Improved adsorbent composition

Abstract

The present invention generally relates to a coated inert core, a method of making a coated core-shell sorbent, and to the use of the core-shell sorbent in gas separation or purification applications. Coating the inert core prior to application of the shell material greatly improves adhesion of the shell to the core material, resulting in reduced wear and fracture. Controlled growth of adsorbent product particle size is achieved using the coated core, resulting in an improved single pass recovery with a predetermined size distribution.

Description

[0001] Related applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 597,482, filed November 9, 2023, which is incorporated herein by reference. Technical Field

[0003] This invention relates to core-shell composite materials that can be used as adsorbents and catalysts, methods for preparing core-shell composite materials, and methods for using core-shell composite materials in gas separation or purification applications. Background Technology

[0004] Core-shell adsorbent materials have been described in this art. Generally, two types of core-shell adsorbent materials exist. The first type uses a porous core material and a shell containing adsorbent. The second type uses a non-porous or low-porosity core and a shell containing adsorbent. This invention relates to improved compositions and methods for preparing these compositions for the second type of material using a low-porosity core type.

[0005] A major problem with core-shell adsorbent particles is the insufficient adhesion of the core and shell components, leading to particle wear and fracturing, where partial or complete shell loss occurs. Commonly, a portion of the core-shell particles suffers fracturing, and the fracturing fragments are often retained along with intact core-shell particles in the final adsorbent product. In adsorption applications, these fracturing fragments can lead to further undesirable effects, including component clogging and increased pressure drop in packed bed applications. Fracturing properties can be readily measured using sieving methods, where material is first separated by size using conventional sieves (with conventional square holes), and then the material separated on each sieve is subsequently passed through a sieve of equivalent diameter, but where the square holes are replaced by slit-shaped holes that allow broken particles to pass through the sieve and be quantified as a percentage of the total weight. A core-shell composition with a low percentage of fracturing while maintaining high performance is desirable.

[0006] To minimize fracturing / wear losses, focus has been placed on using binders to form core-shell agglomerates with better adhesion of the shell material to the inert core starting material. Geng et al. described the preparation of carbon monoxide adsorbents with a core-shell structure using 5% to 8% by weight of a silane coupling agent in CN116809040A. Microsphere cores were dispersed in an alcohol-water mixture, and the silane coupling agent was added under ultrasonic conditions while stirring and heating at 50°C to 60°C, followed by the addition of the remaining components. The adsorbent was then subjected to a first temperature treatment for 1 to 3 hours under a protective environment, such as nitrogen at 350°C to 500°C, followed by a second temperature treatment for 5 to 10 hours at 150°C to 220°C under a reducing atmosphere.

[0007] The inventors of this invention have discovered attractive alternatives to using large amounts of binders, large amounts of silane coupling agents in the presence of organic solvents, ultrasonic treatment, and heat treatment in a reducing atmosphere. In this invention, the method of adding the binder (also referred to herein as a coating material) is different, wherein the coating material is added directly to the core, and the coated core green particles are subjected to heat treatment in air, with air acting as an oxidizing atmosphere to ensure that carbonaceous material is substantially removed from the coated core particles. The resulting coated core particles provide better adhesion of the shell material to the coated core. Core-shell adsorbent beads containing these coated cores are suitable for use in adsorption gas separation methods. Such adsorbents, their preparation methods, and their use in adsorption gas separation methods are the subject of this invention.

[0008] Another significant issue associated with core-shell adsorbent materials involves poor manufacturing yields, particularly those resulting from the forming process. A common finding is that core-shell bead preparation leads to low single-pass yields, defined as the percentage of particles within a specified particle size distribution after the bead-forming step. Single-pass yields are critical because recycling core-shell agglomerates with both oversized and undersized particles is more demanding compared to conventional formulations without a core. In conventional forming, undersized material is typically recycled directly, while oversized material is ground back into powder and added back to the process in this manner. Undersized core-shell material can be recycled as described, but oversized material requires shell removal from the core so that both can be recycled. These steps are complex and require new equipment and processes compared to conventional forming of non-core-shell materials.

[0009] The inventors have discovered that coating the core, as described below, can significantly improve single-pass yield, thereby minimizing the amount of material requiring further processing and increasing the ease of manufacturing core-shell materials. Another aspect of the invention is to improve single-pass manufacturing yield. Summary of the Invention

[0010] This invention relates generally to a core-shell adsorbent comprising a coated inert core, also referred to as a coated core; the core-shell adsorbent is also referred to as a coated core-shell adsorbent made therefrom, and relates to the use of the core-shell adsorbent in gas separation methods. Coating the inert core with an adhesive before applying the shell material significantly improves the adhesion of the shell to the core material, thereby leading to reduced wear and fracturing. This invention also relates to a method for preparing core-shell composite materials using the coated core.

[0011] In one aspect, the present invention is a core-shell adsorbent, also known as a core-shell composite material, comprising a core having a porosity of 0% to ≤10% as determined by Hg porosity determination; and a porosity greater than 0.8 J / cm³. 3The core has a volumetric heat capacity value of -°K, wherein the core is coated with an adhesive also known as an adhesive coating material or coating material, the adhesive being selected from clay, alumina, silica, organosilicon derivatives, alumina-silica reagents, and wherein the adhesive coating has a thickness of about 0.1 μm to about 50 μm as measured on the final product. Preferably, the inert core has an adhesive coating (coating) with a thickness of about 0.5 μm to about 30 μm, more preferably, the inert core has a coating with a thickness of about 1 μm to about 25 μm.

[0012] In another aspect, the present invention is a method for preparing a core-shell adsorbent comprising a shell containing an active adsorbent material and a binder material, the shell surrounding an inert core coated with a coating material, the coated core having a coating of about 1 μm to about 25 μm thickness on the final product of the core-shell composite material (also referred to as a core-shell adsorbent).

[0013] In another aspect, the present invention is a core-shell composite adsorbent comprising a coated core for separating bulk gases in a circulating adsorbent process or for use in a circulating adsorption pre-purification process, wherein about 35 vol% to 96 vol% of the composite material is the adsorbent shell, and the coated core comprises about 4 vol% to about 65 vol% of the composite material. Preferably, the adsorbent shell comprises one or more of zeolite, alumina, silica, carbon, activated carbon, molecular organic framework (MOF), transition metal-substituted silica, zinc silicate, titanate, and mixtures thereof. More preferably, the adsorbent shell comprises one or more zeolites. The zeolite may be selected from X, LSX, Y, A, L, ZSM-5, mordenite, clinoptilolite, chalcogenite, and mixtures thereof.

[0014] In another aspect, the present invention is a core-shell composite material, wherein the shell comprises a zeolite having a SiO2 / Al2O3 ratio of about 1.9 to 10, and wherein the zeolite contains a cation selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof. Preferably, the core-shell adsorbent contains a zeolite, wherein the zeolite is LiX or LiLSX, wherein the degree of Li exchange is greater than or equal to 90% on an equivalent basis.

[0015] In another aspect, the core-shell composite material comprises a shell containing approximately 0% to 12% by weight of a binder; the binder (if present) is selected from clay, alumina, silica, alumina-silica reagent, and hydroxides, wherein the hydroxides, upon calcination, become one or more of alumina-silica, silica, and alumina. The core-shell composite material contains an inert core comprising approximately 4% to approximately 65% ​​by volume of the composite adsorbent. The inert core has a porosity of approximately 0% to less than or equal to 5% and a porosity greater than or equal to 3 J / cm³. 3 Volumetric heat capacity at -°K.

[0016] In another aspect of the invention, the core-shell composite material is used in a circulating gas separation method for separating at least two gaseous components with different adsorption properties from a gaseous mixture. The method includes feeding the gaseous mixture into an adsorption container containing the core-shell composite adsorbent, wherein the composite adsorbent preferentially adsorbs one component of the gaseous mixture and separates it from the unadsorbed component that passes through the adsorbent container as a recovered product. The separation is performed by vacuum swing adsorption, pressure swing adsorption, or pressure swing adsorption. The recovered product may be oxygen, hydrogen, helium, nitrogen, carbon dioxide, or purified air. Attached Figure Description

[0017] Figure 1 This is a simplified flowchart of the manufacturing process for preparing coated core-shell composite adsorbent products.

[0018] Figure 2 shows SEM images of bauxite beads: (a) uncoated, (b) coated, (c) coated bauxite trench wall, and (d) elemental diagrams of Si (dark gray) and Al (light gray).

[0019] Figure 3 shows SEM images of silica sand particles: (a) uncoated, (b) coated, (c) coated silica sand trench walls, and (d) elemental diagrams of Si (light gray) and Al (dark gray).

[0020] Figure 4 shows cross-sectional SEM images of (a) core-shell beads prepared with coated bauxite cores and (b) core-shell beads prepared with uncoated bauxite cores.

[0021] Figure 5 This is a high-magnification SEM image of a core-shell bead prepared using the core-coating method (the present invention), with thickness measurement points marked.

[0022] Figure 6 This is a graph showing the size distribution of product particles prepared with and without a core coating. Detailed Implementation

[0023] As described above, the present invention relates to an improved core-shell adsorbent made using an inert core with an adhesive coating. Core-shell adsorbent technology described in the art faces the problem of insufficient adhesion of the shell component to the core, leading to abrasion and fracturing of the adsorbent particles. To minimize fracturing / abrasion losses, focus has been placed on adding a binder as part of the shell composition to enhance the core-shell agglomerates formed using the inert core starting material. The present invention provides an alternative to increasing the amount of binder material in the core-shell adsorbent, wherein the inert core is coated with an adhesive to improve adhesion before the application of the shell material, and the resulting core-shell adsorbent exhibits commercially acceptable abrasion and fracturing resistance properties.

[0024] Figure 1 This is a simplified block diagram of a manufacturing process for preparing a core-shell composite material (core-shell adsorbent). In process step 100, a shell formulation is prepared. The shell formulation comprises at least one active adsorbent material, at least one binder material, and optional additives. In process step 200, a coated inert core is prepared. The coated inert core comprises an inert core material having a predefined composition and properties, such as porosity, density, and thermal conductivity. In process step 200, an adhesive is used to form an adhesive coating, also referred to as a coating layer, on the outer surface of the inert core. In process step 300, a core-shell agglomerate is prepared. The components used in process step 300 include the shell formulation from process step 100 and the coated core prepared in process step 200. Process step 300 is performed such that the shell-containing shell formulation grows on the coated core to form a coated core-shell agglomerate of a predetermined size. In the coated core-shell agglomerate, the shell grows on the coated inert core. In process step 400, the coated core-shell agglomerate (green agglomerate) formed in process step 300 is heated at a low temperature sufficient to remove moisture and / or any solvent used in previous steps to form a dried agglomerate. The dried agglomerate may be treated in optional process step 500 to alter the composition of the agglomerate. Examples of optional treatments include chemical digestion, ion exchange, etc., to alter the composition. Depending on whether optional process step 500 is performed, the dried agglomerate or treated agglomerate may be calcined in process step 600 to form a coated core-shell composite adsorbent, also known as a coated core-shell adsorbent, and subsequently, in step 700, the coated core-shell adsorbent product of a predetermined size is recovered. Known process steps can be used ( Figure 1 (Not shown) The product is further processed and packaged for use in industrial-scale gas separation and / or gas purification processes. The core-shell adsorbent product contains an oxide-containing adhesive coating derived from the coating material used in process step 200. The thickness of this adhesive coating on the inert core in the product can be determined by the following cross-sectional SEM method.

[0025] Cross-sectional SEM method

[0026] Scanning electron microscopy (SEM) instruments and methods are well known and have been used in the art for imaging adsorbent materials (see Chao et al., U.S. Patent No. 6,425,940, and Kikkinides et al., Adsorption (2014) 20, 5-20 DOI 10.1007 / s10450-013-9544-1). See also Goldstein et al., Textbook Scanning Electron Microscopy and X-ray Microanalysis, 2nd Edition, 1994, Plenum Press, New York and London, ISBN: 0-306-44175-6 and Echlin's Handbook of Sample Preparation for Scanning Electron Microscopy and X-Ray Microanalysis, Springer, 2009, ISBN: 978-0-387-85730-5, provide detailed descriptions of each aspect.

[0027] The cross-sectional SEM method described herein includes the following steps: sample preparation (a) to (d), SEM image acquisition (e) and coating thickness measurement (f).

[0028] a. Prepare samples impregnated with epoxy resin.

[0029] b. Grind and polish the epoxy-impregnated sample to produce a cross-section of the sample for imaging.

[0030] c. Plasma etching of the sample's cross-section to remove any debris.

[0031] d. The cross-section of the sputter-coated sample after plasma etching.

[0032] e. Obtain a backscattered electron SEM image in the desired field of view, showing the core, coating, and shell components.

[0033] f. Measure the coating thickness at four or more locations on the SEM image and calculate the average coating thickness.

[0034] Steps (a) and (b) involve impregnating the sample with epoxy resin and grinding / polishing to create a cross-section. .

[0035] Samples used for cross-sectional SEM methods are prepared by impregnating agglomerated particles with a low-viscosity epoxy resin, followed by grinding and polishing the epoxy-impregnated samples to expose the cross-section of the particles, approximately at the midpoint of the particles. A representative method for epoxy impregnation, grinding, and polishing is described in the publication of Kjellsen et al. (Knut O. Kjellsen et al., “Preparation of flat-polished specimens for SEM-backscattered electron imaging and X-Ray microanalysis – importance of epoxy impregnation”, Cement and Concrete Research (2003) 33: 611 – 616, DOI:10.1016 / S0008-8846(02)01029-3, Elsevier). The aim of this stage of sample preparation is to essentially eliminate defects (e.g., pores, cracks) in the sample for high-resolution SEM imaging.

[0036] Step (c) Plasma etching of cross-sectional sample

[0037] Once the epoxy-impregnated sample has been sufficiently polished, a low-temperature oxygen plasma treatment is used to etch the polished sample surface. The purpose of oxygen plasma etching is to remove any volatile components, thereby achieving a clearer SEM image. A representative method for oxygen plasma etching is described in the publication of Isabell et al. (Thomas C. Isabell et al., “Plasma cleaning and its applications for electron microscopy”, Microscopy and Microanalysis (1999) 5: 126 – 135, DOI: 10.1017 / S1431927699000094, Oxford Academic).

[0038] Step (d) Sputter coating of the cross section

[0039] Finally, before collecting SEM data, the sample is coated with a metal by sputtering to reduce the charge in the SEM instrument. Representative methods for sputtering coating are described in Chapter 11 of the Echlin textbook. In the examples presented here, platinum is the metal chosen for sputtering.

[0040] The sputter-coated samples were then mounted on a SEM to record images at the core-shell interface and to obtain core-coating thickness measurements from these representative images.

[0041] Step (e) Obtain a backscattered electron SEM image in the desired field of view, showing the core, coating, and shell components. .

[0042] Due to the relatively small thickness of the coating, a high-resolution instrument should be used to record the SEM images. A suitable instrument is the Helios 5 UC DualBeam from ThermoFisher Scientific, which has an electron beam resolution of 0.7 nm at 1 kV in backscattered electron imaging mode at the optimal working distance. For the coating thickness measurements in this paper, the accelerating voltage was 10 kV, the working distance was 4.1 mm, and the magnification was 2000x. These values ​​may need to be adjusted for different instruments, as described in the instruction manual accompanying the instrument. The magnification may also need some adjustment to achieve a suitable field of view. If the coating thickness is 1 μm or greater, a field of view of 200 to 250 μm is required to capture part of the shell, the core, and all coated areas in the SEM image. If the coating thickness is less than 1 μm, the magnification should be increased to obtain a field of view of 20 to 25 μm. At this higher magnification, part of the core, the shell, and all the coating must still be visible in the image. The coating thickness can be estimated using calculation methods, and this can help guide the magnification requirements for coating imaging and measurement of average thickness.

[0043] In backscattered electron mode, up to three agglomerates should be imaged, and each image should be sized. The criteria for selecting these three agglomerates for imaging and sizing are as follows:

[0044] i. The particle size is close to the average particle size of the adsorbent particles. The average particle size is determined by sieving using a US mesh sieve.

[0045] ii. The core is visible and has no obvious defects, such as “holes” or “cracks” from the grinding and / or polishing process.

[0046] iii. For up to three agglomerated particles, the core, shell, and coating materials are visible.

[0047] The selection process for agglomerated particles involves first observing the entire particle at low magnification, where the full cross-sectional diameter of the particle is visible, to confirm compliance with criteria (i) and (ii), and then obtaining an image at higher magnification to confirm compliance with criterion (iii). The required magnification is discussed above based on the field of view for different coating thickness ranges. The coating will be located near the core and identified by morphological differences relative to the core and shell and / or by porosity differences, wherein the porosity of the coated region is lower than that of the adsorbent shell region, which is further away from the core and located behind the coating.

[0048] f. Perform thickness measurements and calculate the average coating thickness. .

[0049] After identifying the coating and selecting an image with the desired field of view (200 to 250 micrometers or 20 to 25 micrometers, see above), select at least four measurement points for coating thickness measurement. The four measurement points should be spaced apart along the core surface. If the coating appears uneven (thickness variation greater than ±25% in four initial thickness measurements), additional measurement points (up to 10) should be used, and an average thickness calculation should be performed using additional particles (up to 3). The number of additional thickness measurements is stopped once the average thickness calculated from the continuous thickness measurements converges to ±5%. For each thickness measurement, a line perpendicular to the core surface and starting from the core surface is extended outwards until it contacts the point where the coating ends and only the shell region begins. This process is repeated for other measurement points. The length of the measurement line is then compared to a scale bar on the SEM image to obtain a thickness value in micrometers. Each individual thickness value is then averaged to provide an average coating thickness in micrometers. This measurement task can be easily performed using SEM analysis software such as ImageJ from the National Institutes of Health and the Laboratory for Optical and Computational Instrumentation. These software programs offer an option to measure the distance between two specified points in an SEM image. As shown above, the first point should be selected at the core surface, and the second point should be selected at the point where the coating ends and only the shell region begins.

[0050] Coated inert core

[0051] The inert cores of this invention typically have a total porosity greater than zero but less than or equal to about 10%, or less than or equal to about 5% in another embodiment. Porosity is defined as the non-solid or pore volume fraction, i.e., pore volume / total volume. Since porosity is a volume ratio, it is dimensionless and is typically reported as a fraction or percentage. The porosity described in this invention is measured using the well-known Hg porosimetry method (see, for example, Chapter 4 of PA Webb and C. Orr, “Analytical Methods in Fine Particle Technology,” 1997, 1st edition, 2nd printing, ISBN 0-9656783-0-X). The contact angle used for Hg porosimetry measurements is 135°. Other data collection parameters for Hg porosimetry measurements are provided in Table 4.1 of the textbook. Preferred low-porosity inert core materials (also known as dense cores) are cores that are substantially non-reactive and do not adsorb chemicals of interest under the operating conditions of gas separation or purification processes. These include, but are not limited to, dense ceramics, proppants, sand (preferably materials known as quartz or silica sand), bauxite, cordierite, analcime, hematite, magnetite, granite, marble, dolomite limestone, shale, and mixtures thereof. In one embodiment, the preferred core comprises bauxite or silica sand.

[0052] The inert core is also selected based on its volumetric heat capacity in order to control the known thermal gradient present in the adsorbent bed. Not wanting to be bound by theory, it is believed that by selecting a heat capacity value greater than 0.8 J / cm³ for the core-shell adsorbent, [further details can be found]. 3 An inert and non-porous core with a core temperature of -°K (volume heat capacity of the core) can improve the performance of the adsorption process, more specifically, the performance of vacuum switching adsorption (VSA), pressure swing adsorption (VPSA), and pressure swing adsorption (PSA). Another benefit of core-shell adsorbents compared to adsorbent particles of the same size made solely of shell material without a core can be improved adsorption and / or desorption kinetics. Unwilling to be bound by theory, the presence of a core reduces the path length for fluid diffusion into and out of the adsorbent material, thereby improving kinetics.

[0053] It should be recognized that excessive addition of the core reduces the adsorption capacity of the core-shell adsorbent beyond the capacity increase achievable by controlling the thermal gradient and / or by improving adsorption / desorption kinetics. Therefore, it is desirable to use materials with the highest possible volumetric heat capacity for the inert core without replacing too much adsorbent material to maximize the dynamic working capacity of the core-shell adsorbent. The heat capacity of the material should be determined using a standard reference under operating conditions. The American National Standards Institute (ANSI) is an example of such a reference. If the core material is a composite material, the heat capacity can be calculated according to accepted conventions. Typical temperatures for the operating applications of interest are 200°K to 500°K.

[0054] A suitable core should not have an abnormal density. Density is defined as the mass per volume of a substance, usually expressed in g / cm³. 3 or kg / m 3 As density increases, processing and transportation costs during material manufacturing, the cost of loading the adsorbent in the container, and the container structure cost all increase. This begins to offset the benefits of higher recovery rates and may ultimately be replaced by other options that improve recovery rates at the expense of cost. Preferred cores will have a density of less than approximately 6 g / cm³. 3 In another embodiment, less than about 5 g / cm 3 The density.

[0055]

[0056] The main inventive feature of this invention is the use of a coated core to achieve better shell-to-core adhesion without relying on the use of increased amounts of binder. The use of large amounts of binder (where large means 15% by weight or more, and typically 18% by weight or more) has been a solution to this problem regarding compositions using uncoated cores. Binders are intended to ensure the cohesion of agglomerated particles, typically in the form of beads, pellets, and extrusions. However, binders do not have significant adsorption properties compared to adsorbent materials, and their sole function is to impart sufficient mechanical strength to the agglomerated particles to withstand the harsh conditions of deployment in packed bed adsorption systems and the vibrations and stresses they experience during specific adsorption processes, such as pressurization and depressurization. The inventors have surprisingly discovered that a coating applied to an inert core produces a superior core-shell material with high performance and a low fracturing percentage at minimal binder dosage. Not wishing to be bound by theory, this coating provides a better interface between the core and shell, reducing the “micro-gaps” that may exist in this region of the core-shell particles, thereby producing a superior core-shell material with high performance and a low fracturing percentage at minimal binder dosage.

[0057] Adhesive coating materials

[0058] The coating material and adhesive can be inorganic or substantially inorganic, or become inorganic or substantially inorganic during the manufacturing process. An adhesive coating is applied to the core particle, and a shell grows on the coated core particle to form a core-shell agglomerate, also known as a coated core-shell composite. Examples of adhesive coating materials include clay, alumina, silica, silicone-derived reagents, and alumina-silica reagents, including hydroxides that, upon calcination, become alumina-silica or silica or alumina, and help provide adhesion of the shell material to the core. In one embodiment, a silicone-derived material is used to coat the inert core of the present invention. These materials can also be used as adhesives in some shell formulations. Organosilicones have the general formula [R₂SiO]ₙ, where "n" refers to the 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, Pieńkowska, Krystyna, Journal of pharmaceutical and biomedical analysis, 200 (7), 58, September 10, 2011). Preferred organosilicones have an "n" value between 10 and 1000, where R is one or more organic side groups selected from C1 to C8 organic compounds, preferably C1 to C4 organic compounds (including linear, branched, and cyclic compounds or mixtures thereof), and wherein the polymeric or oligomeric organosilicones are typically end-capped by hydroxyl, methoxy, ethoxy, or mixtures thereof. Organosilicones of interest typically have a molecular weight ranging from about 100 to greater than 500. The R side group can also represent other organic groups, such as vinyl or trifluoropropyl, and a wide range of organosilicones are believed to be available for use in this invention.

[0059] Examples of organosilicones include, but are not limited to, polydimethylsiloxanes and polydiphenylsiloxanes, such as those identified by Chemical Abstracts Service (CAS) Registry Nos. 63148-62-9 and 63148-59-4, and those having a dimethyl group in polymeric form with methyl or octylsilsesquioxanes, such as CAS Registry No. 897393-56-5 (available from Dow Corning under the name IE 2404); methylsilsesquioxanes, such as CAS Registry No. 68554-66-5; and (2,4,4-trimethylpentyl)triethoxysilanes, such as CAS Registry No. 35435-21-3. Preferred organosilicones are selected from hydroxyl, methoxy, or ethoxy-terminated polymeric dimethylsiloxanes or mixtures thereof with methylsilsesquioxanes, octylsilsesquioxanes, methyloctylsilsesquioxanes, or mixtures thereof.

[0060] More than one type of silicone can be used, and silicone can be used in conjunction with other organic or inorganic compounds. Common additional components include water, copolymer stabilizers, emulsifiers, and surfactants, and silicone emulsions and suspensions can be used as precursors for silicone binders. These additional components are typically used to stabilize a specific form of silicone, which is typically used in the form of an emulsion, solution, or resin. The amount of adhesive coating material on the core should be sufficient to coat the core to achieve a thickness of about 0.1 μm to about 50 μm in the final product; in another embodiment, about 0.5 μm to about 30 μm; in yet another embodiment, 1 μm to about 25 μm. The adsorbent shell, the adsorbent material, can be grown on the resulting coated core to form a coated core-shell green agglomerate, which, after further processing, can be used as a coated core-shell adsorbent product in adsorption gas separation applications.

[0061] The inert core volume is 4% to 65% of the total volume of agglomerated particles, with the preferred core volume set according to the dynamic capacity requirements of the application. Typically, for bulk separation where the main adsorbed component is present in the feed at a concentration of 5% by volume or higher, the required core volume will be less than about 30%, and can be as low as 4%. For purification where the contaminant is present at less than 5% by volume, the core volume can be greater than 30% up to about 65%. The average particle size of the coated core-shell composite product should be in the range of 0.4 mm to 5.0 mm. For a given gas separation or purification application, the average particle size of the product is determined by the specific application requirements and tolerances. In addition to the dynamic capacity discussed above, these requirements and tolerances include, but are not limited to, the required adsorption / desorption kinetics, acceptable system pressure drop, and fluidization avoidance for some bed configurations.

[0062] In one embodiment, the coated inert core of the present invention typically has a porosity of 0% to at most 10% and a porosity greater than 0.8 J / cm². 3- °K volumetric heat capacity. An adhesive coating material is applied to the outer surface of the inert core to form an adhesive coating with a thickness of about 0.1 μm to about 50 μm in the final product. The coating material is inorganic or substantially inorganic, or becomes inorganic or substantially inorganic during the manufacturing process, and the coating exists as at least a partial layer and preferably as a whole layer on the core and between the core and shell materials. For some coating and shell materials, the coating may not be completely separated from the core and shell, but some shell components may be encapsulated within the coating layer, and the migration of the coating material into the shell can extend the thickness of the area where the coating mainly resides.

[0063] The coated inert core of the present invention, also known as a coated core, is typically made by placing an inert core of appropriate size in an inclined rotary drum mixer with sufficient internal working volume and stirring at an appropriate speed, while adding the required amount of coating material using a suitable device (e.g., a sprayer, plastic pipette) to uniformly coat the inert core. Ideally, the coating step should be completed within approximately 10 to 30 minutes to form the desired coated core particles.

[0064] To design the amount of adhesive coating to be used and estimate the resulting thickness, calculations can be performed. The calculation method requires the following inputs: core diameter (in mm), core density (in g / cm³). 3 (Calculated), total core mass used (in g), coating oxide content fraction and coating density (in g / cm³) 3 (Calculation). After obtaining these inputs, perform the calculations using the following steps. In this specification, coating liquid refers to coating material, and silica coating refers to an oxide-containing coating on the core after calcination in an oxygen-containing atmosphere.

[0065] 1. Use 4 / 3 × π × (core radius) 3 Determine in mm 3 The volume of each core is calculated, where the core radius is in mm.

[0066] 2. Use (in mm) 3 Calculate the mass of each core in gm by multiplying the volume of each core by the core density by 1000, where the core density is expressed as gm / cm³. 3 .

[0067] 3. Calculate the total number of core particles to be used for the total core mass using (core mass) ÷ (mass of each core particle), where both masses are in gm.

[0068] 4. Calculate the mass of the silica coating per core particle in gm using (mass of coating liquid) × (silica content of coating liquid) ÷ (total number of core particles), where mass is in gm and silica content is a fraction.

[0069] 5. Mass of silica coating per core particle (in gm) × 1000 ÷ (in gm / cm³) 3 The density of the silica coating (calculated in mm) is calculated. 3 The volume of the silica coating on each core particle is calculated.

[0070] 6. Calculate the total volume of the core and coating using (volume of each core) + (volume of the silica coating), where all volumes are in mm. 3 count.

[0071] 7. Calculate the cube of the radius using (total volume with silica coating × 3) ÷ (4 × π).

[0072] 8. Calculate the radius of the silica-coated core in mm using the cube root of the cube of the radius.

[0073] 9. Calculate the thickness of the silica coating in micrometers using {(total radius of the silica coating) - (core radius)} × 1000, where both radii are in millimeters.

[0074] Calculations were performed for two different core materials (bauxite and silica sand) and two different adhesive coatings. The coating chosen for bauxite was organosilicon-derived, presumably transforming into the silica phase upon calcination, while the coating chosen for silica sand was alumina. Table 2 provides the results from these calculations for both different core materials. Table 2 summarizes the calculation inputs, core properties, coating properties, and calculated thicknesses. The results from these calculations indicate that, using the cores and coating amounts in Table 2, coated cores with thicknesses ranging from the expected 1 μm to 25 μm were obtained.

[0075]

[0076] Based on the design calculations summarized in Table 2, two different coated inert cores were experimentally prepared to demonstrate that different types of coated cores can be formed using different coating materials. In one preparation, 400 g of 14x16 mesh (0.7 mm average diameter) bauxite (obtained from Agsco) was used as the inert core. 2405 silicone resin (4 g) was slowly added as an adhesive coating material over a 2-minute period to coat the bauxite balls. During this time, the coated bauxite was subjected to shallow tray drying (…). Figure 1Process step 400), followed by calcination (process step 600). The drying and calcination processes were completed in a General Signal Blue M electric oven under 200 scfh of dry air purging (dew point at least -80℉). The material was spread on a stainless steel mesh tray (maximum thickness 0.5 mm) and heated from room temperature to 600°C over a 270-minute period, held at 600°C for 30 minutes, and then cooled. The oven temperature was lowered to 400°C, and a heat packing process was used, in which the material was removed from the oven at the temperature and packaged and sealed in dry glass jars. In another preparation, a different coating material was used, namely a 20% Al2O3 colloidal dispersion in water (purchased from Fischer Scientific), as the adhesive coating material, and a different core type, silica sand (12×16 US mesh particle size, average particle size 1.43 mm, purchased from Agsco). 150 g (150 g) of 12×16 US mesh silica sand was placed in a 12” diameter rotary disc granulator and stirred at 30 rpm. Under the rotation of the silica sand, alumina (20% colloidal dispersion in water) adhesive coating material was added dropwise over a 15-minute period. A total of 4.2 g of colloidal alumina reagent was added. At this point, the coated silica sand particles are recovered from the disc granulator and calcined using the same equipment, methods, and parameters as the coated bauxite particles, i.e., calcined at 600°C in a General Signal Company Blue M electric oven under dry air purging.

[0077] For comparative purposes, uncoated bauxite particles and uncoated silica sand particles were calcined at 600°C using the same equipment and methods as coated bauxite particles and coated silica sand particles.

[0078] This resulted in two distinct coated cores without an adsorbent shell: bauxite-coated core particles and silica sand-coated core particles. This was intended to produce samples for SEM imaging, where the goal was to image the presence of the adsorbent coating and to obtain coating thickness and composition measurements using a combination of focused ion beam (FIB) and elemental mapping. Prior to SEM imaging, a platinum coating was applied to the particles to be imaged to reduce charge effects in the SEM instrument.

[0079] Scanning electron microscopy (SEM) images of the outer region / surface of the coated inert core particles were obtained using a Thermo Fisher Scios Dualbeam microscope with a variable pressure chamber, employing both secondary and backscattered electron modes, and were obtained using Oxford X-max microscopes. N 150mm 2 Energy dispersive spectroscopy (EDS) is obtained using a windowed EDS detector.

[0080] SEM and EDS results of coated bauxite cores

[0081] Figure 2(a) shows a SEM image of the outer surface of the uncoated bauxite particles. The surface exhibits significant roughness, clearly visible in the image. Figure 2(b) shows a SEM image of the outer surface of the coated bauxite particles. In contrast to the image in Figure 2(a), the surface of the coated bauxite particles is much smoother. Since the only difference between the two samples is the presence or absence of a coating, the smooth surface of the coated sample is attributed to the coating itself, which fills the gaps and smooths out the sharp features present on the outer surface of the uncoated bauxite sample.

[0082] The coated bauxite sample was further analyzed below. An FIB attachment was used to ablate the area of ​​the coated bauxite core and “dig out” a trench in the surface of the coated bauxite particles, with the trench being at least 20 μm wide and approximately 40 μm deep. The SEM image shown in Figure 2(c) is an SEM image of the trench wall extending approximately 20 μm downwards from the outer surface of the coated bauxite particles. An EDS attachment was also used to obtain elemental mappings of Al and Si while the SEM images were being taken. Since the substrate is bauxite, the elemental mappings of the aluminum-rich areas confirm the location of the substrate, and since the coating is derived from a silicon-containing material, the silicon-rich areas distinguish the coated areas and their position relative to the substrate. The elemental mappings show that aluminum is located in the lower section of the trench, and silicon is only located in the upper part of the trench. This is consistent with the presence of a silica coating on top of the bauxite core. Since bauxite is primarily alumina and the coating used is primarily silica, after calcination, the identification of the silicon-rich areas corresponds to the coating, and the identification of the aluminum-rich areas corresponds to the original bauxite. The element map in Figure 2(d) shows the Si-rich region (darker color) on top of the Al-rich region (lighter color). Thickness measurements can be taken from the locations of the Si-rich and Al-rich regions. As shown in Figure 2(c), the thickness of the Si-rich region is determined at five points along the trench wall. The measurements are as follows: 7.4 μm at point 1; 5.8 μm at point 2; 7.1 μm at point 3; 11.5 μm at point 4; and 11.4 μm at point 5. Taking the average of these five measurements yields a thickness of 8.6 μm. Based on the design calculations summarized in Table 2, the estimated average coating thickness is 7.81 μm.

[0083] SEM and EDS results of coated silica sand cores

[0084] The coated and uncoated silica sand particles were analyzed using the SEM analysis equipment and methods described above. Figure 3(a) shows the surface of a representative silica sand particle. The main characteristic of the SEM image is the surface roughness of the silica sand, where numerous small silica clusters reside on the sand surface, contributing to a gravelly texture. Figure 3(b) shows an SEM image of silica sand particles coated with an alumina reagent. Clearly, the gravelly morphology of the uncoated particles has been covered by the alumina-containing coating, which imparts a different texture to the sand particles.

[0085] The coated silica sand sample is further analyzed below. An FIB attachment was used to ablate the area of ​​the coated silica sand core and "dig out" a trench in the surface of the coated silica sand particles, with the trench being at least 20 μm wide and approximately 40 μm deep. The SEM image shown in Figure 3(c) is an SEM image of the trench wall extending approximately 20 μm downwards from the outer surface of the coated silica sand particles. Since the silica sand is primarily silica and the coating used is primarily alumina, the identification of the Al-rich areas after calcination corresponds to the coating, and the identification of the Si-rich areas corresponds to the original silica sand. An EDS attachment was also used to obtain elemental mappings of Si and Al while taking the SEM images. The elemental mapping in Figure 3(d) shows the Al-rich areas (lighter colors) on top of the Si-rich areas (darker colors). Thickness measurements can be performed from the locations of the Si-rich and Al-rich areas. As shown in Figure 3(c), the thickness of the Al-rich areas is determined at the four marked points. At points 1 and 2, the coating thickness is 2.0 μm, and at points 3 and 4, the coating thickness is 2.4 μm. From these four data points, the average thickness of the alumina-derived coating on the silica sand particles was 2.2 micrometers. Based on the design calculations summarized in Table 2, the estimated average thickness was 1.02 micrometers. EDS elemental mapping confirmed the location of the coating. Since the substrate is silica sand, silicon mapping can confirm the location of the substrate, and since the coating is derived from alumina, aluminum mapping can distinguish the coating and its location relative to the substrate. The elemental mapping shows that silicon is located in the lower section of the trench, and aluminum is only located in the upper part of the trench. This is consistent with the presence of an alumina coating on top of the silica sand core.

[0086] Active adsorbent materials in shell formulations

[0087] Adsorbent types other than the exemplary LiX that can be used in the shell of the composite adsorbent of the present invention include other zeolites, alumina, silica, carbon (including activated carbon), molecular organic frameworks (MOFs) and related compositions, as well as other porous solids, including transition metal-substituted silica (e.g., zinc silicates and titanates), and mixtures thereof. The selection of zeolite types for effective air separation is preferably from the octahedral zeolite group, and especially zeolites X and Y. Particularly preferred zeolite compositions for air separation via VSA / VPSA / PSA methods are zeolites X having a SiO2 / Al2O3 ratio of less than or equal to 2.5 and including a low silica X (or SiO2 / Al2O3 = 2.0) grade. Zeolite X typically contains Na, Ca, or Li charge-balanced cations and / or mixtures thereof. Other cations are selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof. Preferred zeolite types include zeolite X, LSX, Y, A, L, ZSM-5, mordenite, clinoptilolite, chalcogenite, and mixtures thereof. For the above-described air separation method, a particularly preferred cation type is Li, wherein the degree of Li exchange, in equivalent weight, is greater than or equal to 90%, and more preferably greater than or equal to 95%. With this core-shell structure described above, both mass transfer rate and heat capacity are significantly improved. The amount of zeolite in the shell of the composite of the present invention is typically in the range of about 75 vol% to 98 vol%; in another embodiment, it is about 80 vol% to 95 vol%; and in yet another embodiment, it is about 85 vol% to 95 vol%.

[0088] In another embodiment, the adsorbent is activated carbon. Activated carbon core-shell composites can be used for hydrogen separation using PSA unit operation. The activated carbon coating represents a range of porous, largely amorphous carbonaceous materials that provide >100m... as measured by standard methods such as nitrogen BET. 2 The large internal surface area of ​​ / gm provides a high adsorption capacity for components present in the crude hydrogen feed stream. These porous amorphous carbons can be produced from precursors such as coconut shells, coal, wood, and polymers using thermal activation methods. For core-shell adsorbent purposes, activated carbon powder can be used or the carbon shell component can be applied by applying the precursor and carbonizing it in a subsequent step. Core-shell adsorbents using activated carbon powder precursors are preferred because they reduce the challenges associated with high-temperature heat treatment and provide the desired higher density carbon core-shell composites.

[0089] In another embodiment, the active adsorbent is silica gel. Silica gel core-shell composites can be used for syngas purification using PSA unit operation. Silica gel represents a range of porous, largely amorphous silica materials that provide >100 μm of silica as measured by standard methods such as nitrogen BET. 2The large internal surface area of ​​ / gm provides a high adsorption capacity for components present in the crude syngas feed stream. For core-shell adsorbent purposes, silica powder or precursors can be used to apply silica.

[0090] The activated adsorbent material typically has an average particle size of at least 1 micrometer, and preferably at least 4 micrometers, to produce agglomerated particles with the pore characteristics described in this invention. Particles with an average size of less than 1 micrometer cannot be used to produce agglomerated particles with a median pore size equal to or greater than 0.45 μm and 10% or less of macropores and mesopores less than or equal to 0.1 micrometers. It is also preferred that the final agglomerated core-shell adsorbent composition (with an adhesive coating, an activated adsorbent material, and a binder core) has an average particle size ranging from 0.4 mm to 5.0 mm, and more preferably from 0.5 mm to 2.0 mm. X zeolites, including LSX types, are particularly suitable as the active component because the manufacturing process can employ heat treatment at temperatures from 400°C to approximately 700°C without degrading the zeolite.

[0091] Binder material in shell formulation

[0092] Regarding the selection of binders for inorganic adsorbents such as zeolites, silica, and alumina, binders are preferably selected from the group including, but not limited to, clay, alumina, silica, organosilicon-derived reagents, and alumina-silica reagents, including usable hydroxides that, upon calcination, transform into alumina-silica and help impart sufficient physical strength to the product composite adsorbent for use. For organic adsorbents and / or adsorbents requiring calcination at 350°C or lower, preferred binders include pitch and tar-based binders, polymeric organic compounds (including cellulose, polyvinyl alcohol, and related compounds), and mixtures thereof.

[0093] The specific binder and its concentration affect the final pore structure of the agglomerated particles, thereby affecting the properties of the adsorbent. It is known that the binder concentration should be as low as possible to reduce mass transfer resistance, which can be negatively affected by excess binder present in the pores. Certain binder materials can be used as temporary binders and processing aids. Therefore, the composition range of the binder is determined based on the minimum amount of binder required to achieve the desired crushing strength and / or abrasion / crack resistance for use. The amount of binder in the composite material of the present invention is typically from about 0 wt% to about 12 wt%; in another embodiment, from about 0 wt% to about 10 wt%, and in yet another embodiment, from about 0 wt% to about 7 wt%. The preferred composition range of the binder has been determined based on the desired crushing strength and abrasion / crack resistance for use in the cyclic adsorption process.

[0094] Additives in shell formulations

[0095] Some shell formulations may require the use of processing additives. Depending on the formulation, these processing additives may be added at different stages of the manufacturing process. For formulations with a preferred low binder dosage, a common problem is the poor green strength of the resulting core-shell agglomerates, where the term green refers to the uncalcined state, and thus green strength refers to the physical properties (crushing strength, fracturing resistance) of the core-shell agglomerates before calcination. If the green strength is low, there is a risk of increased agglomerate breakage and / or excessive yield loss. In these cases, it is preferable to use shell formulations containing a temporary binder as an additive to increase green strength. An example of a suitable temporary binder is methylcellulose (usually labeled as methocel). A key characteristic of these processing additives is that they are not present in the final core-shell adsorbent composition. Removal typically occurs during the calcination step, where these additives are removed by combustion using high temperatures and oxygen-containing gases such as air. Another example of an additive is a wetting agent, such as Flexiwet. This additive is used in conjunction with formulations containing hydrophobic components. If these formulations containing hydrophobic components require aqueous processes, such as ion exchange, their hydrophobicity is detrimental. The use of wetting agents can overcome hydrophobicity and improve the efficiency of any aqueous processing step. In this case, Flexiwet is added to the agglomerated particles at the beginning of the aqueous processing step. After the aqueous processing is completed, a washing process can remove Flexiwet from the final core-shell composite product. The aforementioned combustion process can also be used for this purpose.

[0096] In a preferred embodiment, the invention includes an improved core-shell adsorbent comprising: a porosity of 0% to at most 10% and a porosity greater than 0.8 J / cm³. 3 A coated inert core with a volumetric heat capacity of -°K, wherein the coated inert core is an inert core coated with an adhesive coating material. The shell material comprises 88% to 100% by weight of at least one adsorbent material and 0% to 12% by weight of at least one binder. The shell material may contain sufficient amount of a temporary binder such as Methocel to produce a core-shell agglomerate with acceptable green strength. The coated inert core accounts for about 4% to about 40% by volume of the core-shell adsorbent. The core-shell adsorbent has a particle size in the range of about 0.4 mm to 5.0 mm.

[0097] The improved composite adsorbent of the present invention typically comprises the following components in proportions specified below:

[0098] • 40% to 96% by volume of the composite adsorbent is used as the adsorbent shell.

[0099] • 0% to 12% by weight, 0% to 10% by weight in another embodiment, and 0% to 7% by weight in yet another embodiment, of the binder, together with one or more of the above-described active adsorbent materials, serve as part of the adsorbent shell during the coagulation process.

[0100] • 4% to 60% by volume of the coated core-shell adsorbent product in one embodiment, 4% to 50% by volume in another embodiment, and 4% to 40% by volume in yet another embodiment, is a coated inert core having extremely low porosity and a larger volumetric heat capacity than one or more active adsorbent materials. In one embodiment, the coated core has a porosity of less than 10%, and in another embodiment less than 5%; and a porosity greater than 0.8 J / cm³. 3 In another embodiment, the volumetric heat capacity is ≥3 J / cm³ at -°K. 3 -°K, to obtain a critical balance between performance, adsorption capacity, heat capacity and strength.

[0101] • The average particle size of the composite product is between 0.4 mm and 4.0 mm, preferably the same as or larger than the particle size used in conventional VSA / VPSA / PSA processes.

[0102] The improved composite adsorbent of the present invention can have the following advantages:

[0103] • The core-shell composite adsorbent product is less than or equal to 5% by weight, in another embodiment ≤ 2.5% by weight, and in yet another embodiment ≤ 1% by weight of fracturing loss to ensure good physical strength.

[0104] • Compared to one or more adsorbents prepared with the same binder content as the shell and with the same average particle size in the absence of a core, the VSA / VPSA / PSA working capacity (measured by circulating bed size factor) achieved with such core-shell composites is 1% to 20% higher. This improvement in working capacity is based on model data comparing the adsorbents of this invention with adsorbents having a volume ratio of 0% (without a core) to greater than 5% volume ratio.

[0105] In another embodiment, zeolite, carbon, or silica are preferred active materials, and the composite adsorbent of the present invention comprises the following components in proportions specified below:

[0106] • 75% to 95% by volume of the composite adsorbent is used as the adsorbent shell, wherein the shell contains zeolite, carbon, or silica adsorbent.

[0107] • In one embodiment, the composite adsorbent may contain 0% to 12% by weight of binder material together with zeolite, carbon or silica as part of the adsorbent shell. In another embodiment, the binder content may be 0% to 10% by weight. In yet another embodiment, the binder content may be 0% to 7% by weight.

[0108] • 5% to 25% by volume of the composite adsorbent is a coated inert core, and preferably 8% to 15% by volume of the composite adsorbent is a coated inert core, wherein the coated inert core has a porosity of less than 10% and a porosity greater than 0.8 J / cm². 3 -°K, preferably greater than 0.8J / cm 3 -°K, more preferably greater than 3.0 J / cm 3 Volumetric heat capacity at -°K.

[0109] • Composite adsorbents can have an average particle size of about 0.4 mm to less than or equal to about 2.5 mm.

[0110] • The composite adsorbent has a wear loss of less than or equal to 2% by weight, preferably less than or equal to 1% by weight, and more preferably less than or equal to 0.5% by weight, as measured on the final core-shell composite adsorbent product.

[0111] Due to its higher heat capacity than that of typical conventional composite materials of the same type, the core-shell composite adsorbent of the present invention (which contains an adsorbent shell surrounding an inert core coated with an adhesive coating) can better control the unfavorable temperature gradients that occur during adsorption and desorption, respectively.

[0112] The invention will now be illustrated by the following non-limiting embodiments.

[0113] Example 1: Core-shell adsorbent coating using 20x30 US mesh bauxite proppant as an inert core

[0114] refer to Figure 1In process step 100, 30,000 g dry weight (37,942 g wet weight) of zeolite LSX powder with an average crystal size between 3 and 4 micrometers, 2,258 g dry weight (2,888 g wet weight) of Actigel-208 clay, and 750 g of Methocel A4M were placed in a plow mixer and mixed at 240 rpm for 15 minutes. Subsequently, 9,000 g of water was pumped in at a rate of 180 ml / min with stirring. At the end of the addition, mixing was continued for 15 minutes. The mixed powder product, hereinafter referred to as "Formulation," was removed and temporarily placed in a container and sealed therein. In process step 200, 7500 g of 20x30 US mesh bauxite proppant (obtained from Agsco) with an average particle size of 0.7 mm was placed in a 32” diameter rotary disc granulator and stirred at 60 rpm. 51.0 g of Dow Chemicals 2405 silicone resin (adhesive coating material) was slowly added over a 3-minute period to coat the bauxite proppant. After the coating step was completed, process step 300 was initiated by slowly spraying water into the granulator while gradually adding the formulation. The combination of water and formulation addition allowed the beads to form and grow. The growth step was controlled to achieve 12×16 To maximize the yield of US mesh size beads, all formulations and 6870.0 g of water were added to a rotating disc over a 540-minute period. The product beads were then subjected to process step 400, air-drying in an oven at 90°C for 180 minutes. No optional treatment, i.e., process step 500, was performed. Shallow tray drying (process step 400) and calcination (process step 600) were performed using a General Signal Company Blue refractory material equipped with a dry air purging device. M electric drying oven. The adsorbent is spread in a stainless steel mesh tray to provide a thin layer (approximately 0.5 inches). During drying, 200 SCFH of dry air is supplied to the oven. The temperature is increased from 90°C to 600°C over a 660-minute period (approximate heating rate = 0.77°C / min) and held at this temperature for 60 minutes, after which the product beads are packaged into sealable glass jars using a heat-packing method. According to the heat-packing method, the oven temperature is gradually reduced to approximately 400°C, and once this temperature is reached, the product beads are directly packaged into pre-dried glass jars and sealed by replacing and securing the lids.

[0115] Example 2: Core-shell adsorption using 20x30 US mesh bauxite proppant as an inert core without an adhesive coating Agent

[0116] Following the procedure described above in Example 1, except that no action is taken from... Figure 1 Core-coating in process step 200. The products from Examples 1 and 2 were analyzed by cross-sectional SEM to obtain representative images and the coating thickness of the sample from Example 1 was measured.

[0117] SEM images at different magnifications were recorded using a Thermo Fisher Helios 5 UC Dualbeam instrument (with an electron beam resolution of 0.7 nm at 1 kV and optimal working distance) in backscattered electron mode. Figures 4(a) and 4(b) provide representative images of the coated core-shell product cross-section and the uncoated equivalent, respectively. In both images, we have a field of view of approximately 207 μm, within which both the core and shell components are visible. In the leftmost part of the image, discrete microcrystals forming the active shell material are visible, and in the rightmost part of the image, some sintered bauxite blocks forming the core are also clearly visible. For the sample where the core is coated, there is no significant gap between the core and shell, and the shell appears to be attached to the core. Conversely, for the sample where no adhesive coating is used, there is a noticeable gap between the core and shell. The scale bar on these SEM images is 40 μm, which was used to measure the size of the gap, yielding values ​​of approximately 10 to 20 μm. At higher magnifications ( Figure 5 The presence of an adhesive coating (“a colloidal material with a different morphology from the bauxite core and zeolite microcrystal shell”) is visible in the region closest to the core. This adhesive coating encapsulates the first few layers of the adsorbent microcrystals and helps them adhere to the bauxite surface. Figure 5 ). In such Figure 5 Thickness measurements were taken at the four locations shown. At measurement point 1, the thickness was 12.3 μm; at measurement point 2, the thickness was 13.1 μm; at measurement point 3, the thickness was 13.1 μm; and at measurement point 4, the thickness was 10.4 μm. The average thickness of these four data points was 12.2 μm. The coated sample was subjected to a fracturing test using a Rotap device and five US penny coins, and the result was an excellent value of 0.04% by weight.

[0118] Example 3: Core-shell adsorbent coating using 14x16 US mesh bauxite proppant as an inert core

[0119] refer to Figure 1In process step 100, 1000 g dry weight (1264.7 g wet weight) of zeolite LSX powder with an average crystal size between 3 and 4 micrometers, 75.4 g Actigel-208 clay (96.3 g wet weight), and 25.0 g Methocel A4M were placed in a Hobart mixer and mixed at low speed for 30 minutes. Subsequently, 75 g of water was pumped in at a rate of 15 ml / min with stirring. At the end of the addition, mixing was continued for 15 minutes. The mixed powder product, hereinafter referred to as "Formulation," was removed and temporarily placed in a container and sealed. In process step 200, 400 g of 14x16 US mesh bauxite proppant (obtained from Agsco) with an average particle size of 1.3 mm was placed in a 12” diameter rotary disc granulator and stirred at 30 rpm. 4.0 g of Dow Chemicals 2405 silicone resin was slowly added over a 2-minute period to coat the bauxite proppant. After the coating step was completed, process step 300 was initiated by slowly spraying water into the granulator while gradually adding the formulation. The combination of water and formulation additions allowed the beads to form and grow. The growth step was controlled to achieve 6×14... The yield of US mesh size beads was maximized. However, based on the size determination results of the adsorbent product from process step 700 summarized below, this shaping resulted in some oversized and undersized beads, with all product particle sizes ranging from 3.5 × 16 mesh. In total, 1256.0 g of formulation and 391.0 g of water were added to the rotating disc over a 90-minute period. The product beads were then subjected to process step 400, air-dried overnight before oven drying. No optional treatment, i.e., process step 500, was performed. Shallow tray drying (process step 400) and calcination (process step 600) were performed using a General Signal Company Blue refractory material equipped with a dry air purging device. M electric drying oven. The adsorbent is spread in a stainless steel mesh tray to provide a thin layer (approximately 0.5 inches). During drying, 200 SCFH of dry air is supplied to the oven. The temperature is increased from 20°C to 600°C over a 270-minute period (approximate heating rate = 2.15°C / min) and held at this temperature for 30 minutes, after which the product beads are packaged into sealable glass jars using a heat-packing method. According to the heat-packing method, the oven temperature is gradually reduced to approximately 400°C, and once this temperature is reached, the product beads are directly packaged into pre-dried glass jars and sealed by replacing and securing the lids.

[0120] Example 4: Core-shell adsorption using 14x16 US mesh bauxite proppant as an inert core without an adhesive coating Agent

[0121] Except for the absence of an adhesive coating material in process step 200, the preparation used the same raw materials, quantities, equipment, processing methods, and time as in Example 3. The products from Examples 3 and 4 were characterized using the dimensional and fracturing test methods described below.

[0122] Size distribution of the products in Examples 3 and 4:

[0123] Product particles from Examples 3 and 4 were prepared in a manner that demonstrates the effect of the adhesive coating on particle growth, and were thus run in both examples to observe the size distribution obtained by processing the same formulation with and without the adhesive coating. There was no effort to direct the formulation toward a specific size target and optimize the yield at that size target, as is typical in commercial processing practices.

[0124] The product particles from Examples 3 and 4 were sieved using a Rotap apparatus equipped with 8” diameter US mesh sieves listed in Table 3. Following the Rotap sieving method, the sieves were ordered from largest to smallest aperture, and 100g of material was added to the topmost sieve before stirring the contents. To prevent any particles from being lost from the apparatus, a tray was placed under a 16-mesh sieve, and a 3.5-mesh sieve was sealed with a lid. The particles were stirred in the Rotap for 15 minutes. The material captured by each individual sieve was weighed, and the percentage of the total was calculated. The results are summarized in Table 3 and illustrated in Figure 3.

[0125]

[0126] It is important to note that the products from Examples 3 and 4 were prepared using the same forming method, formulation, equipment, and time, except that an adhesive coating material was used to coat the core in Example 3. These experiments were intentionally run comparatively and to demonstrate the effect of using a coated core during manufacturing and how this also leads to improved final product properties. There is a very large difference in particle size distribution between Example 3 (with an adhesive coating) and Example 4 (without a coating). The average particle size of Example 3, calculated from the data in Table 3, is 2.28 mm, and the average particle size of Example 4 is 2.67 mm. Particle size distribution from Example 3 (see Table 3). Figure 6 The distribution is closer to the desired normal distribution, with a single peak maximum at 2.18 mm, close to the average value, where the particles are distributed around this average value. In the case of Example 4, the distribution is wider and closer to bimodal, with two distinct peak maximums at 1.55 mm and 3.03 mm, respectively, which bisect the average value. From an adsorption perspective, bimodality and a wider distribution are undesirable; therefore, from the perspective of packaging and adsorption properties, particles of similar size are preferred.

[0127] Not wanting to be bound by theory, the bimodal distribution in Example 4 likely stems from a common problem in core-shell particle agglomeration, where some particles struggle to form and grow, while others grow excessively. The use of a coated core in Example 3 overcomes this problem by making each core more likely to accept formulation and grow in a more controlled and uniform manner. Achieving better particle size distribution in conventional forming processes is one example of the benefits of using the coated core described herein.

[0128] Fracturing properties of core-shell adsorbent products from Examples 3 and 4 :

[0129] For any core-shell material (where the core is substantially inactive and the shell contains active material), a crucial property is the fracturing and loss-prone nature of the shell material. As a result, we developed a test designed to measure the amount of fracturing material from a given sample. The test principle involves stirring the adsorbent particles, subsequently recovering and quantifying the amount of fractured-fractured material. More specifically, the test involves pre-sieving each sample to the desired starting size range using conventional sieving methods and a US mesh sieve. The pre-sieved material is calcined in dry air at 600°C. Calcination is performed using a General Signal Company Blue M electric oven and method as described in Example 3. After calcination, 100g of sample is placed with five US pennies on a special sieve with slit-shaped orifices instead of regular square orifices. The reason for using the slit-shaped orifice type of sieve is to allow “half-moon” shaped and other related shapes to pass through the sieve, while these types of fractured particles would remain on a regular sieve with square orifices. The slotted screen was then placed in a Rotap screen vibrator and sealed inside using a top cover and a bottom disc. The cover and disc prevented loss from the device during the agitation phase. The intensity of the test was increased by using 5 US pence to provide an additional means of damaging the particles (e.g., through contact with a moving pence). The agitation time was 5 minutes. After agitation, the amount of material retained on the slotted screen was measured, and the percentage loss relative to the original mass of material added to the screen was determined. To measure the fracturing properties of the products from Examples 3 and 4, the following experimental parameters were used:

[0130] • The products from Examples 3 and 4 were sieved into 12×14 US mesh and 8×12 US mesh sizes, respectively. Then, as described above, the two sieved grades of each example were calcined separately at 600°C.

[0131] • For both 12×14 US mesh and 8×12 US mesh initial material sizes, the Rotap mixing step uses a 14 US mesh slotted screen from Retsch. This slotted screen has an 8-inch diameter and 1.4mm × 20mm slot dimensions. Multiple slots are present throughout the screen to allow broken fragments to pass through. In each case, the material retained on the 14 US mesh slotted screen is considered intact, and the material that passes through the screen is counted as fracturing material.

[0132] The fracturing results summarized in Table 4 show a considerable difference between the products of Example 3 and Example 4 at particle sizes of 12×14 (approximately 1.55 mm) and 8×12 (approximately 2.00 mm). At the smaller 12×14 US mesh size, even minor breakage can produce at least one particle with a slit diameter less than 1.4 mm, and the use of a slit screen ensures that even these slightly damaged particles can pass through the screen. The results for the Example 4 (uncoated) material in Table 4 show that for the initial 12×14 US mesh size, only 0.7% of the original material remained on the slit screen, therefore 99.3% of the material was fractured during the test. In contrast, for the Example 3 (coated core) material, 64.2% remained intact for the initial 12×14 mesh particles. For the larger 8×12 US mesh initial beads, a greater amount of intact material was observed for both coated and uncoated products (from Examples 3 and 4), but the difference between the two materials remained significant. For the coated core prepared in Example 3, 79.5% of the 8×12 mesh was intact after the fracturing test, compared to 16.6% for the material in Example 4, in which no coating was used.

[0133]

[0134] The results show that, compared to particles prepared without any interfacial coating between the core and shell, particles of equivalent size are less likely to fracture when prepared using an adhesive coating. Not wanting to be bound by theory, we believe that adhesive coatings contribute to the production of better beads in several ways, resulting in a more robust product. Better growth and size distribution achieved using adhesive coatings produce beads with more consistent physical properties. Furthermore, adhesive coatings can help reduce and / or prevent the formation of gaps between the core and shell. These “microgaps” can become weaknesses where impacts or pressures in these areas can lead to fracture.

[0135] Adsorption separation applications

[0136] This invention also relates to a core-shell composite adsorbent comprising the coated core of this invention, and the use of said core-shell composite adsorbent in optimized VSA / VPSA / PSA bed designs, wherein the specific adsorbent capacity of the VSA / VPSA / PSA bed for adsorbing pollutants is significantly increased and an increased cycle time is allowed. Compared to the prior art, this allows the VSA / VPSA / PSA system to operate with an increased adsorption cycle time at the same purge rate. Furthermore, the cycle time can be extended without a significant decrease in permissible flow rate. Therefore, the frequency of venting is reduced, thereby reducing total exhaust losses, and compression power is also significantly reduced.

[0137] The benefits of higher mass transfer rates have been well-documented, and the benefits of higher heat capacity produced by VSA / VPSA / PSA are independently demonstrated by the introduction of a solid core. This invention is built upon the identification of preferred performance characteristics in real-world environments. Due to the remarkably preferred range of core volume percentage from approximately 5% to 40%, this inexpensive core-shell composite material significantly improves VSA / VPSA / PSA performance while exhibiting unparalleled abrasion / cracking resistance and low commercial manufacturing costs. A core volume percentage of approximately 5% to 40% corresponds to a diameter ratio of approximately 37% to 78%.

[0138] Numerous compositions and manufacturing processes are known in the art for preparing adsorbents for air separation processes and / or for hydrocarbon processing. The primary method for adsorbent formation is disc granulation using accretion disks. A challenge in the development and commercialization of advanced adsorbents is balancing physical and adsorption properties. Materials with higher crushing rates tend to have lower physical strength, as measured by crushing strength and abrasion / fracture rates.

[0139] The term composite material is used herein to refer to agglomerated particles containing at least one adsorbent and optionally at least one binder that form a shell around a non-porous inert core. In this invention, the inert core is coated with a material that enhances the adhesion of the shell to the coated inert core.

[0140] Composite adsorbents are easily distinguishable from adsorbent mixtures because the aforementioned components exist within individual aggregated particles and are combined during the adsorbent manufacturing process, and are not physically mixed or blended together thereafter. In this invention, composite adsorbent compositions for VSA / VPSA / PSA processes are described, wherein one or more adsorbents are selected and blended together, and coated / aggregated onto a non-porous inert core (such as bauxite or sand) and calcined to prepare composite particles.

[0141] The composite material of the present invention is suitable for use in any bulk VSA / VPSA / PSA production process for recovering products such as oxygen, hydrogen, helium, nitrogen, carbon dioxide, and purified air. A preferred adsorbent design for oxygen production systems is a two- to three-layer system, wherein a desiccant (preferably 13X) is positioned at the feed end of the bed and designed to remove substantially all incoming moisture and potentially some or all of the incoming carbon dioxide. Subsequently, a new composite adsorbent is positioned as a second discontinuous layer and can remove N2 more efficiently, as described herein. A third layer can be obtained by separating the second layer by size, wherein there are larger particles at the feed end and smaller particles at the product end. Bulk gas is generally defined as containing more than 5% by volume of the gas to be adsorbed. For O2 VPSA / VSA / PSA systems, the use of layered beds comprising a first layer of adsorbent (such as 13X or silica gel or alumina) followed by a second layer of N2 selective adsorbent (such as LiX or LiLSX zeolite or CaX or CaLSX zeolite) is commonly known in the art. Carbon and zeolite are known for their use in H2 PSA to remove N2, CH4, and CO, as are silica gels in syngas purifiers. The primary purpose of the first layer, located near the feed inlet, is to remove most of the H2O from the feed, although some contaminants can also be removed through co-adsorption in areas with lower H2O loading. The second zeolite-containing layer aims to remove most of the remaining contaminants. This invention further relates to improvements in the second or subsequent adsorbent layers.

[0142] VSA / VPSA / PSA cycles typically use two or more beds to ensure feed continuity. The typical steps in the cycle are as follows: (1) adsorption (feed) at high pressure to produce products / provide purging, (2) equilibration with a second bed, (3) countercurrent venting (exhausting) to low pressure, (4) countercurrent purging with a relatively impurity-free gas, (5) pressurization equilibration with another bed, and (6) repressurization to high pressure with feed air or purified air. Therefore, adsorbent regeneration in the VSA / VPSA / PSA process is achieved through a combination of simple depressurization and purging with a low-impurity product gas. Even at the end of the regeneration steps, a considerable amount of residual impurity adsorbent load remains on the adsorbent. The difference between the adsorbent bed load at the end of the feed step and the adsorbent bed load at the end of the purging step is called the operating capacity. This dynamic load is a function of various operating conditions (such as feed and purging pressures, temperature, and purging rate) and also depends on the selectivity and capacity of the adsorbent. Claims (as amended under Article 19 of the Treaty) 1. A core-shell adsorbent comprising a coated core and an adsorbent shell surrounding the coated core, wherein the coated core has a flux density greater than 0.8 J / cm³. 3-°K heat capacity value, wherein the coated core comprises an oxide-containing adhesive coating, wherein after calcination of the adsorbent, the oxide-containing adhesive coating has an average thickness of about 0.1 μm to about 50 μm as measured by cross-sectional SEM, and wherein the adsorbent shell comprises one or more of zeolite, alumina, silica, carbon, activated carbon, molecular organic framework (MOF), transition metal-substituted silica, zinc silicate, titanate, and mixtures thereof. 2. The core-shell adsorbent according to claim 1, wherein the oxide-containing coating is derived from one or more of clay, alumina, silica, organosilicon derivatives, and alumina-silica reagents. 3. The core-shell adsorbent according to claim 2, wherein after calcination of the adsorbent, the oxide-containing adhesive coating has an average thickness of about 1 μm to about 25 μm. 4. The core-shell adsorbent according to claim 1, wherein the coated core has a porosity of about 0% to about 10% as determined by the Hg porosity determination method. 5. The core-shell adsorbent according to claim 5, wherein the zeolite is selected from X, LSX, Y, A, L, ZSM-5, mordenite, clinoptilolite, chalcogenite, and mixtures thereof. 6. The core-shell adsorbent according to claim 5, wherein the zeolite has a SiO2 / Al2O3 ratio of about 1.9 to 10, and wherein the zeolite contains cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof. 7. The core-shell adsorbent according to claim 5, wherein the adsorbent is LiX or LiLSX, wherein the degree of Li exchange is greater than or equal to 90% in equivalent terms. 8. The core-shell adsorbent of claim 5, wherein the adsorbent shell comprises about 0% to about 12% by weight of a binder. 9. The core-shell adsorbent according to claim 9, wherein the binder is selected from clay, alumina, silica, alumina-silica reagent and hydroxide, wherein the hydroxide becomes alumina-silica after calcination. 10. The core-shell adsorbent according to claim 5, wherein the core-shell adsorbent is used for bulk phase separation of gases, and wherein the core volume ratio of the adsorbent is about 4% to about 25%. 11. The core-shell adsorbent according to claim 5, wherein the core-shell adsorbent is used for the pre-purification of gas, and wherein the core volume ratio of the adsorbent is from about 25% to about 65%. 12. A circulating gas separation method for separating at least two gaseous components with different adsorption properties from a gaseous mixture, the method comprising feeding the gaseous mixture into an adsorption container containing an adsorbent according to claim 5, wherein the adsorbent preferentially adsorbs one component of the gaseous mixture, thereby separating it from the unadsorbed component that passes through the adsorbent container as a recovery product. 13. The method according to claim 13, wherein the separation is performed by vacuum adsorption, vacuum pressure swing adsorption, or pressure swing adsorption. 14. The method of claim 13, wherein the recovered product is oxygen, hydrogen, helium, nitrogen, carbon dioxide, or purified air. 15. The method of claim 13, wherein the adsorbent shell comprises about 35% to 96% of the adsorbent by volume, and wherein the average core volume ratio of the coated core to the adsorbent ranges from about 4% to about 65%. 16. The method of claim 16, wherein the method is used for bulk phase separation of gases, wherein the core volume ratio of the adsorbent is from about 4% to about 25%. 17. The method of claim 16, wherein the method is used for the pre-purification of a gas, wherein the core volume ratio of the adsorbent is from about 25% to about 65%. 18. A method for preparing a core-shell adsorbent comprising a coated core, the method comprising: a. The core is coated with one or more of clay, alumina, silica, organosilicon derivatives, and alumina-silica reagents to form a coated core; b. Contacting the coated core with an adsorbent shell formulation comprising an adsorbent material, about 0% to about 12% by weight of a binder, water, and optional processing additives to form an adsorbent shell surrounding the coated core, thereby obtaining a green core-shell adsorbent, wherein the adsorbent shell comprises one or more of zeolite, alumina, silica, carbon, activated carbon, molecular organic framework (MOF), transition metal-substituted silica, zinc silicate, titanate, and mixtures thereof; and c. Calcining the green core-shell adsorbent to obtain the final adsorbent product; The coated core has a strength greater than 0.8 J / cm². 3 -°K of heat capacity, and wherein, after calcination of the green core-shell adsorbent, the coating on the core has an average thickness of about 0.1 μm to about 50 μm as measured by cross-sectional SEM. 19. The method of claim 19, wherein the zeolite is selected from X, LSX, Y, A, L, ZSM-5, mordenite, clinoptilolite, chalcogenite, and mixtures thereof. 20. The method of claim 20, wherein the zeolite has a SiO2 / Al2O3 ratio of about 1.9 to 10, and wherein the zeolite contains cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof. 21. The method of claim 21, wherein the adsorbent is LiX or LiLSX, wherein the degree of Li exchange is greater than or equal to 90% in equivalent terms. 22. The method of claim 18, wherein the binder is selected from clay, alumina, silica, alumina-silica reagent, and hydroxide, wherein the hydroxide is converted into alumina-silica after calcination. 23. The method of claim 18, wherein the core is inert and has a porosity of about 0% to about 10% as determined by Hg porosity determination.

Claims

1. A core-shell adsorbent comprising a coated core and an adsorbent shell surrounding the coated core, wherein the coated core has a volumetric heat capacity value greater than 0.8 J / cm 3 °K, wherein the coated core comprises an oxide-containing adhesion coating, wherein the oxide-containing adhesion coating has an average thickness of about 0.1 pm to about 50 pm as measured by cross-sectional SEM method after calcination of the adsorbent.

2. The core-shell adsorbent of claim 1, wherein the oxide-containing coating is derived from one or more of clay, alumina, silica, organosilicon derived materials, alumina-silica reagents.

3. The core-shell adsorbent of claim 2, wherein the oxide-containing adherent coating has an average thickness of about 1 μιη to about 25 μιη after calcination of the adsorbent.

4. The core-shell adsorbent of claim 1, wherein the coated core has a porosity of about 0% to about 10% as determined by Hg porosimetry.

5. The core-shell adsorbent of claim 1, wherein the adsorbent shell comprises one or more of zeolite, alumina, silica, carbon, activated carbon, molecular organic frameworks (MOF), transition metal substituted silica, zincosilicate, titanosilicate, and mixtures thereof.

6. The core-shell adsorbent of claim 5, wherein the zeolite is selected from X, LSX, Y, A, L, ZSM-5, mordenite, stilbite, chabazite, and mixtures thereof.

7. The core-shell adsorbent of claim 5, wherein the zeolite has a Si02 / AI203 ratio of about 1.9 to 10, and wherein the zeolite contains cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof.

8. The core-shell adsorbent of claim 5, wherein the adsorbent is LiX or LiLSX, wherein the degree of Li exchange is greater than or equal to 90% on an equivalent basis.

9. The core-shell adsorbent of claim 5, wherein the adsorbent shell comprises about 0 wt% to about 12 wt% of a binder.

10. The core-shell adsorbent of claim 9, wherein the binder is selected from clay, alumina, silica, alumina-silica reagents, and hydroxides that become alumina-silica upon calcination.

11. The core-shell adsorbent of claim 5, for use in bulk separation of gases, wherein the core volume ratio of the adsorbent is about 4% to about 25%.

12. The core-shell adsorbent of claim 5, for use in pre-purification of gases, wherein the core volume ratio of the adsorbent is about 25% to about 65%.

13. A cyclic gas separation process for separating at least two gaseous components having different adsorption characteristics from a gaseous mixture, the process comprising feeding the gaseous mixture to an adsorption vessel comprising the adsorbent of claim 5, wherein the adsorbent preferentially adsorbs one component of the gaseous mixture, thereby separating it from the unadsorbed components passing through the adsorbent vessel as a recovery product.

14. The process of claim 13, wherein the separation is by vacuum swing adsorption, vacuum swing pressure adsorption, or pressure swing adsorption.

15. The process of claim 13, wherein the recovery product is oxygen, hydrogen, helium, nitrogen, carbon dioxide, purified air.

16. The method of claim 13, wherein the adsorbent shell comprises about 35% to 96% by volume of the adsorbent, and wherein the average core to adsorbent volume ratio of the coated core to the adsorbent ranges from about 4% to about 65%.

17. The method of claim 16, for bulk separation of gases, wherein the core volume ratio of the adsorbent is about 4% to about 25%.

18. The method of claim 16, for pre-purification of gases, wherein the core volume ratio of the adsorbent is about 25% to about 65%.

19. A method of making a core-shell adsorbent comprising a coated core, the method comprising: a. coating the core with one or more of a clay, an alumina, a silica, an organosilicon derived material, an alumina-silica reagent, thereby forming a coated core; b. contacting the coated core with an adsorbent shell formulation comprising an adsorbent material, about 0% to about 12% by weight of a binder, water, and optionally processing additives, thereby forming an adsorbent shell around the coated core, to obtain a green core-shell adsorbent; and c. calcining the green core-shell adsorbent so as to obtain a final adsorbent product; wherein the coated core has a volumetric heat capacity value greater than 0.8 J / cm 3 °K, and wherein after calcination of the green core-shell adsorbent, the coating on the core has an average thickness of about 0.1 μιη to about 50 μιη as measured by cross-sectional SEM method.

20. The method of claim 18, wherein the adsorbent material comprises one or more of a zeolite, an alumina, a silica, a carbon, an activated carbon, a molecular organic framework (MOF), a transition metal substituted silica, a zincosilicate, a titanosilicate, and mixtures thereof.

21. The method of claim 19, wherein the zeolite is selected from X, LSX, Y, A, L, ZSM-5, mordenite, stilbite, chabazite, and mixtures thereof.

22. The method of claim 20, wherein the zeolite has a Si02 / Al203ratio of about 1.9 to 10, and wherein the zeolite contains cations selected from H, Li, Na, K, Mg, Ca, Sr, Ba, Ag, Cu, and mixtures thereof.

23. The method of claim 21, wherein the adsorbent is LiX or LiLSX, wherein the degree of Li exchange is greater than or equal to 90% on an equivalent basis.

24. The method of claim 18, wherein the binder is selected from a clay, an alumina, a silica, an alumina-silica reagent, and a hydroxide that becomes alumina-silica upon calcination.

25. The method of claim 18, wherein the core is inert and has a porosity of about 0% to about 10% as determined by Hg porosimetry.

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