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  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
  • B01J20/16—Alumino-silicates
  • B01J20/18—Synthetic zeolitic molecular sieves
  • B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
  • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
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  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J20/28078—Pore diameter
  • B01J20/2808—Pore diameter being less than 2 nm, i.e. micropores or nanopores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/60—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the type L, as exemplified by patent document US3216789
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/7003—A-type
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
  • B01D2253/1085—Zeolites characterized by a silicon-aluminium ratio
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2256/00—Main component in the product gas stream after treatment
  • B01D2256/24—Hydrocarbons
  • B01D2256/245—Methane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/50—Carbon oxides
  • B01D2257/504—Carbon dioxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/22—After treatment, characterised by the effect to be obtained to destroy the molecular sieve structure or part thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/30—After treatment, characterised by the means used
  • B01J2229/36—Steaming
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

• the field of invention relates to zeolites. More specifically, the field relates to partially collapsed zeolites for the purification of hydrocarbon based gaseous fractions such as natural gas.
• sub-quality natural gas often has a nitrogen concentration exceeding 4 mole percent and a CO 2 concentration in a range of about 0.2 mole percent to about 1 mole percent with respect to the wellhead gas. Both nitrogen and CO 2 have no heating value and therefore reduce the thermal quality of the wellhead gas.
• CO 2 is an "acid gas" that, in the presence of water, forms carbonic acid. The resulting acid reacts rapidly with carbon steel and other metals susceptible to acidification and produces corrosion, a common problem in areas along a pipeline where pools of aqueous liquids may form.
• CO2 is normally removed during natural gas refinement and processing by the process of amine scrubbing using gas-liquid contactors operating at a temperature range of from about 323 K to about 333 K.
• the resulting (saturated) alkanolamine is regenerated in a temperature range of from about 383 K to about 403 K and releases the purified carbon dioxide.
• This energy intensive process typically involves the handling of a corrosive and toxic solvent.
• the removal of nitrogen from methane, the primary component in natural gas is very difficult.
• the only commercial process commonly used for separating nitrogen from methane is cryogenic distillation, where a turboexpander reduces the temperature of the gas to about 220 K.
• the nitrogen-poor product stream must be recompressed to transport it through pipelines effectively. Both turboexpansion and recompression are energy-intensive and therefore increase the costs associated with natural gas processing.
• Adsorption processes using zeolites are capable of performing certain CH4-CO2 and CH4-N2 separations.
• Molecular Gate ® Engelhard Corp.; Iselin, New Jersey
• ETS and CTS configurations titanosilicate-based zeolites
• Other adsorbents include carbon based molecular sieves for CH4-N2 separations.
• CMS 3A carbon molecular sieve 3A
• Zeolite 13X which is an aluminosilicate zeolite, has been shown to reduce carbon dioxide levels in flue gases at low temperatures.
• Zeolites are thermochemically stable, available in the market and their surfaces can be controlled through post- modifications such as ion-exchange.
• Zeolites have well-defined microporous structures with mean diameters in a range of from about 0.3 nanometers (nm) to about 1.5 nm, allowing a zeolite material to advantageously provide a molecular sieve type effect for separating certain unwanted constituents found in natural gas.
• titanosilicate materials two significant problems are associated with the broad use of titanosilicate materials: 1) they have lower thermal stability, so it is more difficult to use them in processes that apply thermal cycling to promote adsorption and desorption; and 2) these materials can be costly and not readily available.
• aluminosilicate-based zeolites are advantageously more commercially available and less expensive than titanosilicate-based zeolites.
• a composition in accordance with the present invention comprises a hydrolyzed, partially collapsed Linde Type A aluminosilicate zeolite, and a plurality of pores characterized by a pore aperture size of from about 0.33 nm to about 0.38 nm.
• the composition is characterized by a carbon dioxide/methane equilibrium selectivity factor in a range of about 3.8 to about 40.
• the Linde Type A aluminosilicate zeolite has a Na/Al ratio in a range of from about 0.60 to about 1.00.
• the Linde Type A aluminosilicate zeolite is hydrolyzed using deionized water.
• the deionized water is present in a phase selected from the group consisting of liquid, saturated steam and superheated steam.
• the Linde Type A aluminosilicate zeolite is decationized and calcined prior to hydrolysis.
• the Linde Type A aluminosilicate zeolite is calcined at a temperature between about 473 K and about 773 K.
• the composition is operable at a temperature in a range of between about 273 K and about 323 K and a pressure in a range of between about 1 bar and about 8 bars.
• the composition further comprises one or more cations selected from sodium, ammonium and combinations thereof.
• the invention relates to a method for synthesizing an amorphous adsorbent material capable of purifying a gas fraction comprising combining at least a stoichiometric amount of a compound comprising at least one exchangeable cation with a stoichiometric amount of a sodium Linde Type A aluminosilicate zeolite compound under temperature and pressure conditions suitable for promoting cation exchange between the compound comprising at least one exchangeable cation and the sodium Linde Type A aluminosilicate zeolite compound; isolating the Linde Type A aluminosilicate zeolite compound comprising the exchangeable cation; calcinating the Linde Type A aluminosilicate zeolite compound comprising the exchangeable cation under conditions such that the Linde Type A aluminosilicate zeolite compound undergoes at least a partial structural collapse and the exchangeable cation is removed to form a calcinated
• the compound comprising at least one exchangeable cation is ammonium nitrate.
• the calcination step is performed at a temperature in a range of about 473 K to about 773 K and at a pressure in a range of about 1 bar to about 8 bars, preferably at a pressure of about 1 bar.
• the invention relates to a method for purifying a natural gas fraction comprising the steps of introducing a natural gas fraction into a vessel containing the composition of claim 1, where the introduced natural gas is a non- upgraded natural gas comprising non-combustible gases and where the amorphous adsorbent is characterized by a carbon dioxide/methane equilibrium selectivity factor in a range of about 3.8 to about 40; contacting the natural gas fraction with the composition of claim 1 ; and maintaining the natural gas fraction in the vessel containing the composition of claim 1 for a sufficient time such that the concentrations of the non- combustible gases are reduced in the natural gas fraction.
• the non-upgraded natural gas fraction may refer to a natural gas fraction that is previously unrefined, previously unprocessed, incompletely refined or incompletely processed.
• a highly selective, ultra-small pore amorphous adsorbent composition in accordance with the present invention is useful for upgrading a sub-quality natural gas.
• the amorphous adsorbent of gaseous contaminants at operating conditions selectively removes at least a portion of contaminants including but not limited to nitrogen and carbon dioxide from the natural gas introduced to it, thereby upgrading the quality of the natural gas for downstream users.
• the adsorbent material is amorphous and allows for higher hydrothermal stability, e.g. in systems that apply thermal cycling as part of an adsorption/desorption process. The use of repeated thermal variations over time in such processes does not modify the pore structure.
• the amorphous adsorbent is advantageously environmentally friendly and non-toxic, unlike many commercially available salt- and solvent-based removal systems.
• Figure 1A shows X-ray diffraction (XRD) patterns for a Linde Type A zeolite ("Reference”) and Samples 1 through 5;
• Figure IB shows X-ray diffraction (XRD) patterns for a Linde Type A zeolite ("Reference”) and Samples 6 through 10;
• Figure 2A shows CO 2 and CH 4 equilibrium gas adsorption capacity plots for a Linde Type A zeolite ("Reference") and Samples 1 through 5 at a temperature (7) of 323 K and a pressure (P) of 8 bars;
• Figure 3 shows CO 2 and CH 4 gas adsorption isotherms for a Linde Type A zeolite ("Reference") and Samples 6 through 10;
• decationize and its conjugated forms such as “decationization”, refers to the process of removing an electrostatically coordinated or adventitiously associated cation from a material. While in no way limiting the context of the present invention to any particular methodology or physicochemical process, decationization may be performed using chemical and/or thermal treatment, including but not limited to solvent washing or solvation as well as heating a composition under conditions capable of thermally evolving a cation such as calcination.
• the term "operable” and its conjugated forms should be interpreted to mean fit for its proper functioning and able to be used for its intended use.
• the term “maintain” and its conjugated forms should be interpreted to mean conditions capable of causing or enabling a condition or situation to continue.
• the term “detect” and its conjugated forms should be interpreted to mean the identification of the presence or existence of a characteristic or property.
• the term “determine” and its conjugated forms should be interpreted to mean the ascertainment or establishment through analysis or calculation of a characteristic or property.
• the interval encompasses each intervening value between the upper limit and the lower limit as well as the upper limit and the lower limit.
• the invention encompasses and bounds smaller ranges of the interval subject to any specific exclusion provided.
• a method comprising two or more defined steps is referenced herein, the defined steps can be carried out in any order or simultaneously except where the context expressly excludes that possibility.
• the present invention relates to a method for using the controlled structural collapse of a crystalline aluminosilicate zeolite to form a highly selective, ultra-small pore size amorphous adsorbent.
• NaA is known to have a high gas adsorption capacity but a low selectivity for heterogeneous gas fractions including those of 1) methane and CO 2 ; and 2) methane and N 2 .
• the method for forming the amorphous adsorbent includes ion-exchange, calcination and liquid H 2 0 treatment (under ambient or heated conditions) of the precursor to irreversibly transform the crystalline aluminosilicate zeolite with a small pore size into the highly selective, ultra-small pore size amorphous adsorbent.
• the liquid H 2 0 treatment of the precursor may be replaced with steam treatment, including superheated steam.
• the resulting composition can adsorb natural gas components under moderate temperature and elevated pressure conditions such that a greater-than-expected selectivity for CO 2 over methane occurs. Under similar conditions, a higher selectivity for N 2 over methane would likewise occur.
• the starting material for the formation of the highly selective, ultra-small pore amorphous adsorbent composition of the present invention is NaA.
• the zeolite is typically synthesized using hydrothermal crystallization techniques from a synthesis gel composition comprising stoichiometric ratios of (3- 4)Na 2 O:Al 2 O 3 :(1.8-3.0)SiO 2 :(50-200)H 2 O, where the parenthetical values represent stoichiometric ranges for each of the chemical components.
• ⁇ average crystal diameter size of 1-3 micrometers
• XRD X-ray diffraction
• the highly selective, ultra-small pore amorphous adsorbent composition of the present invention may be formed by initially reacting an ion-exchange material having an exchangeable cation with an aluminosilicate zeolite having a cation, for instance NaA, such that the cationic exchange results in an ion-exchanged zeolite.
• a higher degree of (thermodynamically driven) cation exchange correlates to a greater degree of structural collapse to produce the amorphous form of the crystalline zeolite during the subsequent calcination step.
• the degree of cation exchange is dependent on both the temperature and the cation concentration in the ion-exchange material.
• the “cation/ Al ratio” is the stoichiometric ratio of the exchangeable zeolite cation to aluminum in the zeolite.
• a sodium aluminosilicate zeolite such as NaA is expressed as a "Na/Al ratio”.
• the ratio will be reduced as the (zeolite) cation is exchanged for the (ion-exchange material) cation.
• concentrations of the cation of the ion-exchange material result in higher cation exchange with the crystalline zeolite.
• the resulting exchanged cation/Al ratio may be lower than expected due to factors including but not limited to transport phenomenon effects inside the crystalline zeolite.
• the exchangeable cation of the ion-exchange material is an ammonium (NH 4 + ) ion.
• NH 4 + ammonium
• the Na/Al ratio will decrease with an increased degree of NH 4 + substitution for the Na + cation of the crystalline zeolite.
• the amorphous adsorbent has a Na/Al ratio in a range of from about 0.60 to about 1.00. In further embodiments, the amorphous adsorbent has a Na/Al ratio in a range of from about 0.60 to about 0.77.
• the method of forming the highly selective, ultra-small pore amorphous adsorbent composition of the present invention includes calcinating the ion-exchanged zeolite at a calcination temperature such that the ion-exchanged zeolite partially collapses and forms a decationized adsorbent.
• the steps of cation exchange and subsequent calcination such that at least some of the positive ion is removed from the ion-exchanged zeolite are collectively referred to as the "decationization" of the zeolite. Decationization is characterized by the partial collapse of the crystalline zeolite into an amorphous, unstructured material.
• the structural portions of the amorphous adsorbent composition where the cation exchange occurs are irreversibly degraded.
• the cation-exchanged zeolite may begin collapsing at temperatures greater than about 373 K.
• the calcination temperature is in a range of from about 473 K to about 773 K, for instance about 673 K.
• thermally collapsing a sodium aluminosilicate zeolite such as NaA in the absence of cation exchange requires high calcination temperatures, for example temperatures greater than about 973 K.
• the resulting collapsed zeolite structure is non-porous and therefore unsuitable for performing molecular separations.
• the cation used in the ion-exchange material is an ammonium ion ( ⁇ 4 + ). While not limited the present invention to any particular theory, it is believed that calcination of the ion-exchanged zeolite causes the NH 4 + ion to thermally degrade into ammonia (NH 3 ) and a hydrogen ion (H + ). The resulting ammonia evolves from the collapsing zeolite, while the hydrogen ion is integrated into the partially-collapsed zeolite structure. The degree of structural collapse during decationization correlates to the degree of cation exchange that occurs.
• a method for forming a highly selective, ultra-small pore amorphous adsorbent composition of the present invention includes introducing water to the decationized adsorbent such that the decationized adsorbent collapses to form the composition.
• Treatment of the decationized adsorbent with water (H 2 O) having no significant mineral, salt or free ion content was found to enhance the structural collapse of the decationized adsorbent by degradation of the silicon/aluminum based structure, while the cation exchange and the calcination steps remove residual (non-ammonium) cations with large atomic radii in the crystalline zeolite material.
• Si/Al ratio refers to the molecular ratio of silicon to aluminum in compositions such as zeolites and compositions of the present invention.
• the Si/Al ratio in the original zeolite is about 1.00.
• the Si/Al ratio of the amorphous adsorbent composition of the present invention is in a range of from about 1.00 to about 1.03.
• the original crystalline zeolite framework collapses and forms an amorphous adsorbent composition in accordance with the present invention.
• the degree of structural collapse can be controlled at each step by the degree of cation exchange in the crystalline zeolite, the extent of decationization during calcination, and the hydrolysis of susceptible silicon-aluminum bonds.
• the methods described herein transform cation-bearing aluminosilicate zeolites such as sodium aluminosilicate zeolites with small pores apertures (less than 4 A), into aluminosilicate based materials characterized by enhanced density and increased amorphous domains.
• the resulting dense, amorphous structure advantageously restricts diffusion to molecules with small diameters, including but not limited to H 2 (2.89 A), H 2 0 (2.7 A), C0 2 (3.3 A), 0 2 (3.46 A), N 2 (3.64 A), Ar (3.3 A) and CH 4 (3.8 A).
• the pore aperture size of the claimed composition allows the adsorption of contaminant gases while restricting the adsorption of methane.
• a highly selective, ultra-small pore amorphous adsorbent composition in accordance with the present invention has a pore aperture size in a range of from about 0.33 nm to about 0.38 nm.
• the composition has carbon dioxide/methane equilibrium selectivity factor in a range of from about 3.8 to about 40 at a temperature of about 323 K and a pressure of about 8 bars.
• the amorphous adsorbent cannot revert back to a Linde Type A structure.
• the structural configuration of titanium-based zeolites like ETS-1 and CTS-1 can rearrange with temperature and/or pressure variations and alter the adsorption properties of these zeolites drastically and unpredictably.
• the amorphous adsorbent compositions of the present invention advantageously retain their adsorptive properties under the variable and wide ranging temperatures and pressures that often characterize chemical separation processes, including conditions associated with gas adsorption/desorption systems.
• the present invention relates to methods for improving the quality of a natural gas fraction or stream comprising introducing the natural gas fraction or stream into a vessel comprising a highly selective, ultra-small pore amorphous adsorbent composition such as those described herein.
• the method includes maintaining the natural gas fraction or stream in the vessel for a sufficient amount of time such that the natural gas contacts the amorphous adsorbent to produce a purified natural gas.
• the natural gas fraction or stream may or may not be previously refined or purified.
• the natural gas fraction or stream is a non-upgraded natural gas comprising a first mole percent of carbon dioxide that, in certain embodiments, are converted in an upgraded natural gas fraction or stream with a second mole percent of carbon dioxide using the methods described herein.
• the first mole percent of carbon dioxide is greater than the second mole percent of carbon dioxide.
• the methods for improving the quality of a natural gas fraction or stream are characterized by a residence time in a range of about two minutes to about 30 minutes.
• Samples 1 through 5 are decationized materials that have been treated using ion- exchange and calcination procedures, while Samples 6 through 10 are five ultra- small pore amorphous adsorbents that have been treated with water following calcination.
• the Reference Sample (described as "Reference” in Figures 1A through 4B) is the zeolite precursor material used to synthesize Samples 1 through 10. The samples were synthesized using the same procedure for each of Samples 1 through 10 except for variations in the concentrations of ammonium nitrate (NH 4 NO 3 ).
• Each sample was synthesized by initially suspending 1 gram of the sodium Linde Type A (NaA) zeolite in 20 mL of NH 4 NO 3 solution at the various molar concentrations given in Table 1. The resulting suspension was stirred for six hours at room temperature to form ion- exchanged zeolite precursors, where the ammonium (NH 4 + ) ion substitutes for the sodium (Na + ) ion to varying degrees based upon the ammonium nitrate concentration. The precursors are collected by filtration, washed with deionized water followed by acetone, and dried at 333 K for 24 hours.
• NaA sodium Linde Type A
• the dried, ion-exchanged zeolite precursors are then calcined in a plug-flow reactor under flowing dry air (25 mL/minute) at 673 K (temperature ramp: 1 K minute) for 2 hours to produce Samples 1 through 5.
• An additional fraction of 1 gram calcined precursors were stirred in 300 mL room temperature water (H 2 0) for 6 hours, collected by filtration, washed with deionized water and dried at 373 K for 24 hours to produce Samples 6 through 10.
• Table 1 Ammonium nitrate concentrations used for the synthesis of and the resulting elemental analysis ratios for the Reference Sample and Samples 1 through 10 as determined via ICP-AES.
• Figure 2A shows CO 2 and CH 4 equilibrium gas adsorption capacity isotherms for the Reference Sample ("Reference") and Samples 1-5 at a temperature of 323 K and a pressure of 8 bars.
• the observed CO 2 and the CH 4 gas adsorption capacities did not significantly change despite extensive decationization. This result indicates that, while NH 4 + exchange followed by calcination can lead to the decationization of the zeolite precursors, the resulting pore structure collapse and pore size narrowing are not significant.
• Samples 6-10 demonstrated decreasing amounts of gas adsorption (both CO 2 and CH 4 ) which correlates to decreases in each sample's Na/Al ratio while inversely correlating to the NH 4 N0 3 concentration used to manufacture Samples 6-10 (Table 1).
• the observed gas adsorption decreases may be attributable to the structural transformation of the crystalline zeolite precursor into the amorphous adsorbent composition during the decationization and water treatment procedures.
• Figure 4A shows a graph of both the CO 2 and CH 4 equilibrium gas adsorption capacities for the Reference Sample ("Reference") and Samples 1 through 10 at a temperature of 323 K and a pressure of 8 bars.
• the gas adsorption capacity for carbon dioxide and methane at a pressure of 8 bars was determined using the values provided in Figure 3.
• the results herein demonstrate that CO 2 and the CH 4 adsorption capacities decrease as the zeolite structural collapse becomes more extensive with the corresponding increase in ammonium nitrate (NK 1 NO 3 ) concentration in the ion- exchange material.
• Sample 10 was synthesized using the highest concentration of NH 4 N0 3 (0.42 M) and did not demonstrate any significant methane adsorption.
• Figure 4B shows CC> 2 /CH 4 equilibrium selectivity factors for the Reference Sample ("Reference") and Samples 6 through 10 as well as the percentage of remaining CO 2 capacity for the Reference Sample (“Reference”) and Samples 6 through 10 at a temperature of 323 K and a pressure of 8 bars.
• the values used to calculate the selectivity factors for CO 2 and CH 4 at the disclosed pressure were determined using the gas adsorption capacity values for both carbon dioxide and methane in Figure 4A. As described above, Sample 10 does not demonstrate any significant methane adsorption, and consequently demonstrated an undefined (infinite) CO 2 /CK 1 equilibrium selectivity factor.
• Sample 6 produced a CO 2 /CK 1 equilibrium selectivity factor in a range of about 3.8 to about 10 with a CO 2 gas adsorption capacity.
• Sample 6 exhibited about 90% to about 95% of the adsorption value produced by the Reference Sample.
• Samples 7 and 8 demonstrated equilibrium selectivity factors in a range of about 10 to about 20.
• Sample 8 exhibited significant CO 2 gas adsorption capacity (equilibrium selectivity factor of about 50 to about 60) in comparison with the Reference Sample.
• Sample 9 produced a CO 2 /CH 4 equilibrium selectivity factor of about 35 to about 40 and a CO 2 gas adsorption capacity in a range of from about 15 % to about 20 % of the Reference Sample's capacity.
• the amorphous adsorbent advantageously is characterized by an equilibrium selectivity factor of CO 2 /CH 4 in a range of from about 3.8 to about 40, preferably in a range of from about 10 to about 40.
• the amorphous adsorbent exhibits a CO 2 gas adsorption capacity in a range of from about 15% to about 95% of the capacity of the aluminosilicate zeolite used to form the amorphous adsorbent, preferably in a range of about 15% to about 45%.
• Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

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