Abstract: A method of separating and selectively removing hydrogen contaminant from hydrogen-containing product and by-product process streams is disclosed. Separation and removal occur when certain Cd containing zeolite, silica, alumina, carbon or clay compositions are placed in contact with a hydrogen-containing process stream. A hydrogen-encapsulated composition is formed by practice of the method. Also disclosed is a reversible storage method for hydrogen using the above-described compositions.

Abstract: An improved adsorption process is provided for purifying hydrogen from a feed gas mixture including hydrogen and at least one impurity selected from the group consisting of carbon monoxide and nitrogen. The process includes providing an adsorption apparatus having a discharge end adsorption layer containing an adsorbent with a Henry's law constant (KH) at 70° F. for the impurity from about 0.5 to about 2.4 mmole/g/atm. The product gas collected from the adsorption apparatus is high purity (99.99+%) hydrogen.

Abstract: A vacuum swing adsorption process is provided for the separation of propylene from a feedstream comprising propylene and propane using an adsorbent comprising AlPO-14 to produce a high purity propylene product stream at high recovery. The vacuum swing adsorption process of the present invention can be employed in a variety of petroleum refining and petrochemical processes to purify and separate propylene from mixtures of propylene and propane alone or in combination with fractionation.

Abstract: A process is provided for the concentration and recovery of propylene from propane using an adsorbent comprising AlPO-14 at adsorption temperatures less than 120° C. and an adsorption pressure comprising a propylene partial pressure between about 0.5 bar and about 4 bar. The AlPO-14 adsorbent can be employed as a selective adsorbent for the separation of propylene from mixtures thereof with propane in vacuum swing adsorption processes, thermal swing adsorption processes, and combinations thereof. A simulated moving bed process using vacuum swing adsorption is used to remove propylene from a C3 hydrocarbon stream comprising propylene and propane and recover a high purity propylene product at a high recovery rate. The simulated moving bed vacuum swing adsorption process of the present invention can be employed in a variety of petroleum refining and petrochemical processes to purify and separate propylene from mixtures of propylene and propane alone or in combination with fractionation.

Abstract: A process is provided for the removal of trace amounts of aromatic hydrocarbons from an acid waste gas feed stream comprising sulfur compounds and the aromatic hydrocarbons. An adsorption process employing an adsorbent such as a high silica zeolite adsorbent having a framework silica-to-alumina ratio greater than about 15 and having a pore size greater than about 6.2 angstroms is used to remove from the feed gas mixture aromatic hydrocarbon contaminants and permit the recovery of a high purity sulfur product from the treated effluent stream. The use of the present invention removes aromatic hydrocarbon contaminants which are responsible for the degeneration of the performance of the downstream sulfur recovery zone.

Abstract: A process, particularly of the TSA type, for separating impurities of the nitrogen protoxide (N2O) and possibly carbon dioxide (CO2) or ethylene (C2H4) type which are contained in a gas stream, such as air. The impurities of nitrogen protoxide type are removed on a faujasite zeolite having a Si/Al ratio of 1 to 1.5 and containing from 0 to 35% of K+ cations, between 1 and 99% of Na+ cations and between 1 and 99% of Ca2+ cations, preferably at least 50% of Ca2+ cations. The separation is preferably carried out at a temperature of approximately −40° C. to +80° C., preferably at room temperature. Advantageously, the process is employed for prepurifying atmospheric air before cryogenic distillation of the air thus prepurified.

Abstract: Process for separating at least carbon dioxide (CO2) contained in a gas stream, preferably air, in which at least carbon dioxide is adsorbed on a zeolite-X having a Si/Al ratio of approximately 1 to 1.5 and containing at most 35% of K+ cations, between 1 and 99% of Na+ cations and at most 99% of Ca2+ cations. This process is carried out at a temperature ranging from −40° C. to +80° C. Optionally, impurities chosen from water vapour and hydrocarbons, particularly ethylene, are also removed. The air thus purified is then capable of being cryogenically distilled.

Abstract: A PSA or VSA process for separating a gas flow, such as air, containing at least one first gas compound, such as nitrogen, which is preferentially adsorbed on at least one adsorbent, and at least one second gas compound, such as oxygen, which is adsorbed less preferentially on at least the one adsorbent than the first gas compound. The adsorbent used comprises particles of faujasite zeolite having a Si/Al ratio <1.5, such as a LSX zeolite, and containing 80 to 99% Li+ cations, 0.01 to 25% Na+ cations, 0.01% to 10% Mg2 cations, 0.01% to 10% Ca2+ cations and 0 to 3% K+ cations.

Abstract: A PSA process for separating a gas flow, such as air, containing a first gas compound, such as nitrogen, which is adsorbed preferentially on an adsorbent, and a second gas compound, such as oxygen, which is adsorbed less preferentially on the adsorbent than the first gas compound. The adsorbent is formed by an aggregate comprising a zeolite phase and a binder, and contains elements Si, Al, Li, Na, Mg, K and Ca, the total proportions of these elements in the adsorbent being such that the Si/Al ratio is between 1 and 2.4, the Na/Li ratio is between 0.012 and 0.300, the Mg/Li ratio is between 0.012 and 0.400, the Ca/Li ratio is between 0.012 and 0.200, and the K/Li ratio is between 0.001 and 0.060.

Abstract: A method of separating and selectively removing hydrogen contaminant from hydrogen-containing product and by-product process streams is disclosed. Separation and removal occur when certain Cd-exchanged zeolite rho compositions are placed in contact with a hydrogen-containing process stream. A hydrogen-encapsulated zeolite rho composition is formed by practice of the method.

Abstract: Ethene is separated from a gas mixture containing ethane by a pressure swing adsorption process carried out at a temperature in the range of about 50 to about 200° C., wherein the adsorption step of the process is conducted by passing the gas mixture through an adsorption zone containing type A zeolite whose exchangeable cations are preferably made up of at least about 60 but not more than 75% sodium ions and more than 25 and up to about 40 percent potassium ions.

Abstract: A pressure swing adsorption process for the separation of hydrogen from a mixture of the same with methane, utilizing two separate PSA stages, one containing a nitrogen selective crystalline zeolite, and the second containing a methane selective adsorbent.

Abstract: A molecular sieve adsorbent for the purification of gas streams containing water vapor and carbon dioxide and a process for its preparation. The adsorbent is a sodium form of a low-silica faujasite having a silica to alumina ratio of about 1.8:1 to about 2.2:1, a residual content of potassium ions less than about 8.0 percent (equiv.), a low content of crystalline and amorphous admixtures and crystal sizes generally within the range of 1-4 &mgr;m, blended with a binder.

Abstract: An adsorbent for separating gases, which comprises a binder and a crystalline low-silica faujasite type zeolite with a SiO2/Al2O3 molar ratio of from 1.9 to 2.1, wherein the average pore diameter of the macropores is equal to or larger than the mean free path of an adsorbable component when desorbing the adsorbable component from the adsorbent, and at least 70% of the total volume of the macropores is occupied by macropores having a diameter equal to or larger than the mean free path of the adsorbable component.

Abstract: A process is provided for the removal of metal carbonyl from gaseous streams in the presence of hydrogen sulphide and/or water using a hydrophobic porous adsorbent with an accessible pore volume for pore sizes between 0.55 and 4 nm of at least 0.005 ml/g.

Abstract: A process for the production of a controlled supported zeolite membrane comprises: (a) forming a gel which is principally localised at the surface of a porous support by bringing it into contact, in succession, with two immiscible liquids which contain the agents necessary for formation of said gel, then (b) crystallising the zeolite from said gel and finally (c) eliminating the residual agents. The supported zeolite membranes obtained are advantageously used in continuous gas separation processes.

Abstract: A method of separating a more strongly adsorbable component from one or more less strongly adsorbable components residing in a gaseous mixture comprising contacting the gaseous mixture at elevated pressure with a composition and adsorbing the more strongly adsorbed gas specie on the composition, wherein the composition is represented by the formulaM.sup.n+.sub.(2x+y)/n [Si.sub.(2-x-y) Al.sub.(y) Zn.sub.(x) ]O.sub.4 ;whereinM is cation selected from Groups 1, 2, 7, 10, 11, 12 and the f block elements as defined by thePeriodic Table of the elements as adopted by IUPAC;n is the valence of the selected cation; M;x is greater than or equal to 0.02 but less than or equal to 1;y is a value less than or equal to 0.98; and2x+y is greater than or equal to 0.80;wherein the composition of matter has a FAU structure and zinc resides in.sub.-- tetrahedral positions in the framework of the FAU structure.

Abstract: A sorbent-based gas storage and dispensing system, including a storage and dispensing vessel containing a solid-phase physical sorbent medium having a sorbate gas physically adsorbed thereon. A chemisorbent material is provided in the vessel to chemisorb the impurities for gas phase removal thereof in the storage and dispensing vessel. Desorbed sorbate gas is discharged from the storage and dispensing vessel by a dispensing assembly coupled to the vessel. The chemisorbent may be provided in a capsule including an impurity-permeable, but sorbate gas-impermeable membrane, and installed in the vessel at the time of sorbent material loading. Semiconductor manufacturing processes and products manufactured by such processes are described.

Abstract: A method for removing trace moisture from a gas is disclosed. The method involves heating a zeolite having a high silica-to-alumina ratio to about 400.degree. C. to remove physically absorbed water from the zeolite, followed by heating the zeolite to a temperature in excess of 650.degree. C., to form a superheated zeolite. Heating to temperatures of 650.degree. C. or above is believed to cause dehydroxylation of the zeolite. A method for the preparation of a dehydroxylated zeolite is also disclosed. The superheated zeolite is contacted with the gas, thereby adsorbing water from the gas. A dehydroxylated zeolite for removing trace moisture from a gas wherein the zeolite has a high silica-to-alumina ratio and a low level of metallic impurities is also disclosed. The zeolite and methods of the invention are particularly useful for removing trace water from acid gases such as hydrogen chloride and hydrogen bromide.

Abstract: This invention relates to the manufacture of a molecular sieve adsorbent for selectively separating methane from its gaseous mixture with nitrogen. More particularly, the invention relates to the manufacture of novel molecular sieve adsorbents useful for the separation of methane-nitrogen gaseous mixture.

Abstract: The invention relates to the manufacture of novel molecular sieve adsorbents which are selective towards oxygen from its gaseous mixture with argon and/or nitrogen. More particularly, this invention relates to the manufacture of novel molecular sieve adsorbents useful for the separation of oxygen-argon-nitrogen gaseous mixture.

Abstract: A catalyzed hydrocarbon trap material washcoat (20) used in a trap (10), which may be placed downstream of a conventional catalyst member (28), is useful for treating internal combustion engine (22) exhaust. Trap (10) traps hydrocarbons during cold operation periods and releases them for oxidation during higher-temperature operating periods. The material comprises palladium and silver dispersed on a high surface area metal oxide support and a zeolite material such as one or more of ZSM-5, Beta, Y, and other suitable zeolites. The trap material is efficiently made by combining in a single vessel the zeolite, the metal oxide support, and aqueous solutions of a palladium compound and a silver compound. Surprisingly, the intimate combination of silver with the palladium does not adversely affect catalytic efficiency of the palladium and provides advantageous results in enhancing catalytic oxidation of hydrocarbons desorbed from the trap (10) and coke which forms thereon.

Abstract: A PSA process for the separation of a feed gas, for example air, containing at least one first component, such as nitrogen, and a second component, such as oxygen, by preferential adsorption of the first component at a high adsorption pressure, on at least one bed of particles of an adsorbent material and recovery of a gas flow enriched in the second component, with desorption of the first component at a low desorption pressure. The ratio (.mu./.sigma.) of the mean granulometry (.mu.) of the adsorbent particles contained in the bed, to the breadth of granulometric distribution (.sigma.) of the particles, is comprised within the range 1.5 to 15, the particles of adsorbent material being particles of zeolite, such as zeolite X or zeolite LSX, exchanged by metallic cations, preferably cations of lithium and/or calcium.

Abstract: Novel gas separation agents with precisely and predictably controlled pore sizes within the range of 3-4 Angstrom units and their preparation from ETS-4 by exchange with cations, particularly multivalent cations such as strontium followed by drying and calcination to effect controlled pore shrinkage is disclosed. These novel materials have utility in gas separation processes particularly the separation of nitrogen from a mixture of the same with methane.

Abstract: A heterogeneous adsorbent for the separation of gases, comprising particles of at least one zeolite containing at least one exchanged metal cation selected from monovalent, divalent and/or trivalent cations, the zeolite having an exchange-factor distribution of given mean having a standard deviation for the exchange-factor distribution of between about 0.3% and 5%, and a PSA, VSA or TSA process for separation of a gas flow, such as air, containing at least a first compound, such as nitrogen, which is adsorbed preferentially on the heterogeneous adsorbent, and at least a second compound, such as oxygen, which is less preferentially adsorbed on the heterogeneous adsorbent than the first compound.

Abstract: A substantially complete coating of a zeolite onto a material such as catalyst particles can be achieved by treating the material prior to or simultaneously with zeolite formation, with a polyelectrolye. Copper catalyst systems show good hydrogen storage while blocking access of hydrocarbons to the catalyst.

Abstract: Carbon dioxide is separated from gaseous hydrocarbons by a cyclic adsorption process using at a temperature in the range of about -50 to about 200.degree. C., wherein the adsorption step of the process is conducted by passing the gas mixture through an adsorption zone containing carbon molecular sieve or type A zeolite whose exchangeable cations are made up of about 50 to about 90% sodium ions and about 10 to about 50 percent potassium ions.

Abstract: For the separation of nitrogen from oxygen in air, an adsorbent is used which preferentially adsorbs the nitrogen. The adsorbent is a heterogeneous zeolite whose particles have a distribution of the capacity to adsorb nitrogen relative to oxygen, with a ratio (.sigma..sub.c /.mu..sub.c) comprised between 0.02 and 0.15, and/or having a distribution of selectivity of adsorption of nitrogen relative to oxygen with a ratio (.sigma..sub.s /.mu..sub.s) comprised between 0.02 and 0.25.

Abstract: A process of modifying the porosity of an aluminosilicate or silica whose porosity is not amenable to modification by acid extraction. The process involves contacting said aluminosilicate or silica with an alkali aluminate, and then extracting the aluminate-treated material with an extraction agent so as to form the porosity-modified aluminosilicate or silica. The process is applicable to zeolites which are unreactive under acid extraction conditions, e.g. ferrierite, and applicable to zeolites which are structurally unstable under acid extraction conditions, such as the mineral bikitaite. Mesoporous compositions are disclosed, including a mesoporous ferrierite and a mesoporous zeolite DCM-3.

Abstract: A method for improving the adsorption properties of a hydrocarbon adsorber which involves contacting a molecular sieve hydrocarbon adsorber with an agent for modifying the acid sites of the molecular sieve to impregnate the molecular sieve with the agent. The resulting acid-modified molecular sieve has the ability to retain adsorbed hydrocarbons at higher temperatures than the molecular sieve in the un-modified state. The acid-modified molecular sieve can be used to remove hydrocarbons from a workstream. The workstream is passed through the modified adsorber at atmospheric pressure at a temperature ranging from room temperature to about 150.degree. C. to cause adsorption and retention of the hydrocarbons. The adsorbed hydrocarbons can then be desorbed at a higher temperature than would otherwise occur with an unmodified adsorber.

Abstract: An adsorbent for separating nitrogen from a feed gas containing at least one other gas having molecular dimensions equal to or larger than methane, the adsorbent comprising clinoptilolite having a sodium ion content of at least 17 equivalent percent of the total ion exchangeable cations and optionally one or more non-univalent cations, which if present comprise in total less than 12 equivalent percent of the total ion exchangeable cations, the balance, if any, being one or more non-sodium univalent cations.

Abstract: The present invention relates to binder-free molecular sieve zeolite granules of lithium zeolite A and lithium zeolite X, a process for preparing these molecular sieve zeolite granules and their use for preparing nitrogen or oxygen from air by pressure swing adsorption.

Abstract: Novel Cd-exchanged rho compositions and compositions of zeolite rho encapsulated with hydrogen made therefrom are disclosed. The Cd-exchanged zeolite rho compositions are useful in separating and selectively removing hydrogen from hydrogen-containing process streams and storing the separated hydrogen therein. Encapsulation of hydrogen can be accomplished in large amounts even at pressures of 1 atmosphere.

Abstract: Bulk separation of carbon dioxide from methane is accomplished using a modified pressure swing adsorption system where the adsorbent used is a naturally occurring sodium-rich clinoptilolite. Most of the carbon dioxide can be removed at low operating pressures, and the principal agent of regeneration is a high volume air rinse rather than pressure reduction.

Abstract: A device for removing at least laughing gas and anesthetic vapor from a gas sample based on a molecular sieve shall be improved such that it possesses good adsorption properties for both gas components. A molecular sieve arrangement is provided, which is flown through from a gas inlet to a gas outlet and comprises a first molecular sieve area with a first pore size between about 0.3 nm and 0.5 nm and a second molecular sieve area with a second pore size between about 0.8 nm and 1 nm.

Abstract: A process and apparatus for the removal of water from corrosive halogen gases, particularly chlorine- or bromine-containing gases, down to .ltoreq.100 ppb water concentration are described. The critical component is a high silica zeolite, preferably high silica mordenite, which in a variety of physical forms is capable of dehydrating such gases to .ltoreq.100 ppb or .ltoreq.50 ppb without being detrimentally affected by the corrosive nature of the gases in the presence of water. The high silica zeolite is produced by the removal of alumina from a natural or synthetic zeolite while retaining the desirable zeolite structure, to a silica:alumina ratio of from 20-2000:1. Metal cations which may be depleted by the alumina removal may be replaced by solution impregnation. Halogen- or halide-containing gases, or those with equivalent corrosion properties, may be dehydrated without deterioration of the high silica zeolite.

Abstract: A process for removing water and ammonia from benzophenone imine reactor effluents resulting from the catalytic reaction of benzophenones of the formula I ##STR1## where R.sup.1 and R.sup.2, have the meaning stated in the specification and wherein ammonia is distilled off from effluents and wherein water is either distilled off from the effluents over removed non-distillatively.

Abstract: In the pressure swing adsorption of nitrogen from gas mixtures with less polar gas components at temperatures of between 20.degree. and 50.degree. C., wherein the gas mixture is passed through an adsorber which is filled with packings of zeolite pellets and has an inlet zone and an outlet zone, the improvement which comprises providing at least two packings in the adsorber, a packing of Li-zeolite X in the inlet zone of the adsorber and a packing of at least one of Ca-zeolite A and Ca-zeolite X in the outlet zone of the adsorber.

Abstract: A crystalline zeolite X adsorbent comprising a crystalline zeolite X having an SiO.sub.2 /A.sub.2 O.sub.3 molar ratio of not larger than 3.0, where lithium cations associated with an AlO.sub.2 tetrahedron unit are 80 to less than 88 mol % of the total cations and the content of alkaline earth metal cations is from 0.5 to less than 4.6 mo % is produced by ion-exchanging with lithium cations at least 90 mol % of the cations associated with an Al.sub.2 O.sub.3 tetrahedron unit of a crystalline zeolite X having an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio of not larger than 3.0, ion-exchanging the crystalline zeolite X again with an aqueous solution of mixed salts of an alkali metal salt and an alkaline earth metal salt to decrease the lithium cations associated with the AlO.sub.2 tetrahedron unit to 80 to less than 88 mol %, followed by washing and drying, and activating the crystalline zeolite X.

Abstract: Industrial grade carbon dioxide may contain unacceptable amounts of sulfur-containing materials, oxygen, and organic materials particularly detrimental to food-related uses of CO.sub.2. These can be effectively removed by a bed of silver-exchanged faujasite and an MFI-type molecular sieve. This permits an on-site, on-demand method of purifying CO.sub.2 ranging from laboratory to tank car seals.

Abstract: Ozone is recovered from an ozone-oxygen mixture by adsorption using an adsorbent which comprises a zeolite selected from the group consisting of L type zeolite, Y type zeolite, ZSM-5, and mordenite in which at least 90% of the exchangeable cation content is in the ammonium form and the molar ratio of potassium to aluminum is less than about 0.25. Alternatively, a proton-exchanged L type zeolite can be used in which at least 90% of the exchangeable cation content is in the proton form and the molar ratio of potassium to aluminum is less than about 0.25.

Abstract: A process for coating zeolite crystals with paraffin, a wax other than paraffin, a fat or oil, or a mixture of at least one QAC and a wax, fat, or oil. Preferably, the crystals are dehydrated until they have about 5% moisture content, and are then mixed with paraffin to produce paraffin-coated zeolite crystals having a desired content of paraffin. When the coated zeolite crystals are used for removing benzene from contaminated water, their paraffin content is preferably about 8% (by weight). Other embodiments are methods for using zeolite coated with paraffin, another wax, a fat, an oil, or a mixture of at least one QAC and a wax, fat, or oil to filter a contaminant from contaminated liquid or gas. The zeolite crystals are optionally impregnated with a chemical such as permanganate before they are coated with the desired wax, fat, oil or mixture. A zeolite crystal having pores coated with wax, fat, oil, or a mixture of at least one QAC and wax, fat, or oil is within the scope of the invention.

Abstract: An improved adsorbent for ozone comprises a crystalline aluminosilicate in which at least 90% of the exchangeable cation content is in the acid form and further which contains between 0.5 and 20 wt % of one or more adsorbed components which are non-reactive with ozone. Preferably the adsorbed component is water, and the total non-framework metal content expressed as metal oxide is less than 0.4 mole %.

Abstract: A process for the adsorption of at least carbon dioxide, water and oxides of nitrogen and preferably acetylene from a feed gas, comprises contacting the feed gas with an adsorbent mixture of a zeolite and an alumina. The process may be operated as a swing adsorption process comprising contacting the gas with the adsorbent at a first temperature and pressure to adsorb at least carbon dioxide, water and oxides of nitrogen therefrom and periodically regenerating the adsorbent by reducing the pressure and or increasing the temperature to which the adsorbent is exposed.

Abstract: A hydrocarbon stream is cracked to produce a hot gaseous stream which is compressed and cooled to condense almost all of the hydrocarbons contained in the stream. A noncondensed stream remaining after the condensation step, comprised predominantly of hydrogen and C.sub.1 to C.sub.3 hydrocarbons, is subjected to pressure swing adsorption or temperature swing adsorption at an adsorption temperature of about 0.degree. to about 250.degree. C. in a bed of adsorbent which selectively adsorbs ethylene and propylene, thereby adsorbing substantially all of the ethylene and propylene from the gas stream. The ethylene and/or propylene is recovered upon bed regeneration.

Abstract: A process system with an integrated gas storage and delivery unit comprising an adsorption-desorption apparatus, for storage and dispensing of a gas wherein the gas is dispensed by pressure differential desorption of the sorbate gas from the sorbent material. A motive fluid driver, e.g., a pump, blower, compressor, eductor, or the like, is arranged for flowing the dispensed gas to a gas-utilizing unit, such as an ion-implant unit, wastewater treatment unit, gas-liquid contacting chamber, chemical vapor deposition reactor, gas laser assembly, etc.

Abstract: An adsorption-desorption apparatus, for storage and dispensing of a sorbable gas, wherein a carbon physical sorbent medium bearing the adsorbed gas to be selectively dispensed is delivered by pressure differential desorption and/or thermal desorption of the sorbate gas from the sorbent material. The carbon sorbent material preferably comprises a material which is characterized by a Sorbent Working Capacity, measured for arsine at 40 Torr and at 650 Torr, of at least 100 grams arsine per liter of bed of the sorbent material, e.g., a carbon sorbent material having the adsorption isotherm characteristic of curve A in FIG. 1 herein.

Abstract: According to the present invention, ceramics which are prepared by calcining a composition comprising raw ceramic materials and a microorganism and/or culture fluid thereof, wherein the microorganisms is capable of producing an antioxidation material. The ceramic of the present invention possesses a variety of activities of, for instance, improving the soil, decomposing sewage or sludge, and deodorizing an unpleasant odor.

Abstract: The invention relates to a process for the separation of a mixture of oxygen and nitrogen into each of its constituents, including bringing the mixture to be separated, in an adsorption zone, into contact with a selective adsorbent for nitrogen, the adsorbent being an agglomerated zeolite exhibiting an Si/Al ratio lower than 5, a porosity of between 0.38 and 0.60 and a parameter a.sub.k of at least 0.5 s.sup.-1, the parameter a.sub.k characterizing the kinetics of adsorption of nitrogen on the adsorbent in the adsorption zone in accordance with the Linear Driving Force model, it being understood that when the adsorbent is a zeolite containing lithium its porosity can vary between 0.25 and 0.60.

Abstract: A gas mixture comprised of nitric oxide and, optionally an inert gas, and containing small amounts of nitrogen dioxide, and perhaps moisture and sulfur dioxide, is purified by passing the gas stream through a bed of zeolite having a silica to alumina ratio not greater than about 200. The concentration of nitrogen dioxide, sulfur dioxide and moisture in the gas stream are reduced to about 1 ppm or less as the gas mixture passes through the bed of zeolite.