Patent Application
20240174523
The present invention relates to a process for synthesis of zeolitic materials having AFT framework structure, use of the zeolitic materials for selective catalytic reduction (SCR) of nitrogen oxides and SCR catalysts comprising the same.
Small-pore zeolites having pore openings of smaller than 5 Angstroms (Å), such as those of CHA, AEI or AFX type, have been found excellent as sorbents or catalysts in various applications, for example for separation of gases or for conversion reaction of organic compounds, such as methanol-to-olefins (MTO). Small-pore zeolites having other framework structures received increasing attention of researchers with the hope of finding more potential candidates for small-pore zeolite sorbents or catalysts.
For example, U.S. Pat. No. 10,343,927 B2 describes a novel aluminosilicate zeolite of AFT type. The zeolite of AFT type are small-pore zeolites, which were first known as aluminophosphate (AlPO) framework structure. The aluminosilicate zeolite of AFT type, designated as SSZ-112 in U.S. Pat. No. 10,343,927 B2, was prepared from a synthesis gel comprising sources of SiO2, Al2O3, Group 1 metal, hydroxide ions, hexamethonium dication ions as the first organic templates (Q1) and one or more of 1-methyl-1-alkylpyrrolidinium cations and 1-methyl-1-alkylpiperidinium cations as the second organic template (Q2), where each alkyl group is independently C1-C5 alkyl. It was mentioned in the patent that the zeolite SSZ-112 may be used as a catalyst for a wide variety of organic or inorganic conversion processes including alkylation, cracking, hydrocracking, isomerization, oligomerization, conversion of organic oxygenates (e.g., methanol and/or dimethyl ether) to olefins (e.g., ethylene, propylene), synthesis of monoalkylamines and dialkylamines, and the catalytic reduction of nitrogen oxides.
The process for preparing the aluminosilicate zeolite of AFT type as reported is limited to the very particular organic structure directing agents (OSDAs). There remains a need of more processes for preparing aluminosilicate zeolites of AFT type, particularly processes which could provide aluminosilicate zeolites of AFT type with desirable catalytic activities in SCR applications.
It is an object of the present invention to provide a novel process for preparing aluminosilicate zeolites having AFT framework structure.
The object was achieved by using N,N,N,N′,N′,N′-hexaethyl alkylenediammonium organic structure directing agent and optionally another organic structure directing agent selected from quaternary ammonium organic structure directing agent, piperidinium organic structure directing agent and pyrrolidinium organic structure directing agent.
Another object of the present invention is to provide an SCR catalyst based on a zeolite having AFT framework structure, which has desirable activity, particularly combined with excellent stability against aging at a high temperature, for example 800° C. or higher.
It has been surprisingly found that the object was achieved by an SCR catalyst composition which comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal.
Accordingly, in one aspect, the present invention relates to a process for preparing an aluminosilicate zeolite having AFT framework structure, which includes
In this aspect, the present invention also relates to a process for preparing an aluminosilicate zeolite having AFT framework structure, which includes
In another aspect, the present invention relates to an aluminosilicate zeolite having AFT framework structure obtained and/or obtainable by the process as described herein.
In still another aspect, the present invention relates to an SCR catalyst composition which comprises an aluminosilicate zeolite having AFT framework structure obtained and/or obtainable by the process as described herein and a promoter metal.
In yet another aspect, the present invention relates to a catalytic article in form of extrudates comprising an SCR catalyst composition or in form of a monolith comprising a washcoat containing an SCR catalyst composition on a substrate, wherein the SCR catalyst composition comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal.
In a further aspect, the present invention relates to an exhaust gas treatment system comprising an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalytic article as described herein is present in the exhaust gas conduit.
The present invention will be described in detail hereinafter. It is to be understood that the present invention may be embodied in many different ways and shall not be construed as limited to the embodiments set forth herein.
Herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. The terms “comprise”, “comprising”, etc. are used interchangeably with “contain”, “containing”, etc. and are to be interpreted in a non-limiting, open manner. That is, e.g., further components or elements may be present. The expressions “consists of” or “consists essentially of” or cognates may be embraced within “comprises” or cognates.
The term “AFT” as used herein refer to AFT framework type as recognized by the International Zeolite Association (IZA) Structure Commission.
The term “aluminosilicate” as used within the context of zeolite is intended to mean the framework constructed primarily of alumina and silica, which may or may not comprise a framework metal other than aluminum and silicon. When a framework metal other than aluminum is present in place of one or more aluminum or silicon framework atoms, the aluminosilicate zeolite may be referred to as “metal-substituted”.
The terms “zeolite having AFT framework structure”, “zeolite of AFT type”, “AFT zeolite” and the like as used herein are intended to refer to a material which shows an XRD pattern of an AFT framework structure, and will be used interchangeably with each other hereinbelow. Those terms are also intended to include any forms of the zeolite, for example as-synthesized form, calcined form, NH4-exchanged form, H-form and metal-substituted form.
The term “as-synthesized” as used herein is intended to refer to a zeolite in its form after crystallization and drying, prior to removal of the organic structure directing agents.
The term “calcined form” as used herein is intended to refer to a zeolite in its form upon calcination.
In the first aspect, the present invention provides a process for preparing an aluminosilicate zeolite having AFT framework structure, which includes
The first organic structure directing agent particularly comprises a N,N,N,N′,N′,N′-hexaethyl alkylenediammonium cation (OSDA1) wherein the alkylene moiety is selected from substituted or unsubstituted straight chain or branched chain C3-C10 alkanediyl, preferably unsubstituted straight chain or branched chain C3-C10 alkanediyl.
The first organic structure directing agent preferably comprises a N,N,N,N′,N′,N′-hexaethyl alkylenediammonium cation (OSDA1) represented by the following formula (IV):
(C2H5)3N+(CH2)nN+(C2H5)3 (IV)
In some embodiments, the first organic structure directing agent comprises a cation selected from the group consisting of N,N,N,N′,N′,N′-hexaethyl-1,3-propanediammonium, N,N,N,N′,N′,N′-hexaethyl-1,4-butanediammonium, N,N,N,N′,N′,N′-hexaethyl-1,5-pentane diammonium, N,N,N,N′,N′,N′-hexaethyl-1,6-hexanediammonium, N,N,N,N′,N′,N′-hexaethyl-1,7-heptanediammonium, and any combinations thereof. Preferably, the first organic structure directing agent comprises a cation selected from the group consisting of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium, N,N,N,N′,N′,N′-hexaethyl-1,6-hexanediammonium, N,N,N,N′,N′,N′-hexaethyl-1,7-heptanediammonium, and any combinations thereof, more preferably N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium.
In some embodiments, the second organic structure directing agent particularly comprises (C2-i) a quaternary ammonium cation represented by formula (I),
The second organic structure directing agent preferably comprises (C2-i) a quaternary ammonium cation represented by formula (I) wherein R1, R2 and R3, independently from each other, are methyl, ethyl, n-propyl or iso-propyl; and R4 is selected from methyl, ethyl, n-propyl, iso-propyl, cyclopentyl, cyclohexyl, cycloheptyl, phenyl and benzyl, each being optionally substituted by one or more hydroxyl groups.
More preferably, the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from N,N,N-triethylmethylammonium, N,N,N-trimethyl-2-hydroxylethylammonium, N,N,N-trimethyl ethylammonium, tetraethylammonium, N,N,N-trimethylcyclopentylammonium, N,N,N-trimethylcyclohexylammonium, N,N,N-trimethylcycloheptylammonium, N,N-dimethyl-N-ethylcyclopentylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-dimethyl-N-ethylcycloheptylammonium, N,N-diethyl-N-methylcyclopentylammonium, N,N-diethyl-N-methylcyclohexylammonium, N,N-diethyl-N-methylcycloheptylammonium, N,N,N-trimethylphenylammonium, N,N,N-triethylphenylammonium, N,N-dimethyl-N-ethylphenylammonium, N-methyl-N,N-diethylphenylammonium, N,N,N-trimethylbenzylammonium, N,N,N-triethylbenzylammonium, N,N-dimethyl-N-ethylbenzylammonium, N-methyl-N,N-diethylbenzylammonium and any combinations thereof.
In certain illustrative embodiments, the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from the group consisting N,N,N-triethylmethylammonium, N,N,N-trimethyl-2-hydroxylethylammonium, tetraethylammonium, N,N,N-trimethylcyclohexylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-diethyl-N-methylcyclohexylammonium, N,N,N-trimethylphenylammonium, N,N-dimethyl-N-ethylphenylammonium, N-methyl-N,N-diethylphenylammonium and any combinations thereof.
Preferably, the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from the group consisting tetraethylammonium, N,N-dimethyl-N-ethylcyclohexylammonium and the combination thereof.
In some other embodiments, the second organic structure directing agent particularly comprises (C2-ii) a piperidinium cation represented by the following formula (II):
The second organic structure directing agent preferably comprises (C2-ii) a piperidinium cation represented by the following formula (II) wherein Ra and Rb, independently from each other, are C1-C5 alkyl, R, and Rg are H, and Rd, Re and Rf independently from each other, are H, hydroxyl or C1-C5 alkyl.
More preferably, the second organic structure directing agent comprises (C2-ii) a piperidinium cation represented by the following formula (II) wherein Ra is C1-C3 alkyl, Rb is C1-C5 alkyl, Rd and Rf independently from each other are H or C1-C5 alkyl, and Rc, Re and Rg are H.
In certain illustrative embodiments, the second organic structure directing agent comprises (C2-ii) a piperidinium cation selected from 1,1-dimethylpiperidinium, 1,1,3,5-tetramethylpiperidinium, 1-methyl-1-ethylpiperidinium, 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1,1-diethylpiperidinium, 1-ethyl-1-n-propylpiperidinium, 1-ethyl-1-n-butylpiperidinium and any combinations thereof. Preferably, the second organic structure directing agent comprises (C2-ii) a piperidinium cation selected from the group consisting of 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1-ethyl-1-n-propylpiperidinium and any combinations thereof.
In some other embodiments, the second organic structure directing agent particularly comprises (C2-iii) a pyrrolidinium cation represented by formula (III):
The second organic structure directing agent preferably comprises (C2-iii) a pyrrolidinium cation represented by formula (III) wherein Ro and Rp, independently from each other, are C1-C5 alkyl, and Rq, Rr, Rs and Rt are H.
In certain illustrative embodiments, the second organic structure directing agent comprises (C2-iii) a pyrrolidinium cation selected from 1-methyl-1-ethylpyrrolidinium, 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium, 1,1-diethylpyrrolidinium, 1-ethyl-1-n-propylpyrrolidinium, 1-ethyl-1-n-butylpyrrolidinium and any combinations thereof. Preferably, the second organic structure directing agent comprises (C2-iii) a pyrrolidinium cation selected from the group consisting of 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium and any combinations thereof.
In some preferable embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, the first organic structure directing agent comprises a N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium cation and the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from the group consisting N,N,N-triethylmethylammonium, N,N,N-trimethyl-2-hydroxylethylammonium, tetraethylammonium, N,N,N-trimethylcyclohexylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-diethyl-N-methylcyclohexylammonium, N,N,N-trimethylphenylammonium, N,N-dimethyl-N-ethylphenylammonium, N-methyl-N,N-diethylphenylammonium and any combinations thereof, (C2-ii) a piperidinium cation selected from 1,1-dimethylpiperidinium, 1,1,3,5-tetramethylpiperidinium, 1-methyl-1-ethylpiperidinium, 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1,1-diethylpiperidinium, 1-ethyl-1-n-propylpiperidinium, 1-ethyl-1-n-butylpiperidinium and any combinations thereof, or (C2-iii) a pyrrolidinium cation selected from 1-methyl-1-ethylpyrrolidinium, 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium, 1,1-diethylpyrrolidinium, 1-ethyl-1-n-propylpyrrolidinium, 1-ethyl-1-n-butylpyrrolidinium and any combinations thereof.
In some further preferable embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, the first organic structure directing agent comprises a N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium cation and the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from the group consisting of tetraethylammonium, N,N-dimethyl-N-ethylcyclohexylammonium and the combination thereof, (C2-ii) a piperidinium cation selected from the group consisting of 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1-ethyl-1-n-propylpiperidinium and any combinations thereof, or (C2-iii) a pyrrolidinium cation selected from the group consisting of 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium and any combinations thereof.
The first and second organic structure directing agents may be used in a molar ratio in terms of respective cations in the range of 10:1 to 1:30, or 5:1 to 1:30, or 4:1 to 1:25, preferably 3:1 to 1:25, more preferably 3:1 to 1:20.
In some exemplary embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation, and the first and second organic structure directing agents are used in a molar ratio in terms of diammonium cation to quaternary ammonium cation in the range of 10:1 to 1:5, or 5:1 to 1:1, preferably 3:1 to 2:1. More preferably, the first organic structure directing agent comprises a N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium cation and the second organic structure directing agent comprises (C2-i) a quaternary ammonium cation selected from the group consisting of N,N,N-triethylmethylammonium, N,N,N-trimethyl-2-hydroxylethylammonium, tetraethylammonium, N, N, N-trimethylcyclohexylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-diethyl-N-methylcyclohexylammonium, N,N,N-trimethylphenylammonium, N,N-dimethyl-N-ethylphenylammonium, N-methyl-N,N-diethylphenylammonium and any combinations thereof, preferably tetraethylammonium, N,N-dimethyl-N-ethylcyclohexylammonium and the combination thereof.
In some other exemplary embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, the second organic structure directing agent comprises (C2-ii) a piperidinium cation, and the first and second organic structure directing agents are used in a molar ratio in terms of diammonium cation to piperidinium cation in the range of 1:1 to 1:30, or 1:2 to 1:25, preferably 1:4 to 1:25, more preferably 1:5 to 1:20. More preferably, the first organic structure directing agent comprises a N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium cation and the second organic structure directing agent comprises (C2-ii) a piperidinium cation selected from the group consisting of 1,1-dimethylpiperidinium, 1,1,3,5-tetramethylpiperidinium, 1-methyl-1-ethylpiperidinium, 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1,1-diethylpiperidinium, 1-ethyl-1-n-propylpiperidinium, 1-ethyl-1-n-butylpiperidinium and any combinations thereof, preferably 1-methyl-1-n-propylpiperidinium, 1-methyl-1-n-butylpiperidinium, 1-ethyl-1-n-propylpiperidinium and any combinations thereof.
In some further exemplary embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, the second organic structure directing agent comprises (C2-iii) a pyrrolidinium cation, and the first and second organic structure directing agents are used in a molar ratio in terms of diammonium cation to pyrrolidinium cation in the range of 1:1 to 1:30, or 1:2 to 1:25, preferably 1:4 to 1:20, more preferably 1:5 to 1:15. More preferably, the first organic structure directing agent comprises a N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium cation and the second organic structure directing agent comprises (C2-iii) a pyrrolidinium cation selected from 1-methyl-1-ethylpyrrolidinium, 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium, 1,1-diethylpyrrolidinium, 1-ethyl-1-n-propylpyrrolidinium, 1-ethyl-1-n-butylpyrrolidinium and any combinations thereof, preferably 1-methyl-1-n-propylpyrrolidinium, 1-methyl-1-n-butylpyrrolidinium and any combinations thereof.
The synthesis mixture may or may not comprise a further organic structure directing agent. In some embodiments, the synthesis mixture does not comprise any organic structure directing agent other than the first and second organic structure directing agents.
Suitably, the first and second organic structure directing agents, independently from each other, are in form of halide such as fluoride, chloride and bromide, hydroxide, sulfate, nitrate and carboxylate such as acetate of respective cations as described herein above, preferably chloride, bromide, hydroxide and sulfate.
Preferably, the first and second organic structure directing agents, independently from each other, are hydroxides of respective cations as described herein above.
The first and second organic structure directing agents may be present in the synthesis mixture in a total molar ratio relative to source(s) for SiO2, calculated as the sum of the cations (OSDA1+OSDA2) to SiO2, in the range of from 0.01 to 1.0, preferably from 0.03 to 0.5, more preferably from 0.05 to 0.3.
There is no particular restriction to the sources for Al2O3 and SiO2. Suitable examples of the source for Al2O3 may include, but are not limited to alumina, aluminates, aluminum alkoxides and aluminum salts, preferably alumina, aluminum tri(C1-C5)alkoxides, AlO(OH), Al(OH)3, aluminum halides, aluminum sulfate, aluminum phosphate and aluminum fluorosilicate.
Suitable examples of the source for SiO2 may include, but are not limited to fumed silica, precipitated silica, silica hydrosols, silica gels, colloidal silica, silicic acid, silicon alkoxides, alkali metal silicates, sodium metasilicate hydrate, sesquisilicate, disilicate and silicic acid esters. Combined sources for Al2O3 and SiO2 may be used alternatively or additionally, for example aluminosilicate zeolite such as FAU zeolite.
In some embodiments of the process for preparing an aluminosilicate zeolite having AFT framework structure, an FAU zeolite as the combined sources for Al2O3 and SiO2 and an additional source for SiO2 are used. Particularly the FAU zeolite is zeolite Y, preferably zeolite Y having a molar ratio of SiO2 to Al2O3 of no more than 40, no more than 30, no more than 20, or even no more than 10. The additional source for SiO2 is selected from the group consisting of fumed silica, precipitated silica, silica hydrosols, silica gels, colloidal silica.
The synthesis mixture provided in step (1) may comprise the source(s) for SiO2 and the source(s) for Al2O3 in a molar ratio calculated as SiO2 to Al2O3 in the range of from 5 to 100, preferably from 30 to 80, more preferably from 40 to 60.
The synthesis mixture provided in step (1) may further comprise a source for alkali metal and/or alkaline earth metal cations (AM), preferably alkali metal cations. The alkali metal is preferably selected from the group consisting of Li, Na, K, Cs and any combinations thereof, more preferably Na and/or K, and most preferably Na. The alkaline earth metal is preferably selected from the group consisting of Mg, Ca, Sr and Ba. Suitable sources for alkali metal and/or alkaline earth metal cations (AM) are typically halide such as fluoride, chloride and bromide, hydroxide, sulfate, nitrate and carboxylate such as acetate of alkali metal and/or alkaline earth metal, or any combinations thereof. Preferably, the sources for the alkali metal and/or alkaline earth metal cations (AM) include chloride, bromide, hydroxide or sulfate of the alkali metal and/or alkaline earth metal, or any combinations thereof. More preferably, hydroxide of alkali metal is used in the synthesis mixture.
The alkali metal and/or alkaline earth metal cations (AM) may be present in the synthesis mixture in a molar ratio relative to the source(s) for SiO2, calculate as AM to SiO2, in the range of from 0.01 to 1.0, preferably from 0.1 to 1.0, more preferably from 0.3 to 0.8.
The synthesis mixture provided in step (1) may also comprise a source for the anion OH−. Useful source for OH− may be for example a metal hydroxide such as alkali metal hydroxide or ammonium hydroxide. Preferably, the anion OH− may be originated from one or more of the source for alkali metal and/or alkaline earth metal cations (AM) and the sources for the first and/or second organic structure directing agents.
The OH− anions may be present in the synthesis mixture in a molar ratio relative to the source(s) for SiO2, calculated as OH− to SiO2, in the range of from 0.1 to 2.0, more preferably from 0.2 to 1.0, more preferably from 0.5 to 1.0.
The synthesis mixture provided in step (1) may also comprise at least one solvent, preferably water, more preferably deionized water. The solvent may be comprised in one or more of starting materials of the synthesis mixture, such as the sources for Al2O3, SiO2 and the first and/or second organic structure directing agents and thus be carried into the synthesis mixture, and/or may be incorporated into the synthesis mixture separately.
In some embodiments, the synthesis mixture has a molar ratio of water to the source(s) for SiO2, calculated as H2O to SiO2, in the range of from 3 to 100, preferably from 10 to 80, more preferably from 20 to 60.
In some exemplary embodiments, the synthesis mixture provided in step (1) have a molar composition as shown in the Table 1 below:
1)the amounts of the sources for Al2O3 and SiO2 are calculated as respective oxides, and the amounts of OSDA1 and OSDA2 are calculated as respective cations
The synthesis mixture may be subjected to crystallization conditions to form an AFT zeolite in step (2) with no particular restriction. The crystallization may be carried out at an elevated temperature in the range of from 80 to 250° C., more preferably from 100 to 200° C. for a period sufficient for crystallization, for example 0.5 to 12 days, 1 to 6 days, or 2 to 5 days. Typically, the crystallization is carried out under autogenous pressure, for example in a pressure tight vessel such as an autoclave. Further, the crystallization is preferably carried out without agitation.
The aluminosilicate zeolite as formed may be subjected to a work-up procedure including isolating for example by filtration, optionally washing, and drying to obtain the as-synthesized AFT zeolite. Accordingly, step (2) in the process according to the present invention optionally further comprises the work-up procedure.
The as-synthesized AFT zeolite typically comprises within its structure pores at least a portion of the first and second organic structure directing agents as described hereinabove.
In some embodiments, the as-synthesized AFT zeolite from step (2) may be subjected to a calcination procedure. Accordingly, the process according to the present invention further comprises step (3) of calcination of the as-synthesized AFT zeolite.
In some embodiments, the as-synthesized or the as-calcined AFT zeolite may be subjected to an ion-exchange procedure such that one or more of ionic non-framework elements contained in the zeolite are exchanged to H+ and/or NH4+. Accordingly, the process according to the present invention further comprises
(4) exchanging one or more of ionic non-framework elements contained in the zeolite obtained in step (2) or (3) to H+ and/or NH4+, preferably NH4+.
Generally, the zeolite having been exchanged to H+ and/or NH4+ in step (4) may be subjected to a work-up procedure including isolating for example by filtration, optionally washing, and drying, and/or subjected to a calcination procedure. Accordingly, step (4) in the process according to the present invention optionally further comprises the work-up procedure and/or calcination procedure.
The calcination in step (3) and/or step (4) may be carried out at a temperature in the range of from 300 to 900° C., for example 350 to 700° C., or 400 to 650° C. Particularly, the calcination may be performed in a gas atmosphere having a temperature in the above-described ranges, which may be air, oxygen, nitrogen, or a mixture of two or more thereof. Preferably, the calcination is performed for a period in the range of from 0.5 to 10 hours, for example 3 to 7 hours, or 4 to 6 hours.
In some variants of the process for preparing an aluminosilicate zeolite having AFT framework structure according to the present invention, the second organic structure directing agent may not be used.
Accordingly, the present invention also provides a process for preparing an aluminosilicate zeolite having AFT framework structure, which includes
In some particular embodiments, no organic structure directing agent other than the organic structure directing agent comprising a N,N,N,N′,N′,N′-hexaethyl alkylenediammonium cation as described hereinabove is used in the process according to the variants.
The N,N,N,N′,N′,N′-hexaethyl alkylenediammonium cations as described generally and preferably for any embodiments hereinabove are applicable here for the process according the variants.
In some particular embodiments according to the variants, the synthesis mixture provided in step (1) may have a molar composition as shown in the Table 2 below:
1)the amounts of the sources for Al2O3 and SiO2 are calculated as respective oxides.
The process may be carried out otherwise in the same manner as described herein above for the process using the first and second organic structure directing agents.
Aluminosilicate zeolites having AFT framework structure could be successfully obtained from the processes as described in the first aspect, as determined by X-ray powder diffraction (XRD) analysis.
Accordingly, in the second aspect, the present invention also provides an aluminosilicate zeolite having AFT framework structure obtainable and/or obtained from the processes as described in the first aspect.
The aluminosilicate zeolite having AFT framework structure has a molar ratio of silica to alumina (SAR) of 10 to 25, preferably 11 to 20, more preferably 11 to 18, as determined in its calcined H-form.
The aluminosilicate zeolite having AFT framework structure according to the present invention typically has an average crystal size of up to 1 μm, or up to 500 nm, for example in the range of from 200 nm to 500 nm. The average crystal size may be determined via scanning electron microscopy (SEM). Particularly, the average crystal size was determined via SEM by measuring the crystal sizes for at least 30 different crystals selected at random from multiple images covering different areas of the sample.
In some embodiments, the aluminosilicate zeolite having AFT framework structure according to the present invention may have a mesopore surface area (MSA) of no more than 60 m2/g, preferably no more than 50 m2/g, more preferably no more than 45 m2/g, for example 1 to 50 m2/g, or 3 to 40 m2/g. Alternatively or additionally, the aluminosilicate zeolite having AFT framework structure has a zeolitic surface area (ZSA) of at least 400 m2/g, or at least 450 m2/g, for example in the range of 450 to 650 m2/g or 450 to 600 m2/g. The mesopore surface area and zeolitic surface area may be determined via N2-adsorption porosimetry.
The aluminosilicate zeolite having AFT framework structure according to the present invention is preferably at least 90% phase pure, i.e., at least 90% of the zeolite framework is of AFT type, as determined by X-ray powder diffraction (XRD) analysis. More preferably, the aluminosilicate zeolite having AFT framework structure is at least 95% phase pure, or even more preferably at least 98% or at least about 99%.
In some embodiments, the aluminosilicate zeolite having AFT framework structure may contain some other framework like AFX or CHA as intergrowth in minor amounts, for example less than 10%, preferably less than 5%, even more preferably less than 2% or less than 1%.
It has been surprisingly found that the aluminosilicate zeolite having AFT framework structure as obtained from the processes as described in the first aspect exhibits significantly higher stability against aging at a temperature of 800° C. or higher in the application of selective catalytic reduction (SCR) of NOx, compared with the catalysts comprising a zeolite having the same framework type but prepared otherwise.
Accordingly, in the third aspect, the present invention further provides an SCR catalyst composition which comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal.
The term “promoter metal” as used herein refers to a non-framework metal capable of improving the catalytic activity of a zeolite. The “non-framework metal” is intended to mean that the metal does not participate in constituting the zeolite framework structure. The promoter metal may reside within the zeolite and/or on at least a portion of the zeolite surface, preferably in form of ionic species.
Particularly, the SCR catalyst composition according to the present invention comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal present within and/or on the aluminosilicate zeolite having AFT framework structure.
The aluminosilicate zeolites having AFT framework structure useful in the SCR catalyst composition according to the present invention are obtained and/or obtainable by the processes as described in the first aspect or are those as described in the second aspect. Any general and particular description with respect to the processes in the first aspect or the aluminosilicate zeolites having AFT framework structure as in the second aspect are incorporated here by reference.
The promoter metal may be any metals known useful for improving catalytic performance of zeolites in the application of selective catalytic reduction (SCR) of NOx. Generally, the promoter metal may be selected from transition metals, for example precious metals such as Au and Ag and platinum group metals, base metals such as Cr, Zr, Nb, Mo, Fe, Mn, W, V, Ti, Co, Ni, Cu and Zn, alkali earth metals such as Ca and Mg, and Sb, Sn and Bi, and any combinations thereof.
In a preferable embodiment, the SCR catalyst composition comprises at least Cu and/or Fe as the promoter metal. In some particular embodiments, the SCR catalyst composition comprises Cu as the promoter metal. Particularly, the promoter metal used in the SCR catalyst composition consists of Cu.
The promoter metal may be present in the SCR catalyst composition at an amount of 0.1 to 10% by weight, preferably 0.5 to 10% by weight, more preferably 1 to 7% by weight, particularly 2 to 5% by weight, on an oxide basis, based on the total weight of the promoter metal and the aluminosilicate zeolite having AFT framework structure. In some particular embodiments wherein copper, iron or the combination thereof is used as the promoter metal, the promoter metal is preferably present in the SCR catalyst composition at an amount of 1 to 5% by weight, more preferably 2 to 4% by weight, on an oxide basis, based on the total weight of the promoter metal and the aluminosilicate zeolite having AFT framework structure.
Alternatively, the promoter metal may be present in the SCR catalyst composition at an amount of 0.1 to 1.0 moles, preferably 0.2 to 0.7 moles, more preferably 0.3 to 0.5 moles, per mole of framework aluminum of the aluminosilicate zeolite having AFT framework structure. In some particular embodiments wherein copper, iron or the combination thereof is used as the promoter metal, the amount of the promoter metal is 0.2 to 0.7 moles, preferably 0.3 to 0.5 moles per mole of framework aluminum of the aluminosilicate zeolite having AFT framework structure.
In some preferable embodiments, the SCR catalyst composition comprises
In some more preferable embodiments, the SCR catalyst composition according to the present invention comprises
In an exemplary embodiment, the SCR catalyst composition according to the present invention comprises
The promoter metal may be incorporated into the aluminosilicate zeolite having AFT framework structure via any known processes, for example ion exchange and impregnation. For example, the promoter metal may be incorporated into the aluminosilicate zeolite having AFT framework structure by mixing the aluminosilicate zeolite into a solution of a soluble precursor of the promoter metal. The zeolite upon ion-exchanging with the promoter metal typically in form of cation may be conventionally washed, dried and calcined. Useful soluble precursors of the promoter metal may be for example salts of the promoter metal, complexes of the promoter metal and a combination thereof. Alternatively, the promoter metal may be incorporated into the aluminosilicate zeolite having AFT framework structure in situ during the preparation of catalytic articles such as extrudates or coated monolith.
It has been found that the SCR catalyst composition according to the present invention has a desirable activity in applications for selective catalytic reduction (SCR) of NOx. Moreover, it has been surprisingly found that the SCR catalyst composition according to the present invention also has an excellent stability against aging at a high temperature, for example 800° C. or higher, particularly in the case that the aluminosilicate zeolite having AFT framework structure is prepared using a particular combination of organic structure directing agents as described herein.
In the fourth aspect, the present invention provides use of the aluminosilicate zeolite having AFT framework structure obtained and/or obtainable by the process as described herein in catalysts for selective catalytic reduction (SCR) of NOx.
For the SCR applications, the aluminosilicate zeolite having AFT framework structure, preferably loaded with the promoter metal as described hereinabove, may be applied in form of extrudates or in form of a washcoat on a monolithic substrate.
Accordingly, in the fifth aspect, the present invention provides a catalytic article in form of extrudates comprising a catalyst composition or in form of a monolith comprising a washcoat containing a catalyst composition on substrate, wherein the catalyst composition comprises the aluminosilicate zeolite having AFT framework structure and the promoter metal as described hereinabove in the second aspect or the catalyst composition is the SCR catalyst composition as described in the third aspect.
The term “extrudates” generally refers to shaped bodies formed by extrusion. According to the present invention, the extrudates comprising the aluminosilicate zeolite having AFT framework structure and the promoter metal typically have a honeycomb structure.
The term “washcoat” has its usual meaning in the art, that is a thin, adherent coating of a catalytic or other material applied to a substrate.
The term “substrate” generally refers to a monolithic material onto which a catalytic coating is disposed, for example monolithic honeycomb substrate, particularly flow-through monolithic substrate and wall-flow monolithic substrate.
The aluminosilicate zeolite having AFT framework structure and the promoter metal may be processed into the application forms by any known processes with no particular restriction.
In a further aspect, the present invention relates to an exhaust gas treatment system comprising an internal combustion engine and an exhaust gas conduit in fluid communication with the internal combustion engine, wherein the catalytic article as described herein is present in the exhaust gas conduit.
Various embodiments are listed below. It will be understood that the embodiments listed below may be combined with all aspects and other embodiments in accordance with the scope of the invention.
(C2H5)3N+(CH2)nN+(C2H5)3 (IV)
wherein
n is an integer of 3 to 10, preferably 4 to 7, most preferably 5.
The invention will be further illustrated by following Examples, which set forth particularly advantageous embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit the present invention.
Scanning electron microscopy (SEM) measurements were performed by a scanning electron microscope (Hitachi SU1510).
X-ray powder diffraction (XRD) patterns were measured with PANalytical X'pert3 Powder Diffractometer (40 kV, 40 mA) using CuKα (λ=1.5406 Å) radiation to collect data in Bragg-Brentano geometry.
463.7 g of an aqueous solution of 1-methyl-1-n-propylpiperidinium hydroxide (12.6 wt %) and 94.2 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 2679.5 g of D.I. water, followed by addition of 174.9 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 106.5 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 836.4 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 13.2 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 23 m2/g and a zeolitic surface area (ZSA) of 527 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
112.79 g of an aqueous solution of tetraethylammonium hydroxide (35 wt %) and 742.33 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 2429.14 g of D.I. water, followed by addition of 148.31 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 69.93 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 884.4 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 16.5 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 37 m2/g and a zeolitic surface area (ZSA) of 484 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
249.2 g of an aqueous solution of N,N-dimethyl-N-ethylcyclohexylammonium hydroxide (9.11 wt %) and 453.57 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 2431.51 g of D.I. water, followed by addition of 163.51 g of sodium hydroxide (99%, solid) and 9.4 g of sodium sulfate. After sodium hydroxide and sodium sulfate dissolved, 68.37 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 864.6 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 17.4 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 22 m2/g and a zeolitic surface area (ZSA) of 545 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
718.45 g of an aqueous solution of 1-methyl-1-n-butyl-piperidinium hydroxide (9.68 wt %) and 27.83 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 2441.18 g of D.I. water, followed by addition of 172.38 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 104.90 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 824.1 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 11.9 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 9 m2/g and a zeolitic surface area (ZSA) of 542 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
1191.3 g of an aqueous solution of 1-ethyl-1-n-propylpiperidinium hydroxide (7.9 wt %) and 47.09 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 1992.65 g of D.I. water, followed by addition of 161.51 g of sodium hydroxide (99%, solid) and 14.63 g of sodium sulfate. After sodium hydroxide and sodium sulfate dissolved, 70.98 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 897.6 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 15.3 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 28 m2/g and a zeolitic surface area (ZSA) of 555 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
535.79 g of an aqueous solution of 1-methyl-1-n-butyl-pyrrolidinium hydroxide (10.09 wt %) and 47.09 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium hydroxide (22.1 wt %) were mixed with 2639.82 g of D.I. water, followed by addition of 174.96 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 106.47 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 836.4 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 11.7 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 22 m2/g and a zeolitic surface area (ZSA) of 477 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
814.6 g of an aqueous solution of 1-methyl-1-n-propylpiperidinium hydroxide (12.6 wt %) and 80.2 g of an aqueous solution of hexamethonium hydroxide (25.3 wt %) were mixed with 2754.5 g of D.I. water, followed by addition of 110.8 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 44.9 g of Zeolite HY (SAR=7.2, from Shandong Duoyou) and 567.6 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 150° C. for 3 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the calcined H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 12.7 as measured on the calcined H-form by XRF, and an MSA of 41 m2/g and ZSA of 524 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
1038.7 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium (22.1 wt %) were mixed with 1989.4 g of D.I. water, followed by addition of 52.38 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 260.95 g of HY (SAR=7.2, from Shandong Duoyou) and 675.0 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 180° C. for 2 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 16.2 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 42 m2/g and a zeolitic surface area (ZSA) of 539 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
1038.7 g of an aqueous solution of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium (22.1 wt %) were mixed with 1989.4 g of D.I. water, followed by addition of 58.44 g of sodium hydroxide (99%, solid). After sodium hydroxide dissolved, 260.95 g of HY (SAR=7.2, from Shandong Duoyou) and 675.0 g of Ludox® AS-40 colloidal silica were added. After stirring at room temperature for 30 mins, the synthesis mixture was transferred into an autoclave for crystallization. The crystallization was carried out at 180° C. for 2 days under static condition. After cooling to room temperature, the zeolite product was collected by filtration and dried at 120° C. overnight. The as-synthesized zeolite was calcined at 550° C. for 6 hours to remove the organic structure directing agents.
The calcined zeolite was crushed and ion-exchanged in a 10 wt % aqueous NH4Cl solution at a solid/liquid ratio of 1:10. The ion exchange process was carried out at 80° C. for 2 hours and repeated twice. After ion exchange, the product was collected by filtration, washed with D.I. water, dried at 120° C. overnight, and calcined at 450° C. for 6 hours to obtain the H-form zeolite.
The zeolite having a SiO2/Al2O3 molar ratio of (SAR) of 15.6 as measured on the calcined H-form by XRF, a mesopore surface area (MSA) of 43 m2/g and a zeolitic surface area (ZSA) of 546 m2/g as measured on the calcined H-form.
The crystal morphology of the zeolite observed from the SEM image and the XRD pattern of the zeolite are shown in
The H-form zeolite powder as obtained was impregnated with an aqueous copper (II) nitrate solution by incipient wetness impregnation and maintained at 50° C. for 20 hours in a sealed container. The obtained solid was dried and calcined in air in a furnace at 450° C. for 5 hours, to obtain a Cu-loaded zeolite.
The Cu-loaded AFT zeolite materials as prepared in accordance with the above general procedure are summarized in the Table 3 below.
For test of SCR performance, the Cu-loaded zeolite materials were slurried with an aqueous solution of Zr-acetate and then dried at ambient temperature in air under stirring, and calcined at 550° C. for 1 hour to provide a product containing 5 wt % ZrO2 as the binder based on the amount of the product. The product was crushed and the powder fraction of 250 to 500 microns was used as samples for the test. A portion of the obtained powder was aged at 650° C. for 50 hours or 820° C. for 16 hours in a flow of 10 vol % steam/air to provide aged samples.
The selective catalytic reduction (SCR) test was carried out in a fixed-bed reactor with loading of 120 mg of the test sample together with corundum of the same sieve fraction as diluent to about 1 mL bed volume, in accordance with following conditions:
NOx conversions as measured from RUN 2 at 200° C. and 575° C. are reported as the test results.
Results of the test samples in fresh state, aged at 650° C. and aged at 820° C. are summarized in Tables 4, 5 and 6 below, respectively.
It can be seen that the catalysts comprising Cu-loaded AFT zeolite according to the present invention are effective for selective catalytic reduction (SCR) of nitrogen oxides in fresh state and after aging at high temperatures.
The inventive catalysts 1.1 to 1.3, 2.1 to 2.3 and 3.1 to 3.3 comprising the AFT zeolites prepared using the combination of N,N,N,N′,N′,N′-hexaethyl-1,5-pentanediammonium diammonium organic structure directing agent and one of tetraalkylammonium and piperidinium organic structure directing agent (Example 1, 2 and 3), respectively show at least comparable NOx conversions at fresh state and after aging at 650° C., compared to the comparative catalysts 4.1 to 4.3 having the same Cu/Al ratio but prepared using the combination of hexamethonium and 1-methyl-1-propylpiperidinium organic structure directing agents (Example 7). It is well-known that the gas hourly space velocity (GHSV) of gas feed for the SCR performance test has an influence of the NOx conversions. The lower the GHSV is, the higher the NOx conversions are, in case of same catalyst being tested under otherwise identical conditions. That is the reason why the NOx conversions of the inventive catalysts are evaluated at least comparable to the comparative catalysts at fresh state and after aging at 650° C. while the inventive catalysts show lower NOx conversions than the comparative catalysts in some cases.
Surprisingly, it has been found that, upon aging at 820° C., the inventive catalysts show greatly improved NOx conversions compared with the comparative catalysts. The inventive catalysts upon aging at 820° C. resulted in NOx conversions @ 200° C. of at least 64%, even up to 85%, and resulted in NOx conversions @ 575° C. of at least 66%, even up to 96%, while the NOx conversions in case of corresponding comparative catalysts are “0” at 200° C. and no more than 10% at 575° C. The comparatively high SCR activity of the inventive catalysts after aging at 820° C. reflects high stability of the AFT zeolite at an extremely high temperature.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/082414 | Mar 2021 | WO | international |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/082250 | 3/22/2022 | WO |
