycle CO2 to the iron FT feed stream. Accordingly, in various embodiments, the process includes recycling at least a portion (e.g., at least 50%, at least 75%, or at least 90%) of CO2 of the downstream cobalt FT product stream to the iron FT feed stream. For example, in the process of FIG. 3, at least a portion of CO2 of the downstream cobalt FT product stream (e.g., at least 50%, at least 75%, or at least 90%) can be recycled to the iron FT feed stream 311 via recycle stream 336. For example, it can be desirable to recycle carbon dioxide from the light product stream, for example, to the iron FT feed stream. For example, in the process of FIG. 3, at least a portion of carbon dioxide of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the iron FT feed stream 311 via recycle stream 336. In various embodiments, the process includes recycling at least a portion of carbon dioxide of the light product stream to the downstream cobalt FT feed stream. For example, in the process of FIG. 4, at least a portion of carbon dioxide of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the cobalt FT feed stream 421 via recycle stream 436. In various embodiments, at least 25%, e.g., at least 50% of carbon dioxide of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In various embodiments, at least 75%, e.g., at least 90% of carbon dioxide of the light product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In some cases, e.g., when CO2 is provided to the downstream cobalt FT feed stream from a CO2 source other than the iron FT product stream, CO2 from the downstream cobalt FT product stream can make up most of the CO2 of the iron FT feed stream, e.g., at least 90%, at least 95%, or at least 98% of the CO2 of the iron FT feed stream. This is shown, e.g., in FIG. 6. Here, the primary CO2 input to the process is through stream 640, which becomes part of the downstream cobalt FT feed stream 621. CO2 of the downstream cobalt FT product stream is included in recycle stream 636, which becomes part of iron FT feed stream 611.

[0080] In many cases, hydrogen, carbon monoxide, and carbon dioxide, of the light product stream will be recycled. [0081] Moreover, when one or more inerts are used in the process steps, it can be desirable to recycle these. For example, in various embodiments, the process includes recycling at least a portion of inerts of the downstream cobalt FT product stream to the iron FT feed stream and/or the downstream cobalt FT feed stream. In various embodiments, the process includes recycling at least a portion of inerts of the downstream cobalt FT product stream to the iron FT feed stream. For example, in the process of FIG. 3, at least a portion of inerts of the downstream cobalt FT product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the iron FT feed stream 311 via recycle stream 336. In various embodiments, the process includes recycling at least a portion of inerts of the downstream cobalt FT product stream to the downstream cobalt FT feed stream. For example, in the process of FIG. 4, at least a portion of inerts of the downstream cobalt FT product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the downstream cobalt FT feed stream 421 via recycle stream 436. In various embodiments, at least 25%, e.g., at least 50% of inerts of the downstream cobalt FT product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In various embodiments, at least 75%, e.g., at least 90% of inerts of the downstream cobalt FT product stream is recycled to the iron FT feed stream or the downstream cobalt FT feed stream. In various embodiments, a purge stream can be incorporated with the recycle stream to prevent uncontrolled accumulation of inerts in the recycle stream (not shown here).

[0082] As would be understood by the person of skill in the art, the downstream cobalt FT product stream will also include water. In various embodiments, the process further comprises separating at least a portion of water from the downstream cobalt FT process stream. This is shown schematically in FIG. 3. In the embodiment of FIG. 3, the iron-based FT catalyst 313 and the cobalt FT catalyst 323 are provided in separate beds in the same reactor. Thus, the iron FT reaction zone 310 is a volume of the reactor 305 that includes the bed 314 containing the iron-based FT catalyst 313, and the cobalt FT reaction zone 320 is a volume of the reactor 305 that includes the bed 324 containing the cobalt FT catalyst 323. Iron FT feed stream 311 is contacted with the iron-based FT catalyst 313 to provide iron FT product stream 312, which is passed directly as the cobalt FT feed stream 321 to the cobalt FT catalyst 323 to provide downstream cobalt FT product stream 322. Here, the process also optionally includes separating at least a portion of water (e.g., at least 50%, at least 75%, or at least 90%) from the cobalt FT product stream 322 to provide water-containing stream 334.

[0083] The carbon dioxide of the light product stream can also be used as a source of carbon monoxide for the process described herein. For example, in some embodiments of the disclosure as described herein, the process further includes reacting at least a portion of the carbon dioxide of the light product stream in a CO generating zone to convert carbon dioxide to carbon monoxide, and including a least a portion of the carbon monoxide from the CO generating zone in the iron FT feed stream and/or the cobalt FT feed stream. The conversion method of carbon dioxide to carbon monoxide is not particularly limited. For example, a reverse water-gas shift or a conversion by a solid oxide electrochemical cell can be used. For example, in the process 500 of FIG. 5, at least a portion of the carbon dioxide of the light product stream 536 is provided to a CO generating zone 562 to convert carbon dioxide to carbon monoxide, and at least a portion of the carbon monoxide from the CO generating zone 554 is provided to the iron FT feed stream 511 and/or the cobalt FT feed stream 521. In FIG. 5, the process 500, iron FT reactor 510, iron FT feed stream 511 , iron FT product stream 512, iron-based FT catalyst 513, cobalt FT reactor 520, cobalt FT feed stream 521 , cobalt FT product stream 522 and cobalt FT catalyst 523 are generally as described above.

[0084] As described above, the light product stream may also include light hydrocarbons that may be recycled to the iron and/or downstream cobalt FT feed stream. There are other uses for the light hydrocarbon stream. For example, in some embodiments, the process further comprises at least partially oxidizing at least a portion of the C1-C4 hydrocarbons of the light product stream in a partial oxidation reaction zone to provide a partial oxidation (pOX) stream comprising carbon monoxide e.g., a CO- and/or CO2-containing partial oxidation (pOX) stream, and including at least a portion of the pOX stream in the downstream cobalt FT feed stream. An example of such a process is shown schematically in FIG. 6, in which the process 600, the iron FT feed stream 611, the iron FT product stream 612, the iron-based FT catalyst 613, the downstream cobalt FT feed stream 621 , the downstream cobalt FT product stream 622 and the downstream cobalt FT catalyst 623 can be as otherwise described herein. Here, the process includes oxidizing at least a portion of the light hydrocarbon stream 638 in a partial oxidation reaction zone 692 to provide a CO- and/or CO2 containing pOX stream, and including at least a portion of the pOX stream 694a stream in the cobalt FT feed stream 621.

[0085] Similarly, in some embodiments as described herein, the process further includes oxidizing at least a portion of C1-C4 hydrocarbons of the light product stream in an oxidation reaction zone to provide an oxidation (OX) product stream comprising carbon dioxide, and including at least a portion of the carbon dioxide of the oxidation product stream to the iron FT feed stream. An example of such a process is shown in FIG. 6, where the process 600 includes oxidizing at least a portion of the light hydrocarbon stream 638 in a partial oxidation reaction zone 692 to provide a CO2 containing OX stream, and including at least a portion of the OX stream 694b stream in the iron FT feed stream 611. [0086] Moreover, the light hydrocarbon stream can be burned to provide heat energy, which can be used to heat various process streams, or to generate electricity. Accordingly, in various embodiments, the process includes burning at least a portion of the light hydrocarbon stream to provide energy, e.g., heat energy or electrical energy. For example, in the process 500 of FIG. 5, a portion of light hydrocarbon stream 538 is burned in a power generation zone (here, in an electrical generator 570), to generate electricity stream 572. In various embodiments, the heat energy may be used to provide the needed heat duty for the iron FT process. For example, in the process 500 of FIG. 5, a portion of the light hydrocarbon stream 538 is burned in a power generation zone (here, in a heat generator 580), to generate heat stream 582. The heat stream 582 is conducted to a heat exchange zone 590 to heat the iron FT feed stream 511.

[0087] The present inventors have noted that it can be desirable to provide for heat exchange with a relatively hot iron FT feed stream to cool the iron FT product stream to a temperature more appropriate for the downstream cobalt FT step and to provide heat elsewhere to the integrated process. For example, in various embodiments of the processes as otherwise described herein, the process further comprises exchanging heat between at least a portion of the iron FT product stream and at least a portion of the iron FT feed stream, thereby cooling at least a portion of the iron FT product stream and heating at least a portion of the iron FT feed stream. An example of such a process is shown schematically in FIG. 4. In FIG. 4, the process 400, iron FT reactor 410, iron FT feed stream 411, iron FT product stream 412, iron-based FT catalyst 413, cobalt FT reactor 420, cobalt FT feed stream 421 , cobalt FT product stream 422 and cobalt FT catalyst 423 are generally as described above. Here, the process 400 includes exchanging heat between at least a portion of the iron FT product stream 412 and a least a portion of the iron feed stream 411 in a first heat exchange zone 430, thereby cooling at least a portion of the iron product stream 412 and heating at least a portion of the iron feed stream 411. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0088] Of course, any excess heat in the iron FT product stream can be additionally or alternatively used for other purposes. For example, in various embodiments the process further comprises exchanging heat between at least a portion of the iron FT product stream and a steam generation zone, thereby cooling at least a portion of the iron FT product stream and providing heat to the steam generation zone. This is shown in FIG. 4. Here, after heat exchange with the iron feed stream 411 , the iron product stream 412 is conducted to steam generation zone 432, to cool the iron FT product stream 412 and provide heat to the steam generation zone 432. Steam can be generated from the heat provided, and electricity can be generated from the steam. For example, in the embodiment of FIG. 4, electricity stream 464 is provided by the generation of electricity using steam generated in the steam generation zone 432. Of course, as would be understood to the person of ordinary skill in the art, the steam generated in the steam generation zone may be used in other processes. In various embodiments, the steam may be used to heat the iron FT feed stream. For example, in the embodiment of FIG. 4, the steam stream 466 generated in the steam generation zone 432 is conducted to the heat exchange zone 490 to heat the iron feed stream 411.

[0089] As with the iron FT product stream, heat can be exchanged from the downstream cobalt FT product stream to provide heat to, for example, a feed stream (e.g., the iron FT or cobalt FT feed streams as described herein) or a steam generation zone. For example, in various embodiments, the process further comprises exchanging heat between at least a portion of the downstream cobalt FT product stream and at least a portion of the iron FT feed stream, thereby cooling at least a portion of the downstream cobalt FT product stream and heating at least a portion of the iron FT feed stream. In process 300 of FIG. 3, heat is exchanged between at least a portion of the downstream cobalt FT product stream 322 and iron FT feed stream 311 in a cobalt FT heat exchange zone 330, thereby cooling the downstream cobalt FT product stream 322 and heating the iron FT feed stream 311. Of course, heat can also be exchanged from the downstream cobalt FT product stream to the downstream cobalt FT feed stream. For example, in various embodiments, the process further comprises exchanging heat between at least a portion of the downstream cobalt FT product stream and at least a portion of the downstream cobalt FT feed stream, thereby cooling at least a portion of the downstream cobalt FT product stream and heating at least a portion of the downstream cobalt FT feed stream. In process 500 of FIG. 5, heat is exchanged between at least a portion of the cobalt FT product stream 522 and cobalt FT feed stream 521 in a cobalt FT heat exchange zone 530, thereby cooling the downstream cobalt FT product stream 522 and heating the downstream cobalt FT feed stream 521. Similarly, in process 600 of FIG. 6, heat is exchanged between at least a portion of the cobalt FT product stream 622 and cobalt FT feed stream 621 in a cobalt FT heat exchange zone 630, thereby cooling the downstream cobalt FT product stream 622 and heating the downstream cobalt FT feed stream 621. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0090] Of course, any excess heat in the downstream cobalt FT product stream can be additionally or alternatively used for other purposes. For example, in various embodiments the process further comprises exchanging heat between at least a portion of the downstream cobalt FT product stream and a steam generation zone, thereby cooling at least a portion of the downstream cobalt FT product stream and providing heat to the steam generation zone. This is shown in FIG. 3. Here, after heat exchange with the iron FT feed stream 311, the downstream cobalt FT product stream 322 is conducted to steam generation zone 332, to cool the downstream cobalt FT product stream 322 and provide heat to the steam generation zone 332. Steam can be generated from the heat provided, and electricity can be generated from the steam (not shown here).

[0091] As noted above, the cobalt FT process step provides a downstream cobalt FT product stream that includes C5+ hydrocarbons (e.g., unsubstituted hydrocarbons like alkanes and alkenes, and/or oxygenated hydrocarbons such as alcohols). Accordingly, in various embodiments, one or more products are provided from at least a portion of C5+ hydrocarbons of the downstream cobalt FT product stream. The C5+ hydrocarbons can be used as the basis of a variety of fuels, e.g., gasoline, diesel, aviation fuel. Other products, like waxes and lubricants, can also be made. And alkenes and oxygenates can be used as feedstocks in a variety of other processes.

[0092] The person of ordinary skill in the art will use conventional post-processing techniques to convert the C5+ hydrocarbon-containing product to desirable products such as desirable fuels. For example, in various embodiments, the process further includes hydroprocessing at least a portion of C5+ hydrocarbons of the downstream cobalt FT product stream. As the person of ordinary skill in the art will appreciate, hydroprocessing is a treatment of the hydrocarbon stream with hydrogen in the presence of a suitable catalyst. A wide variety of hydroprocessing techniques are known and the person of ordinary skill in the art will apply them here. For example, in the process 300, 500, and 600 of FIGs. 3, 5, and 6, respectively, downstream cobalt FT product streams 322, 522, and 622 are hydroprocessed in hydroprocessing reactors 350, 550, and 650, to provide hydroprocessed product streams 352, 552, and 652.

[0093] The processes described herein can be operated in a wide variety of reactor systems. In some embodiments, the iron FT reaction zone (i.e. , in which the iron FT process step is performed) comprises a iron FT reactor in which an iron-based FT catalyst is disposed, and the downstream cobalt FT reaction zone (i.e., in which the cobalt FT process step is performed) comprises a downstream cobalt FT reactor in which the downstream cobalt FT catalyst is disposed. Examples of such processes are shown schematically in FIGS. 1 , 2, 4, 5, and 6. In these examples, the process (100, 200, 400, 500, 600) is performed in a reactor system that includes an iron FT reactor (110, 210, 410, 510, 610) in which the iron-based FT catalyst (113, 213, 413, 513, 613) is disposed, and a downstream cobalt FT reactor (120, 220, 420, 520, 620) in which the downstream cobalt FT catalyst (123, 223, 423, 523, 623) is disposed. The reactors used for the integrated process of the present disclosure as described herein are not particularly limited, and the person of ordinary skill in the art will be able to select an appropriate reactor.

[0094] But other embodiments are possible. For example, in some embodiments, the process is performed in a reactor system comprising iron-based FT catalyst bed in which the iron-based FT catalyst is disposed, and wherein the cobalt FT reaction zone comprises a cobalt FT catalyst bed in which the cobalt FT catalyst is disposed. In some embodiments, the iron FT reactor bed and the cobalt FT reactor bed are disposed within the same reactor. Such a configuration is shown in FIG. 3, in which the iron-based FT catalyst 313 is disposed in an iron-based FT catalyst bed 314, and the downstream cobalt FT catalyst 323 is disposed in a downstream cobalt FT catalyst bed 324. Here, the catalyst beds 314 and 324 are in the same reactor, with process gases flowing between them. Such a configuration can be especially desirable when the iron FT temperature and the cobalt FT temperature are relatively close to one another. However, such a configuration is not particularly limited, as the person of ordinary skill in the art can implement more cooling or less heat input in the downstream cobalt FT section to accommodate Fischer-Tropsch processes where there is a relatively large difference in temperature between the iron FT and cobalt FT processes.

[0095] In various embodiments, the process is performed in a reactor system comprising one or more iron-based FT catalyst containers in which the iron-based FT catalyst is disposed, and wherein the downstream cobalt FT reaction zone comprises one or more downstream cobalt FT catalyst containers in which the cobalt FT catalyst is disposed. These can be provided in the same reactor, such as described above with respect to catalyst beds.

[0096] As noted above, the iron FT process step using the iron-based FT catalysts described herein and the cobalt FT process step can be performed under similar conditions. Accordingly, in various embodiments, the iron-based FT catalyst and the cobalt FT catalyst can be provided together in the same catalyst bed, e.g., mixed together. Such an embodiment is shown in FIG. 7. Here, the process 700 is performed in a reactor system that includes a reactor 705 in which the iron-based FT catalyst 713 and the cobalt FT catalyst 723 are mixed together in a single catalyst bed 724. Here, iron FT feed stream 711 and cobalt FT product stream 722 can be substantially as described herein. The iron FT product stream and the cobalt FT feed stream are understood to be the mixture of process gases within the mixed catalysts.

[0097] In the embodiments particularly-described above, separate iron FT and cobalt FT catalysts are used, e.g., in separate reactors, in separate regions of the same reactor, or even comingled in the same region of a reactor. [0098] As described above, CO2 and H₂ are substantial inputs to the process as described herein. Advantageously, the present inventors have recognized that each of these can come from renewable or otherwise environmentally responsible sources.

[0099] CO2 can be captured from the environment generally or more directly from processes that form CO₂ (especially in difficult-to-abate sectors). This can make the eventual hydrocarbon product substantially carbon-neutral or of lower carbon intensity. Accordingly, in some embodiments of the disclosure as described herein, at least a part of the CO2 of the iron FT feed stream and/or the downstream cobalt FT feed stream is from a renewable source. In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO₂ of the iron FT feed stream and/or the cobalt FT feed stream is from direct air capture. In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO₂ of the iron FT feed stream and/or the downstream cobalt FT feed stream is from a manufacturing plant such as a bioethanol plant (e.g., CO2 produced fermentation), a steel plant, or a cement plant. Accordingly, the rWGS-Fischer Tropsch integrated processes of the disclosure as described herein can be not only carbon neutral, but in some cases a net consumer of carbon dioxide. These benefits in particular make the integrated processes highly attractive for decarbonizing transportation fuels, for both automotive and aviation sectors, since the carbon monoxide produced by the rWGS activity of the iron-based FT catalyst can be readily utilized by well-established technologies to synthesize liquid hydrocarbon fuels by cobalt-based FT processes.

[00100] Similarly, H₂ can be provided from environmentally-responsible sources. In some embodiments, at least a part of the H₂ of the iron FT feed stream and/or the downstream cobalt FT feed stream is from a renewable source. For example, in various embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H₂ of the iron FT feed stream and/or the downstream cobalt FT feed stream can be so-called “green” hydrogen, e.g., produced from the electrolysis of water operated using renewable electricity (such as wind, solar, or hydro-electric power). In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H₂ of the iron FT feed stream and/or the downstream cobalt FT feed stream may be from a so-called “blue” source, e.g., from a natural gas reforming process with carbon capture. Of course, other sources of H₂ can be used in part or in full. For example, in some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H₂ of the iron FT feed stream and/or the downstream cobalt FT feed stream is grey hydrogen, black hydrogen, brown hydrogen, pink hydrogen, turquoise hydrogen, yellow hydrogen, and/or white hydrogen.

[00101] The present inventors have noted that electrolysis of water is a desirable way to provide hydrogen to the claimed processes. Accordingly, in some embodiments, the process includes providing at least a portion of H₂ to the iron FT feed stream and/or the downstream cobalt FT feed stream by electrolysis of water. In some embodiments, the electrolysis of water is performed using at least partially electricity from a renewable source, e.g., to provide so-called “green hydrogen.” However, the present inventors have noted that electricity can be generated as part of the claimed process, e.g., using heat exchange from the iron FT or cobalt FT product stream, or by burning light hydrocarbons as described above. In some embodiments, the electrolysis of water is performed using at least partially electricity generated according to the processes as described herein. For example, in the process 400 of FIG. 4, water 418 separated from the iron FT product stream is electrolyzed in electrolyzer 460, using electricity 464 generated from steam made in the steam generation zone 432 by heat exchange from the iron FT product stream. H₂ generated in the electrolysis is provided via stream 465 to the iron FT feed stream. In some embodiments, at least a portion of O₂ generated in the electrolysis 463 is provided to a partial oxidation reaction zone as described herein.

[00102] Various aspects of the disclosure are illustrated by the following enumerated embodiments, which may be combined in any number and in any combination not technically or logically inconsistent:

Embodiment 1. A process for preparing hydrocarbons, comprising providing an iron FT feed stream comprising carbon dioxide and hydrogen; in an iron FT reaction zone, contacting the iron FT feed stream with an iron-based FT catalyst under conditions sufficient to form an iron FT product stream comprising C5+ hydrocarbons and carbon monoxide; providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the iron FT product stream; and in a downstream cobalt FT reaction zone, contacting the downstream cobalt FT feed stream with a downstream cobalt-based FT catalyst under conditions sufficient to form a downstream cobalt FT product stream comprising C5+ hydrocarbons.

Embodiment 2. The process of embodiment 1 , wherein the iron FT feed stream has a ratio of hydrogen to oxides of carbon in the range of 1 :1 to 6:1, e.g., 1.5:1 to 3:1.

Embodiment 3. The process of embodiment 1 or embodiment 2, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with a CO₂ conversion in the range of 5-60%, e.g., 5-55%, or 5-50%, or 5- 45%, or 5-40%, or 10-60%, or 10-55%, or 10-50%, or 10-45%, or 10-40%, or 15-60%, or 15- 55%, or 15-50%, or 15-45%, or 15-40%, or 20-60%, or 20-55%, or 20-50%, or 20-45%, or 20-40%.

Embodiment 4. The process of any of embodiments 1-3, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with a C5+ selectivity of at least 40%, e.g., at least 50%, or at least 60%.

Embodiment 5. The process of any of embodiments 1-4, wherein the contacting of the iron-based FT catalyst with the iron FT feed stream to provide the product stream is performed with a C2-4 selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%.

Embodiment 6. The process of any of embodiments 1-5, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity of at least 10%, e.g., at least 15%, or at least 20%.

Embodiment 7. The process of any of embodiments 1-5, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity in the range of 10-80%, e.g., 15-80%, or 20-80%, or 10-60%, or 15-60%, or 20-60%, or 10-50%, or 15-50%, or 20-50%, or 10-40%, or 15-40%, or 20- 40%.

Embodiment 8. The process of any of embodiments 1-7, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted at a temperature in the range of 260-350 °C.

Embodiment 9. The process of any of embodiments 1-7, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted at an iron FT temperature in the range of 180-280 °C, e.g., 180-260 °C, or 180-240 °C, or 180-220 °C, or 200-280 °C, or 200-260 °C, or 200-240 °C, or 220-280 °C, or 220-260 °C.

Embodiment 10. The process of any of embodiments 1-9, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in iron FT iron FT reaction zone is conducted at a pressure of at least 10 barg, e.g., in the range of 10-60 barg.

Embodiment 11. The process of any of embodiments 1-10 wherein the iron-based FT catalyst is an alkali-promoted iron-based FT catalyst. Embodiment 12. The process of any of embodiments 1-11 , wherein substantially all the iron FT product stream is provided to the downstream cobalt FT feed stream.

Embodiment 13. The process of any of embodiments 1-12 wherein substantially all water present in the iron FT product stream is provided to the downstream cobalt FT feed stream.

Embodiment 14. The process of any of embodiments 1-11 , further comprising separating the iron FT product stream to provide a water-rich iron FT product stream and a water-poor iron FT product stream, wherein at least a portion of (e.g., all of) the water-poor iron FT product stream is provided to the downstream cobalt FT feed stream.

Embodiment 15. The process of embodiment 14, wherein at least a portion of (e.g., all of) the carbon monoxide of the water-poor iron FT product stream is provided to the downstream cobalt FT feed stream.

Embodiment 16. The process of any of embodiments 1-11 , further comprising separating the iron FT product stream to provide a condensate-rich iron FT product stream enriched in water and C5+ hydrocarbons and a condensate-poor iron FT product stream lean in water and C5+ hydrocarbons, wherein at least a portion of (e.g., all of) the condensatepoor iron FT product stream is provided to the downstream cobalt FT feed stream.

Embodiment 17. The process of any of embodiments 1-16, wherein hydrogen from a source other than the iron FT product stream is included in the downstream cobalt FT feed stream.

Embodiment 18. The process of any of embodiments 1-17, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted with a C5+ selectivity of at least 75%, e.g., at least 80%, or at least 85%.

Embodiment 19. The process of any of embodiments 1-18, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a C5+ selectivity (i.e., from CO2 input) of at least 65%, e.g., at least 70%, or at least 75%. Embodiment 20. The process of any of embodiments 1-19, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a Cg+ selectivity (i.e., from CO2 input) of at least 50%, e.g., at least 55%, or at least 60%.

Embodiment 21 . The process of any of embodiments 1-20, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream FT reaction zone is conducted at a temperature in the range of 150-250 °C, e.g., 195-230 °C.

Embodiment 22. The process of any of embodiments 1-21 , wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted at a pressure of at least 10 barg, e.g., in the range of 10-60 barg.

Embodiment 23. The process of any of embodiments 1-22, further comprising, in a downstream separation zone, separating the downstream cobalt FT product stream to provide a light product stream rich in hydrogen, carbon monoxide, carbon dioxide and C1-C4 hydrocarbons; and a heavy product stream rich in C5+ hydrocarbons.

Embodiment 24. The process of embodiment 23, further comprising including at least a portion of hydrogen, carbon monoxide and carbon dioxide of the light product stream in the iron FT feed stream.

Embodiment 25. The process of embodiment 23 or embodiment 24, further comprising reacting at least a portion of carbon dioxide of the light product stream in a CO generating zone to convert carbon dioxide to carbon monoxide, for example, via a reverse water-gas shift or a conversion by a solid oxide electrochemical cell, and including at least a portion of the carbon monoxide from the CO generating zone in the iron FT feed stream.

Embodiment 26. The process of any of embodiments 23-25, further comprising including at least a portion of hydrogen, carbon monoxide and carbon dioxide of the light product stream in the downstream cobalt FT feed stream.

Embodiment 27. The process of any of embodiments 23-26, further comprising reacting at least a portion of carbon dioxide of the light product stream in a CO generating zone to convert carbon dioxide to carbon monoxide, for example, via a reverse water-gas shift or a conversion by a solid oxide electrochemical cell, and including at least a portion of the carbon monoxide from the CO generating zone in the downstream cobalt FT feed stream.

Embodiment 28. The process of any of embodiments 23-27, further comprising at least partially oxidizing at least a portion of C1-C4 hydrocarbons of the light product stream in a partial oxidation reaction zone to provide a partial oxidation product stream comprising carbon monoxide, and including at least a part of the carbon monoxide of the partial oxidation product stream in the downstream cobalt FT feed stream.

Embodiment 29. The process of any of embodiments 23-28, further comprising oxidizing at least a portion of C1-C4 hydrocarbons of the light product stream in a oxidation reaction zone to provide an oxidation product stream comprising carbon dioxide, and including at least a part of the carbon dioxide of the oxidation product stream to the iron FT feed stream.

Embodiment 30. The process of any of embodiments 1-29, wherein the iron FT reaction zone and the downstream cobalt FT reaction zone are within the same reactor, e.g., as separate beds within the same reactor.

Embodiment 31 . The process of any of embodiments 1-30, wherein the iron FT reaction zone and the downstream cobalt FT reaction zone are in separate reactors.

[00103] The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention, the description taken with the drawings and/or examples making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Thus, before the disclosed processes and devices are described, it is to be understood that the aspects described herein are not limited to specific embodiments, apparatuses, or configurations, and as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and, unless specifically defined herein, is not intended to be limiting. [00104] The terms “a,” “an,” “the” and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[00105] All methods described herein can be performed in any suitable order of steps unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[00106] Unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. Words using the singular or plural number also include the plural and singular number, respectively. Additionally, the words “herein,” “above,” and “below” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of the application.

[00107] As will be understood by one of ordinary skill in the art, each embodiment disclosed herein can comprise, consist essentially of or consist of its particular stated element, step, ingredient or component. As used herein, the transition term “comprise” or “comprises” means includes, but is not limited to, and allows for the inclusion of unspecified elements, steps, ingredients, or components, even in major amounts. The transitional phrase “consisting of’ excludes any element, step, ingredient or component not specified. The transition phrase “consisting essentially of” limits the scope of the embodiment to the specified elements, steps, ingredients or components and to those that do not materially affect the embodiment.

[00108] Unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[00109] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00110] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[00111] Some embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[00112] Furthermore, it is to be understood that the embodiments of the invention disclosed herein are illustrative of the principles of the present invention. Other modifications that may be employed are within the scope of the invention. Thus, by way of example, but not of limitation, alternative configurations of the present invention may be utilized in accordance with the teachings herein. Accordingly, the present invention is not limited to that precisely as shown and described.

Claims

We claim:

Claim 1. A process for preparing hydrocarbons, comprising providing an iron FT feed stream comprising carbon dioxide and hydrogen; in an iron FT reaction zone, contacting the iron FT feed stream with an iron-based FT catalyst under conditions sufficient to form an iron FT product stream comprising C5+ hydrocarbons and carbon monoxide; separating the iron FT product stream to provide a water-rich iron FT product stream and a water-poor iron FT product stream; providing a downstream cobalt FT feed stream comprising carbon monoxide and hydrogen, the downstream cobalt FT feed stream comprising at least a portion of the carbon monoxide of the water-poor iron FT product stream; and in a downstream cobalt FT reaction zone, contacting the downstream cobalt FT feed stream with a downstream cobalt-based FT catalyst under conditions sufficient to form a downstream cobalt FT product stream comprising C5+ hydrocarbons.

Claim 2. The process of Claim 1 , wherein the iron FT feed stream has a ratio of hydrogen to oxides of carbon in the range of 1 :1 to 6:1.

Claim 3. The process of Claim 1 or Claim 2, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with a CO2 conversion in the range of 10-60%.

Claim 4. The process of any of Claims 1-3, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with a C5+ selectivity of at least 50%

Claim 5. The process of any of Claims 1-4, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted with an overall CO selectivity of at least 15%.

Claim 6. The process of any of Claims 1-5, wherein the contacting of the iron FT feed stream with the iron-based FT catalyst in the iron FT reaction zone is conducted at an iron FT temperature in the range of 180-280 °C, e.g., 180-260 °C, or 180-240 °C, or 180-220 °C, or 200-280 °C, or 200-260 °C, or 200-240 °C, or 220-280 °C, or 220-260 °C.

Claim 7. The process of any of Claims 1-6, wherein substantially all the iron FT product stream is provided to the downstream cobalt FT feed stream.

Claim 8. The process of any of Claims 1-6, further comprising separating the iron FT product stream to provide a condensate-rich iron FT product stream enriched in water and C5+ hydrocarbons and a condensate-poor iron FT product stream lean in water and C5+ hydrocarbons, wherein at least a portion of the condensate-poor iron FT product stream is provided to the downstream cobalt FT feed stream.

Claim 9. The process of any of Claims 1-8, wherein hydrogen from a source other than the iron FT product stream is included in the downstream cobalt FT feed stream.

Claim 10. The process of any of Claims 1-9, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted with a C5+ selectivity of at least 75%.

Claim 11. The process of any of Claims 1-10, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a C5+ selectivity (i.e. , from CO2 input) of at least 65%.

Claim 12. The process of any of Claims 1-11 , wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream cobalt FT reaction zone is conducted such that the overall process has a C9+ selectivity (i.e., from CO2 input) of at least 50%.

Claim 13. The process of any of Claims 1-12, wherein the contacting of the downstream cobalt FT feed stream with the downstream cobalt-based FT catalyst in the downstream FT reaction zone is conducted at a temperature in the range of 150-250 °C.

Claim 14. The process of any of Claims 1-13, further comprising, in a downstream separation zone, separating the downstream cobalt FT product stream to provide a light product stream rich in hydrogen, carbon monoxide, carbon dioxide and C1-C4 hydrocarbons; and a heavy product stream rich in C5+ hydrocarbons, preferably further comprising including at least a portion of hydrogen, carbon monoxide and carbon dioxide of the light product stream in the iron FT feed stream and/or in the downstream cobalt FT feed stream.