WO2025057011A1

WO2025057011A1 - Multi-metal oxide catalysts for oxidative dehydrogenation

Info

Publication number: WO2025057011A1
Application number: PCT/IB2024/058474
Authority: WO
Inventors: Ce YANG; David Sullivan; Vasily Simanzhenkov; Yoonhee Kim
Original assignee: Nova Chemicals International SA
Current assignee: Nova Chemicals International SA
Priority date: 2023-09-13
Filing date: 2024-08-30
Publication date: 2025-03-20
Anticipated expiration: 2026-03-13

Abstract

A catalyst and method for making the catalyst are provided. An exemplary catalyst includes the formula: Mo_aV_bTe_cTa_dB_leO_x. In this formula, a is 1.0, b is about 0.01 to about 1.0, c is about 0.01 to about 0.5, d is about 0.01 to about 0.5, e is about 0.005 to about 0.1, and x is the number of oxygen atoms necessary to render the catalyst electrically neutral, wherein the values a, b, c, d, and e are determined based on the amount of each starting material used to form the catalyst. The catalyst is used for the oxidative dehydrogenation of ethane to ethylene.

Description

MULTI-METAL OXIDE CATALYSTS FOR OXIDATIVE DEHYDROGENATION

TECHNICAL FIELD

The present disclosure relates generally to catalysts and systems for oxidative dehydrogenation (ODH). More specifically, the catalyst contains molybdenum (Mo); vanadium (V); tellurium (Te); tantalum (Ta); bismuth (Bi); and oxygen (O).

BACKGROUND ART

Olefins like ethylene, propylene, and butylene, are basic building blocks for a variety of commercially valuable polymers. Since naturally occurring sources of olefins do not exist in commercial quantities, polymer producers rely on methods for converting the more abundant lower alkanes into olefins. The method of choice for today's commercial scale producers is steam cracking, a highly endothermic process where steam-diluted hydrocarbons are subjected very briefly to a temperature of at least 600°C. The fuel demand to produce the required temperatures and the need for equipment that can withstand that temperature add significantly to the overall cost. In addition, the high temperature promotes the formation of coke, which accumulates within the system, resulting in the need for costly periodic reactor shutdowns for maintenance and coke removal.

Selective oxidation processes, such as oxidative dehydrogenation (ODH), are an alternative to steam cracking that are exothermic and produce little or no coke. In ODH, a lower alkane, such as ethane, is mixed with oxygen in the presence of a catalyst and optionally an inert diluent, such as carbon dioxide or nitrogen or steam, which may be performed at temperatures as low as 300°C, to produce the corresponding alkene. Various other oxidation products may be produced in this process, including carbon dioxide and acetic acid, among others. ODH suffers from lower conversion rates when compared to steam cracking, a fact that when combined with lower selectivity may have prevented ODH from achieving widespread commercial implementation. There is a need for a catalyst for an ODH of ethane process with high ethylene selectivity, activity, and longevity.

SUMMARY OF INVENTION

An embodiment described herein provides a catalyst including the formula MoaVbTecTadBieOx. In the catalyst formula, a is 1.0; b is about 0.01 to about 1.0; c is about 0.01 to about 0.5; d is about 0.01 to about 0.5; e is about 0.005 to about 0.1; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, d, and e are determined based on the amount of each starting material used to form the catalyst. In an aspect, b is about 0.4 to about 0.8; c is about 0.1 to about 0.3; d is about 0. 1 to about 0.3; and e is about 0.01 to about 0.05.

In an aspect, b is about 0.6 to about 0.75; c is about 0. 1 to about 0.25; d is about 0.1 to about 0.25; and e is about 0.02 to about 0.03.

In an aspect, the catalyst has the formula Mo1V0.60-0.75Te0.10-0.25Ta0.10-0.25Bi0.01-0.05Ox.

In an aspect, the catalyst has an ethane conversion of at least about 50 mol.% and a value-added products selectivity of at least about 90 mol.% for about 48 hours; wherein the value-added products comprise ethylene, C1-C4 oxygenated organic compounds, or a combination thereof. In an aspect, the C1-C4 oxygenated organic compounds include acetic acid, acetaldehyde, formaldehyde, formic acid, ethanol, acetone, or a combination thereof.

In an aspect, a reaction temperature is kept constant over the 48 hours. In an aspect, the catalyst maintains an ethane conversion over the 48 hours within about 5 mol.% of an initial ethane conversion; wherein the reaction temperature is in a range of about 400°C to about 500°C.

Another embodiment described herein provides a catalyst material comprising a catalyst described herein and a catalyst support or carrier. In an aspect, the catalyst support or carrier is selected from the group consisting of precipitated synthetic silica, fumed synthetic silica, silica-alumina, a-alumina, y-alumina, titania, WCh-ZrCh, silicon carbide, MgAl spinel, calcium aluminate, zirconia and boron nitride.

Another embodiment described herein provides a process for the oxidative dehydrogenation of ethane. The process includes contacting a gaseous feed comprising ethane and oxygen with a catalyst described herein in a reactor to produce an effluent comprising ethylene.

Another embodiment described herein provides a method for preparing a catalyst. The method includes combining a first mixture comprising bismuth nitrate and nitric acid with a second mixture comprising an ammonium molybdenum tellurium oxide hydrate to form a MoTeBi mixture; combining the MoTeBi mixture with a third mixture comprising vanadium oxide sulfate to form a MoVTeBi mixture; combining the MoVTeBi mixture with a fourth mixture comprising tantalum oxalate to form a MoVTaTeBi mixture; heating the MoVTaTeBi mixture to form a catalyst precursor; and calcining the catalyst precursor to form the catalyst.

In an aspect, the MoTeBi mixture has a pH in a range of about 2.0 to about 3.0.

In an aspect, the method includes heating the MoVTaTeBi mixture by: ramping a temperature from ambient to a temperature in a range between 100°C and 200°C over a ramping time between 1 hours and 10 hours; and holding the temperature at a holding temperature in a range between 100°C and 200°C for a holding time between 12 hours and 60 hours.

In an aspect, the method includes calcing the catalyst by: placing the catalyst in a furnace under an oxygen-free environment; ramping a temperature of the furnace from ambient to a temperature in a range between 500°C and 620°C over a ramping time between 2 hours and 10 hours; and holding the temperature of the furnace at a holding temperature in a range between 500°C and 620°C for a holding time between 1 hour and 10 hours.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is plot of the conversion (mol.%) of ethane overtime on stream (TOS) at 20 psig and 5.46 h'¹ for Sample IE and Sample 2C.

Figure 2 is a plot of the conversion (mol.%) of ethane over time on stream (TOS) at 20 psig and 5.46 h'¹ for Sample 2C.

Figure 3 is a plot of the selectivity of ethylene (mol.%) overtime on stream (TOS) at 20 psig and 5.46 h'¹ for Sample IE and Sample 2C.

DESCRIPTION OF EMBODIMENTS

Selective oxidation (SO) is generally used in oxidative dehydrogenation (ODH) reactions to form alpha-olefins from corresponding alkanes, such as to form ethylene from ethane. Embodiments described herein provide a catalyst with the formula MoVTeTaBiOx, for example, for the ODH process.

Previously disclosed ODH catalysts have suffered from an initial activity loss. The catalyst disclosed herein, which includes bismuth in the catalyst formula, was found to improve catalyst stability and longevity and avoid an initial activity loss compared to a catalyst that does not include bismuth. In some embodiments, the catalyst exhibits no activity loss within the first 16 hours of an ODH process. This can eliminate the need for an equilibration period for the catalyst to stabilize. The enhanced stability of the catalysts disclosed herein can allow for better predictability and simpler operational procedures. For example, by removing the need to change reaction parameters to adjust for a loss in activity.

Further, the catalyst disclosed herein can exhibit higher initial activity compared to other ODH catalysts, such as ODH catalysts that do not include bismuth. This can allow for reduction of the size of the reactor, or an increase in throughput using the same size reactor. In some embodiments, the catalyst was found to maintain higher conversions while maintaining comparable ethylene selectivity to other ODH catalysts. Provided herein is an oxidative dehydrogenation catalyst material that includes molybdenum (Mo); vanadium (V); tellurium (Te); tantalum (Ta); bismuth (Bi); and oxygen (O). The catalyst is represented by the formula MoaVoTccTaoBieOx. In each of these formulations, a is 1.0, and x refers to the number of oxygen atoms necessary to render the catalyst electrically neutral. The values of a, b, c, d, and e may refer to the values based on the amount of each starting material used to form the catalyst. The values of a, b, c, d, and e may also refer to values measured by elemental analysis, for example by inductively coupled plasma mass spectroscopy (ICP-MS), neutron activation analysis (NAA), x-ray fluorescence (XRF), ion chromatography mass spectrometry (IC-MS), proton induced x-ray emission (PIXE), or energy-dispersive x-ray spectroscopy (EDS).

In some embodiments, b is about 0.01 to about 1.0. In some embodiments, b is about 0.04 to about 0.8. In some embodiments, b is about 0.6 to about 0.75. In some embodiments, b is about 0.6 to about 0.7. In some embodiments, b is about 0.66. In some embodiments, b is about 0.4 to about 0.7, about 0.3 to about 0.5, or about 0.4 to about 0.45.

In some embodiments, c is about 0.01 to about 0.5. In some embodiments, c is about 0.1 to about 0.3. In some embodiments, c is about 0.1 to about 0.25. In some embodiments, c is about 0.1 to about 0.2. In some embodiments, c is about 0.15 to about 0.2. In some embodiments, c is about 0.17. In some embodiments, c is about 0.1 to about 0.15.

In some embodiments, d is about 0.01 to about 0.5. In some embodiments, d is about 0.01 to about 0.3. In some embodiments, d is about 0.1 to about 0.25. In some embodiments, d is about 0.1 to about 0.2. In some embodiments, d is about 0.15 to about 0.2. In some embodiments, d is about 0.175.

In some embodiments, e is about 0.005 to about 0.1. In some embodiments, e is about 0.01 to about 0.05. In some embodiments, e is about 0.01 to about 0.03. In some embodiments, e is about 0.02 to about 0.03. In some embodiments, e is about 0.025.

In some embodiments, the values of a, b, c, d, and e are determined based on the amount of each starting material used to form the catalyst. For example, the values of a, b, c, d, and e are determined based on the ratio amounts (molar equivalents) of each Mo, V, Te, Ta, and Bi compound used in a hydrothermal synthesis reaction. In some embodiments, the catalyst has the formula Mo1V0.60-0.75Te0.10-0.25Ta0.10-0.25Bi0.01-0.05Ox, wherein the formula is determined based on the amount of each starting material used to form the catalyst. In some embodiments, the catalyst has the formula MoiVo.66Teo.i7Tao.i75Bio.o250x, wherein the formula is determined based on the amount of each starting material used to form the catalyst. In some embodiments, the values of a, b, c, d, and e are determined by elemental analysis, such as EDS. In some embodiments, the catalyst has the formula M01V0.40- 050Ta0.10-0.20Te0.10-0.20Bi0.005-0.05Ox, wherein the formula is determined by EDS. In some embodiments, the catalyst has the formula Mo1V0.43-0.44Ta0.15-0.i6Te0.12-0.14Bi0.01-0.02Ox, wherein the formula is determined by EDS. In some embodiments, the value of b determined by EDS is lower than the value of b determind based on the amount of the starting material used to form the catalyst.

The catalyst formula with respect to the ratios of values a, b, c, d, and e can be selected to affect the activity, selectivity, purity, and stability of the catalyst. In some embodiments, the values of d and e are optimized to improve catalyst reactivity while maintaining good catalyst stability.

In some embodiments, the catalyst is essentially free of a niobium compound. The term “essentially free”, as used herein, means less than 10 ppm, less than 5 ppm, less than 2 ppm, or less than 1 ppm.

As used herein, the term “catalyst” generally refers to the active catalyst portion of a catalyst material. The catalyst is generally processed in further steps to form a catalyst material. The catalyst material may also be processed in further steps to form a final catalyst material.

Also provided herein is a catalyst material that includes a catalyst, such as a catalyst of the present disclosure, and a catalyst support or carrier. As used herein, the term “catalyst material” refers to a material that includes an active catalyst that can promote the oxidative dehydrogenation of ethane to ethylene, for example, on a support. The catalyst material can be a plurality of particles or a formed catalyst material. Non-limiting examples of formed catalyst materials include extruded catalyst materials, 3D-printed catalyst materials, spheronized catalyst materials, pressed catalyst materials, and cast catalyst materials. Nonlimiting examples of pressed and cast catalyst materials includes pellets, such as tablets, ovals, and spherical particles. In some embodiments, a binder is used to aid in catalyst forming. In some embodiments, catalyst material formation includes optional workup steps such as: debinding, calcining/sintering, and/or activating/pre-treatment. Workup steps may be introduced to prepare the catalyst to be loaded into a reactor and produce an expected productivity and mitigate any unexpected thermal runaways during startup.

Some supports are particularly suitable for the catalyst, for example, they are chemically compatible (e.g., there is no substantial impact on ethylene selectivity or there is an improvement to ethylene selectivity). Other supports may be less compatible, meaning they may lead to substantial reduction of catalyst performance, for example, ethylene selectivity. Consequently, not just any support can be chosen; the support should be selected in a judicious matter based off both short-term and longer-term catalysis performance testing. In some embodiments, there is an emphasis on long-term testing showing no loss of selectivity with time on stream (for example, TOS of >48 hours). As used herein, “time on stream (TOS)” refers to the time the catalyst material spends in the ODH process without interruption.

In some embodiments, the catalyst support or carrier is selected from the group consisting of precipitated synthetic silica, fumed synthetic silica, silica-alumina, a-alumina, y-alumina, titania, WCh-ZrCh, silicon carbide, MgAl spinel, calcium aluminate, zirconia, and boron nitride. In some embodiments, the catalyst support or carrier is selected from the group consisting of precipitated synthetic silica, fumed synthetic silica, silica-alumina, a-alumina, and anatase titania. In some embodiments, the catalyst support or carrier is a-alumina.

Also provided herein is a process for the oxidative dehydrogenation of ethane. The process includes contacting a gaseous feed comprising ethane and oxygen with a catalyst described herein in a reactor to produce an effluent comprising ethylene. The catalysts provided herein can be used for the oxidative hydrogenation of ethane to form ethylene and other value-added products. The term “value-added products”, as used herein, refers to ethylene and C1-C4 oxygenated organic compounds produced from the oxidative hydrogenation of ethane, and does not include CO2 or CO. For example, the C1-C4 oxygenated organic compounds can include alcohols, organic acids, ketones, and alydehydes. In some embodiments, the C1-C4 oxygenated organic compounds include acetic acid, acetaldehyde, formaldehyde, formic acid, ethanol, acetone, or a combination thereof. The term “C1-4 oxygenated organic compounds” is specifically intended to include compounds having one carbon atom, two carbon atoms, three carbon atoms, and four carbon atoms, and include subcombinations of these ranges, such as C1-2 oxygenated organic compounds. In some embodiments, the value-added products comprise ethylene, acetic acid, acetaldehyde, formaldehyde, formic acid, ethanol, acetone, or a combination thereof. In some embodiments, the value-added products comprise ethylene and acetic acid.

In some embodiments, the catalyst has a value-added products selectivity of at least about 90 mol.% at an ethane conversion of at least about 50 mol.%. In some embodiments, the catalyst has an ethylene selectivity of at least about 85 mol.%, at least about 88 mol.%, or at least about 90 mol.% at an ethane conversion of at least about 50 mol.%. In some embodiments, the catalyst has an ethane conversion of at least about 50 mol.% for about 12 hours, about 24 hours, or about 48 hours. In some embodiments, the catalyst has an initial ethane conversion of at least about 50 mol.%. In some embodiments, the catalyst has an ethane conversion of at least about 50 mol.% for at least the first hour, two hours, four hours, 12 hours, 24 hours, or 48 hours of time on stream.

In some embodiments, the catalyst has an ethane conversion of at least about 50 mol.% and a value-added products selectivity of at least about 90 mol.% for about 48 hours. In some embodiments, the catalyst has an ethane conversion of at least about 50 mol.% and an ethylene selectivity of at least about 90 mol.% for about 48 hours.

In some embodiments, a reaction temperature is kept constant over the time on stream (e.g., about 48 hours). In some embodiments, the reaction temperature is about 400°C or higher. In some embodiments, the reaction temperature is in a range of about 400°C to about 500°C. As used herein, “kept constant” with respect to the reaction temperature refers to within about 5 °C, within about 2°C, or within about 1 °C of an initial temperature. In some embodiments, the catalyst maintains an ethane conversion over the time on stream of at least about 50 mol.%, wherein the temperature is kept constant.

In some embodiments, the catalyst maintains an ethane conversion over the time on stream (e.g., about 48 hours) within about 10 mol.%, about 5 mol.%, or about 3 mol.% of an initial ethane conversion. In some embodiments, the catalyst maintains an ethane conversion over 48 hours within about 5 mol.% of an initial ethane conversion, wherein the temperature is about 400°C or higher.

Conversion of the ethane feed gas to products by the ODH process can be calculated as a volume flow rate change of ethane in the product compared to feed ethane mass flow rate using the following formula:

In Equation 1, C is the percent of ethane feed gas that has been converted from ethane to another product (i.e., ethane conversion) and X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature.

Furthermore, the gas exiting the reactor can be analyzed by gas chromatography to determine catalyst or catalyst material selectivity to ethylene (i.e., the percentage on a molar basis of ethane that forms ethylene). Selectivity to ethylene can be determined using the following equation:

In Equation 2, SEthyiene is the selectivity to ethylene and X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature.

In some embodiments, the gaseous feed contains ethane in a range of about 10 mol.% to about 50 mol.%, about 10 mol.% to about 30 mol.%, or about 20 mol.%. In some embodiments, the gaseous feed further comprises oxygen in a range of about 1 mol.% to about 40 mol.%, about 1 mol.% to about 25 mol.%, or about 10 mol.%. In some embodiments, the gaseous feed further comprises nitrogen in a range of about 50 mol.% to about 90 mol.%, about 60 mol.% to about 80 mol.%, or about 70 mol.%. In some embodiments, the gaseous feed comprises about 20 mol.% ethane, about 10 mol.% oxygen, and about 70 mol.% nitrogen.

In some embodiments, a reaction pressure is in a range of about 10 psig to about 30 psig. For example, the reaction pressure can be about 20 psig. In some embodiments, the ODH process is carried out under about 20 psig nitrogen.

In some embodiments, the weight hourly space velocity (WHSV) is in a range of about 1 h'¹ to about 30 h’¹. In some embodiments, the WHSV is in a range of about 5 h'¹ to about 6 h’¹. For example, the WHSV is about 5.46 h’¹.

In some embodiments, the gas hourly space velocity (GHSV) is in the range of about 1,000 h'¹ to about 30,000 h’¹. In some embodiments, the GHSV is in a range of about 5,500 h'¹ to about 6,500 h’¹. GHSV (gas hourly space velocity) is defined as volumetric flow of the reactor feed gas divided by the volume of the catalyst bed. As used herein, the term “volume of the catalyst bed” refers to the volume occupied by catalyst particles, optional diluent particles, and any void spaces within the catalyst bed. For GHSV values of Catalyst Materials, the catalyst bed is treated as catalyst only (not including support) where an assumption was made that the total volume of the catalyst material measured when multiplied by the wt.% of catalyst is the volume of the catalyst. The GHSV was calculated based off the measured volume of the pressed particles (before mixing with quartz sand) and varied depending on each catalyst or catalyst material bulk density. For catalyst materials, the GHSV reported is for the catalyst only, where an assumption was made that the total volume of the catalyst material measured when multiplied by the wt.% of catalyst is the volume of the catalyst. As used herein, the term “oxidative dehydrogenation” or “ODH” refers to processes that couple the endothermic dehydrogenation of an alkane with the strongly exothermic oxidation of hydrogen as is further described herein. For testing catalysts, the ODH reactions herein are assumed to be referring to the ODH of ethane.

Also provided herein is a method for preparing a catalyst including combining a first mixture comprising bismuth nitrate and nitric acid with a second mixture comprising an ammonium molybdenum tellurium oxide hydrate to form a MoTeBi mixture; combining the MoTeBi mixture with a third mixture comprising vanadium oxide sulfate to form a MoVTeBi mixture; combining the MoVTeBi mixture with a fourth mixture comprising tantalum oxalate to form a MoVTaTeBi mixture; heating the MoVTaTeBi mixture to form a catalyst precursor; and calcining the catalyst precursor to form the catalyst.

In some embodiments, the bismuth nitrate is bismuth nitrate pentahydrate. In some embodiments, the first mixture is essentially free of bismuth hydroxide. Bismuth nitrate was found to be advantageous over bismuth hydroxide due to improved solubility.

In some embodiments, the ammonium molybdenum tellurium oxide hydrate is (NH4)eMo6TeO24-7H2O. In some embodiments, the second mixture has a pH of about 4 to about 6, about 4.5 to about 5.5, or about 5. For example, a pH of about 4.92.

In some embodiments, the MoTeBi mixture has a pH in a range of about 2.0 to about 3.0, such as about 2.5 to about 3.0. For example, a pH of about 2.74. In some embodiments, the pH is adjusted to improve solubility and achieve a clear solution.

In some embodiments, the vanadium oxide sulfate is vanadium oxide sulfate hydrate, e.g. VOSO4 3.36H2O. In some embodiments, the MoVTeBi mixture has a pH of about 1 to 3, about 1.5 to about 2.5, or about 2. For example, a pH of about 2.05.

In some embodiments, the tantalum oxalate is H| TaiCbChfi | .

The catalyst is formed in a hydrothermal synthesis reaction by heating the MoVTaTeBi mixture. Any suitable reaction vessel may be used for the hydrothermal synthesis reaction. For example, a reaction vessel suitable for carrying out a reaction at elevated temperature and pressure, including but not limited to an autoclave, a digestion tank, a pressure vessel, a hydrothermal synthesis reactor, or a PTFE high-pressure tank. In some embodiments, the reaction vessel is an autoclave.

In some embodiments, the MoVTaTeBi mixture is heated by: ramping a temperature from ambient to a temperature in a range between 100°C and 200°C over a ramping time between 1 hours and 10 hours; and holding the temperature at a holding temperature in a range between 100°C and 200°C for a holding time between 12 hours and 60 hours. For example, the MoVTaTeBi mixture is heated by ramping a temperature from ambient to a temperature of about 175°C over a ramping time of about 2 hours; and holding the temperature at a holding temperature of about 175°C for a holding time of about 48 hours. The ramping of the temperature can be used to avoid surface boiling of the reaction mixture. The term “holding temperature”, as used herein, refers to the temperature at which the reaction vessel is held, which can be measured by the ambient temperature of the oven the reaction vessel was placed in.

In some embodiments, the method further comprises washing the catalyst with water. For example, the catalyst may be washed with water until the fdtrate is colorless.

In some embodiments, the catalyst is calcined by: placing the catalyst in a furnace under an oxygen-free environment; ramping a temperature of the furnace from ambient to a temperature in a range between 500°C and 620°C over a ramping time between 2 hours and 10 hours; and holding the temperature of the furnace at a holding temperature in a range between 500°C and 620°C for a holding time between 1 hour and 10 hours. For example, the catalyst is calcined by placing the catalyst in a furnace; ramping a temperature of the furnace from ambient to a temperature of about 600°C over a ramping time of about 6.25 hours; and holding the temperature of the furnace at a holding temperature of about 600°C for a holding time of about 2 hours. As used herein, the term “temperature of the furnace” refers to the external surface temperature of the calcining vessel.

As used herein, an “oxygen-free environment” refers to an environment having a molecular oxygen content below 10 ppm. For example, the furnace is under an inert atmosphere, such as a purified nitrogen atmosphere or a purified argon atmosphere, or the furnace is under a CO2 and/or steam atmosphere.

The catalysts prepared from the methods disclosed herein include molybdenum (Mo); vanadium (V); tantalum (Ta); tellurium (Te); and oxygen (O). In some embodiments, the prepared catalyst has a formula MoaVbTecTaaBieOx, wherein a, b, c, d, e, and x are as defined herein.

Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties, which the present disclosure desires to obtain. 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.

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

In addition, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10; that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.

EXAMPLES

Preparation of Example IE

Tantalum oxalate was prepared from tantalum oxide according to Grasseli, et al., Topics in Catalysis, 2006, vol. 38, pp. 7-16. Oxalic acid (about 3.27g) and 30 mL DI water were heated in a water bath to 60°C while stirring to dissolve. The 60°C oxalic acid solution was added to tantalum ethoxide (4.78g, 2.73 mL, in a sealed flask under nitrogen atmosphere) all at once. 10 mL water was used for rinsing, and the solids were broken up with a spatula. The formed white suspension was heated to 60°C in an oil bath while stirring. The solution was left stirring at 60°C for at least 2 days to dissolve, and became a clear solution.

(NH4)6Mo6TeC>24-7H2O was prepared according to a procedure described in U.S. Patent No. 11,077,430.

Bi(NC>3)3-5H2O (about 0.81 g) was charged in a 100 mL conical flask. 12 mL of DI water was added, followed by 860 uL of concentrated HNO3 (15.8 M). The mixture was stirred for at least 30 minutes to obtain a clear solution.

(NH4)6Mo6TeO24^,7H2O(s) (about 14.789 g) was charged in a 500 mL round bottomed flask. The white solid was dissolved in 200 mL of distilled water (set aside 50 mL distilled water for rinsing) with aid of 60°C warm water bath and stirring to create a clear, colorless solution having pH 4.92. VOSO4*3.36H2O (about 9.91 g) was charged into a beaker. The blue solid was dissolved in 60 mb of distilled water with aid of 60°C warm water bath and stirring to create a clear, blue solution.

The BiNCh solution was added into the MoTe solution to obtain a turbid white MoTeBi solution having pH 2.74.

Without cooling, the aqueous VOSO4 solution was added dropwise into the 60°C, aqueous MoTeBi solution over approximately 11 minutes (2-3 drops/sec, target 11 minutes) resulting in a black MoVTeBi solution having pH 2.05.

Without any holding time, the tantalum oxalate H[Ta(C2O4)3](aq) solution (0.4 mol Ta/L), was added slowly dropwise (over about 8-14 mins) to the 60°C, black, MoTeVBi solution to produce an olive green MoVTaTeBi solution. The olive-green solution can be optionally stirred in air at 60°C for 1 hour to obtain fine a fine precipitate.

The 60°C olive-green slurry was poured to a glass liner for a 600 mb autoclave glass liner. The total volume of solution was 320 mb. After a few minutes, separation of the olive green precipitate and sage green mother liquor was observed.

The autoclave was closed and the atmosphere inside of the autoclave was evacuated (vacuum) and filled with nitrogen (20 psig from bulk nitrogen line) 10 times. The reactor was sealed under 20 psig bulk nitrogen and close the valve. The vacuum and N2 line were disconnected.

The reactor was placed in an oven with a heating profile of 175°C for 48 hours heating with a ramping time of 2 hours. After 48 hours, the reactor was allowed to cool to room temperature and excess carbon dioxide (from oxalic acid decomposition) and nitrogen pressure were vented into a fume hood. The purple solid was filtered through a Buchner funnel with 3x layers of quantitative filter paper to separate the blue mother liquor from the dark purple (almost black) solids.

The solids were rinsed with approximately five portions of 400 mb of distilled water until the filtrate no longer had any visible blue color after passing through the solids. The solids were dried in an oven at 90°C overnight to produce 17.22 g of product.

The dried dark purple (almost black) solid was grinded into a using a mortar/pestle. The 17.22 g of product was loaded in a quartz boat and the boat was placed into quartz tube for calcination. The quartz tube is purged with bulk nitrogen (<10 ppm oxygen) at flow rate of 30 seem, with the outlet side of the tube being vented through a silicone oil bubbler to help maintain the tube under an anaerobic atmosphere. The tube atmosphere is purged for 6 hours with bulk nitrogen (<10 ppm oxygen) and then the inlet bulk nitrogen was redirected through an oxygen trap (LabClear™ Oxiclear™ gas purifier) to purge the tube with purified nitrogen (<1 ppm oxygen) for an additional 12 hours. The calcination proceeded under 30 seem purified nitrogen flow with the following heating conditions: ambient temperature to 600°C in 6.25 hours (1.6°C/min), held at 600°C for 2 hours, and left to cool naturally.

After calcination, 15.7140 g (91.25 wt.% calcination yield) of black, sintered solid was obtained.

The catalyst formula for Sample IE based on the molar ratio of starting materials used was Mo1V0.66Te0.17Ta0.175Bi0.025.

The catalyst formula for Sample IE was also determined by EDS, and was analyzed after the sample was freshly prepared and after Sample IE was exposed to the ODH process. EDS was conducted using a JEOL JED-2300 DRY SDD Energy Dispersive Spectrometer detector. The EDS scan was conducted on the largest rectangular area that was covered by the sample (approximately 2.8 mm x 2.1 mm, typically at ~50x magnification but this can vary depending on sample size and coverage). The data analysis software was Analysis Station provided by JEOL. The scan was conducted at 25kV accelerating voltage.

The freshly prepared sample IE had a formula Mo1V0.43Ta0.15Te0.14Bi0.01Ox as determined by EDS. The same sample IE after ODH experimentation had a formula Mo1V0.44Ta0.i6Te0.12Bi0.02Ox as determined by EDS. These minor differences are within the experimental error of EDS.

Preparation of Comparative Example 2C

Tantalum oxalate was prepared from tantalum oxide according to Grasseli, et al., Topics in Catalysis, 2006, vol. 38, pp. 7-16. Anhydrous oxalic acid (C2O4H2, 12.7259 g, 141 mmol) and 118 mb DI water were heated in a water bath to 60°C while stirring to dissolve, resulting in a clear, colorless solution. The 60°C oxalic acid solution was added to tantalum ethoxide (1) (19. 10 g, 47 mmol, in a sealed flask under nitrogen atmosphere) all at once, producing a white suspension. The suspension was heated to 65°C over 2 days to form a clear, colorless, aqueous solution of 0.4 molTa/L H[Ta(C2C>4)3](aq).

(NH4)eMo6TeO24-7H2O was prepared according to a procedure described in U.S. Patent No. 11,077,430.

VOSO4*3.36H2O (39.4405 g) was charged into a beaker. The blue solid was dissolved in 240 mb of distilled water with aid of 60°C warm water bath and stirring to create a clear, blue solution. Without cooling, the aqueous VOSO4 solution was dropwise added into the 60°C, aqueous (NH4)eMo6TeO24 solution over approximately 11 minutes resulting in a black solution.

Without any holding time, the H[Ta(C2C>4)3](aq) (not entirely clear, some white turbidity) solution (0.4 molTa/L), 47 mmolTa) was added slowly dropwise to the 60°C, black, MoTeV solution to produce an olive green solution. The olive-green solution was allowed to stir in air at 60°C for 1 hour, during which a fine precipitate formed.

The 60°C olive-green slurry was poured to a glass liner for a 2,000 mL PARR autoclave which is equipped with an overhead stirred reactor head (i.e. wetted Hastelloy agitator and Hastelloy thermowell). The autoclave was closed and the atmosphere inside of the autoclave was evacuated (vacuum) and filled with nitrogen (12 psig from bulk nitrogen line) 10 times. The reactor was sealed under 12 psig bulk nitrogen.

The autoclave was put into heating mantel setup, well insulated and heated to at 175°C surface/control temperature for 48 hours. The temperature of the solution, as measured via a thermocouple through the Hastelloy thermowell was recorded as 166°C. The heat up time from room temp to inside temp of 164°C was ~4.5 hours. The reactor head was equipped to a tube-in-tube exchanger (condenser) that had cooling water circulating on the outside tubing at ~25°C (controlled via closed system, cooling bath) and the inside tubing was connected to the reactor (process) to allow venting of excess gaseous pressure via a backpressure regulator. The backpressure regulator setpoint was set to 140 psig and that pressure was recorded on the second day of reaction. The pressure setpoint of 140 psig was determined via referring to the steam table pressure of water heated at 175°C and a pressure slightly above what is indicated on the steam table was chosen to ensure the liquids reach temperature (i.e. elevated boiling point). Some release of pressure could be observed via a glass water bubbler attached to the outlet side (vent) of the backpressure regulator. Slow bubbling (venting of excess CCh(g) pressure from decomposition of oxalic acid) was observed only on the second day of the 48 hour reaction.

After 48 hours, the reactor was allowed to cool to room temperature and excess carbon dioxide (from oxalic acid decomposition) and nitrogen pressure were vented into a fume hood, the purple slurry was stirred producing vigorous bubbling of carbon dioxide. The purple solid was filtered through a Buchner funnel with 3x layers of qualitative filter paper to separate the blue mother liquor from the dark purple (almost black) solids.

The solids were rinsed with approximately five portions of 400 mL of distilled water until the filtrate no longer had any visible blue color after passing through the solids. The solids were dried in an oven at 90°C overnight to produce 60.30 g of product at 82.53% yield (assuming 73.06 g is theoretical yield for the oxides).

The dried dark purple (almost black) solid was grinded into a using a mortar/pestle. A portion of the of the recovered product (17.0023 g) was loaded in a quartz boat and the boat was placed into quartz tube for calcination. The quartz tube is purged with bulk nitrogen (<10 ppm oxygen) at flow rate of 30 seem, with the outlet side of the tube being vented through a silicone oil bubbler to help maintain the tube under an anaerobic atmosphere. The tube atmosphere is purged for 6 hours with bulk nitrogen (<10 ppm oxygen) and then the inlet bulk nitrogen was redirected through an oxygen trap (LabClear Oxiclear gas purifier) to purge the tube with purified nitrogen (<1 ppm oxygen) for an additional 12 hours. The calcination proceeded under 30 seem purified nitrogen flow with the following heating conditions: ambient temperature to 600°C in 6.25 hours (1.6°C/min), held at 600°C for 2 hours, and left to cool naturally.

After calcination, 15.4261 g (90.70 wt.% calcination yield) of black, sintered solid was obtained.

Catalyst Testing

The catalysts described herein were tested for their ability to catalyze the oxidative dehydrogenation (ODH) of ethane using a microreactor unit (MRU). The MRU has a reactor tube made from stainless-steel SWAGEUOK® Tubing, which had an outer diameter of 0.5 inches (1.27 cm), an internal diameter of about 0.4 inches (1.02 cm), and a length of about 13.4-15 inches (34.0 - 38.1 cm). Experimental temperatures of the MRU are measured using a 6-point WIKA Instruments Ltd. K-type thermocouple, which had an outer diameter of 0. 125 inches (0.318 cm) and was inserted through the reactor. The 6-point thermocouple is used to measure and control the temperature within the catalyst bed. A room temperature stainless steel condenser is located after the reactor to collect water/acetic acid condensates. The gas product flow was allowed to either vent or was directed to an Agilent 8890 “hot gas” Gas Chromatograph (HGGC) during times when product gas analysis was required.

The samples were pressed into pellets using a steel die and hydraulic press, then the pellet was pulverized and particle sizes of 425 - 710 pm were sieved out for loading into the MRU. Approximately 2 g of sample was placed in the reactor. Once the catalyst bed was loaded into the reactor and connected to the MRU equipment, the testing was conducted as described herein. The catalyst bed was loaded in the middle zone of the reactor and the remaining volume of the reactor was packed with quartz sand to produce the catalyst bed volume of 6 mL to ensure the catalyst volume was sufficient to cover the thermocouple area. The reactor loading was then secured with glass wool on both the top and the bottom of the reactor. Quartz sand was added to produce the catalyst bed volume of 6 mL to ensure the catalyst volume was sufficient to cover the thermocouple area.

The flow rate of the gas feed was adjusted to a weight hourly space velocity (WHSV) of 5.46 h’¹. The gas hourly space velocity (GHSV) was in the range of 5,500 to 6,500 h'¹ and is reported in the Figures for each experiment. The target gas feed composition was 20 mol.% ethane, 10 mol.% oxygen and 70 mol.% nitrogen for all testing, which corresponds to an ethane:oxygen mol ratio of 1:0.5. The target pressure was 20 psig. Gas composition was determined by gas chromatography (GC) using an Agilent 6890N Gas Chromatograph, and analyzed using Chrom Perfect - Analysis, Version 6.1. 10 for data evaluation.

The gas exiting the reactor was analyzed by gas chromatography. Conversion (C) of the ethane feed gas was calculated as a volume flow rate change of ethane in the product compared to feed ethane mass flow rate using the following formula:

In Eq. 1, X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature.

The gas exiting the reactor was analyzed by GC to determine catalyst or catalyst material selectivity to ethylene (i.e., the percentage on a molar basis of ethane that forms ethylene). Selectivity to ethylene (SEthyiene) was determined using the following equation:

In the above equation 2, SEthyiene is the selectivity to ethylene and X is the molar concentration of the corresponding compound in the gaseous effluent exiting the reactor at corresponding temperature.

Summary of Catalyst Performance:

Figure 1 is a plot of the ethane conversion (mol.%) overtime on stream (TOS), at 20 psig and 5.46 h'¹ for Sample IE and Sample 2C, wherein Sample IE is Bi-doped. As shown in Figure 1, Sample IE displayed an enhanced ethane conversion as well as an improved conversion stability within the first 48 hours of TOS, as compared to Sample 2C. Catalyst stability is recognized by ethane conversion (mol.%) values that do not decrease with TOS.

For Sample IE, the reaction temperature was kept constant at about 436°C over the 48 hours TOS, and the catalyst maintained an ethane conversion rate of at least 50 mol.% over the 48 hours (54.4±2.2% over 24 hours). In contrast, sample 2C exhibited a decrease in ethane conversion during the initial TOS when held at a reaction temperature of about 440°C, going from 50% to 46.5% within the first about 17 hours. The reaction temperature was increased to 448°C to achieve at least 50 mol.% ethane conversion. At 17 hours, 26 minutes, the ethane conversion for Sample IE was 51.24%, but continued to drop to about 48%, which then stabilized after about 48-72 hours, as shown in Figure 2.

Figure 3 is a plot of the accompanying ethylene selectivity (mol.%) for the data shown in Figure 1. As can be seen in Figure 3, Sample IE achieves comparable selectivity toward ethylene compared to Sample 2C, even when operated at slightly higher conversions. Sample IE operated at approx. 4-6 mol.% absolute more ethane conversion than Sample 2C, and still produced about 91 mol.% ethylene selectivity.

Other implementations are also within the scope of the following claims.

Each reference, including all patent, patent applications, and publications, cited in the present application is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

Catalysts and catalyst materials for oxidative dehydrogenation of alkanes, such as the oxidative dehydrogenation of ethane to ethylene.

Claims

CLAIMS What is claimed is:

1. A catalyst having the formula:

MoaVbTecTadBieOx wherein: a is 1.0; b is about 0.01 to about 1.0; c is about 0.01 to about 0.5; d is about 0.01 to about 0.5; e is about 0.005 to about 0.1; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, d, and e are determined based on the amount of each starting material used to form the catalyst.

2. The catalyst of claim 1, wherein: b is about 0.4 to about 0.8; c is about 0.1 to about 0.3; d is about 0. 1 to about 0.3; and e is about 0.01 to about 0.05.

3. The catalyst of claim 1 or 2, wherein: b is about 0.6 to about 0.75; c is about 0.1 to about 0.25; d is about 0. 1 to about 0.25; and e is about 0.02 to about 0.03.

4. The catalyst of any one of claims 1 to 3, wherein the catalyst has the formula:

Mo1V0.60-0.75Te0.10-0.25Ta0.10-0.25Bi0.01-0.05Ox.

5. The catalyst of any one of claims 1 to 4, wherein the catalyst has an ethane conversion of at least about 50 mol.% and a value-added products selectivity of at least about 90 mol.% for about 48 hours; wherein the value-added products comprise ethylene, C1-C4 oxygenated organic compounds, or a combination thereof.

6. The method of claim 5, wherein the C1-C4 oxygenated organic products comprise acetic acid, acetaldehyde, formaldehyde, formic acid, ethanol, acetone, or a combination thereof.

7. The catalyst of claim 5 or 6. wherein a reaction temperature is kept constant over the 48 hours.

8. The catalyst of claim 7, wherein the catalyst maintains an ethane conversion over the 48 hours within about 5 mol.% of an initial ethane conversion; wherein the reaction temperature is in a range of about 400°C to about 500°C.

9. A catalyst material comprising the catalyst of any one of claims 1 to 8 and a catalyst support or carrier.

10. The catalyst material of claim 9, wherein the catalyst support or carrier is selected from the group consisting of precipitated synthetic silica, fumed synthetic silica, silica- alumina, a-alumina, y-alumina, titania, WOi-ZrOi. silicon carbide, MgAl spinel, calcium aluminate, zirconia and boron nitride.

11. A process for the oxidative dehydrogenation of ethane, the process comprising contacting a gaseous feed comprising ethane and oxygen with a catalyst in a reactor to produce an effluent comprising ethylene, wherein the catalyst has the formula:

MoaVbTecTaaBieOx wherein: a is 1.0; b is about 0.01 to about 1.0; c is about 0.01 to about 0.5; d is about 0.01 to about 0.5; e is about 0.005 to about 0.1; and x is the number of oxygen atoms necessary to render the catalyst electrically neutral; wherein a, b, c, d, and e are determined based on the amount of each starting material used to form the catalyst.

12. The process of claim 10, wherein: b is about 0.4 to about 0.8; c is about 0.1 to about 0.3; d is about 0. 1 to about 0.3; and e is about 0.01 to about 0.05.

13. The process of claim 11 or 12, wherein the catalyst has the formula:

Mo1V0.60-0.75Te0.10-0.25Ta0.10-0.25Bi0.01-0.05Ox.

14. The process of any one of claims 11-13, wherein the catalyst has an ethane conversion of at least about 50 mol.% and value added products selectivity of at least about 90 mol.% for about 48 hours; wherein the value-added products comprise ethylene, C1-C4 oxygenated organic compounds, or a combination thereof.

15. The process of claim 14, wherein the value-added products comprise acetic acid, acetaldehyde, formaldehyde, formic acid, ethanol, acetone, or a combination thereof.

16. The process of claim 14 or 15, wherein a reaction temperature is kept constant over the 48 hours.

17. The process of claim 16, wherein the catalyst maintains an ethane conversion over the 48 hours within about 5 mol.% of an initial ethane conversion; wherein the reaction temperature is in a range of about 400°C to about 500°C.

18. A method for preparing a catalyst comprising: combining a first mixture comprising bismuth nitrate and nitric acid with a second mixture comprising an ammonium molybdenum tellurium oxide hydrate to form a MoTeBi mixture; combining the MoTeBi mixture with a third mixture comprising vanadium oxide sulfate to form a MoVTeBi mixture; combining the MoVTeBi mixture with a fourth mixture comprising tantalum oxalate to form a MoVTaTeBi mixture; heating the MoVTaTeBi mixture to form a catalyst precursor; and calcining the catalyst precursor to form the catalyst.

19. The method of claim 18, wherein the MoTeBi mixture has a pH in a range of about 2.0 to about 3.0.

20. The method of claim 18 or 19, comprising heating the MoVTaTeBi mixture by: ramping a temperature from ambient to a temperature in a range between 100°C and 200°C over a ramping time between 1 hours and 10 hours; and holding the temperature at a holding temperature in a range between 100°C and 200°C for a holding time between 12 hours and 60 hours.

21. The method of any one of claims 18-20, comprising calcining the catalyst by: placing the catalyst in a furnace under an oxygen-free environment; ramping a temperature of the furnace from ambient to a temperature in a range between 500°C and 620°C over a ramping time between 2 hours and 10 hours; and holding the temperature of the furnace at a holding temperature in a range between 500°C and 620°C for a holding time between 1 hour and 10 hours.

22. The method of any one of claims 18-21, wherein the catalyst has the formula:

23. The method of claim 22, wherein: b is about 0.4 to about 0.8; c is about 0.1 to about 0.3; d is about 0. 1 to about 0.3; and e is about 0.01 to about 0.05.

24. The method of any one of claims 22 or 23, wherein the catalyst has the formula:

Mo1V0.60-0.75Te0.10-0.25Ta0.10-0.25Bi0.01-0.05Ox.