CN118142569A - Preparation method and application of zeolite-encapsulated metal bifunctional catalyst - Google Patents
Preparation method and application of zeolite-encapsulated metal bifunctional catalyst Download PDFInfo
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- 229910052751 metal Inorganic materials 0.000 title claims abstract description 95
- 239000002184 metal Substances 0.000 title claims abstract description 90
- 239000003054 catalyst Substances 0.000 title claims abstract description 86
- 230000001588 bifunctional effect Effects 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 229910021536 Zeolite Inorganic materials 0.000 claims abstract description 53
- 239000010457 zeolite Substances 0.000 claims abstract description 50
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims abstract description 48
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 48
- 239000002808 molecular sieve Substances 0.000 claims abstract description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000008367 deionised water Substances 0.000 claims abstract description 26
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 26
- 238000003756 stirring Methods 0.000 claims abstract description 26
- 238000002425 crystallisation Methods 0.000 claims abstract description 18
- 230000008025 crystallization Effects 0.000 claims abstract description 18
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 238000005406 washing Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 11
- 238000011065 in-situ storage Methods 0.000 claims abstract description 10
- 239000013110 organic ligand Substances 0.000 claims abstract description 8
- 239000007864 aqueous solution Substances 0.000 claims abstract description 6
- 150000004696 coordination complex Chemical class 0.000 claims abstract description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims abstract description 5
- 150000003839 salts Chemical class 0.000 claims abstract description 5
- 239000008139 complexing agent Substances 0.000 claims abstract description 3
- 238000001308 synthesis method Methods 0.000 claims abstract description 3
- 238000006243 chemical reaction Methods 0.000 claims description 51
- 239000000243 solution Substances 0.000 claims description 44
- 238000000034 method Methods 0.000 claims description 37
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- 239000011148 porous material Substances 0.000 claims description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 20
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 10
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052710 silicon Inorganic materials 0.000 claims description 9
- 239000010703 silicon Substances 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 7
- 229940073455 tetraethylammonium hydroxide Drugs 0.000 claims description 7
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 6
- LPSKDVINWQNWFE-UHFFFAOYSA-M tetrapropylazanium;hydroxide Chemical compound [OH-].CCC[N+](CCC)(CCC)CCC LPSKDVINWQNWFE-UHFFFAOYSA-M 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- 229910052708 sodium Inorganic materials 0.000 claims description 3
- 239000011734 sodium Substances 0.000 claims description 3
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 claims description 2
- UUEWCQRISZBELL-UHFFFAOYSA-N 3-trimethoxysilylpropane-1-thiol Chemical compound CO[Si](OC)(OC)CCCS UUEWCQRISZBELL-UHFFFAOYSA-N 0.000 claims description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 2
- 229910052681 coesite Inorganic materials 0.000 claims description 2
- 229910052906 cristobalite Inorganic materials 0.000 claims description 2
- 238000010335 hydrothermal treatment Methods 0.000 claims description 2
- PHQOGHDTIVQXHL-UHFFFAOYSA-N n'-(3-trimethoxysilylpropyl)ethane-1,2-diamine Chemical compound CO[Si](OC)(OC)CCCNCCN PHQOGHDTIVQXHL-UHFFFAOYSA-N 0.000 claims description 2
- 239000005543 nano-size silicon particle Substances 0.000 claims description 2
- 239000012266 salt solution Substances 0.000 claims description 2
- 239000000741 silica gel Substances 0.000 claims description 2
- 229910002027 silica gel Inorganic materials 0.000 claims description 2
- 229910052682 stishovite Inorganic materials 0.000 claims description 2
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- 230000000694 effects Effects 0.000 abstract description 8
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- CXWXQJXEFPUFDZ-UHFFFAOYSA-N tetralin Chemical compound C1=CC=C2CCCCC2=C1 CXWXQJXEFPUFDZ-UHFFFAOYSA-N 0.000 description 7
- 238000001354 calcination Methods 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
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- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 5
- 150000001768 cations Chemical class 0.000 description 5
- VTEKZTULWDCXOK-UHFFFAOYSA-N cyclohexane 1,2,3,4-tetrahydronaphthalene Chemical compound C1CCCC2=CC=CC=C12.C1CCCCC1 VTEKZTULWDCXOK-UHFFFAOYSA-N 0.000 description 5
- 238000005538 encapsulation Methods 0.000 description 5
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
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- 150000001412 amines Chemical class 0.000 description 2
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- TXDNPSYEJHXKMK-UHFFFAOYSA-N sulfanylsilane Chemical class S[SiH3] TXDNPSYEJHXKMK-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a preparation method and application of a zeolite-encapsulated metal bifunctional catalyst, belonging to the technical field of bifunctional catalysts, and comprising the following steps: dissolving salt containing metal to be packaged into a certain amount of deionized water, adding a certain proportion of organic ligand as complexing agent, and uniformly stirring to obtain metal complex aqueous solution; obtaining zeolite initial gel by adopting an in-situ synthesis method; dropwise adding the metal complex aqueous solution into zeolite initial gel, and uniformly stirring to obtain a gel mixture; transferring the gel mixture into a crystallization kettle for crystallization, and washing, drying, roasting and exchanging ammonium to obtain the zeolite-encapsulated metal bifunctional catalyst. The prepared bifunctional catalyst has the performance advantages of high crystallinity and high dispersion; the encapsulated metal is closely contacted with the carrier molecular sieve, and the proper distance between the active components promotes the mutual coordination of the metal center and the acid center, so that the low-temperature activity of the metal components is improved.
Description
Technical Field
The invention relates to the technical field of bifunctional catalysts, in particular to a preparation method and application of a zeolite-encapsulated metal bifunctional catalyst.
Background
The preparation and modification methods of the bifunctional catalyst are roughly classified into a post-treatment method and an in-situ encapsulation method. Post-treatment methods include ion exchange and impregnation methods. The traditional aluminosilicate zeolite frameworks have negative charges and the cations used for balancing can move freely and can also be exchanged with other metal cations (e.g., filtered metal cations in solution). Generally, conventional exchange processes require repeated exchange steps to achieve the desired metal loading. Neutral framework molecular sieves (such as pure silica molecular sieves and aluminum phosphate molecular sieves) are not ion exchanged. For neutral framework molecular sieves, impregnation is a widely used method for introducing metal precursors. Typically, the metal precursor is primarily physically adsorbed into the channels of the human molecular sieve. The isovolumetric impregnation method is the most commonly used impregnation method, i.e. mixing the dehydrated molecular sieve with an equal volume of metal solution and introducing the solution into the channels of the molecular sieve. The catalyst metal components prepared by the impregnation method are distributed on the outer surface and part of pore channels of the molecular sieve, so that the defect of low metal dispersity exists, and the carbon deposition deactivation rate of the catalyst is easy to accelerate. In practical applications, a high metal loading is required in order to be able to ensure sufficient catalytic activity. However, an increase in metal loading generally results in the formation of larger volume metal particles on the surface.
Compared with the post-treatment method, the in-situ encapsulation method is not limited by the pore diameter of the molecular sieve, because the encapsulation process of the metal is synchronous with the crystallization process of the molecular sieve. The in situ constraint strategy is that the metal nanoparticles or precursors can be introduced into the zeolite crystals by a one-step hydrothermal synthesis method. The method comprises the steps of firstly mixing synthesized metal nano particles or soluble metal precursors with zeolite synthesis gel (such as a structure directing agent, a silicon source, water, sodium hydroxide and the like), then carrying out high-temperature crystallization, and further calcining the synthesized product to remove organic matters. However, during molecular sieve crystallization under hydrothermal conditions, most of the metal cations tend to precipitate as hydroxides in the basic initial gel, which will lead to the formation of large particles on the molecular sieve crystal surface and even to the separation of the metal species from the molecular sieve support. In addition, because of the higher surface energy of the metal clusters, there is a tendency for severe aggregation in the molecular sieve precursor. Therefore, there is a need to develop more protection methods during in situ synthesis to limit severe aggregation or rapid precipitation of metal clusters encapsulated in the molecular sieve framework.
Ligand stabilization is the use of organosilicon ligands containing N or S to effectively address the aggregation of metal species under molecular sieve crystallization conditions. Amine-based ligands, such as ammonia and ethylenediamine, are ligands that are frequently used to stabilize metal cations in the in situ synthesis of molecular sieve encapsulated metals because of the good water solubility and excellent stability of these metal-amine complexes in high pH synthesis systems. Some metal ions, such as Au 3+ ions, are not easily stabilized by amine ligands even at low temperatures, but can form stable complexes under the action of mercaptosilanes, which remain stable even under alkaline hydrothermal conditions. Mercaptosilanes are strong ligands that stabilize metal ions and encapsulate metal clusters within a molecular sieve.
In addition to stabilizing metal ions with organic ligands, the use of amorphous silica precursors as stabilizers to immobilize metal clusters is also an effective method for in situ synthesis of molecular sieve encapsulation MNPs (metal nanoparticles). In this synthesis system, the pre-prepared metal clusters are first embedded in the SiO 2 matrix as a precursor for molecular sieve crystallization. Under hydrothermal conditions, the silica-coated metal cluster precursor is crystallized, and as the silica is consumed, the internal metal clusters are simultaneously encapsulated in the prepared molecular sieve. In order to overcome the problem that MNPs cannot completely fill the inside of molecular sieves, researchers have developed solvent-free methods and improved Kirkendall growth methods to reduce the amount of solvent used in the crystallization process of molecular sieves.
Zeolite molecular sieves are crystalline materials having a uniform microporous structure and are widely used in the catalytic field. For example, Y-type zeolites have been widely used in the catalytic cracking (FCC) of heavy oils; ZSM-5 type molecular sieves with mesoporous channels have been used for upgrading fuels. Researchers successfully prepare zeolite molecular sieve domain-limited MNPs bifunctional catalysts, and find that the zeolite molecular sieve domain-limited MNPs bifunctional catalysts have better catalytic performance in hydrogenation, dehydrogenation, cracking and isomerization reactions. The MNPs@zeolite molecular sieve material has the advantages of both zeolite molecular sieve and high-activity MNPs: the open nanochannels facilitate molecular diffusion, enabling it to contact fixed metal species; the uniform nano-pores can effectively screen molecules with different sizes, molecules smaller than the diameter can diffuse into the nano-pores, and larger molecules are completely blocked; the adjustable molecular sieve composition and structure realizes mass transfer adjustment at the molecular level; the active center in the framework is matched with the metal nano particles in the limited domain to form the multifunctional catalyst. In addition, the zeolite molecular sieve pore structure stabilizes MNPs, avoids aggregation or leaching in the catalytic process, and obtains the sintering-resistant catalyst under the high-temperature reaction condition.
In some high temperature reactions, metal particles tend to agglomerate or deactivate due to metal leaching. The metal nano particles are fixed in the zeolite, which is superior to the traditional supported catalyst. The catalyst prepared by the in-situ encapsulation method can generally encapsulate metal in the pore canal of the molecular sieve, and has good dispersity, more effective active sites are easy to expose, and the catalyst has high catalytic performance and good stability. These composite catalysts exhibit excellent catalytic activity in various catalytic reactions due to inherent structural advantages of mesoporous zeolite and the restraining effect of immobilized metal nanoparticles. For hydrogenation reactions, noble metals such as Pt, rh, ru, pd exhibit good catalytic performance, however, these metals face problems of limited resources, high cost, etc.; some non-noble metals also face these problems. Coating the catalytically active component in the zeolite molecular sieve structure is an effective method of dispersing and stabilizing the metal component. The spatial confinement of the molecular sieve pore channels can effectively limit the aggregation of metal particles during catalyst preparation and reaction, so that they have very good sintering resistance. Thereby producing a high activity zeolite molecular sieve encapsulated metal particle system.
The MNPs@zeolite molecular sieve catalyst not only shows excellent catalytic activity, but also has higher stability and shape selective catalytic property; in addition, the synergistic effect of the MNPs of the limited domain and the nano-pore skeleton with the active site can further improve the catalytic activity of the composite catalyst. Since zeolite immobilized metal nanoparticles have the advantage of leaching and aggregation resistance, they have been attracting more and more attention of students. It is a future research direction to synthesize more metal @ zeolite catalysts with unique characteristics and conduct important industrial catalytic reactions on these metal @ zeolite catalysts.
Disclosure of Invention
Based on the prior research and the existing problems, the invention provides a preparation method and application of the zeolite-encapsulated metal bifunctional catalyst after further research and analysis.
In order to achieve the above purpose, the present invention provides the following technical solutions: a preparation method of zeolite-encapsulated metal bifunctional catalyst comprises the following specific steps:
s1, dissolving salt containing metal to be packaged into a certain amount of deionized water, adding a certain proportion of organic ligand as a complexing agent, and uniformly stirring to obtain a metal complex aqueous solution;
s2, obtaining zeolite initial gel by adopting an in-situ synthesis method;
S3, dropwise adding the metal complex aqueous solution into zeolite initial gel, and uniformly stirring to obtain a gel mixture;
S4, transferring the gel mixture into a crystallization kettle for crystallization, and washing, drying, roasting and performing ammonium exchange to obtain the zeolite-encapsulated metal bifunctional catalyst.
Preferably, the metal active component encapsulated in the S1 is any one or more of Pt, pd, ru, cu, co, ni, mo, W, the metal is encapsulated in the pore canal of the zeolite molecular sieve in a cluster form, and the metal salt solution is nitrate or chloride.
Preferably, the organic ligand is one of ammonia water, ethylenediamine, diethylenetriamine, N- (2-aminoethyl) -3-aminopropyl trimethoxy silane and mercaptopropyl trimethoxy silane, and the molar ratio of the organic ligand to the metal salt is 1-10.
Preferably, the preparation method of the zeolite initial gel in S2 specifically comprises the following steps:
S101, mixing and stirring a silicon source, a template agent and a certain amount of deionized water for a certain time to obtain a solution A;
s102, mixing and stirring an alkali source, an aluminum source and a certain amount of deionized water for a certain time to obtain a solution B;
s103, dripping the solution B into the solution A, and stirring for 3-6 hours to obtain zeolite initial gel.
Preferably, in S101, the silicon source may be any one of nano silicon dioxide, tetraethyl orthosilicate, and solid silica gel.
Preferably, in S102, sodium metaaluminate or aluminum nitrate is used as the aluminum source.
Preferably, in the process of preparing zeolite initial gel, tetraethylammonium hydroxide is used as a template agent, and the feeding ratio is a silicon source: aluminum source: tetraethylammonium hydroxide: alkali source = 1: (0.005-0.025): 0.4:0.0047.
Preferably, in the process of preparing zeolite initial gel, tetrapropylammonium hydroxide is used as a template agent, and the feeding ratio is that of an aluminum source: silicon source: TPAOH: naOH: h 2 o=1: (5-25): (1-5): (4-16): (200-370).
Preferably, in S54, washing the crystallized gel mixture by deionized water, wherein the pH value of the washing solution is 7-8; drying at 100-200 deg.c for 6-12 hr and roasting at 450-550 deg.c for 6-8 hr; the ammonium exchange condition is that the mass ratio of the catalyst to 1M NH 4 Cl is 1: and 10, carrying out hydrothermal treatment at 90 ℃ for 3 hours.
The invention also provides application of the zeolite-encapsulated metal bifunctional catalyst, the catalyst is prepared by adopting the preparation method, and the catalyst can be applied to hydroisomerization reaction.
Compared with the prior art, the invention provides a preparation method and application of a zeolite-encapsulated metal bifunctional catalyst, and the preparation method has the following beneficial effects:
(1) The encapsulated metal-zeolite bifunctional catalyst prepared by the method provided by the invention has the advantages that the zeolite molecular sieve grows on the outer surface of the metal, the metal is encapsulated in the zeolite pore canal, the high crystallinity of the zeolite and the high dispersity of the metal can be maintained, the aggregation of metal particles is effectively inhibited, the size of the active metal particles is reduced to be sub-nanometer size, the accessibility of active sites can be obviously improved, and the temperature required by the reaction is reduced; the structure of the molecular sieve limited domain metal-acid double active center enhances the electron transfer effect between the metal and the carrier, thereby improving the selectivity and low temperature activity of the catalyst.
(2) The zeolite-encapsulated metal bifunctional catalyst can be applied to hydroisomerization reaction, performance evaluation is carried out on the prepared zeolite-encapsulated metal bifunctional catalyst, the zeolite-encapsulated metal bifunctional catalyst has metal hydrogenation and dehydrogenation activities and carrier molecular sieve ring opening, isomerism and other acidic activities, the model compound tetrahydronaphthalene simulates the reaction path of catalytic cracking diesel in hydroisomerization reaction, the evaluation result shows that the prepared catalyst has high raw material conversion rate, the selectivity of hydroisomerization products is effectively improved, and the zeolite-encapsulated metal bifunctional catalyst has very wide application prospect.
Drawings
FIG. 1 is XRD patterns of zeolite-encapsulated metal bifunctional catalysts of examples 1 to 5;
Fig. 2 is an SEM image of the zeolite-encapsulated metal bifunctional catalyst in examples 1 to 5.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.
In order to more clearly and in detail describe the preparation method of the zeolite-encapsulated metal bifunctional catalyst provided in the embodiment of the present invention, a description will be given below with reference to specific embodiments.
Example 1
600.00G of nano-silica was weighed into a reaction vessel A, 1400.00g of deionized water and 2356.00g of tetraethylammonium hydroxide (25 wt%) were added and stirred for 1 hour to obtain a solution A. Adding 775.00g deionized water, 19.00g sodium hydroxide and 83.00g Al (NO 3)3·9H2 O) into a reaction kettle B, stirring for 1h to obtain a solution B, then dripping the solution B into the solution A, stirring and aging for 3h, adding 300.00g deionized water, 29.00gNi (NO 3)2·6H2 O and 12.00g ethylenediamine into the reaction kettle C, stirring and dissolving, dripping the solution into the zeolite initial gel, stirring for 30min, crystallizing the stirred zeolite gel at 150 ℃ for 5 days, washing the formed pale green solid with deionized water to be neutral after crystallization, drying at 100 ℃, calcining at 550 ℃ for 6h, and obtaining the encapsulated Ni@Na-Beta dual-function catalyst with a silicon-aluminum ratio of 45 and a Ni content of 1wt%, adding the prepared Ni@Na-Beta into an NH 4 Cl solution of 1M according to a mass ratio of 1/10, exchanging for 3h under a hydrothermal condition at 90 ℃, washing, drying at 100 ℃, and calcining at 550 ℃ for 6h, thus obtaining the dual-function catalyst with the pore channel structure shown in the table 1.
In a high-pressure fixed bed reactor filled with 50ml of the catalyst prepared in example 1, a 20wt% tetrahydronaphthalene-cyclohexane solution was used as a model compound to simulate the hydroisomerization reaction of catalytic cracking diesel, the reaction temperature was 300 ℃, the liquid hourly space velocity was 2.0h -1, the conversion rate of tetrahydronaphthalene was 47.48% and the selectivity of the heterogeneous product was 16.63% under the reaction pressure of 4MPa, and the obtained results are shown in table 2.
Example 2
600.00G of nano-silica was weighed into a reaction vessel A, 1400.00g of deionized water and 2356.00g of tetrapropylammonium hydroxide (25 wt%) were added and stirred for 1h to obtain a solution A. Meanwhile, 775.00g of deionized water, 19.00g of sodium hydroxide and 165.00g of Al (NO 3)3·9H2 O) are added into a reaction kettle B and stirred for 1h to obtain a solution B, then the solution B is dripped into the solution A and stirred for 5h continuously to obtain zeolite initial gel, then 300.00g of deionized water, 29.00gNi g of NO 3)2·6H2 O and 12.00g of ethylenediamine are added into the reaction kettle C and stirred for dissolving, then the zeolite initial gel is dripped into the reaction kettle C and stirred for 30min, the stirred zeolite gel is crystallized at 170 ℃ for 3 days, the formed solid is washed to be neutral by the deionized water after crystallization, and is dried at 100 ℃, then calcined at 550 ℃ for 6h, and the packaged Ni@ZSM-5 dual-function catalyst with the silicon-aluminum ratio of 20 and the Ni content of 1wt% is obtained, wherein the Ni@Na-ZSM-5 is added into a NH 4 Cl solution of 1M according to the mass ratio of 1/10, exchanged for 3h under the hydrothermal condition of 90 ℃, then washed, dried at 100 ℃ and calcined for 6h, and the dual-function catalyst structure of the Ni@ZSM-5 is obtained.
In a high-pressure fixed bed reactor filled with 50ml of the catalyst prepared in example 2, a 20wt% tetrahydronaphthalene-cyclohexane solution was used as a model compound to simulate the hydroisomerization reaction of catalytic cracking diesel, the reaction temperature was 300 ℃, the liquid hourly space velocity was 2.0h -1, the reaction pressure was 4MPa, the conversion of tetrahydronaphthalene was 33.36%, and the selectivity of the heterogeneous product was 14.55%, and the obtained results are shown in table 2.
Example 3
600.00G of nano-silica was weighed into a reaction vessel A, 1400.00g of deionized water and 2356.00g of tetraethylammonium hydroxide (25 wt%) were added and stirred for 1 hour to obtain a solution A. Meanwhile, adding 775.00g deionized water, 19.00g sodium hydroxide and 83.00g Al (NO 3)3·9H2 O) into a reaction kettle B, stirring for 1h to obtain a solution B, then dropwise adding the solution B into the solution A, stirring and aging for 3h, obtaining zeolite initial gel, adding 300.00g deionized water, 77.00g (NH 4)6MoO24·4H2 O and 8.00g ethylenediamine) into the reaction kettle C, stirring and dissolving, dropwise adding the mixture into the zeolite initial gel, stirring for 30min, crystallizing the stirred zeolite gel at 150 ℃ for 5 days, washing the generated pale yellow solid with deionized water to be neutral after crystallization, drying at 100 ℃, calcining at 550 ℃ for 6h, obtaining the encapsulated Mo@Na-Beta dual-function catalyst with a silicon-aluminum ratio of 45 and a Mo content of 1wt%, adding the prepared Mo@Na-Beta into a NH 4 Cl solution of 1M according to a mass ratio of 1/10, exchanging for 3h under a hydrothermal condition at 90 ℃, washing, drying at 100 ℃ for 6h, and calcining at 550 ℃ to obtain the dual-function catalyst pore channel structure of the catalyst.
In a high-pressure fixed bed reactor filled with 50ml of the catalyst prepared in example 3, a 20wt% tetrahydronaphthalene-cyclohexane solution was used as a model compound to simulate the hydroisomerization reaction of catalytic cracking diesel, the reaction temperature was 300 ℃, the liquid hourly space velocity was 2.0h -1, the conversion rate of tetrahydronaphthalene was 58.22% and the selectivity of the heterogeneous product was 11.71% under the condition of a reaction pressure of 4MPa, and the obtained results are shown in table 2.
Example 4
600.00G of nano-silica was weighed into a reaction vessel A, 1400.00g of deionized water and 2356.00g of tetraethylammonium hydroxide (25 wt%) were added and stirred for 1 hour to obtain a solution A. Meanwhile, 775.00g of deionized water, 19.00g of sodium hydroxide and 83.00g of Al (NO 3)3·9H2 O are stirred for 1h to obtain a solution B, then the solution B is dropwise added into the solution A, stirring and ageing are continued for 3h to obtain zeolite initial gel, then 300.00g of deionized water, 8.00g of (NH 4)6H2W12O40 and 4.00g of ethylenediamine) are added into the reaction kettle C, stirring and dissolving are carried out, then the mixture is dropwise added into the zeolite initial gel, stirring is carried out for 30min, the stirred zeolite gel is crystallized for 5 days at 150 ℃, the generated solid is washed to be neutral by deionized water after crystallization is finished, and is dried at 100 ℃, then calcined at 550 ℃ for 6h to obtain the encapsulated W@Na-Beta dual-function catalyst with the silicon-aluminum ratio of 45 and the W content of 1wt%, the prepared W@Na-Beta is added into a NH 4 Cl solution of 1M according to the mass ratio of 1/10, exchanged for 3h under the hydrothermal condition of 90 ℃, then washed, dried at 100 ℃ and calcined for 6h to obtain the dual-function catalyst W@H pore channel structure shown in table 1.
In a high-pressure fixed bed reactor filled with 50ml of the catalyst prepared in example 4, a 20wt% tetrahydronaphthalene-cyclohexane solution was used as a model compound to simulate the hydroisomerization reaction of catalytic cracking diesel, the reaction temperature was 300 ℃, the liquid hourly space velocity was 2.0h -1, the reaction pressure was 4MPa, the conversion of tetrahydronaphthalene was 42.96%, and the selectivity of the heterogeneous product was 13.12%, and the obtained results are shown in table 2.
Example 5
Weighing 100.00g of sodium metaaluminate (NaAlO 2) in a reaction kettle A, dissolving in 1210.00g of H 2 O, adding 134.00g of NaOH, uniformly mixing, continuously adding 300.00g of gTPAOH, uniformly mixing by using ultrasound, dropwise adding 1230.00g of 30% silica sol (SiO 2·6.5H2 O) in mass fraction into the mixed system under the condition of strong stirring, and forming a synthetic Y molecular sieve system by using SiO 2 to obtain zeolite initial gel; adding 300.00g deionized water and 18.00gNi g ethylenediamine (NO 3)2·6H2 O and 8.00g ethylenediamine) into a reaction kettle B, stirring for dissolving, dripping the mixture into zeolite initial gel, stirring for 30min, carrying out 110 ℃ static crystallization on the mixed solution for 10 days, filtering, washing and drying after crystallization, roasting a sample at 350 ℃ for 2h to obtain a packaged Ni@Na-Y dual-functional catalyst with a silicon-aluminum ratio of 12 and a Ni content of 1wt%, adding the prepared Ni@Na-Y into a 1M NH 4 Cl solution according to a mass ratio of 1/10, exchanging for 3h at 90 ℃, washing, drying at 100 ℃, and calcining at 550 ℃ for 6h to obtain the Ni@H-Y dual-functional catalyst with a catalytic effect, wherein the pore structure properties of the catalyst are shown in a table 1.
In a high-pressure fixed bed reactor filled with 50ml of the catalyst prepared in example 5, a 20wt% tetrahydronaphthalene-cyclohexane solution was used as a model compound to simulate the hydroisomerization reaction of catalytic cracking diesel, the reaction temperature was 300 ℃, the liquid hourly space velocity was 2.0h -1, the conversion rate of tetrahydronaphthalene was 22.81% and the selectivity of the heterogeneous product was 16.58% under the reaction pressure of 4MPa, and the obtained results are shown in table 2.
TABLE 1 principal Properties of zeolite-encapsulated Metal bifunctional catalyst pore Structure
As can be seen from Table 1, the pore structure properties of the zeolite-encapsulated metal bifunctional catalysts of different types are not greatly different, which indicates that the prepared catalyst has uniform specific surface area, pore diameter and pore volume.
TABLE 2 hydroisomerization reaction results with zeolite-encapsulated metal dual-function catalyst
| Catalyst | Tetrahydronaphthalene conversion (%) | Isomerism product Selectivity (%) |
| Example 1 | 47.48 | 16.63 |
| Example 2 | 33.36 | 14.55 |
| Example 3 | 58.22 | 11.71 |
| Example 4 | 42.96 | 13.12 |
| Example 5 | 22.81 | 16.58 |
As can be seen from the hydroisomerization reaction results in Table 2, the zeolite-encapsulated metal dual-function catalyst has higher raw material conversion and isomerism product selectivity, which indicates that the prepared catalyst maintains the high crystallinity of zeolite and the high dispersity of metal, and improves the accessibility of the active site of the catalyst and the low-temperature activity. As can be seen from examples 1, 3 and 4, when different metals are encapsulated by the beta molecular sieve, the hydrogenation activity of the metals is different, and under the condition of higher conversion rate of raw materials, the selectivity of the isomerised product is highest in example 1, which shows that the synergistic effect of the metal center and the acid center is higher. Examples 1,2 and 5 show that the same metal is encapsulated by different types of molecular sieves, the catalyst performance is greatly different, the three-dimensional pore canal and BEA topological structure of the beta molecular sieve show stable catalytic activity in the hydrocracking reaction of polycyclic aromatic hydrocarbon, and meanwhile, the raw material conversion rate and the isomerisation product selectivity are very high.
From the XRD pattern of the zeolite-encapsulated metal bifunctional catalyst shown in FIG. 1, it can be seen that the intensity of the characteristic diffraction peaks of different types of zeolite is higher, and the characteristic diffraction peaks of no encapsulated metal are shown, which indicates that the synthesized molecular sieve keeps the high crystallinity of zeolite; by combining with the SEM image of the zeolite-encapsulated metal bifunctional catalyst in FIG. 2, it can be seen that no larger metal clusters are attached to the surface of the molecular sieve, which indicates that the zeolite-encapsulated metal catalyst is successfully synthesized, the metal is mainly distributed in the pore channels of the molecular sieve, and the synergistic effect of the metal center and the acid center is enhanced, so that the catalytic performance of the catalyst is improved.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting thereof; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (10)
1. A preparation method of a zeolite-encapsulated metal bifunctional catalyst is characterized by comprising the following steps:
s1, dissolving salt containing metal to be packaged into a certain amount of deionized water, adding a certain proportion of organic ligand as a complexing agent, and uniformly stirring to obtain a metal complex aqueous solution;
s2, obtaining zeolite initial gel by adopting an in-situ synthesis method;
S3, dropwise adding the metal complex aqueous solution into zeolite initial gel, and uniformly stirring to obtain a gel mixture;
S4, transferring the gel mixture into a crystallization kettle for crystallization, and washing, drying, roasting and performing ammonium exchange to obtain the zeolite-encapsulated metal bifunctional catalyst.
2. The method for preparing a zeolite-encapsulated metal bifunctional catalyst of claim 1, wherein the metal active component encapsulated in S1 is one or more of Pt, pd, ru, cu, co, ni, mo, W, the metal is encapsulated in the pores of the zeolite molecular sieve in the form of clusters, and the metal salt solution is nitrate or chloride.
3. The method for preparing the zeolite-encapsulated metal bifunctional catalyst of claim 1, wherein the organic ligand is one of ammonia water, ethylenediamine, diethylenetriamine, N- (2-aminoethyl) -3-aminopropyl trimethoxy silane and mercaptopropyl trimethoxy silane, and the molar ratio of the organic ligand to the metal salt is 1-10.
4. The method for preparing the zeolite-encapsulated metal bifunctional catalyst of claim 1, wherein the method for preparing the zeolite initial gel in S2 comprises:
S101, mixing and stirring a silicon source, a template agent and a certain amount of deionized water for a certain time to obtain a solution A;
s102, mixing and stirring an alkali source, an aluminum source and a certain amount of deionized water for a certain time to obtain a solution B;
s103, dripping the solution B into the solution A, and stirring for 3-6 hours to obtain zeolite initial gel.
5. The method for preparing a zeolite-encapsulated metal bifunctional catalyst of claim 4, wherein in S101, the silicon source is any one of nanosilicon dioxide, tetraethyl orthosilicate, and solid silica gel.
6. A zeolite-encapsulated metal bifunctional catalyst as recited in claim 4 or 5, wherein in S102, sodium metaaluminate or aluminum nitrate is used as the aluminum source.
7. The method for preparing the zeolite-encapsulated metal bifunctional catalyst of claim 6, wherein in the process of preparing the zeolite initial gel, tetraethylammonium hydroxide is used as the template agent, and the feeding ratio is silicon source: aluminum source: tetraethylammonium hydroxide: alkali source = 1: (0.005-0.025): 0.4:0.0047.
8. The method for preparing the zeolite-encapsulated metal bifunctional catalyst of claim 6, wherein in the process of preparing the zeolite initial gel, tetrapropylammonium hydroxide is used as the template agent, and the feed ratio is an aluminum source: silicon source: TPAOH: naOH: h 2 o=1: (5-25): (1-5): (4-16): (200-370).
9. The method for preparing a zeolite-encapsulated metal bifunctional catalyst of claim 1, wherein in S54, the crystallized gel mixture is washed with deionized water, and the pH of the washing solution is 7-8; drying at 100-200 deg.c for 6-12 hr and roasting at 450-550 deg.c for 6-8 hr; the ammonium exchange condition is that the mass ratio of the catalyst to 1M NH 4 Cl is 1: and 10, carrying out hydrothermal treatment at 90 ℃ for 3 hours.
10. Use of a zeolite-encapsulated metal bifunctional catalyst obtainable by a process for the preparation of a zeolite-encapsulated metal bifunctional catalyst as claimed in any one of claims 1 to 9, characterized in that the catalyst is used in hydroisomerization reactions.
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