WO2025101613A1

WO2025101613A1 - Direct exchange of adsorbent agglomerates

Info

Publication number: WO2025101613A1
Application number: PCT/US2024/054733
Authority: WO
Inventors: Steven J. Pontonio; Philip A. Barrett; Katie Held
Original assignee: Praxair Technology Inc
Current assignee: Praxair Technology Inc
Priority date: 2023-11-09
Filing date: 2024-11-06
Publication date: 2025-05-15
Anticipated expiration: 2026-05-09

Abstract

An improved process for manufacturing ion-exchanged adsorbent product having sufficient mechanical strength for use in industrial scale gas separation or gas purification adsorbers. The ion exchange step is performed on shaped adsorbent particles, directly without a high temperature calcination step first. After the completion of ion exchange step, the resulting ion-exchanged adsorbent particles are subjected to the high temperature calcination step.

Description

Direct Exchange of Adsorbent Agglomerates

Related Applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63/597,504, filed on November 9, 2023, which is incorporated herein by reference. Field of the Invention

[0002] The invention relates to manufacturing processes of ion-exchanged adsorbent and adsorbent formulations having sufficient mechanical strength for use in industrial scale gas separation or gas purification adsorbers.

Background of the Invention

[0003] Manufacturing processes exist whereby the ion exchange step is performed on adsorbent material to alter the composition of the starting adsorbent material. In some process schemes the ion exchange step is performed on an adsorbent powder prior to forming shaped particles such as beads, pellets, extrudates and the likes for use in industrial scale adsorptive gas separation systems. In some other process schemes the ion exchange step is performed on shaped adsorbent particles which are formed using an adsorbent material and at least one binder material.

[0004] The present invention relates to the latter category of manufacturing process schemes. Adsorbent product yield losses from the ion exchange step when performed on calcined and rehydrated agglomerated adsorbent particles, in a batch process or in a column ion exchange process, can be excessive and therefore detrimental to manufacturing and cost of said adsorbents. Agglomerated adsorbent particles containing low binder content, for example binder content < 10 wt% and/or core-shell formulations containing low binder content can have low particle crush strength and/or attrition resistance. This often translates to high yield losses in the ion exchange unit operation, and in turn, this impacts the cost to manufacture such products. It is common to see the crush strength, a measure of the particle integrity, decrease from higher values after calcination to lower values prior to and after liquid phase ion exchange. Without wishing to be bound by theory, it is believed that this weakening of the particles, from the traditional process, prior to liquid phase ion exchange, is one reason for yield issues with this part of the manufacturing process.

[0005] The present invention is a direct exchange method which contains fewer manufacturing steps and can be performed on traditional adsorbent materials, wherein yield losses during ion exchange are not an issue. The improved yield loss and fewer manufacturing steps of the present invention can provide productivity savings.

[0006] In conventional manufacturing process schemes the ion exchange step is carried out in a certain order as shown in Figures 1 and 2. In the process scheme shown in Figure 1, the ion exchange is performed on adsorbent powder and thereafter the adsorbent powder is calcined at elevated temperatures (e.g., 450°C - 700°C). In the process scheme shown in Figure 2, the ion exchange is performed on agglomerated particles of adsorbent material after calcination at elevated temperatures. After ion exchange, the agglomerated particles are processed in an activation step which requires heating the ion exchanged agglomerates to lower the moisture content to about 1 wt% or less. The temperature requirements for activation are those that enable lowering the moisture content to a value to be achieved. For zeolite materials, the activation temperature is usually in the range of 300°C - 450°C. As disclosed in the U.S. Patent Number 5,932,509, there are also hybrid processes where some ion exchange is performed on the powder and then some is performed on the agglomerated material, after calcination. As explained in U.S. Patent Number 6,649,556, it is important to carry-out ion exchange with expensive cations, such as lithium, in a manner where losses of shaped particles which prevent realizing the full value of expensive lithium, are minimized. As shown in Figure 2, the solution has been to perform ion exchange on agglomerated materials containing binding agents, after calcination. These agglomerated materials can then be used in column or batch ion exchange processes to minimize losses and maximize lithium utilization. However, when applying the conventional process of ion-exchange after calcination on adsorbent compositions wherein the binder content is low (for example < 10 wt% binder and more particularly < 7 wt% binder and/or core-shell materials containing binding agents at similar, and even slightly higher contents (at most 25 wt% and more typically 15 wt%), the outcome has been poor manufacturing yields. [0007] A batch of a formulation of zeolite X with only 5 wt% clay binder, prepared without a core and without any binder conversion steps (e.g., caustic digestion process), was processed in accordance with process scheme shown in Figure 2. The manufacturing yields were running at an acceptable 90% through agglomeration and calcination. The material was moved forward to rehydration and lithium ion exchange and the manufacturing yield from this part of the process decreased to 75%. In and amongst the product recovered from the ion exchange system was “chips” and broken pieces of the agglomerated particles. A yield of 75% is comparatively poor against a threshold of minimum 90% and given that the waste now contains expensive lithium, the economic penalty is high.

[0008] Thus, the need continues to maintain or improve manufacturing yields for low binder formulations and binder containing core-shell formulations, wherein postagglomeration ion exchange is needed. The manufacturing yields for these advanced product types need to be at least comparable to standard commercial adsorbents, otherwise their performance advantage is diluted by higher manufacturing costs. A new manufacturing method, compatible with existing equipment is therefore required.

[0009] In manufacturing operations, the first-time yield, also known as first pass yield, is used as a measure of the effectiveness of operations in producing an on-spec product, a product which satisfies end-user specifications. This yield can be expressed as percentage of product produced without any defect on the first attempt. Each step in a multi-step manufacturing process will have a first-time yield. Arguably the first-time yield is the most important yield metric, since it measures the amount of product that meets the requirement without needing to be reworked. The total yield is the total final output of a manufacturing line and can include any reworked material in one or more of the steps.

[0010] The end-user specifications can be multi-dimensional, some based on composition, some based on physical properties such as particle size, crush strength, attrition resistance. For example, assuming the specification is for particles to have a crush strength of at least 5 N, then product particles which do not meet the specification will be considered to have a defect and the product yield will be less than 100%. Depending on the product and manufacturing step, some of the defective product particles and unconverted or partially converted raw materials can be recovered and reworked. However, there are parts of the process whereby material losses from the process are non-recoverable (e.g. dust removed from the adsorbent particles during processing and captured in filters and baghouses). These unrecoverable material losses also count as defective product and affect the first pass yield.

[0011] For the ion exchange step, when performed on agglomerated particles, manufacturers have high expectations of first pass yield, over 90% minimum and preferably over 95% minimum. This is understandable, since ion exchange on agglomerated particles often involves the use of expensive components, especially lithium and silver, and losses of high-cost components must be avoided. In the case mentioned above for the 5% clay formulation, product from the ion exchange step included “chips” and broken pieces of the agglomerated particles resulting in 75% yield, comparatively poor from manufacturer’s perspective. Many adsorbent materials, including LiX zeolites for air separation applications, have been the subject of continuous improvement.

[0012] An important direction for improvements involves preparation of these compositions at low binder contents, wherein the binder content is < 10 wt%. Reducing the amount of binder has been advantageous to help improve the working capacity of these adsorbents, by maximizing the amount of active adsorbent within each particle. Another benefit is that lowering the binder content tends to lead to LiX materials with improved adsorption kinetics, since at lower binder contents, the presence of rate-limiting binder rich regions, inside the particles, is minimized. For these advanced forms of LiX adsorbents, manufacturing process schemes like those shown in Figures 1 and 2 have been found to be less preferred and sometimes economically unfavorable. For processes such as shown in Figure 1, wherein the ion exchange is performed directly after synthesis, the challenges have been to obtain high exchange levels, as well as cost management from yield losses of an intermediate which has been made more expensive due to the early ion exchange with a high-cost component. The process shown in Figure 2 was designed to solve these cost and ion exchange level issues. However, hydration and ion exchange after calcination of adsorbent particles containing lower binder content, now becomes the stage where the yield losses are the greatest. After calcination, these low binder products, and core-shell materials, possess adequate crush strength for some applications (e.g., > 5 N and often > 7 N at a particle size of at least 1.4 mm). However, after rehydration and during the liquid phase ion exchange process, these particles weaken substantially, and unacceptable yield losses now occur, in the post-calcination ion exchange process.

[0013] To enable post-agglomeration ion exchange, at competitive yields, for products like the low binder adsorbents and binder containing core-shell materials, a new manufacturing process has been developed. Figure 3 is a simplified block diagram of the basic unit operations in the present invention herein referred to as Direct Exchange Method. All or only a fraction of material produced in a given block, which meets predefined specification becomes feed to the next process block, and at the end of the manufacturing line, comes out as ion-exchanged adsorbent product. Any product of a step that does not meet the pre-defined specifications can be re-worked in that step or recycled to an earlier step to obtain higher overall yield from the manufacturing line. However, as discussed above there are unrecoverable losses of materials that must also be considered and minimized.

Summary of the Invention

[0014] A new manufacturing process, direct exchange method, for preparing an ion exchanged adsorbent product from green adsorbent agglomerates is described. The green agglomerates are treated in a curing step to form cured agglomerates which are then fed to an ion exchange step to form ion exchanged agglomerates, directly without first subjecting the cured agglomerates to a calcination step, herein also referred to as a high temperature thermal step. According to the present invention, the ion exchanged agglomerates are then subjected to a high temperature thermal step to form calcined agglomerates from which adsorbent product is recovered.

[0015] In traditional adsorbent manufacturing processes, ion exchange methods are commonly used to alter the chemical composition of an adsorbent material. For some products, the ion exchange step is performed on the adsorbent powder before it is agglomerated. This method of powder exchange works for adsorbent compositions, wherein the ion exchange levels required are modest e.g., < 85% and wherein the ion exchange isotherm is favorable. This ion exchange step is typically performed directly after the synthesis and synthesis related washing steps (see Figure 1). To reach ion exchange levels > 85 % and/or to overcome more unfavorable ion exchange isotherms, ion exchanges are often performed on adsorbent materials, after agglomeration (see Figure 2). The motivation to delay the ion exchange step until late into the manufacturing process, is that when expensive cations (e.g., Li or Ag) are required in the final adsorbent product, performing the ion exchange after calcination, can lead to more efficient use of these expensive components and lower overall losses thereof. Since, every unit operation in the flow sheet, has a yield associated with it, performing the ion exchange after calcination, can avoid yield losses of the expensive components early in the manufacturing process. Once the ion exchange step is completed, the ion-exchanged adsorbent product needs to be dried and activated by heating to elevated temperature. Thus, in the process scheme shown in Figure 2, thermal energy is consumed to heat the agglomerated adsorbent formulations prior to ion exchange step and then after the ion exchange step.

[0016] In contrast the present invention, direct exchange method shown in Figure 3 has only one high temperature step. The present invention first processes green agglomerates to a curing step, then after the curing step feeds the agglomerates to an ion exchange step without first subjecting the agglomerates to a high temperature thermal step. Only after ion exchange step the agglomerates are subjected to a high temperature thermal step.

[0017] In one aspect the invention is a direct exchange method also referred to as direct ion-exchange method to produce an adsorbent product from a plurality of green adsorbent agglomerates having a pre-defined size. The term green adsorbent agglomerates used herein, also referred to as green agglomerates are shaped particles comprising a mixture of at least one active adsorbent material and at least one binder material, wherein the green agglomerates have not been subjected to a calcination step which is a high temperature thermal step typically employed to set any permanent binder or binders prior to an ion exchange step. Typically, the green adsorbent agglomerates will comprise particles of average size from 0.4 to 5.0 mm and compared to their calcined counterparts, contain significant amounts of moisture or other solvents used in the forming and other early manufacturing steps, including adsorbent synthesis. For binder-containing traditional adsorbents (non-core-shell), the amount of residual moisture or other solvents can be greater than 15 wt% and can be greater than or equal to 30 wt%. The green adsorbent agglomerates can optionally contain an inert core wherein the inert core has a porosity of from about 0% to about 10% as measured by the Hg porosimetry method, and a volumetric thermal capacity of greater than about 0.8 J/cm³-°K. The plurality of green adsorbent agglomerates containing the inert core, core-shell agglomerates utilize the at least one active adsorbent material and the at least one binder material in the form of an adsorptive shell surrounding the inert core. The core-shell agglomerates can optionally contain a coating of an adhesion agent on the inert core and the adsorptive shell surrounds the resulting coated core, wherein the adhesion coating comprises one or more of clays, aluminas, silicas, silicone derived materials, alumina-silica reagents and mixtures thereof, and gets converted to oxide containing coating during the calcination step. The adsorbent shell will have residual moisture or other solvent concentrations in the same range as for the traditional adsorbents, but the mass-fraction of the core must be considered, when measuring or converting these values to a total particle basis. A simpler method for core-shell materials is to use appropriate mechanical means to remove the shell material, from a sample of the agglomerates, and make the measurement on the shell-only material. A technique such as Loss on Ignition or LOI at 550°C is sufficient to measure the quantity of residual moisture or other solvent concentrations in the shell material with adequate precision. The LOI value is simply the weight loss upon heating the material from room temperature to “the LOI temperature” (in this case 55O°C), expressed on a percentage basis. The sample weight should be at least 1 g and the hold time at the LOI temperature should be at least 1 hour.

[0018] For the purposes of this invention the at least one active adsorbent material can be selected from zeolites, molecular organic frameworks (MOFs), zincosilicates, titanosilicates, and mixtures thereof. The zeolite can be selected from X, LSX, Y, A, L, ZSM-5, Mordenite, Clinoptilolite, Chabazite and mixtures thereof. The zeolite can have a SiO2/AhO3 ratio of from about 1.9 to 10. The zeolite contains cations which are exchanged with one or more cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu and mixtures thereof to produce an ion exchanged zeolite. Tn one embodiment the ion exchanged adsorbent contains LiX or LiLSX wherein the extent of Li exchange is greater than or equal to 90% on an equivalent’s basis.

[0019] For the purposes of this invention, the adsorbent product produced by the direct exchange method contains the binder materials and the active adsorbent materials in a weight ratio of from about 2/98 to about 12/88. The adsorbent products referred to as low binder-content composite agglomerates are those wherein the binder content is at most 10 wt%. For core-shell agglomerates the binder content refers to the binder content in the shell only and the content is at most 20 wt%.

[0020] For the purposes of this invention, direct exchange method for preparing an adsorbent product, the green agglomerates can be low binder-content agglomerates, coreshell agglomerates, or composite agglomerates and said method comprises: a curing step to convert green adsorbent agglomerates into cured agglomerates; an ion exchange step to convert cured agglomerates into ion exchanged agglomerates; a calcination step to convert ion exchanged agglomerates into calcined agglomerates; a product recovery step to recover said adsorbent product of pre-defined size from calcined agglomerates.

• The curing step comprises one or more of: i) a low temperature heating step to drive off volatiles wherein the green agglomerates are heated to a temperature of about 50°C to 95 °C and held for a time period of about 1 hour to about 4 hours, ii) an aging step wherein the green agglomerates are kept in a hydrated state at a pressure from near ambient to about 5 bar and a temperature less than about 100°C and held for a time period of 0.5 to about 10 days. iii) a chemical curing step wherein the green agglomerates are contacted with at least one chemical compound which sets curable component(s) in the green agglomerates by reacting or by promoting chemical reaction(s) to form cured agglomerates which meet the minimum 5 N crush strength criterion.

• The ion exchange step comprises a batch process or a column process wherein, the active adsorbent material composition is altered to form an active ion exchanged adsorbent material, and the ion exchanged agglomerate composition can be differentiated from the green agglomerate composition by the extent of cation exchange on an equivalents basis.

• The calcination step comprises known high temperature thermal processing step such as subjecting the ion exchanged agglomerates to a pre-defined temperaturetime profile of heating wherein agglomerates are heated to a temperature of about 450°C to about 700°C while holding at a pre-defined temperature for a time period of at least 30 minutes.

[0021] In another aspect the present invention is a direct exchange method wherein a plurality of green adsorbent agglomerates which can be low binder content agglomerates, core-shell agglomerates or composite agglomerates or mixture thereof are subjected to a curing step followed by an ion exchange step wherein the agglomerates fed to the ion exchange step have not been calcined, and have a crush strength of at least 5 N both before and after the ion exchange step as measured by the single particle crush test method wherein a total of 40 individual particles are tested and the result is expressed as the average of the 40 data points. The sample for this crush strength test is preconditioned, by drying at 90°C for at least 1 hour. This low temperature drying is intended to ensure that the adsorbent agglomerates are free-flowing and therefore suitable for crush strength measurement. For example the low temperature dried agglomerates can be free-flowing at a Loss On Ignition (LOI) value of about 15 wt% or more, with the LOI measured at 550°C.

[0022] In another aspect the present invention is a direct exchange method wherein a plurality of green adsorbent agglomerates which can be low binder content agglomerates, core-shell agglomerates or composite agglomerates or mixture thereof are treated in an ion exchange step wherein the agglomerates fed to the ion exchange step have not been calcined, and have a crush strength of at least 5 N both before and after the ion exchange step, and the ion exchanged agglomerates after calcination also have a crush strength of at least 5 N as measured by the single particle crush test method wherein a total of 40 individual particles are tested and the result is expressed as the average of the 40 data points. The sample for this crush strength test is preconditioned, by drying at 90°C for at least 1 hour. This low temperature drying is intended to ensure that the adsorbent agglomerates are free-flowing and therefore suitable for crush strength measurement. [0023] In another aspect the invention is a process for producing an ion-exchanged adsorbent product for use in gas separation or gas purification adsorbers. The process comprises feeding a collection of green adsorbent agglomerates comprising an active adsorbent material and one or more binder materials to a curing step, wherein the curing step comprises one or more of:

(a) a low temperature heating step to drive off volatiles wherein the green agglomerates are heated to a temperature of about 50°C to 95°C and held for a time period of 1 hour to about 4 hours such that the crush strength of the green agglomerate meets the minimum 5 N criterion, described above,

(b) an aging step wherein the green agglomerates are subjected to certain conditions of temperature, pressure, and humidity for sufficient time, such that the green agglomerates are hardened and meet the minimum 5 N crush strength criterion described above. The exact conditions required will depend on the adsorbent agglomerate composition. An important aspect is maintaining or increasing the humidity and not allowing the adsorbent agglomerates to dry-out. The green agglomerates are kept in a hydrated state at a pressure from near ambient to about 5 bar and a temperature less than about 100°C and held for a time period of 0.5 to about 10 days

(c) a chemical curing step wherein the green agglomerates are contacted with at least one chemical compound which sets curable component(s) in the green agglomerates by reacting or by promoting chemical reaction(s) to form cured agglomerates which meet the minimum 5 N crush strength criterion.

[0024] The cured agglomerates are then subjected to an ion exchange step prior to subjecting said agglomerates to a calcination step, wherein said agglomerates after ion exchange have a crush strength of at least 5 N and subsequently subjected to a calcination step to obtain said ion exchanged adsorbent product. An overview of the calcination process, as applied to adsorbent materials is provided by Barrett et al in Zeolites and Ordered Porous Solids (ISBN: 978-84-8363-707-4 (2011)), Section 3 in Chapter “Adsorption Properties of Zeolites”. As described in this reference the goal of this process step is to remove any removable components including moisture, as well as thermally set any binding agent or agents, if used. These items are achieved by careful temperature ramping and control, as well as provision of adequate amounts of a suitable purge gas. The calcination step comprises treating ion exchanged agglomerates to a predefined temperature-time profile of heating said agglomerates, under an appropriate purge gas (such as dry air) to the temperature set-point wherein the binding agent or agents, if used are set.

For example the ion exchanged agglomerates can be heated to a temperature of about 450°C to about 700°C at a ramp rate of about l°C/min to about 20°C/min while holding at the maximum temperature for a time period of at least 30 minutes. The calcined agglomerates also have a crush strength of at least 5 N as measured by the single particle crush test method wherein a total of 40 individual particles are tested and the result is expressed as the average of the 40 data points. The sample for this crush strength test is preconditioned, by drying at 90°C for at least 1 hour. This low temperature drying is intended to ensure that the adsorbent agglomerates are free-flowing and therefore suitable for crush strength measurement, while retaining a lot of adsorbed moisture (Loss On Ignition (LOI) value of about 15 wt% or more, with the LOI measured at 550°C).

[0025] In another aspect the invention is a process for producing an ion-exchanged coreshell adsorbent product also referred to as core-shell adsorbent for use in gas separation or gas purification adsorbers. The process comprises feeding a collection of green adsorbent agglomerates to a curing step wherein green adsorbent agglomerates comprise an inert core of porosity in the range of about 0% to about 10%, a volumetric thermal capacity of about 0.8 J/cm³-°K to greater than about 3 J/cm³-°K, a shell comprising an active adsorbent material, one or more binder materials and optionally an additive, and wherein the curing step comprises one or more of

(b) an aging step wherein the green agglomerates are subjected to certain conditions of temperature, pressure, and humidity for sufficient time, such that the green agglomerates are hardened and meet the minimum 5 N crush strength criterion described above. The exact conditions required will depend on the adsorbent agglomerate composition. An important aspect is maintaining or increasing the humidity and not allowing the adsorbent agglomerates to dry-out. In general, increasing the temperature can speed up the aging process, while maintaining the humidity levels. Pressures around ambient to about 5 bar are suitable for this aging process.

[0026] The cured agglomerates are then subjected to an ion exchange step prior to subjecting said agglomerates to a calcination step, wherein said agglomerates after ion exchange have a crush strength of at least 5 N and subsequently subjected to a calcination step to obtain said ion exchanged adsorbent product. The calcination step comprises treating ion exchanged agglomerates to a pre-defined temperature-time profile of heating said agglomerates, under an appropriate purge gas (such as dry air) to a temperature of about 450°C to about 700°C at a ramp rate of about l°C/min to about 20°C/min while holding at the maximum temperature for a time period of at least 30 minutes. The calcined agglomerates also have a crush strength of at least 5 N as measured by the single particle crush test method wherein a total of 40 individual particles are tested and the result is expressed as the average of the 40 data points. The sample for this crush strength test is preconditioned, by drying at 90°C for at least 1 hour. This low temperature drying is intended to ensure that the adsorbent agglomerates are free-flowing and therefore suitable for crush strength measurement, while retaining a lot of adsorbed moisture (Loss On Ignition (LOI) value of about 15 wt% or more, with the LOI measured at 550°C).

[0027] The inert core in the core-shell adsorbent product used in gas separation applications occupies about 4 vol% to about 65 vol% of the adsorbent product, and the inert core in the core-shell adsorbent product used in prepurification applications occupies about 35 vol% to 96 vol% of the adsorbent product.. [0028] The ion exchange step has a single pass yield > 70 %, preferably > 90%, more preferably > 95%. The yield is calculated by dividing the amount of ion exchanged agglomerates produced which meets pre-defined product specifications by the total amount of agglomerates fed from the curing step to the ion exchange step.

Detailed Description of the Figures

[0029] Figure 1. Prior Art - Ion exchange during synthesis step but prior to agglomeration.

[0030] Figure 2. Prior Art - Ion exchange performed post agglomeration and post calcination.

[0031] Figure 3. Direct ion exchange method - Ion exchange performed post agglomeration but prior to calcination.

Detailed Description of the Invention

[0032] As described above, the present invention is a direct ion-exchange method to produce an adsorbent product from a plurality of green agglomerates containing adsorbent material. The method includes a curing step to convert green agglomerates into cured agglomerates; an optional rehydration step, an ion exchange step to convert cured agglomerates into ion exchanged agglomerates; a calcination step to convert ion exchanged agglomerates into calcined agglomerates; a product recovery step to recover adsorbent product of pre-defined size from calcined agglomerates for use in industrial scale gas separation or gas purification adsorbers.

[0033] Green (adsorbent) agglomerate types that are suitable for the present invention include:

- composite particle, a mixture of at least one active adsorbent material and at least one binder material shaped to have a pre-defined size and composition.

- core-shell, agglomerate containing an inert core meeting certain requirements and adsorbent shell. The inert core is the substantially non-adsorbing inner region of the core-shell agglomerate. The inert core has a porosity in the range of about 0% to about 10% as measured by the Hg porosimetry method, and a volumetric thermal capacity of about 0.8 J/cm³-°K to greater than about 3 J/cm³-°K. An example of a suitable core is bauxite alumina particle, often sold as proppants for the fracking industry, another example of a suitable core is silica sand particle. The shell is the adsorptive outer region of the core-shell agglomerate. The shell comprises at least one active adsorbent material, and at least one binding agent in concentration of at most 20 wt% and preferably from about 2 wt% to about 12 wt% of the shell composition, as measured on a dry weight basis. The role of the binding agent is to impart crush strength, attrition resistance and fracturing resistance to the adsorbent product, at least after completion of the calcination step.

[0034] Referring to Figure 3, the present invention direct exchange method has only one high temperature thermal step. The ion exchange step is performed on cured agglomerated particles, which have not undergone calcination, a high temperature thermal step. The calcination step is delayed until after the completion of ion exchange step. Calcination is endothermic, requires heat input from an external source, and substantially adds to processing costs.

Curing of green agglomerates

[0035] The purpose of the curing step is to increase the crush strength of the agglomerated and uncalcined particles sufficiently for the ion exchange procedure. The calcination step is delayed until the end of the manufacturing process and in its place, the curing step, which may include subjecting the green agglomerates to one or more of the following is carried out:

- low temperature heating step. This may involve heating the green agglomerates containing temporary binding agents to a temperature well below the calcination temperature in order to meet the minimum 5 N crush strength criterion required for successful ion exchange. This method of curing can be used on any formulations that respond well to low temperature heating and achieve the crush strength criterion. It is important to note that this minimum crush strength criterion is to be satisfied before and after the ion exchange step. In particular, formulations that respond well to low temperature heating include those containing additives that can be converted to temporary binding agents, by the low temperature heating. In this way these temporary binding agents now supplement the other components and serve to increase the crush strength of the agglomerates which meet the minimum requirement. An example of a suitable additive is methylcellulose and even low concentrations of this additive (e.g., 1-3 wt%) are sufficient to act as a temporary binder, after heating to a temperature in the range of 50°C to 95°C. Any material used as a temporary binding agent is preferentially removed from the composition during the calcination stage. To choose a suitable additive to function as a temporary binder it is important to understand the solubility properties of additive and ensure that the conditions of the ion exchange operation are compatible with the choice made.

- aging step. This is another form of curing step which may involve subjecting the agglomerates to certain pressure, humidity, and temperature conditions for sufficient time to meet the 5 N minimum crush strength criterion. This method of curing is applicable to formulations which contain components that are responsive to aging treatments, such that after aging the minimum crush strength criterion is achieved. An example of such a formulation is one that contains silicones. Silicone-derived binding agents have been shown to be effective for producing advanced adsorbent materials, whereupon after calcination, the silicones are converted to a silica-rich form that acts as the binding agent. We call this silicone-derived binding agent. However, many silicones are receptive to aging treatments and harden because of these treatments, whilst still maintaining their organic-silicon components. By subjecting the green agglomerates containing silicone components to a moist atmosphere at a pressure in the range of near ambient to 5 bar and a temperature less than 100°C, the agglomerates can be hardened to meet the minimum crush strength criterion. Since, moisture is involved in the aging process, the aged product is fully compatible with the aqueous ion exchange process and the minimum crushing strength is maintained through the ion exchange process.

- chemical curing step. This is another form of curing step which may involve the use of a chemical to catalyze reactions within components in the formulation or react with curable components in the formulation to achieve the minimum crush strength criterion. For example, silicones are often cured by condensation reactions between polymer or elastomer units. Aging processes, described above can provide environments where these reactions occur with sufficient rapidity. However, catalysts can also be used to speed up these condensation reactions and cure the agglomerates to the minimum crush strength criterion in shorter times. Suitable catalysts for silicone curing include the K-KAT zinc-based products from King Industries Specialty Chemicals. These catalysts can be combined with an appropriate solvent or dispersant and sprayed onto the green agglomerates to effect the cure. Suitable solvents or dispersants for the K-KAT products include ethanol and polyethylene glycol. This disclosure refers to the use of at least one chemical compound which can be a catalyst or other chemical compound which is able to react with at least one component of the green adsorbent agglomerates to form cured agglomerates which meet the minimum 5 N crush strength criterion.

[0036] The purpose of the curing step is to strengthen the agglomerated and uncalcined particles sufficiently for the ion exchange procedure. For formulations, whereby curing by aging or chemical means is not applicable or not preferred, low temperature heating with an appropriate temporary binder is always an option and this will be the preferred pathway for such formulations. Combinations of curing means are also acceptable, provided the 5 N before and after ion exchange crush strength criterion is met.

[0037] Since a high temperature thermal step is not performed, prior to ion exchange, the rehydration step can be milder or may not be required, as the agglomerate will have retained a lot of the moisture used during synthesis and agglomeration. If the curing is carried out by a low temperature drying step at modest temperatures whereunder, the agglomerate is not substantially dehydrated, but is somewhat dehydrated, it may be preferable to perform a mild rehydration step, prior to ion exchange. The decision to perform the rehydration step can be made based on whether any significant amount of steam is generated by contacting the somewhat dehydrated adsorbent with water. Excessive steam generation is detrimental to many adsorbent materials since hydrothermal damage/steaming damage may result and this should be avoided. If low or no steam is generated, upon contact of the low temperature dried adsorbent with water, the rehydration step can be omitted. In other cases, especially if the curing is achieved by aging or chemical curing, the rehydration step can be omitted, but for more sensitive materials, it is preferrable to perform a rehydration step to increase the moisture content of the agglomerates, in preparation for ion exchange.

Ion Exchange Step

[0038] The ion exchange step is performed next, in either a batch or column process. The conditions of the ion exchange operation (e.g., temperature, pressure, solution concentration, solution pH and flow rate) can be those that are known, for example such as those described in U.S. Patent No. 8,969,229 issued to Barrett, et al., on Mar. 3, 2015, the teachings of which are incorporated herein by reference in their entirety. Depending on the method of curing used, some known modifications may be required. If the curing method involved a temporary binding agent, then, the solubility properties of the temporary binder must be considered and the process is operated under conditions that do not lead to substantial, if any, removal of the temporary binder from the agglomerated particles, during the ion exchange operation with liquids present. If aging or chemical curing is used as curing means, less changes are expected for the ion exchange operation versus normal practice. Typically, the ion exchange operation have four phases, an initiation phase, the ion exchange phase, a post-exchange washing phase and an unloading or material recovery phase. In the initiation phase, the system is loaded with agglomerated particles and liquid flow, or immersion is initiated. The ion exchange phase comes next, wherein a salt solution of the desired cation or cations is contacted with the agglomerated particles, until the required level of ion exchange has been achieved. This is typically determined by chemical analysis methods, like Inductively Coupled Plasma Analysis on either the liquid leaving the system, or on samples of the adsorbent material or both. The next stage involves washing, usually with deionized water, to remove excess salt solution from the adsorbent pores, prior to draining the equipment and recovery of the ion-exchanged agglomerated particles. The agglomerated particles are often subjected to dewatering and/or drying, prior to the calcination step.

Calcination Step

[0039] In the calcination step, high temperature thermal step, the temperature is gradually increased, under an appropriate purge gas, to remove any removable components from the ion-exchanged agglomerated particles and thermally set the inorganic binding agent 1 or agents. At this time, any temporary binder is removed from the composition. The agglomerated particles may be subjected to a final stage of screening to remove any further oversize and undersized material before the product is packaged in preparation for use in gas separation or gas purification adsorbers.

[0040] The calcination step is vital and involves a ramp in temperature from a low temperature, below 100°C to the calcination temperature (450°C to 700°C, more preferably 475°C to 650°C). The ramp rate must be controlled to prevent unwanted hydrothermal damage. A minimum hold at the top temperature for 30 minutes and more preferably 1 hour is recommended, followed by a natural or controlled cooling step. The air flow during the calcination must be sufficient to promote complete combustion of any organic species contained in the agglomerate. Carbon residues are detrimental to capacity and mass transfer properties of the adsorbent. The calcination purge gas and purge gas flow rates are selected such that when combined with the temperature profile, achieve a final product with at most 1 wt% residual moisture and preferably at most 0.5 wt% residual moisture content, as measured by the Karl Fischer titration method using a furnace temperature of 1000°C for the Karl Fischer measurement.

Agglomerate Formulations

[0041] In terms of formulations which are compatible with the present invention direct exchange method: the formulation must comprise at least one ion exchangeable compound and at least one binding agent. The at least one ion exchangeable compound is preferably a zeolite and the at least one binding agent is preferably a clay or silicone derived material or mixtures thereof. Preferred zeolites are those with SiCh/AkOs ratio of from about 1.9 to 10. Examples of suitable zeolites include zeolite X, zeolite LSX, zeolite Y, zeolite A, zeolite L, ZSM-5, chabazite, clinoptilolite, mordenite and mixtures thereof. The clay is preferably attapulgite, halloysite, kaolin and their mixtures. Silicone-derived binding agents may also be used. Silicones are synthetic compounds comprised of polymerized or oligomerized units of silicon together with predominately carbon, hydrogen, and oxygen atoms. Silicones, also commonly known as siloxanes or poly siloxanes, are considered a hybrid of both organic and inorganic compounds since they contain organic side chains on an inorganic -Si-O-Si-O- backbone. Their structures can include linear, branched, cross-linked and cage-like variants.

[0042] Silicones have the general formula [R2SiO]n, where "n" refers to degree of polymerization (Size exclusion chromatography with evaporative light scattering detection as a method for speciation analysis of polydimethylsiloxanes. III. Identification and determination of dimeticone and simeticone in pharmaceutical formulations, Pienkowska, Krystyna, loumal of pharmaceutical and biomedical analysis, 200 (7), 58, Sep 10, 2011). Preferred silicones have a value of “n” between 10 to 1000, R is one or more organic side groups selected from Cl to C8 organic compounds, preferably Cl to C4 organic compounds, including linear, branched, and cyclic compounds or mixtures thereof and wherein the polymeric or oligomeric silicones are typically terminated by hydroxy, methoxy, ethoxy groups or mixtures thereof. The silicones of interest generally have molecular weights ranging from about 100 to more than 500. The R side group can also represent other organic groups such as vinyl or trifluoropropyl and a wide range of silicones are believed to be useful in this invention.

[0043] Examples of silicones include, but are not limited to, polydimethylsiloxanes and polydiphenylsiloxanes such as those identified by Chemical Abstracts Service (CAS) Registry Numbers 63148-62-9 and 63148-59-4 and those with di-methyl groups in polymeric forms with methyl, octyl silsesquioxanes such as CAS Registry Number of 897393-56-5 (available from Dow Corning under the designation IE 2404); methyl silsesquioxanes such as CAS Registry Number of 68554-66-5; and (2,4,4- trimethylpentyl) tri ethoxy silane such as CAS Registry Number 35435-21-3. Preferred silicones are selected from hydroxy, methoxy, or ethoxy terminated polymeric dimethylsiloxane or mixtures thereof with methyl-silsesquioxanes, octyl-silsesquioxanes, methyl octyl-silsesquioxanes, or mixtures thereof.

[0044] Silicones of more than one type can be used and the silicones can be used with other organic or inorganic compounds. Common additional components include water, co-polymer stabilizing agents, emulsifying agents and surfactants and silicone emulsions and suspensions can be employed as the silicone binder precursors. These additional components are often present to stabilize the particular form of the silicone which is typically used in the form of an emulsion, solution, or resin.

[0045] The binding agent concentration in adsorbent product is at most 10 wt% for products without a core and 20 wt% maximum of the adsorbent shell in adsorbent products of the core-shell type.

[0046] Optionally an additive can be employed as a formulation ingredient to provide sufficient crush strength to the agglomerates of the above components. The additive content can be about 5 wt% maximum, preferably about 3 wt% maximum of the green agglomerate fed to the curing step. Prior to calcination, the agglomerates should be maintained intact through out the post-agglomeration ion exchange step (direct-exchange step), such that manufacturing yields of at least 90% are achievable from the ion exchange unit operation. A suitable additive which can be used is Methocel A4M. Other materials that meet the following requirements can also be used:

• provide and maintain a crush strength of at least 5 N to the agglomerates of adsorbent material and binder material after low temperature drying and throughout the ion exchange process, as measured by the single particle crush strength method (40 particle average). The validation crush strength measurements should be performed on the products from the ion exchange unit operation, after drying under ambient conditions for 2 hours (i.e., to eliminate surface liquid and have the agglomerated particles in a free-flowing state).

• additive incorporated agglomerates to have above required crush strength at an additive content of 5 wt% maximum and preferably at an additive content of 3 wt% maximum.

• organic/combustible species in the additive and/or silicone-derived binding agent can be substantially and preferably removed by the calcination process; carbon residues are detrimental to the capacity and mass transfer properties of the adsorbent. • final product has a crush strength of at least 5 N, measured in the calcined state. The measurement method is again the single particle crush strength method with 40 particles average.

[0047] For core-shell type products, the cores should be substantially inorganic and have porosities of at most 10% when measured by the Hg porosimetry method. The cores should also have a volumetric heat capacity of at least 0.8 J/ cm³-°K. Examples of suitable cores include bauxite alumina materials and silica sand materials.

Direct Exchange Process

[0048] With reference to Figure 3, the present invention produces ion-exchanged adsorbent particles for use in industrial cyclic adsorptive gas separation or gas purification systems. For illustrative purposes, the process is shown to contain a sequence of process blocks wherein material produced in a given block becomes feed to subsequent block. Any material produced which is not suitable for processing in the subsequent block is either discarded or recycled. Thus, each block has a single pass manufacturing yield which can be calculated by dividing the amount of material from a given block which can be processed in the subsequent block divided by the total amount of material fed to the given block. Focusing on the ion exchange step, present invention can have a single pass yield of greater than 90% wherein measure of the single pass yield includes product of the ion exchange step having a pre-defined crush strength; calculated by dividing the amount of ion exchanged material produced which meets the crush strength specification by the total amount of material from the previous block fed to the ion exchange block.

Examples

Example 1 (Inventive") - Green Agglomerates cured by low temperature drying [0049] Twenty one thousand nine hundred and twenty three (21923) grams wet weight (16003 grams dry weight) of zeolite Na,K LSX powder was blended together with 1650 grams wet weight (1204 grams dry weight) of Actigel 208 clay from Active Minerals and 400 grams Methocel A4M (Dow Chemical) in a 50 L plow mixer. After addition of these solids, the mixer was started at 240 rpm for 15 minutes. At this point, while mixing at 240 rpm, 6200 grams de-ionized water was pumped in at 180 ml/min. After completion of the water addition, the mixer was stopped, and the mixed powder product recovered. Next, green agglomerates were formed by slowly adding the mixed powder product, while spraying deionized water over the particles, as needed, using a tilted rotating drum mixer with 75 L internal volume. This exercise of powder and water addition were continued over about 3 h time period until the beads grew to 10x12 US mesh. In total this process consumed all the plow mixed powder, as well as about 2210 grams of deionized water.

[0050] In accordance with the present invention about 500 grams of green agglomerates of size, 10x12 US mesh, were subjected to the curing step. In this example, the curing step was a low temperature heating step carried out by placing the green agglomerates in a Blue-M oven and heated at 90°C for 4 hours using a dry air purge. This step is employed to set Methocel A4M temporary binder.

[0051] The cured agglomerates were subsequently cooled to room temperature and maintained in a shallow tray for further two hours (at room temperature) to enable some rehydration from contact of the agglomerates with ambient air, prior to ion exchange. After rehydration, the cured agglomerates were placed in a 2-inch diameter by 24-inch length glass ion exchange column. About 2 Liters of de-ionized water at 80°C was pumped through the column at 150 ml/min., followed immediately by 20 Liters IM LiCl solution which was pumped through the column at 20 ml/min. at 92°C, followed by approximately 18 Liters of de-ionized water at 75°C at 100 ml/min. At no point in this process did the column temperature drop below 75°C, which ensured that the Methocel A4M temporary binder did not dissolve and remained within the agglomerates. The ion exchange step was concluded by draining the liquid from the column and then recovering the ion-exchanged agglomerates.

[0052] Finally, the agglomerates were subjected to the high temperature thermal step, calcination step, by first air-drying for at least 2 hours then heating in a Blue-M oven using dry air purge. The agglomerates were subjected to the following heating profile: 6 hours at 90°C; 6 hour ramp to 200°C; 2 hour ramp to 300°C; 3 hour ramp to 600°C; 1 hour soak at 600°C. The calcined agglomerates were recovered from the oven using a hot packaging process. Example 2 (Comparative)

[0053] The same formulation was prepared as in Example 1, and green agglomerates of 10x12 US mesh size were prepared as described in Example 1. At this point instead of curing the green agglomerates and performing the ion exchange and calcination steps, as described in Example 1, the traditional manufacturing process was followed instead. The green agglomerates were calcined by heating in a Blue-M oven using dry air purge. The agglomerates were subjected to the following heating profile: 6 hours at 90°C; 6 hour ramp to 200°C; 2 hour ramp to 300°C; 3 hour ramp to 600°C; 1 hour soak at 600°C. After calcination, the agglomerates were allowed to cool to room temperature, before being rehydrated, in preparation for ion exchange. The rehydration was completed by subjecting the cooled agglomerates, on shallow trays, to ambient air for 12 hours.

[0054] Next the rehydrated agglomerates were ion exchanged with lithium using the same reagent amounts and process conditions as described in Example 1. This includes the deionized water wash and column draining processes. At this point, the ion exchanged agglomerates were air dried for 2 hours, prior to activation. The activation step was performed in a Blue-M oven using dry air purge. The ion exchanged agglomerates were subjected to the following heating profile: 6 hours at 90°C; 6 hour ramp to 200°C; 2 hour ramp to 300°C; 3 hour ramp to 450°C; 1 hour soak at 450°C. The calcined agglomerates were recovered from the oven using a hot packaging process.

Characterization of Intermediate and Final Product from Example 1 (Inventive) and Example 2 (Comparative)

[0055] The crush strength data was obtained using a Pharmatron 8M instrument, using a 0-50N load cell and sample of 40 single particles (beads). The value reported is the average of the 40 individual measurements.

[0056] The attrition value is determined by agitating 100g of sample in a Retch RM 200 sieve-shaker equipped with a lid, 35 US mesh screen and a pan to collect the fines. The sample is agitated for 30 minutes at an average amplitude of 2.2 mm. Particles or fines which pass through the 35 US mesh screen are counted as attrition. These particles or fines are weighed and the result expressed as a percentage of the original sample weight. [0057] Mercury (Hg) porosimetry measurements to determine the adsorbent porosity were performed using a Micromeritics AutoPore IV instrument. Approximately, 1 g of sample was used for each measurement. The contact angle was fixed at 135° and intrusion and extrusion data were recorded over the pressure range from 0.5 psia to 61,000 psia. Other experimental parameters for mercury porosimetry, (were those given in Table 4.1 in Chapter 4 of the Textbook “Analytical Methods in Fine Particle Technology” P.A. Webb and C. Orr, published by Micromeritics Instrument Corporation, 1997, ISBN 0-9656783-0-X). The results from these characterization tests are provided in Table 1.

Table 1. Characterization results for samples from Example 1 (Ex. 1) and Example 2 (Ex. 2).

[0058] Referring to the data in Table 1 and beginning with the sample from comparative Example 2 (Ex. 2): In the traditional process, the green agglomerates are calcined, prior to ion exchange. After calcination, the sample from Example 2 had a crush strength of 6.7 N. The next manufacturing step is rehydration and in order to measure crush strength values, the samples were rehydrated and afterwards air dried to at least remove any surface moisture and make the rehydrated materials free-flowing and testable by the crush strength method. After rehydration and air-drying, we see a significant reduction in crush strength, prior to ion exchange, with the value now at 1.6 N. The next measurement was taken after ion exchange, where again the sample was air dried to at least remove any surface moisture and make the post-ion exchange materials free- flowing. The crush strength for this sample showed a small but further decrease to 1.3 N. The next manufacturing step, in the traditional process, is calcination step herein referred to as an activation step and the material from this step is the final product. For comparative Example 2, we see that the activation step leads to an increase in the crush strength to 3.8 N for the final product.

[0059] In contrast, the direct-ion exchange process takes the cured green agglomerates directly to the ion exchange process. As a result, there is no calcination step prior to ion exchange, and this is reflected in Table 1 by the “N/A” label for the crush strength for this manufacturing step. Depending on the curing means, the rehydration step may be omitted or is much shorter, due to the absence of the high temperature calcination step, prior to ion exchange. In inventive Example 1 (Ex. 1), the curing means was low temperature drying and the rehydration was completed by air-drying the cured green agglomerates. After air-drying and before ion exchange, the crush strength of the material from Example 1 was 10.3 N. Similarly, after the ion exchange and air-drying the crush strength was essentially unchanged at 10.4 N. Reorganization or loss of binding agent was a possibility since the binder material in the agglomerates was not yet set by the calcination process and the liquid phase ion exchange operation could have facilitated movement of the binding agent particles. The crush strength values of the particles prior to ion-exchange and post ion-exchange are similar, suggesting that the direct ion exchange did not result in any substantial reorganization or loss of binding agent. Thus, maintaining yield and crush strength of uncalcined agglomerates when subjected to ion exchange treatment are surprising results of the present invention. At this point, calcination was performed to create the final product. For Example 1, the final product had a crush strength of 7.6 N, an acceptable crush strength, however, lower than the the 10.3 N crush strength of cured agglomerates before ion exchange process and 10.4 N crush strength of ion exchanged agglomerates after the ion exchange process.

[0060] Results summarized in Table 1 indicate that the direct-exchange process product has improved crush strength as well as significantly improved attrition resistance. Finally, the porosity measurements in Table 1 shows that materials from both Example 1 and Example 2 were of similar porosity. This is important since, it is known that porosity can influence both crush strength and attrition resistance. The materials with higher porosity often have lower crush strength and higher attrition. The closeness of the porosity of the Example 1 and Example 2 materials, as well as the use of the same formulation means that the characterization results are directly comparable and the differences are due to the manufacturing processes used in each case.

Example 3 - Green Agglomerates cured by aging

[0061] The green agglomerates prepared in this example were of core-shell type. The shell precursor was prepared by placing 800 grams dry weight (1023.0 grams wet weight) of LSX powder in a Hobart mixer and with the mixer agitating, 59.5 grams Dow 2405 Silicone Resin was pumped in at a rate of 4 ml/min. At the end of the addition, mixing was continued for 15 minutes. Thereafter, 255.0 grams of water was pumped in at a rate of 14 ml/min. The resulting shell precursor labeled hereinafter “the shell formulation” was removed and temporarily placed in a container.

[0062] Green agglomerates were prepared by placing 175 grams of 20x30 mesh Bauxite proppants obtained from Agsco in a 12" diameter rotating pan granulator and agitated therein at a speed of 30 rpm. Slowly 1.2 grams of Dow 2405 Silicone Resin was added over a period of two minutes. Water was slowly sprayed in while gradually adding the shell formulation. Beads which grew into the 12x16 mesh size were removed as product. In total, 937.0 grams of the shell formulation, and 111.0 grams water were added to the rotating pan over a period of 90 minutes.

[0063] The green agglomerates were then cured using an aging step which was carried in two stages. In the first stage, the 12x16 mesh green agglomerates were air dried for 16 hours; in the second stage, 125 ml of the air-dried green agglomerates were placed in two liters of deionized water at 90°C for 16 hours. The total aging time was 32 hours.

[0064] The aged particles were then transferred to a 2-inch diameter by 24-inch length glass ion exchange column. Approximately two liters of 0.5% Flexiwet solution at 80°C was pumped through the column at 150 ml/min. The aged particles were then soaked in the Flexiwet solution in the column at 80°C for about 30 minutes. Next, 20 liters IM LiCl solution was pumped through the column at 20 ml/min. at 92°C, followed by about 18 liters of deionized water at 75°C at 100 ml/min. At this point, the ion exchange step was concluded by draining the liquid from the column and then recovering the ion exchanged particles.

[0065] Initially, the ion exchanged particles were air-dried for at least 2 hours in preparation for the calcination step. The calcination was completed in a Blue-M oven using dry air purge (dewpoint at least -80°F) with the following heating profde: 6 hours at 90°C, 6 hour ramp to 200°C, 2 hour ramp to 300°C, 3 hour ramp to 600°C, 1 hr. soak at 600°C. The calcined product were recovered from the oven using a hot packaging process.

Example 4 - Green Agglomerates cured by chemical means

[0066] The green agglomerates prepared in this example were of core-shell type. The shell precursor was prepared by placing 800 grams dry weight (1023.0 grams wet) of LSX powder in a Hobart mixer and with the mixer agitating, 59.5 grams Dow 2405 Silicone Resin was pumped in at rate of 4 ml/min. At the end of the addition, mixing was continued for 15 minutes. Thereafter, 255.0 grams of water was pumped in at rate of 14 ml/min. The resulting shell precursor labeled hereinafter “the shell formulation” was removed and temporarily placed in a container.

[0067] Green agglomerates were prepared by placing 175 grams of 20x30 mesh Bauxite proppants obtained from Agsco in a 12" diameter rotating pan granulator and agitated therein at a speed of 30 rpm. Slowly 1.2 grams of Dow 2405 Silicone Resin was added over a period of two minutes. Water was slowly sprayed in while gradually adding the shell formulation. Beads which grew into the 12x16 mesh size were removed as product. In total, 937.0 grams of the shell formulation, and 111.0 grams water were added to the rotating pan over a period of 90 minutes. The green agglomerates, 12x16 mesh beads were allowed to dry in ambient air until they were free flowing and non-sticky, in preparation for curing.

[0068] The curing of green agglomerates was carried out by chemical means by placing 150 ml of the air-dried beads in a 12" diameter rotating pan granulator and agitating therein at a speed of 30 rpm followed by slowly adding one gram PEG-200 per gram K- 1 Kat 670 from King Industries solution over a period of two minutes. The beads were then heated in a Blue-M oven at 90°C for 6 hours and resulting beads herein referred to as chemically cured beads.

[0069] The chemically cured beads were then transferred to a 2-inch diameter by 24” length glass ion exchange column and approximately two liters of 0.5% Flexiwet solution at 80°C was pumped through the column at 150 ml/min. The beads were then soaked in the Flexiwet solution in the column at 80°C for about 30 min. Next, 20 liters of IM LiCl solution was pumped through the column at 20 ml/min. at 92°C, followed by about 18 liters de-ionized water at 75°C at 100 ml/min. At this point, the ion exchange step was concluded by draining the liquid from the column and then air-drying the ion exchanged beads initially for at least 2 hours before being prepared for the calcination step.

[0070] Finally, the beads were calcined in a Blue-M oven using dry air purge with the following heating profile: 6 hours at 90°C, 6 hour ramp to 200°C, 2 hour ramp to 300°C, 3 hour ramp to 600°C, 1 hr. soak at 600°C. The product beads were recovered from the oven using a hot packaging process.

Characterization Results

[0071] The adsorbent beads made in Examples 3 and 4 described above were characterized as follows and results are summarized in Table 2.

• average particle size was determined by a conventional screen analysis, using US Mesh screens

• porosity and median pore diameter were measured by Hg porosimetry, using a Micromeritics Autopore IV porosimeter. Experimental parameters, were the same as those in Example 2. Other experimental parameters for mercury porosimetry , are given in Table 4.1 in Chapter 4 of the Textbook “Analytical Methods in Fine Particle Technology” P.A. Webb and C. Orr, published by Micromeritics Instrument Corporation, 1997, ISBN 0-9656783-0-X calculated shell porosity accounts for the presence of the bauxite core • packed density was measured using the established tap packed density method, using 250 ml volumetric cylinder filled initially to at least 200 ml with sample and tapped 5000 times

• N2 capacity of the shell as stated is the N2 capacity of the shell only as measured after careful extraction of the shell material from the core. The measurement was performed on a Micromeritics ASAP 2050 and the sample was activated on the instrument under vacuum at 400°C. For core-shell beads of Examples 3 and 4, the N2 capacity of the core-shell bead was measured at 25°C, 1 atm using the same method as for shell, the values were 16.9 ml/g and 19 ml/g, respectively.

• mass transfer time is derived from a low dead volume test, as described in U.S. Patent Number 6,500,234. In particular, the Mass Transfer Time (MTT) is the time required for the oxygen concentration to decrease from 90% to 30%. Smaller MTT values represent faster adsorption kinetics.

• final product crush strength represents the crush strength measured on the ion- exchanged agglomerates (LiLSX beads), after ion exchange and subsequent calcination at 600 °C. The measurement was performed on a Pharmatron 8M instrument, using a 0-50 N load cell and sample of 40 single particles (beads). The value reported is the average of the 40 individual measurements.

Table 2. Characterization results of samples from Examples 3 and 4

[0072] The adsorbent beads from Examples 3 and 4 are high-performance material as evidenced by the mass transfer time of 1.2 seconds or less for their average particle size of 1.6 mm particles, shell N2 capacity greater than 26 ml/g and Exchanged Crush Strength (N) exceeding the target of 5 N.

[0070] The direct exchange method of present invention is applicable to conventional adsorbents with binding agent concentrations of about 2 wt% to about 10 wt% and coreshell adsorbent particles with binding agent concentrations of about 2 wt% to about 20 wt% in the shell of core-shell adsorbent particles. The binder content range is higher for the core-shell materials, since achieving manufacturing yields > 90% is still demanding despite greater amounts of binding agent, due to the core-shell configuration.

Furthermore, the compositions applicable to the present invention direct exchange method are those that require ion exchange, as part of their manufacturing and wherein the ion exchange is performed on agglomerated particles of the adsorbent. An example is LiX or LiLSX adsorbents for VPSA 02 production wherein the lithium is added by ion exchange and since the lithium ion exchange isotherm is comparatively unfavorable, to achieve the desired high levels of Li exchange (e.g. > 90% and often > 95%), column ion exchange processes on agglomerated materials are preferred to help overcome the unfavorable nature of the isotherm.

[0073] The present invention, a process to produce ion exchanged adsorbent product could be applied to particles other than agglomerates, beads, e.g., pellets or sheets or other shaped forms of the adsorbent. For traditional products containing higher binder content, the yield from conventional manufacturing process shown in Figure 2 may be acceptable, but the present invention direct exchange method (Figure 3) offers productivity advantages due to the use of only one high temperature thermal step, reduced energy usage, as well as the need for less, if any rehydration.

[0074] The present invention enables completion of manufacturing process in a shorter time period. The new manufacturing method can be augmented with additional steps. A hybrid process can be imagined whereby a powder ion exchange step, as shown in Figure 1 after the synthesis step, can be added to the inventive manufacturing process shown in Figure 3. This would enable elements which are required in low ion exchange levels (< 85%) to be added and/or elements wherein the ion exchange isotherm is more favorable (especially divalent and/or trivalent cations) to be added using the powder exchange method.

[0075] In summary, the present invention, a direct exchange method is an improved manufacturing process (Figure 3) which enables manufacturing of certain adsorbent compositions at high yields (> 90%) wherein manufacturing of these adsorbents by traditional processes (Figures 1 and 2) had resulted in lower yields of the ion-exchanged product, < 50% or in the best cases produced unsatisfactory yields in the 70-80% range. The higher yields from the improved process, could reduce adsorbent material cost as well as manufacturing costs since it utilizes only one high temperature step (reduced thermal energy requirement). The comparative process in Figure 2 contains two high temperatures steps , namely calcination at an elevated temperature of up to 700°C and activation at a temperature suitable to remove moisture in the ion exchanged adsorbent to about 1 wt% or less, as measured by the Karl Fischer titration method using a furnace temperature of 1000°C. A key feature of the present invention direct exchange method is that the ion exchange step is performed on agglomerates, shaped adsorbent particles, directly without a high temperature calcination step first. According to the new method, the high temperature calcination step is performed after the ion exchange and washing steps. In traditional adsorbent manufacturing processes, ion exchange methods are commonly used to alter the chemical composition of an adsorbent material. For some products, the ion exchange step is performed on the adsorbent powder before it is agglomerated. This method of powder exchange works for adsorbent compositions, wherein the ion exchange levels required are modest e.g., < 85% and wherein the ion exchange isotherm is favorable. This ion exchange step is typically performed directly after the synthesis and synthesis related washing steps (see Figure 1). To reach ion exchange levels > 85 % and/or to overcome more unfavorable ion exchange isotherms, ion exchanges are often performed on adsorbent materials, after agglomeration (see Figure 2). Another motivation to delay the ion exchange step until late into the manufacturing process, is that when expensive cations (e.g., Li or Ag) are required in the final adsorbent product, performing the ion exchange after calcination, can lead to more efficient use of these expensive components and lower overall losses thereof. Since, every unit operation in the flow sheet, has a yield associated with it, performing the ion exchange after calcination, can avoid yield losses of the expensive components early in the manufacturing process, however the ion-exchanged particles require another calcination step. The present invention surprisingly can achieve high yields by curing green agglomerates, followed by ion exchange, and then subjecting the ion-exchanged agglomerates to calcination, a high temperature thermal step, thus utilizing only one high temperature step which translates into efficient production of adsorbent using less energy.

[0076] It should be apparent to those skilled in the art that the subject invention is not limited by the examples provided herein which have been provided to merely demonstrate the operability of the present invention. The selection of appropriate adsorbent components and processes for use can be determined from the specification without departing from the spirit of the invention as herein disclosed and described. The scope of this invention includes equivalent embodiments, modifications, and variations that fall within the scope of the attached claims.

Claims

We claim:

1. A direct ion-exchange method for preparing an adsorbent product from a plurality of green adsorbent agglomerates having a pre-defined size, wherein said green adsorbent agglomerates comprise at least one active adsorbent material at least one binder material, and optionally an inert core having a porosity of from about 0% to about 10% as measured by the Hg porosimetry method, and a volumetric thermal capacity of greater than about 0.8 J/cm³-°K, wherein said method comprises: a) Curing said green adsorbent agglomerates to form cured agglomerates, b) Subjecting said cured agglomerates to an ion exchange step forming ion exchanged agglomerates, c) Calcining said ion exchanged agglomerates, forming an adsorbent product, and, d) Recovering said adsorbent product.

2. The method of claim 1 wherein prior to calcining step c) said ion exchanged agglomerates have a crush strength greater than 5 N as measured by single particle crush test method.

3. The method of claim 1 wherein the adsorbent product comprises binder materials and active adsorbent material in a weight ratio of from about 2/98 to about 12/88.

4. The method of claim 1 wherein the green adsorbent agglomerate is a core-shell adsorbent which comprises the inert core surrounded by an adsorbent shell comprising the at least one active adsorbent material, and the at least one binder material.

5. The method of claim 4 wherein the inert core is coated with an adhesion agent selected from one or more of one or more of clays, aluminas, silicas, silicone derived materials, alumina-silica reagents and mixtures thereof.

6. The method of claim 1 wherein the curing step comprises one or more of: i) a low temperature heating step to drive off volatiles wherein the green agglomerates are heated to a temperature of about 50°C to 95 °C and held for a time period of about 1 hour to about 4 hours, ii) an aging step wherein the green agglomerates are kept in a hydrated state at a pressure from near ambient to about 5 bar and a temperature less than about 100°C and held for a time period of 0.5 to about 10 days. iii) a chemical curing step wherein the green agglomerates are contacted with at least one chemical compound which sets curable component(s) in the green agglomerates by reacting or by promoting chemical reaction(s) to form cured agglomerates which meet the minimum 5 N crush strength criterion.

7. The method of claim 1 wherein the ion exchange step comprises a batch process or a column process wherein, the active adsorbent material composition is altered to form an active ion exchanged adsorbent material, and the ion exchanged agglomerate composition can be differentiated from the green agglomerate composition by the extent of cation exchange on an equivalents basis.

8. The method of claim 1 wherein the calcination of ion exchanged agglomerates is carried out at a pre-defined temperature-time profile of heating said agglomerates to a temperature of about 450°C to about 700°C while holding at a pre-defined temperature for a time period of at least 30 minutes.

9. The method of claim 1 wherein said adsorbent comprises one or more of zeolites, molecular organic frameworks (MOFs), zincosilicates, titanosilicates, binder materials and mixtures thereof.

10. The method of claim 1 wherein the adsorbent comprises a zeolite selected from X, LSX, Y, A, L, ZSM-5, Mordenite, Clinoptilolite, Chabazite and mixtures thereof.

11 . The method of claim 10 wherein said zeolite has a SiCh/AhCh ratio of from about 1 .9 to 10, and wherein the zeolite contains cations which are exchanged with one or more cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu and mixtures thereof to produce an ion exchanged zeolite.

12. The method of claim 11 wherein the ion exchanged adsorbent is LiX or LiLSX wherein the extent of Li exchange is greater than or equal to 90% on an equivalents basis.

13. A process for producing an ion-exchanged adsorbent product for use in gas separation or gas purification adsorbers, said process comprising feeding a collection of agglomerates to an ion exchange step prior to subjecting said agglomerates to a calcination step, wherein said agglomerates after ion exchange have a crush strength of at least 5 N and subsequently subjected to a calcination step to obtain said ion exchanged adsorbent product.

14. The process of claim 13 wherein said collection of agglomerates fed to said ion exchange step are formed by feeding a collection of green agglomerates to a curing step wherein the curing step comprises one or more of i) a low temperature heating step to drive off volatiles wherein the green agglomerates are heated to a temperature of about 50°C to 95 °C and held for a time period of 1 to about 4 hours, ii) an aging step wherein the green agglomerates are kept in a hydrated state at a pressure from near ambient to about 5 bar and a temperature less than about 100°C and held for a time period of 0.5 to about 10 days. iii) a chemical curing step wherein the green agglomerates are contacted with at least one chemical compound which sets curable component(s) in the green agglomerates by reacting or by promoting chemical reaction(s) to form cured agglomerates which meet the minimum 5 N crush strength criterion.

15. A process for producing an ion-exchanged core-shell adsorbent product for use in gas separation or gas purification adsorbers, said process comprising feeding a collection of core-shell agglomerates to an ion exchange step prior to subjecting said agglomerates to a calcination step, wherein said agglomerates after ion exchange have a crush strength of at least 5 N and subsequently subjected to a calcination step to obtain said ion exchanged adsorbent product.

16. The process of claim 16 wherein said collection of agglomerates fed to said ion exchange step are formed by feeding a collection of core-shell green agglomerates to a curing step wherein the curing step comprises one or more of: i.) a low temperature heating step to drive off volatiles wherein the green agglomerates are heated to a temperature of about 50°C to 95 °C and held for a time period of 1 to about 4 hours, ii.) an aging step wherein the green agglomerates are kept in a hydrated state at a pressure from near ambient to about 5 bar and a temperature less than about 100°C and held for a time period of 0.5 to about 10 days. iii.) a chemical curing step wherein the green agglomerates are contacted with at least one chemical compound which sets curable component(s) in the green agglomerates by reacting or by promoting chemical reaction(s) to form cured agglomerates which meet the minimum 5 N crush strength criterion.