EP3962644A2 - Methods of preparation of metal exchanged zeolites - Google Patents

Abstract

Methods of preparation of metal exchanged zeolites by ion exchange of metals such as copper, iron or manganese with aluminosilicates and silicoaluminophosphates such as CHA, MFI, BEA and small pore zeolite frameworks are disclosed. The method uses a combination of a liquid reaction medium with a gaseous reaction medium wherein the metal to be exchanged is preferably in the elemental metallic form and the gaseous reaction medium comprises at least carbon dioxide. These metal exchanged zeolites are useful as catalysts for the reduction of oxides of nitrogen from gaseous streams by Selective Catalytic Reduction with ammonia or urea.

Description

METHODS OF PREPARATION OF METAL EXCHANGED ZEOLITES

L Technical Field:

Embodiments of this invention relate to novel methods of preparation of metal exchanged aluminosiliicate and silicoaluminophosphate zeolites for use as catalysts for the treatment of exhaust gases.

II. Background Art:

Zeolites are microporous materials formed by tetrahedra structures, T_h where T_h=Si, Al, P, Ti, Ge, Sn etc. which are interconnected by the oxygen atoms creating pores and cavities with uniform size and shape of molecular dimension range (3-15 A). The first synthetic zeolite was described by Barrer in 1948. [Barrer, J. Chem. Soc. 127 (1948)]. Since this discovery, more than 200 new zeolitic structures have been discovered, all of them containing different pore architectures (http://www.iza-online.org/). Indeed, zeolites can be classified depending on the size of their pores, whose ring openings are defined by a number of T_h atoms. In this sense, small pore zeolites show openings with 8- T_h atoms, medium pore zeolites present openings with 10- T_h atoms, large pore zeolites have openings with 12- T_h atoms, and finally, extra-large pore zeolites present openings with more than 12- T_h atoms.

Those crystalline microporous materials have been broadly applied as excellent catalysts in numerous chemical processes. The use of a zeolite with specific physico-chemical properties for a particular chemical process will directly depend on the nature of reactants and products involved in the process (such as size, shape, hydrophobicity, etc.), and also on the reaction conditions. On one hand, the nature of the reactants and products will affect to the diffusion of those molecules within the pores and cavities of the zeolite, and consequently, the selection of the zeolite with the adequate pore topology for the chemicals involved in the reaction will be essential. On the other hand, the zeolite must be stable, both structurally and chemically, on the required reaction conditions.

The formation of nitrogen oxides (NOx) during the combustion of fossil fuels has become a real environmental problem, since they are one of the major air pollutants. Selective catalytic reduction (SCR) of NOx by ammonia in presence of zeolite has emerged as an efficient emission control. Iwamoto et al. discovered that copper-exchanged zeolites, including Beta and ZSM-5, were active catalysts for the SCR of NOx [Iwamoto et al. J.Chem.Soc, Chem.Comm., 1986, 1272] . In the last few years, it has been described that some copper containing small-pore zeolites show much better hydrothermal stability than large pore zeolites [Bull, et al. U.S. Patent 7,601,662 (2009); Moliner, et al. PCT/EP2012/057795; Korhonen, et al, Chem. Commun., 2011, 47, 800]. This higher hydrothermal stability can be explained by the coordination of copper atoms to the double six- membered rings units (D6R) present in the large cavities of these small-pore zeolites, as suggested Fickel and Lobo [J. Phys. Chem. C, 2010, 114, 1633].

It is widely accepted that when a metal ion is exchanged with zeolite, the hydrothermal stability of the zeolite significantly improves. It is well known in the prior art that metal exchanged zeolites are prepared by ion-exchange techniques using zeolite and metal ions.

Main methods of preparation of metal doped or metal ion exchanged zeolites cited in prior art are ion exchange in the liquid or solid state, impregnation by incipient wetness or by sublimation or CVD (Chemical Vapor Deposition) or direct synthesis wherein the metal is incorporated during the crystallization of the zeolite.

The methods cited in prior art provide catalysts for selective catalytic reduction of NOx. All the above methods use either solutions of salts or solid salts of the metals to be exchanged as precursors. These salts are relatively more expensive than the metal to be ion exchanged. Further, they tend to be acidic or alkaline in nature. They generate either a residual liquid or gaseous effluent stream which needs post treatment prior to discharge to the environment. In case of impregnation by incipient wetness or sublimation there is no control over the fraction of metal which is ion exchanged with the acid sites of the zeolite and that which is deposited on the external and internal surface of the zeolite as the salt upon evaporation/removal of the solvent. In case of CVD specialized equipment is required which add to costs. Thus, there is a need to develop a simple eco-friendly and cost-effective solution for exchanging the metal on to the zeolite. The current invention directly uses the metal to be exchanged as its elemental form. It is less expensive than the corresponding salts of the metal. It uses demineralized water as the medium for liquid ion exchange without adding any acid or alkali to the medium. The residual liquid after ion exchange does not require any further treatment nor is any gaseous pollutant evolved. Carbon dioxide which is a greenhouse gas is used along with water in this invention. Thus, the method of the current invention addresses the problems existing with prior art methods.

III. Problems with the Prior Art: Selective catalytic reduction with ammonia is used for abatement of oxides of nitrogen from exhaust gas streams. Metal exchanged zeolites are used. Activity at low temperature around 200°C and stability at high temperature 650-750°C are critical for this application. Copper exchanged SSZ-13 with CHA framework is considered as amongst the best suited catalysts for this application. It is desirable to prepare catalysts which have high activity at low temperature and also good hydrothermal stability. Different methods of preparation of copper exchanged CHA, MFI and BEA are disclosed in prior art. These methods use ion exchange in liquid state or solid state for exchanging the metal with ion exchange sites on the zeolite. Inorganic salts or organometallic compounds of the metal to be exchanged are used as reactants. Media used for the exchange in liquid state are either acidic or basic in nature. The filtrate after exchanging the metal with ion exchange sites still contains significant amount of residual metal ions and other chemicals which can pose hazard to the environment. It can be recycled for a limited number of times. Its disposal requires treatment which not only adds to cost but also to the effluent load. The use of the above metal salts or organometallic compounds as precursors of the metal to be exchanged with the ion exchange sites of the zeolite (instead of directly using the metal in its elemental form) also adds to cost. Specialized equipment is required for methods such as CVD or sublimation·

There is thus a need to develop methods of preparation of metal exchanged zeolite catalysts which use more benign or ecofriendly chemistry and which are cost effective. It is an embodiment of the present invention to provide such a method for the preparation of metal exchanged aluminosilicate zeolites.

IV. Prior Art

US patent 9895660B2 assigned to Haldor Topsoe claims preparation of metal exchanged microporous materials through dry mixing of one or more microporous materials with one or more metal compounds, heating the mixture in a gaseous atmosphere containing ammonia and one or more oxides of nitrogen at elevated temperature for sufficient time to initiate solid state ion exchange between ions of the metal compound and the microporous material and obtain metal exchanged microporous material. AEI, AFX, CHA, KFI, LTA, IMF, ITH, MEF, MFI, SZR, TUN, *BEA, BEC, FAU, FER, MOR, FEV zeolite or zeotype materials are claimed microporous materials. Zeolite or zeotype materials from the group consisting of ZSM-5, zeolite Y, beta zeolite, SSZ-13, SSZ-39, SSZ-62, Chabazite, and SAPO-34, SAPO-44, Ferrierite, TNU-9 are claimed. H or NH4 forms of the zeolites or zeotypes are claimed. Presence of an organic structure directing agent in these microporous materials is also claimed. Metals to be exchanged are selected from the group Fe, Co, Cu. Metal compounds which are precursors of these metals include oxides, nitrates, phosphates, sulfates, oxalates, acetates or combination thereof. Use of ammonia or oxides of nitrogen during the metal exchange step is claimed. Oxygen and water contents in the gaseous atmosphere are claimed <1% and <5% respectively and temperatures <300°C. Use of these materials for removal of nitrogen oxides from exhaust gas by selective reduction using ammonia or hydrocarbons as reductant is claimed. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in this patent. Neither is use of a liquid medium claimed or disclosed in this patent. A gaseous medium during incorporation of the metal into the zeolite is claimed but it is restricted to ammonia and oxides of nitrogen.

US patent 9889437 assigned to BASF claims a SCR catalyst comprising a zeolite with framework of Si and A1 atoms, wherein a fraction of the silicon atoms is isomorphously substituted with Ti. Zeolitic frameworks selected from CHA, AFX, and AEI are claimed. Promoters are disclosed as Cu and Fe or their combination and these are incorporated by ion-exchange into the zeolite. The zeolite used is an aluminosilicate in which Ti is isomorphously substituted. Use of these materials for treating exhaust gases is claimed. Articles wherein the substrate is ceramic or metal having honeycomb structure catalytic coating of the materials disclosed in this patent are claimed. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US patent 9889436 assigned to TOSOH claims a CHA type zeolite with SAR < 15. Avg particle size 1-2.67 mhi, and crystal particle are rhombohedral or cuboidal. 90 vol% of zeolite has particle size <15 pm. Inclusion of Cu [Cu/AL 0.1 to 1.00]; with such Cu occupying ion exchange sites is claimed in a dependent claim. Crystal structure is claimed as SSZ-13 in a dependent claim. RM of Cu are either soluble or insoluble materials such as nitrates, sulfates, acetates, chlorides, complex salts, oxides, and composite oxides which include copper. Methods of incorporating copper are listed in body of patent as ion exchange, impregnation, evaporation to dryness, precipitation, physical mixing, and framework substitution are disclosed in the body of the patent. Ion exchange using Cu acetate as precursor of Cu is cited in the examples. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9656254 assigned to BASF corporation claims a catalyst comprising a copper ion exchanged aluminosilicate having CHA structure SAR 20-40, Cu:AL 0.25-0.5 wherein the catalyst contains ion exchanged and non-ion exchanged (free) Cu. The method of preparation of the catalyst is not claimed. Ion exchange from aqueous solution of salts of Cu with copper sulfate as an example is cited in the body of the patent and also demonstrated in examples. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent. Further in the method claimed in this patent, excess copper which is not ion exchanged with the exchange sites of the zeolite is present in the catalyst composition. It is not removed from the ion exchanged zeolite by washing after ion exchange step. It is disclosed as beneficial.

US 7601662 assigned to BASF claims a catalyst comprising CHA crystal structure SAR > about 15; and an atomic ratio Cu:Al >0.25. A dependent claim cites the SAR range from 15 to 256 and atomic ratio of Cu: A1 0.25 to 0.50. According to another dependent claim the catalyst composition contains ion and non-exchanged Cu. Non exchanged Cu salt is left on the zeolite. Examples are provided which use aq Cu sulfate ion pH adj to 3.5 with HN03, at 80°C, lh, exchanged solid filtered and washed / not washed to retain free Cu. Incipient wetness method using aqueous solution of copper sulfate is also provided in examples; The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

Further in the method disclosed in this patent excess copper which is not ion exchanged is present in the catalyst. It is not removed from the zeolite after ion exchange. It is disclosed as beneficial.

US 8293198 assigned to BASF claims a process for preparation of copper containing molecular sieve with CHA structure SAR > about 10; comprising ion exchanging Cu into Na form of the molecular sieve with CHA structure with SAR > about 10 using liquid Cu soln 0.001 to 0.4 molar; Dependent claims describe the weight of water used to prepare the copper solution to weight of the zeolite used for copper exchange step in the range 2-80; reaction temperature of exchange step as 10-100C; Source of copper is claimed as copper acetate or an ammoniacal solution of copper ions; cone of Cu 0.075-0.3 molar, Cu acetate or ammoniacal solution of Cu ions is claimed as source of Cu; Sodium content of the copper exchanged CHA zeolite is claimed to be <2500 ppm. The weight ratio of exchanged Cu to Cu oxide is claimed to be at least about 1. The SAR range of the CHA zeolite is claimed from 15 to 40 and Copper: aluminum atomic ratio 0.25 to 0.50. Characteristics of this catalyst using TPR; UV-VIS; Diffuse reflectance FTIR are claimed. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst in this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8293199 assigned to BASF claims a process for preparation of Cu containing Molecular sieve with CHA structure, SAR > about 10; comprising reacting the Molecular sieve with a Cu source, wherein Cu exchange step is conducted via wet state exchange prior to coating step and wherein in Cu exchange step a liquid Cu solution is used wherein Cu is 0.001-0.25 molar using Cu acetate and or ammoniacal solution of Cu as Cu source. The copper is exchanged into sodium or ammonium form of CHA, and the copper containing zeolite contains weight ratio of exchanged Cu: Cu oxide at least about 1 as per dependent claims. The SAR range of the CHA zeolite is claimed from 15 to 40 and Copper: aluminum atomic ratio 0.25 to 0.50. Characteristics of this catalyst using TPR; UV-VIS; Diffuse reflectance FTIR are claimed. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8535629 assigned to Johnson Matthey Public Ltd Co. claims a catalyst composition comprising zeolite material having mean crystal size 0.5 pm, CHA framework, SAR 10-25; an extraframework promoter metal disposed in said zeolite as free and/or exchanged metal, wherein the extraframework metal is selected from Cu or Fe or mixtures, M:A1 0.10 - 0.24 based on framework Al. Dependent claims describe the zeolite as SSZ-13 isotype, mean crystal size 1-5 pm, promoter metal Cu wherein majority of said Cu is exchanged Cu. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8715618 assigned to BASF claims a process for the direct preparation of Cu containing zeolites having CHA structure, wherein the process comprising: (i) preparing an aqueous solution comprising at least one source for X.sub.20.sub.3, at least one source for YO.sub.2, at least one structure directing agent suitable for preparing a zeolitic material having a CHA framework structure, and at least one Cu source, wherein said aqueous solution does not comprise a phosphor source and has an alkali metal content of 1000 ppm or less; and (ii) hydrothermally crystallizing the aqueous solution of the preparing (i) which does not comprise a phosphor source, to obtain a suspension comprising the copper-containing zeolitic material having a CHA framework structure; wherein the structure directing agent is a mixture of 1-adamantyltrimethyl-ammonium hydroxide and benzyltrimethylammonium hydroxide, or a mixture of 1 -adamantyltrimethylammonium hydroxide and tetramethylammonium hydroxide, or a mixture of 1 -adamantyltrimethylammonium hydroxide and tetramethylammonium hydroxide, or a mixture of 1 -adamantyltrimethylammonium hydroxide and benzyltrimethylammonium hydroxide and tetramethylammonium hydroxide, wherein a molar ratio of 1 -adamantyltrimethylammonium hydroxide to benzyltrimethylammonium hydroxide or to tetramethylammonium hydroxide, or to a sum of benzyltrimethylammonium hydroxide and tetramethylammonium hydroxide, is in a range of from 1:5 to 1: 1, and wherein the copper-containing zeolitic material has a composition comprising a molar ratio (nY0.sub.2):X.sub.20.sub.3 wherein X is a trivalent element, Y is a tetravalent element, and n is at least 10. A dependent claim describes the source of Cu as an aqueous solution comprising Cu and ammonia. Another dependent claims that no Cu source is employed after crystallization of the zeolite. Thus, Cu is incorporated into the zeolite product during crystallization of the zeolite (direct synthesis). Further the use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8795626 assigned to TOSOH claims CHA type zeolite having Cu and an alkali earth metal supported thereon. In a dependent claim the alkali earth metal is disclosed as from the group (Ca, Mg. Ba). Ratios of Cmalkali earth metal and alkali earth metakAl are claimed in dependent claims. The copper and alkali earth metals are claimed to occupy ion exchange sites of the zeolite. The raw materials used for supporting copper and the alkali earth metal may be copper and the alkali earth metal, or a nitrate, sulfate, acetate, chloride, complex salt, oxide or composite oxide or the like containing both metals. Either soluble or insoluble materials can be used as these raw materials. Aq. Cu acetate is used in examples cited in this patent. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8821820 assigned to Umicore AG & Co claims a method of improving the catalytic activity of a copper-promoted zeolitic catalyst having a chabazite structure, wherein a zeolitic catalyst having a chabazite structure is treated with a copper salt solution and subsequently treated thermally under oxizing conditions in order to form the copper-promoted zeolitic catalyst having a chabazite structure which in the temperature -programmed reduction (TPR) by means of hydrogen at a heating rate of 10 K/min and a hydrogen content in the test gas of 5% by volume has a signal in the temperature range from 230.degree. C. to 240.degree. C., where the weight used in the TPR is such that the sample to be examined contains from 3 to 8 milligram of copper calculated as metal. A dependent claim discloses that the copper salt solution is a compound selected from among copper(II) sulfate, copper(II) nitrate, copper(II) acetate and copper(II) acetylacetonate dissolved in water and/or a polar solvent selected from the group consisting of acetylacetone, short-chain alcohols having up to three carbon atoms, acetonitrile, acetone, dimethyl sulfoxide (DMSO), methyl ethyl ketone and mixtures thereof. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8865120 assigned to Umicore claims a process for the production of metal doped Zeolites or Zeotypes comprising the steps of: i) providing a dry intimate mixture of a Zeolite or Zeotype with one or more precursor compound or compounds comprising a complex formed out of a transition metal and a ligand, which has a structure of formula I: ML.sup. l.sub.mL.sup.2.sub.n (I) wherein: M is a metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ru, Rh, Pd, Ag, and Ce; and L.sup.l is carbonyl, amine, alkyl, alkoxy, alkene, arene, phosphine or other neutral coordinating ligand; m is a number ranging from 0 to 6; n is a number equal to the valence of M; and L.sup.2 is a diketonate, ketoiminato or related member of this homologous series like a ligand of formula II: ##STR00002## wherein: R1 and R2 are independently alkyl, substituted alkyl, aryl, substituted aryl, acyl and substituted acyl; and ii) calcining the mixture without reduced pressure at a temperature and a time sufficient to mobilise and decompose the precursor compound; and iii) obtaining the metal-doped Zeolite or Zeotype. Dependent claims disclose the zeolites as FAU, MFI, CHA or zeotypes. Calcination temperature 200-650C for l-5h. This is a dry method which does not use a solution during production of the metal doped zeolite. Further the use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent. US 8883119 assigned to BASF claims a process for the preparation of zeolites having CHA framework structure and a composition comprising the molar ratio (n Si0.sub.2):X.sub.20.sub.3, wherein X is a trivalent element, and wherein n is at least 10, the process comprising: (i) preparation of an aqueous solution containing: at least one source for X.sub.20.sub.3, wherein X is selected from Al, B, Ga, and a mixture of two or more, at least one source for SiO.sub.2, at least one organic structure directing agent (SDA) other than Tetramethylammonium hydroxide (TMAOH) as a template for the CHA structure, and Tetramethylammonium hydroxide (TMAOH), wherein the SDA or mixtures thereof are employed in such amounts that the aqueous solution in (i) exhibits a molar ratio of SDA:TMAOH in the range of 0.01 to 5; (ii) hydrothermal crystallization of the aqueous solution according to (i); wherein the aqueous solution of (i) contains copper in an amount less than 0.005 Cu:((n Si0.sub.2)+X.sub.20.sub.3) where n is at least 10. A dependent claim cites that the aqueous solution which is used for crystallization is free of alkali and alkaline earth metals. Ion exchange with Cu using its acetate as the source is disclosed in examples. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8906329 assigned to JM PLC claims a catalyst composition comprising a. a zeolite material having a CHA crystal structure and a silica to alumina mole ratio (SAR) of about 10 to about 25; and b. a non-aluminum base metal (M), wherein said zeolite material contains said base metal in a base metal to aluminum ratio (M:A1) of about 0.10 to about 0.24. Independent claims disclose that the zeolite has a mean crystal size of about 1 to 5 microns, SAR of 10 to 20, non-phosphorus CHA structure, base metal M which is selected from the group consisting of Cr, Ce, Mn, Fe, Co, Ni and Cu. Methods to incorporate M are cited as blending or ion-exchange in the body of this patent. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent. US 8987162 assigned to UT-Battelle, LLC claims a catalyst composition comprising a heterobimetallic zeolite characterized by a chabazite structure loaded with copper ions and iron(III) ions, wherein said copper ions are present in said catalyst in a loading amount of above 1 wt % and said iron(III) ions are present in said catalyst in a loading amount of less than 1 wt %, and said copper and iron loading amounts are effective to achieve a NO.sub.x conversion at 150.degree. C. of at least 50% in the presence of an ammonia reductant. Dependent claims disclose that the iron (III) ions are in combination with at least one other trivalent metal ion which is a transition metal or lanthanide trivalent ion. Another dependent claim discloses the zeolite comprises CuFe-SSZ-13. In the body of the patent the Cu component of the catalyst is described as Cul+ or Cu2+ ions with Cu loading up to 2.5 wt%. Metal impregnation using solutions is described as the method for incorporating the metal into the zeolite. The metal ions are generally in the form of metal salts. Preferably, the metal salts are completely dissolved in the liquid carrier. The metal salt contains one or more metal ions in ionic association with one or more counter anions. Any one or more of the metal ions described above can serve as the metal ion portion. The counter-anion can be selected from, for example, halides (F.sup.-, Cl.sup.-, Br.sup.-, or I.sup.-), carboxylates (e.g., formate, acetate, propionate, or butyrate), sulfate, nitrate, phosphate, chlorate, bromate, iodate, hydroxide, .beta.-diketonate (e.g., acetylacetonate), and dicarboxylates (e.g., oxalate, malonate, or succinate). In some examples of the present invention, the counter-anion may contain one or more metals, including one or more metals to be loaded into the zeolite. Some examples of such counter-anions include titanate, zirconate, vanadate, niobate, tantalate, chromate, molybdate, tungstate, arsenate, antimonate, stannate, and tellurate. In other examples of the present invention, one or more classes or specific types of any of the foregoing counter-anions are excluded from the impregnating solution (or alternatively, excluded from being incorporated into the zeolite). In particular examples of the present invention, the catalyst is prepared by forming a slurry containing zeolite powder and the metals to be incorporated. The resulting slurry is dried and fired to form a powder. The powder is then combined with organic and/or inorganic binders and wet- mixed to form a paste. The resulting paste can be formed into any desired shape, e.g., by extrusion into rod, honeycomb, or pinwheel structures. The extruded structures are then dried and fired to form the final catalyst. In other examples of the present invention, the zeolite powder, metals, and binders are all combined together to form a paste, which is then extruded and fired. The use of the metal in its elemental form or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. The use of metal formate for impregnation of the zeolite is disclosed in the body of the patent. However, neither a liquid ion exchange method nor the presence of a gaseous reaction medium during incorporation of the metal into the zeolite are claimed or disclosed in this patent.

US 9011807 assigned to BASF claims a selective catalytic reduction catalyst comprising an 8-ring small pore molecular sieve promoted with greater than 5 wt. % iron so that the catalyst is effective to catalyze the selective catalytic reduction of nitrogen oxides in the presence of a reductant at temperatures between 200.degree. and 600.degree. C. The catalyst wherein the iron-promoted 8- ring small pore molecular sieve is selected from the group consisting of iron-promoted zeolite having a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT, and SAV. Iron promoted SSZ-13 is disclosed in dependent claim. SAR 5-100; Fe203 content 5.1 to 10 wt%. Ion exchange is disclosed at one method for incorporation of the metal into the zeolite. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9162218 assigned to BASF claims a catalyst comprising: an aluminosilicate zeolite having the CHA crystal structure and a mole ratio of silica to alumina from about 15 to about 150 and an atomic ratio of copper to aluminum from about 0.25 to about 1, the catalyst effective to promote the reaction of ammonia with nitrogen oxides to form nitrogen and H.sub.20 selectively, wherein the zeolite comprises Cu-SSZ-13. Dependent claims disclose that the catalyst contains ion- exchanged copper and non-exchanged copper. Use of copper sulphate solution for incorporating the Cu into the zeolite is disclosed in examples. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9302256 assigned to BASF claims a selective catalytic reduction catalyst comprising an 8-ring small pore molecular sieve promoted with greater than 5 wt. % iron so that the catalyst is effective to catalyze the selective catalytic reduction of nitrogen oxides in the presence of a reductant, wherein the 8-ring small pore molecular sieve has a silica to alumina ratio in the range of 10 and 100. Independent claims disclose that the catalyst wherein the iron-promoted 8-ring small pore molecular sieve is selected from the group consisting of iron-promoted zeolite having a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT, and SAV. Another claim covers iron promoted SSZ-13. Ion exchange or inclusion into the colloid used for crystallizing the zeolite are described in the body of the patent as methods of metal incorporation. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9656253 assigned to IBIDEN Co. claims a zeolite comprising: a CHA structure; a Si0.sub.2/Al.sub.20.sub.3 composition ratio less than about 15; an average particle size from about 0.1 pm to 0.46 pm; and Cu supported on the zeolite. PXRD specifics of the zeolite are claimed. Cu content 3.5-6.0 wt% by mass of zeolite is claimed. Cu ion exchange is carried out by immersing the zeolite in an aqueous solution of one selected from copper acetate, copper nitrate, copper sulfate, and copper chloride. Preferred among these is an aqueous solution of copper acetate. The reason for this is that a large amount of Cu can be supported at once. For example, copper is supported on the zeolite by performing ion exchange with an aqueous solution of copper acetate (II) having a copper concentration of 0.1 to 2.5% by mass and a solution temperature of room temperature to 50.degree. C. under atmospheric pressure. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9539564 assigned to Toyota Jidosha claims a method for producing Fe supported CHA comprising mixing Fe (II) chloride and zeolite heat treating under reducing atmosphere and a hydrogen reduction. Followed by oxidizing step after the reduction step. In dependent claims the CHA is disclosed as a silicoaluminophosphate. The method of mixing is not limited but examples of physical mixing of solid-state components is disclosed in examples. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 9352307 assigned to BASF claims a catalyst for use in selective catalytic reduction (SCR), said catalyst comprising: one or more zeolites of the MFI structure type, and one or more zeolites of the CHA structure type, wherein at least part of the one or more zeolites of the MFI structure type contain iron (Fe), wherein at least part of the one or more zeolites of the CHA structure type contain copper (Cu), wherein the weight ratio of the one or more zeolites of the MFI structure type relative to the one or more zeolites of the CHA structure type ranges from 1:2 to 2: 1, wherein the molar ratio of silica to alumina (SAR) in the one or more zeolites of the MFI structure type ranges from 20 to 50, wherein the molar ratio of silica to alumina (SAR) in the one or more zeolites of the CHA structure type ranges from 20 to 55, wherein the amount of Fe in the one or more zeolites of the MFI structure type ranges from 2.5 to 5.5 wt-% based on the weight of said one or more zeolites, and wherein the amount of Cu in the one or more zeolites of the CHA structure type ranges from 1.0 to 1.0 wt-% based on the weight of said one or more zeolites. The SAR of CHA is disclosed as 5-100, Cu 0.05-15 wt%. Specific methods of incorporating Cu into the CHA zeolite are not disclosed in this patent. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent. US 10202284 assigned to IBIDEN Co, claims a method for producing zeolite having a CHA structure in which Cu is carried, the method comprising: mixing a powder of the zeolite having the CHA structure and a powder of Cu salt, which is at least one salt selected from the group including copper sulfate, copper nitrate, copper acetate, and copper chloride, with each other to produce powder mixture; and heating the powder mixture under atmospheric pressure. Independent claims disclose the water content of the powder mix <30 wt%, heating temperature 250-800C, source of Cu salt is copper nitrate, atmosphere during heating step is oxidizing atmosphere, Cu/Al 0.2-0.5 molar, SAR pf CHA < 15, average particle size of the CHA zeolite is 0.5 pm or less. Other sources of the Cu salt used are cited in body of this patent as preferably at least one salt selected from the group consisting of copper sulfate, copper nitrate, copper acetate, and copper chloride. The patent cites that these Cu salts are low in cost, and can further lower the cost in the method for producing the zeolite. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

US 8906329 assigned to JMPL Co claims a catalyst composition comprising a. a zeolite material having a CHA crystal structure and a silica to alumina mole ratio (SAR) of about 10 to about 25; and b. a non-aluminum base metal (M), wherein said zeolite material contains said base metal in a base metal to aluminum ratio (M:A1) of about 0.10 to about 0.24. Dependent claims disclose zeolite mean crystal size at least 1 um, 1-5 um; particle size 1-100 um; non-phosphorus CHA structure, M = Cr,Ce,Mn,Fe,Co, Ni, Cu; zeolite material contains about 80 to about 120 grams of Cu per cubic foot of zeolite material; M may be disposed in the zeolite as free and/or exchanged metal, Method of metal exchange is disclosed in the body of the patent as - in one example, a metal-exchanged molecular sieve is created by blending the molecular sieve into a solution containing soluble precursors of the catalytically active metal. The pH of the solution may be adjusted to induce precipitation of the catalytically active cations onto or within the molecular sieve structure. For example, in a preferred embodiment a chabazite is immersed in a solution containing copper nitrate for a time sufficient to allow incorporation of the catalytically active copper cations into the molecular sieve structure by ion exchange. Un-exchanged copper ions are precipitated out. Depending on the application, a portion of the un-exchanged ions can remain in the molecular sieve material as free copper. The metal-exchanged molecular sieve may then be washed, dried and calcined. When iron and/or copper is used as the metal cation, the metal content of the catalytic material by weight preferably comprises from about 0.1 to about 10 percent by weight, more preferably from about 0.5 to about 10 percent by weight, for example about 1 to about 5 percent by weight or about 2 to about 3 percent by weight, based on the weight of the zeolite. The use of the metal in its elemental form or a metal formate salt solution or soluble compound of alkyl ammonium hydroxide of the metal as a precursor of the metal to be exchanged is neither claimed nor disclosed in the method used to prepare the catalyst of this patent. Neither is use of a gaseous reaction medium during incorporation of the metal into the zeolite claimed or disclosed in this patent.

V. Description of the Present Invention

Figure 1 shows the Temperature programmed Reduction pattern of Cu-SSZ-13 catalyst of Example 1 which is prepared as per the method of the current invention. Two major peaks are observed, one at about 170°C and the other at about 410°C.

Figure 2 shows Diffuse Reflectance UV-VIS spectrum of Cu-SSZ-13 catalyst of Example 1 which is prepared by the method of the current invention. It shows a strong peak at about 220 nm.

Figure 3 shows catalytic performance results for SCR of catalysts of Examples 1 and 3 which are prepared as per the method of the current invention. Details of the test are provided in Example 12. As seen from Figure 3 the catalyst samples prepared by the method of the current invention show good SCR activity over a wide range of temperature ranging from 180°C to 510°C.

Method comprising combination of elemental source of the metal to be ion exchanged, gaseous reaction medium comprising at least carbon dioxide and a liquid reaction medium comprising water or organic solvents. In the present invention it is surprisingly found that the zeolite exchanges with the target metal which is present in its elemental form in the presence of demineralized water and atmospheric air, and, preferably along with the presence of added carbon dioxide gas.

Steps in preparation of the metal exchanged zeolite as per the above-mentioned method are provided below.

1. The crystalline zeolite or a mixture of crystalline zeolites used for ion exchange may be in their alkali form, ammonium form or proton form. Using alkali form is advantageous because it saves costs incurred on ion exchange to ammonium or proton form. The alkali form may be either or both of sodium and potassium.

2. The liquid reaction medium of the method comprises demineralized water. It is taken in a vessel such as an autoclave in sufficient quantity to form a slurry of the zeolites when they are added to it.

3. The metal to be ion exchanged with the zeolite, such as for example copper, is added in its elemental (metallic) form to the demineralized water (liquid reaction medium).

4. The zeolite or a mixture of zeolites is added to the above mixture. And the mixture is stirred/agitated.

5. The pH of the liquid reaction medium is close to neutral. It typically ranges 7±1.

6. The weight ratio of liquid reaction medium to the zeolite ranges from 200 to 2.

7. A gaseous reaction medium such as atmospheric air or carbon dioxide is then added to the vessel. Where added carbon dioxide is used, the ratio of metal to carbon dioxide in the reaction medium ranges from 0.5 to 0.001 molar ratio.

8. Where hydrogen is used along with carbon dioxide as the gaseous reaction medium, the ratio of carbon dioxide to hydrogen in the reaction medium ranges from 3: 1 to 100:0 molar ratio

9. The above mixture is heated to temperature 15 to 200°C. From an energy cost perspective, it is advantageous to carry out the method at lower temperature such as ambient temperature.

10. The pressure of the ion exchange step ranges from 0.1 to 50 bar g. This pressure comprises both the pressure due to the gaseous reaction medium which is added to the vessel as well as autogenous pressure arising from vapor pressure of the liquid medium depending on the temperature of the process. 11. The duration of the ion exchange step for completion of the ion exchange step typically ranges from 0.1 to 48h.

12. Where the ion exchanged zeolite is washed after the ion exchange step the temperature of the water used for washing ranges from 5 to 98°C. The washing step can be avoided and it results in cost savings.

13. The ion exchanged zeolite is recovered by filtration.

14. The ion exchanged zeolite with or without washing is dried at 90 to 150°C and calcined in a gaseous medium comprising a mixture of nitrogen and oxygen.

15. Repeating the steps 2 to 14 above with the ion exchanged zeolite from step 14 instead of a sample of fresh zeolite in step 4, until the desired extent of metal exchange is achieved on the zeolite.

16. The ion exchanged zeolites prepared as per the above method are active for the selective reduction of NOx in the temperature range 150-750°C. They show good hydrothermal stability up to 750°C. Hydrothermal aging is carried out for 16h at 750°C in a stream of air containing 10 mol% water, gas hourly space velocity 900 h ¹. Decrease in activity of the aged catalyst is less than 5% relative to the fresh catalyst prior to aging.

17. The unreacted metal which is used for ion exchange is recovered and reused.

18. The liquid reaction medium can also be reused.

In an embodiment of the present invention the method of preparation of metal exchanged zeolite materials or their mixtures involves the process of carrying out the ion exchange step in the presence of both a liquid reaction medium and a gaseous reaction medium and wherein the precursor of the metal to be exchanged is preferably in the form of the elemental metal itself.

In another embodiment of the present invention the elemental metal which is used for exchanging with ion exchange site of the zeolite can be in any shape, size or form. For example, this metal can be in the form of a fine powder or regular or irregularly shaped granules or extrusions or filings or ingots or any other shape and size.

In a further embodiment of the present invention the liquid reaction medium is a single liquid substance or mixtures of liquid substances which are polar by chemical nature. In a preferred embodiment the liquid reaction medium is preferably water.

In a further embodiment of the present invention the metal in its elemental form is one or more of Copper, Iron, Manganese or Cobalt. In preferred embodiments of the method of the present invention the unreacted metal if any remaining behind after the ion exchange step and the liquid reaction medium are recovered and reused.

In another embodiment of the present patent the gaseous reaction medium is carbon dioxide. In a still further embodiment of the present patent the gaseous reaction medium can be a mixture of carbon dioxide with air or oxygen or nitrogen or hydrogen or argon or helium. Atmospheric air alone also suffices as the gaseous reaction medium. Source of carbon dioxide can also be flue gas from combustion of fossil or renewable fuels/materials. Carbon dioxide is a greenhouse gas and its utilization for useful purposes is desirable from an environmental standpoint.

In further embodiments of the present patent the zeolite is selected from the group having framework CHA, MFI, BEA, AEI (SSZ-39), AFX (SSZ-16/SAPO-56), KFI(ZK-5), LTA (Type A), intergrowth zeolite with AFX/CHA structure, CHA/AEI intergrowth structure, SSZ-52, SSZ- 27, SSZ-28, SSZ-98, SSZ-99, SSZ-104, , ITQ3, SSZ-105, The CHA includes both

aluminosilicate and silicoaluminophosphate materials. Silica alumina molar ratios of the zeolites ranging from about 6 to 200. Crystal size of the zeolites range from 0.02 to 10 pm and particle size of the zeolite in powder form range from 1 to 200 pm. The zeolites may be in any size shape or form such as powder, extrude or beads, trilobes, quadralobes, computer designed shape, tablets or rings etc. Alkali contents of the zeolites are typically less than or equal to about 5000 ppm.

VI. Method Variant 1: Using a soluble compound of alkyl ammonium hydroxide of the metal to be ion exchanged as the precursor of the metal which is to be ion exchanged:

In a variant of the above method, copper metal is reacted with water solution of Alkyl ammonium hydroxide to prepare soluble copper compound. The soluble copper compound is then reacted with zeolite to form corresponding Cu-Zeolite. The subject soluble copper compound i.e. Copper Alkyl Ammonium Hydroxide solution is prepared by reacting Copper metal with Alkyl ammonium hydroxides using the following molar composition relative to one mole of copper metal: 0.1 to 10 moles of Alkyl Ammonium hydroxide; 2 to 200 moles of Water.

1. Cu metal is reacted with water solution of Alkyl Ammonium Hydroxides (Quaternary Alkyl Ammonium Hydroxide) 2. The aforementioned based mixture obtained is then subjected to stirring for 20 minutes to 120 minutes.

3. The mixture obtained is then subjected to thermal or hydrothermal synthesis at a temperature range of 50 to 150 degree Celsius at atmospheric or autogenous pressure from 0-30 bar g in an autoclave for 20 minutes to 180 minutes

4. The soluble Cu solution obtained in above step is separated from the unreacted metal by filtration.

5. Zeolite is added to the soluble Cu solution and the solution is reacted (ion exchanged) with Zeolite to prepare Cu-Zeolite.

6. The zeolite after copper loading is separated by filtration and subjected to drying and calcination or the zeolite after copper loading is spray dried to obtain Cu-Zeolite powder, which is subjected to drying and calcination.

7. Repeating steps 5 and 6 with the Cu-zeolite from step 6 instead of a fresh sample of zeolite until the desired extent of metal exchange is achieved on the zeolite. The Alkyl Ammonium Hydroxides (Quaternary Alkyl Ammonium Hydroxide) may be Tetra Methyl Ammonium Hydroxide or Tetra Ethyl Ammonium Hydroxide or Tetra Propyl Ammonium Hydroxide or Tetra butyl Ammonium Hydroxide or combinations thereof.

VII.Method Variant 2: Using a solution of the formate salt of the metal to be ion exchanged as the precursor of the metal which is to be ion exchanged:

In another variant of the above method copper metal is reacted with aqueous solution of formic acid at elevated temperature (about 90°C with stirring) to form a solution of copper formate. The solution is evaporated to dryness and then redissolved a number of times till pH of the aqueous solution reaches at least 6.0. It is finally evaporated to dryness. An aqueous solution of this solid is used for ion exchange with the zeolite at elevated temperature such as 60°C for 5h. This is followed by washing to remove excess free copper salt which is not bound to the zeolite. This is followed by drying and calcination.

Steps in preparation of the metal exchanged zeolite using a solution of metal formate (Method variant 2) are provided below. 1. The zeolite used for ion exchange may be in its alkali form, ammonium form or proton form. Using alkali form is advantageous because it saves costs incurred on ion exchange to ammonium or proton form.

2. The metal to be exchanged, such as for example copper, is reacted with formic acid at elevated temperature to form a solution of the metal formate.

3. The above solution is evaporated to dryness and redissolved multiple times until the pH of the solution reaches about 6.0.

4. An appropriate amount of the above solution is added to demineralized water and heated to about 60°C.

5. The zeolite is added to the above mixture. And the mixture is stirred/agitated.

6. The weight ratio of liquid reaction medium to the zeolite ranges from 200 to 2.

7. The duration of the ion exchange step ranges from 0.1 to 48h.

8. The ion exchanged zeolite is washed after the ion exchange step. The temperature of the water used for washing ranges from 20 to 70°C.

9. The ion exchanged zeolite is then dried at 90 to 150°C and calcined in a gaseous medium comprising a mixture of nitrogen and oxygen.

10. The copper exchanged CHA zeolite exhibits temperature programmed desorption peaks in the temperature range 150-300°C and 450-600°C and UV-VIS signal in the range 190-300 nm.

11. The ion exchanged zeolite is active for the selective reduction of NO x in the temperature range 150-750°C. It shows good hydrothermal stability up to 750°C.

VIII. Examples

Example 1.

Preparation of Copper exchanged SSZ-13 in accordance with the present invention: 17.24 g copper powder was mixed with 500 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 8.5%) and 3000 ml of demineralized water in a 5L capacity stainless steel autoclave. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 105 °C and continuously stirred for 22 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the autoclave. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 3.5 wt% copper in the ion exchanged SSZ-13 zeolite. Two major reduction peaks were found in H2-TPR at 170°C and 410°C (Fig. 1) and a prominent absorption band at 220 nm in DRUV-Visible spectrum (Fig. 2). Filtrate contained 0.9 ppm Copper. The concentration of dissolved copper remaining behind in the solution after its use for ion exchange is shown in (Table 1). As seen from the Table, the concentration is very low. It is largely less than 1 ppm which is desirable from effluent quality standpoint as well as from loss of valuable metal standpoint.

Table 1: Copper content present in Copper loaded zeolite samples (Cu wt% in final sample) and dissolved Cu content present in mother liquor after filtration

Example 2.

Preparation of Copper exchanged SSZ-13 in accordance with the present invention with washing step: 17.24 g copper powder was mixed with 500 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 8.5%) and 3000 ml of demineralized water in a 5L capacity stainless steel autoclave. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 105 °C and continuously stirred for 22 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the autoclave. Unreacted copper metal was separated. The slurry was filtered, thoroughly washed with deionized water, dried in air 120°C and calcined at 550°C. The product was a greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 3.5 wt% copper in the ion exchanged SSZ-13 zeolite. Two major reduction peaks were found in H2- TPR at 170°C and 400°C and a prominent absorption band at 220 nm in DRUV-Visible spectrum.

Example 3.

Preparation of Copper exchanged SSZ-13 in accordance with the present invention with reduced copper concentration and temperature: 8.62 g copper powder was mixed with 325 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 8.5%) and 3000 ml of demineralized water in a 5L capacity stainless steel autoclave. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 90 °C and continuously stirred for 2 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the vessel. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a mildly greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 2.7 wt% copper in the ion exchanged SSZ-13 zeolite. Two major reduction peaks were found in H2-TPR at 170°C and 400°C and a prominent absorption band at 220 nm in DRUV-Visible spectrum.

Example 4.

Preparation of Copper exchanged SSZ-13 in accordance with the present invention in open atmosphere: 4.31 g copper powder was mixed with 100 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 8.5%) and 800 ml of demineralized water in 2L capacity stainless steel autoclave. Reaction medium was atmospheric air. This mixture was heated to 90 °C and continuously stirred for 6 hours. The slurry consisting of the liquid reaction medium and the copper exchanged zeolite was allowed to settle down. Unreacted copper metal settled down. The slurry was decanted and filtered, dried in air 120°C and calcined at 550°C. The product was a greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 2.5 wt% copper in the ion exchanged SSZ-13 zeolite. Two major reduction peaks were found in H2-TPR at 170°C and 400°C and a prominent absorption band at 220 nm in DRUV- Visible spectrum.

Example 5.

Synthesis of Copper exchanged ZSM-5 in accordance with the present invention: 17.24 g copper powder was mixed with 500 g H-form of ZSM-5 (SAR = 30; LOI at 540°C = 6.5%) and 3000 ml of DM water in a 5L capacity stainless steel autoclave and stirred well. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 90 °C and continuously stirred for 2 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the vessel. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a mildly greenish blue colored powder of Copper containing ZSM-5. Powder X-ray diffraction pattern was characteristic of ZSM-5 structure. Chemical analysis of the sample confirmed the presence of 1.7 wt% copper in the ion exchanged ZSM-5 zeolite.

Two major reduction peaks were found in H2-TPR at 170°C and 270°C and a prominent absorption band at 220 nm in DRUV-Visible spectrum.

Example 6.

Synthesis of Copper exchanged H-Beta Zeolite in accordance with the present invention: 17.24 g copper powder was mixed with 500 g H-form of H-Beta zeolite (SAR = 30; LOI at 540°C = 7.8%) and 3000 ml of DM water in a 5L capacity stainless steel autoclave and stirred well. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 90 °C and continuously stirred for 2 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the vessel. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a mildly greenish blue colored powder of Copper containing Beta zeolite. Powder X-ray diffraction pattern was characteristic of BEA structure. Chemical analysis of the sample confirmed the presence of 2.1 wt% copper in the ion exchanged Beta zeolite.

Two major reduction peaks were found in H2-TPR at 210°C and 300°C and a prominent absorption band at 220 nm in DRUV-Visible spectrum. Example 7.

Synthesis of Copper exchanged SAPO-34 in accordance with the present invention: 17.24 g copper powder was mixed with 500 g SAPO-34 (containing 10 wt% Si02) and 3000 ml of DM water in a 5L capacity stainless steel autoclave and stirred well. Pressurized the autoclave with Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 90 °C and continuously stirred for 2 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the vessel. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a mildly greenish blue colored powder of Copper containing SAPO-34. Powder X-ray diffraction pattern was characteristic of SAPO-34 zeolite. Chemical analysis of the sample confirmed the presence of 1.4 wt% copper in the ion exchanged SAPO-34 zeolite.

One major reduction peak was found in H2-TPR at 230°C and a medium intensity peak at 430°C and a prominent absorption band at 220 nm in DRUV-Visible spectrum.

Example 8.

Preparation of Copper exchanged SSZ-13 in accordance with the present invention using a mixture of C02 and H2 gas: 17.24 g copper powder was mixed with 500 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 8.5%) and 3000 ml of demineralized water in a 5L capacity stainless steel autoclave. Pressurized the autoclave with a mixture of Carbon dioxide and Hydrogen in 3 : 1 ratio at 3 kg/cm2 g. This mixture was heated to 105 °C and continuously stirred for 22 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the autoclave. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 3.53 wt% copper in the ion exchanged SSZ-13 zeolite. Two major reduction peaks were found in H2-TPR at 170°C and 410°C and a shoulder peak at 250 °C. A prominent absorption band at 220 nm in DRUV-Visible spectrum is observed.

Example 9. Preparation of Copper exchanged SSZ-13 using Na-form of SSZ-13 in accordance with the present invention: 17.24 g copper powder was mixed with 500 g of Na-SSZ-13 (SAR = 23; LOI at 540°C = 9.8%) and 3000 ml of demineralized water in a 5L capacity stainless steel autoclave. Pressurized the autoclave with a mixture of Carbon dioxide gas at 3 kg/cm2 g. This mixture was heated to 90 °C and continuously stirred for 4 hours. At the end of this step the gases were vented and the slurry consisting of the liquid reaction medium and the copper exchanged zeolite was drained from the autoclave. Unreacted copper metal was separated. The slurry was filtered, dried in air 120°C and calcined at 550°C. The product was a greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 2.5 wt% copper in the ion exchanged SSZ-13 zeolite. Three major reduction peaks were found in H2-TPR at 200, 300 and 410°C. A prominent absorption band at 220 nm along with shoulder at 280 nm in DRUV-Visible spectrum was observed.

Example 10.

Synthesis of Copper exchanged SSZ-13 using copper and formic acid in accordance with the present invention: 34.48 g Copper powder is digested with stoichiometric excess of formic acid at 90°C until entire copper powder is converted into blue colored copper formate salt solution. The solution is evaporated to dryness in rotaevaporator followed by redissolution in deionized water and further evaporation to dryness. This process was repeated till the aqueous solution of this solid had pH 6.0. It was finally evaporated to dryness in rotaevaporator. The dried copper formate salt was dissolved in 3000 ml of deionized water. To 1500 ml of above solution, 500 g SSZ-13 powder was added and stirred at 60°C for 5 hours. The ion exchanged powder was filtered and washed with equal amount of water, dried at 120°C and calcined at 550°C. The calcined powder was further subjected to a second exchange by repeating the exchange procedure. The final powder is greenish blue colored Copper containing SSZ-13 powder. Powder X-ray diffraction pattern was characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 2.0 wt% copper in the ion exchanged SSZ-13 zeolite. Three reduction peaks were found in H2-TPR at 200, 300 and 650°C. Two prominent absorption bands were observed at 220 and 280 nm in DRUV- Visible spectrum.

Comparative Example 1. Synthesis of Copper exchanged SSZ-13 using copper acetate as per prior art: 30 g CU(CH₃C00)₂H₂0 is dissolved in 1L deionized water to which 100 g H-SSZ-13 Zeolite powder was added. The slurry was stirred in a R.B flask equipped with condenser at 60 °C for 4-5 hours. The slurry is then filtered and washed with 1L of deionized water. The solid was dried at 120°C and subsequently calcined at 550 °C. This exchange process was repeated using the calcined powder. Chemical analysis of the sample confirmed the presence of 3.2 wt% Copper in the ion exchanged SSZ-13 powder. Two reduction peaks were found in H2-TPR at 170 and 420 °C. A major absorption band at 220 nm was observed in DRUV-Visible spectrum.

Example 11.

Coating of copper containing microporous solid on honeycomb type substrate: 100 g of the calcined zeolitic material containing Cu obtained according to example 1 was mixed with both 145 ml of deionized water and 32.66 g Bindizil 2034 DI binder.

The slurry was coated onto 1 " outer diameter x 3" length cylindrical cellular ceramic core having a cell density of 400 cpsi (cells per square inch) and a wall thickness of 6.5 mm. The coated cores were dried at 110° C for 3 hours and calcined at 550°C for 1 hour. The coating process was repeated once to obtain a target washcoat loading of 110 g/1. The washcoat loading is defined as the dry weight gain on the honeycomb with respect to the volume.

Example 12.

Catalytic tests on SCR of NOx over substrates coated with Copper containing microporous solids synthesized by the present invention: Nitrogen oxides selective catalytic reduction (SCR) efficiency of a fresh catalyst core were measured by adding a feed gas mixture of 500 ppm of NO, 550 ppm of NH3, 10% 02, 5% H20, 5%C02, balanced with N2 to a steady state reactor containing a l " outer diameter x 3" length catalyst core.

For the catalytic test, the washcoated honeycomb substrate was placed inside a reactor tube heated by an electrical furnace. The gases NO, NH3, 02, N2, C02 and H20 were preheated in a preheater furnace before entering the reactor.

The reaction was carried at a space velocity of 60,000 h-1 across a 180° C. to 550° C. temperature range. Space velocity is defined as the gas flow rate comprising the entire reaction mixture divided by the geometric volume of the catalyst substrate. The data is presented in Figure 3. A typical method of synthesizing soluble copper compound i.e Cu tetra alkyl ammonium hydroxide and preparing Cu-SSZ-13 (Method variant 1) comprises steps mentioned in below example 13. Example 13.

Preparation of Cu alkyl ammonium hydroxide: 10 g of Cu metal is reacted with 229.6 g of 25 wt% of Tetramethyl ammonium hydroxide (water solution). The solution mixture is then subjected to stirring for 30 minutes. The mixture is then subjected to thermal treatment at a temperature of 145 degree Celsius at atmospheric pressure in a flask for 120 minutes with a condenser. The solution mixture is filtered to separate unreacted Cu metal and soluble Cu solution. The unreacted Cu metal separated is 1 g, indicating 9 g of Cu is reacted with Tetramethyl ammonium hydroxide solution to form Cu tetra methyl ammonium hydroxide solution. The Cu content in Cu tetra methyl ammonium hydroxide is confirmed.

Preparation of Cu-SSZ-13 using Cu tetra alkxl ammonium hydroxide solution:

Preparation of Copper SSZ-13: 238 g of Cu tetra methyl ammonium hydroxide solution is mixed with 306 g of proton form of SSZ-13 (SAR = 23; LOI at 540°C = 5%) and 80 g of demineralized water in a mixing vessel. Additional amount of water is added to make uniform paste or slurry. The content is continuously mixed for 1 hours. The material is dried in air at 120°C and calcined at 550°C. The product is a light greenish blue colored powder of Copper containing SSZ-13. Powder X-ray diffraction pattern is characteristic of SSZ-13. Chemical analysis of the sample confirmed the presence of 2.86 wt% copper in the Cu-SSZ-13 zeolite.

Claims

We claim:

1. A process for producing a metal exchanged zeolite or mixtures of metal exchanged

zeolites, the process comprising:

i) preparing a mixture of a crystalline zeolite material(s), the desired metal(s) to be exchanged in its elemental form, a liquid reaction medium and a gaseous reaction medium

ii) heating the resulting mixture for sufficient duration until the metal has substantially exchanged with ion exchange sites on the zeolite

iii) filtering the resulting slurry to recover the ion exchanged zeolite

iv) separating and recovering unreacted metal if any from the recovered ion exchanged zeolite material

v) drying and calcination of the resulting ion exchanged material to obtain metal exchanged zeolite which is useful for selective catalytic reduction of oxides of nitrogen. vi) repeating the above steps by substituting the crystalline zeolite(s) in step (i) with the metal exchanged zeolite from step (v) above until the desired extent of metal exchange is achieved.

2. The process of claim 1 wherein at least one element of the gaseous reaction medium is carbon dioxide or a gas mixture containing it.

3. The process of claim 1 wherein the metal exchanged zeolite is optionally washed with water after step (iv).

4. The process of claim 1 wherein the gaseous reaction medium is added till a desired target pressure is achieved.

5. The process of claim 4 wherein part of the target pressure may be autogenous due to vaporization of the liquid reaction medium

6. The process of claim 1 wherein the gaseous reaction medium is atmospheric air with or without added carbon dioxide

7. The process of claim 1, wherein the liquid reaction medium is water or a polar solvent or mixtures thereof

8. The process of claim 7, wherein the pH of the liquid reaction medium ranges from about 6 to 8.

9. The process of claim 1, wherein the weight ratio of the liquid reaction medium water to the said zeolite is from 200 to 2

10. The process of claim 1, wherein the gaseous reaction medium is carbon dioxide.

11. The process of claim 1 wherein the gaseous reaction medium is a mixture of carbon

dioxide and one or more of hydrogen, air, oxygen, nitrogen, argon, helium or flue gas containing carbon dioxide resulting from combustion of fossil or renewable fuels.

12. The process of claims 1, 10 or 11, wherein the molar ratio of the metal to be exchanged to C02 is 0.5 to 0.001.

13. The process of claim 11, wherein the molar ratio of C02:H2 or air ranges from 3: 1 to

100:0.

14. The process of claim 1, wherein the temperature to which the mixture is subjected to in step (ii) of claim 1 ranges from 20°C to 200°C.

15. The process of claim 1, wherein the pressure to which the mixture is subjected in step (ii) ranges from 0.1 bar g to 50 bar g

16. The process of claim 1, wherein the said duration in step (ii) ranges from 0.1 h to 48h

17. The process of claim 3, wherein the step of the metal exchanged zeolite being washed with water is performed at temperature ranging from 5°C to 98°C

18. The process of claim 1, wherein the steps of drying and calcination of step (v) of claim 1 are performed at the temperature of 90-120°C and 450-650°C respectively.

19. The process of claim 1, wherein the metal exchange can be done on zeolite in multiple forms like powder, extrude or beads, trilobes, quadralobes, computer designed shape, tablets or rings etc.

20. The process of claim 1 and 19, wherein the metal exchange can be done on neat zeolite (free of binder)

21. The process of claim 19, wherein the zeolite can be bound with a binder such as silica, alumina, zirconia, titania, clays, bentonite etc.

22. A process for preparing a metal exchanged zeolite, the process comprising: i) adding the metal to be exchanged in its elemental form to an aqueous solution of an alkyl ammonium salt

ii) stirring the mixture for 20-120 minutes. iii) heating the above mixture to 50-150°C in a closed vessel under autogeneous pressure or open vessel at atmospheric pressure for 20- 180 minutes to obtain the soluble metal alkyl ammonium complex.

iv) The soluble metal alkyl ammonium solution complex obtained in step (iii) is filtered to separate unreacted metal and soluble metal tetra alkyl ammonium compound.

v) adding the zeolite or a mixture of zeolites to be impregnated or ion exchanged with the above metal tetra alkyl ammonium compound solution, adding water and mixing the same. vi) heating the mixture obtained in step (v) to a temperature of 20-120°C in a closed vessel for a duration of 0.1 to 48h to facilitate the process of ion exchange or impregnation vii) in case of ion exchange wherein additional water is used, filtering the resultant mixture to recover the solids from the ion exchanged zeolite solution.

viii) drying and calcining the ion exchanged zeolite. ix) repeating the steps (v) to (viii) by substituting the zeolite in step (v) with the ion exchanged zeolite from step (viii) above until the desired extent of metal exchange is achieved on the zeolite.

23. The process of claim 22 wherein the soluble metal compound of the alkyl ammonium salt in step (i) is prepared at autogenous pressure ranging from 0 to 30 bar g.

24. The process of claim 22 wherein the soluble metal compound of the alkyl ammonium salt is diluted with water to either impregnate or ion exchange with zeolite.

25. The process of claim 22 wherein the alkyl ammonium salt in step (i) is Tetra Methyl Ammonium Hydroxide, Tetra Ethyl Ammonium Hydroxide, Tetra Propyl Ammonium Hydroxide, Tetra butyl Ammonium Hydroxide or combinations thereof.

26. The process of claim 22 wherein the soluble metal compound of the alkyl ammonium salt in step (i) is prepared at a temperature of 50-150°C.

27. The process of claim 22 wherein the soluble metal compound of the alkyl ammonium salt in step (i) is prepared over a duration of 20 to 180 minutes at the process conditions.

28. The process of claim 22 wherein the mole ratio of the alkyl ammonium salt to the metal, for example copper, ranges from 0.1 to 10.

29. The process of claim 22 wherein the mole ratio of water used for preparation of soluble metal compound of the alkyl ammonium salt to the metal ranges from 2 - 200.

30. The process of claim 22 wherein the process of ion exchange of the zeolite with the soluble metal compound of the alkyl ammonium salt is carried out at 20-120°C.

31. The process of claim 22 wherein the process of ion exchange of the zeolite with the soluble metal compound of the alkyl ammonium salt is carried out at pressure ranging from atmospheric to 30 bar g autogenous.

32. The process of claim 22 wherein the process of ion exchange of the zeolite with the soluble metal compound of the alkyl ammonium salt is carried out over a duration of 0.1 to 48h

33. The process of claim 22 wherein the ion exchanged catalyst is dried at a temperature of about 90-120°C and calcined in a mixture of nitrogen and air at 450-650°C in step (viii).

34. The process of claims 1 or 22 wherein the crystalline zeolite material has CHA or MFI or BEA framework or mixtures thereof

35. The process of claim 34, wherein the zeolite material has SSZ-13 and/or SAPO-34

structure.

36. The process of claim 34, wherein the Si02/A1203 molar ratio of the CHA, MFI or BEA zeolite material ranges from 6 to 200;

37. The process of claim 35, wherein the silica content in SAPO-34 varies from 6-15 wt% as Si02.

38. The process of claim 34, wherein the zeolite material with CHA framework has

Si02/A1203 molar ratio ranging from 6 to 150

39. The process of claim 34 wherein the zeolite material is in the alkali form and the said alkali is either or both of sodium and potassium

40. The process of claim 34, wherein the alkali content of the zeolite material is < about 1000 ppm.

41. The process of claim 34, wherein the zeolite material is in the proton form

42. The process of claim 34, wherein the zeolite material is in the ammonium form

43. The process of claim 34, wherein the crystallite size of the zeolite material ranges from 0.2 to 5 pm

44. The process of claims 1 or 22, wherein the zeolite material is CHA in the proton form with crystal size 0.3 to 3 pm and the residual alkali present if any is either or both of sodium and potassium

45. The process of claims 1 or 22, wherein the metal to be exchanged with the zeolite material in steps (i) is Cu, Fe, Mn, Co or mixtures thereof.

46. The process of claim 1 wherein the metal to be exchanged is in the form of its formate salt.

47. The process of claim 46 wherein the pH of aqueous solution of the formate salt is brought to about 6 by multiple dissolutions and recrystallization.

48. The process of claim 45, wherein the copper exchanged zeolite has at least two reduction peaks in H2-TPR signal in the range 150-300 °C and 350-650°C.

49. The process of claim 45, wherein the copper exchanged zeolite has at least one UV signal in the range 190-300 nm.

50. The process of claim 1 or 22, wherein the metal loading of the ion exchanged zeolite is in the range of 0.1 to 10 wt%.