CN116425171A - Preparation method of high-performance hydroisomerization catalyst mesoporous and microporous step structure ZSM 48 molecular sieve - Google Patents
Preparation method of high-performance hydroisomerization catalyst mesoporous and microporous step structure ZSM 48 molecular sieve Download PDFInfo
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 46
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 46
- 239000003054 catalyst Substances 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 19
- 239000013078 crystal Substances 0.000 claims abstract description 18
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000003513 alkali Substances 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 239000010703 silicon Substances 0.000 claims abstract description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 5
- 238000005216 hydrothermal crystallization Methods 0.000 claims abstract description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 8
- 239000011734 sodium Substances 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 229910021485 fumed silica Inorganic materials 0.000 claims description 6
- 229920002401 polyacrylamide Polymers 0.000 claims description 6
- 229910052708 sodium Inorganic materials 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 claims description 4
- OKIZCWYLBDKLSU-UHFFFAOYSA-M N,N,N-Trimethylmethanaminium chloride Chemical compound [Cl-].C[N+](C)(C)C OKIZCWYLBDKLSU-UHFFFAOYSA-M 0.000 claims description 4
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 3
- 239000001267 polyvinylpyrrolidone 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
- 229910018072 Al 2 O 3 Inorganic materials 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
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 claims description 2
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 2
- 238000006243 chemical reaction Methods 0.000 abstract description 17
- DCAYPVUWAIABOU-UHFFFAOYSA-N hexadecane Chemical compound CCCCCCCCCCCCCCCC DCAYPVUWAIABOU-UHFFFAOYSA-N 0.000 abstract description 16
- 238000002156 mixing Methods 0.000 abstract description 7
- 238000011065 in-situ storage Methods 0.000 abstract description 3
- 238000006317 isomerization reaction Methods 0.000 abstract description 3
- 238000010189 synthetic method Methods 0.000 abstract description 2
- 230000003197 catalytic effect Effects 0.000 abstract 1
- 239000000047 product Substances 0.000 description 14
- 238000001228 spectrum Methods 0.000 description 6
- 229910021536 Zeolite Inorganic materials 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 5
- 239000012065 filter cake Substances 0.000 description 5
- 239000010457 zeolite Substances 0.000 description 5
- 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 description 4
- 238000005336 cracking Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 description 2
- VFGVNLNBQPXBKA-UHFFFAOYSA-N diazanium;dibromide Chemical compound [NH4+].[NH4+].[Br-].[Br-] VFGVNLNBQPXBKA-UHFFFAOYSA-N 0.000 description 2
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000010687 lubricating oil Substances 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 238000001308 synthesis method Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- GETQZCLCWQTVFV-UHFFFAOYSA-N trimethylamine Chemical compound CN(C)C GETQZCLCWQTVFV-UHFFFAOYSA-N 0.000 description 2
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- 241001573881 Corolla Species 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000002199 base oil Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/04—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof using at least one organic template directing agent, e.g. an ionic quaternary ammonium compound or an aminated compound
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
- B01J29/703—MRE-type, e.g. ZSM-48
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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Abstract
A preparation method of a high-performance hydroisomerization catalyst mesoporous step structure ZSM-48 molecular sieve comprises the steps of uniformly mixing Beta seed crystal, a silicon source, an aluminum source, an alkali source, an organic template agent, a mesoporous structuring agent and water to form gel, and obtaining the ZSM-48 molecular sieve with a low silicon-aluminum ratio ranging from 40 to 100 after hydrothermal crystallization, wherein the grain length is 2-5 mu m, the diameter is 0.5-2.0 mu m, and the ZSM-48 molecular sieve has a needle-shaped structure. The mesoporous number is adjusted by controlling the adding type and proportion of the mesoporous constructor, so that the ZSM-48 with the mesoporous step structure is synthesized in situ. The result of carrying 0.5wt% Pt and then carrying out the hydroisomerization reaction on the n-hexadecane shows that the isomerization yield of the synthetic method is increased to about 80wt%, the yield of the double-branched product is increased by about 5wt%, and the yield of the triple-branched product is increased by about 3wt%, so that the ZSM-48 with the mesoporous step structure has excellent hydroisomerization catalytic performance.
Description
Technical Field
The invention belongs to a synthesis method of a multistage mesoporous zeolite molecular sieve, and relates to a preparation method of a high-performance hydroisomerization catalyst ZSM-48 molecular sieve with a mesoporous step structure.
Background
Zeolite molecular sieve ZSM-48 is a high silicon molecular sieve with a ten membered ring pore structure having a one-dimensional straight channel structure that facilitates the reaction of hydroisomerization of linear alkanes. The prior oil products are aggravated in heavy and poor quality, and the isomerization of straight-chain alkane is an effective method for improving the quality of the oil products, such as increasing the octane number in the gasoline fraction, reducing the solidifying point of the diesel fraction and increasing the yield of the lubricating oil base oil product on the basis of keeping the viscosity of the lubricating oil. ZSM-48 zeolite molecular sieve has the problems of high silica-alumina ratio, low acid content, insufficient number of exposed apertures and the like, and these factors restrict the wide application of ZSM-48 molecular sieve. Therefore, how to prepare ZSM-48 molecular sieves with high acid content and rich mesopores or external specific surface pores is an urgent problem to be solved at present.
In Chinese patent CN105800635B, one or more of hexamethylenediamine, octanediamine and trimethylamine are used as a template agent, starch is used as a mesoporous structure agent to synthesize the ZSM-48 molecular sieve with a mesoporous-microporous hierarchical structure, the silicon-aluminum ratio is 330, the aging is carried out for 1-8 hours at 90-140 ℃, the crystallization is carried out for 4-15 days at 160-260 ℃, and the defects of higher silicon-aluminum ratio and overlong crystallization time exist. CN110562999a discloses a method for synthesizing ZSM-48 with low silicon-aluminum ratio by crystal assistance, which has a smaller number of mesoporous synthetic catalyst, is unfavorable for hydroisomerization reaction of n-hexadecane macromolecules, affects mass transfer rate, and causes lower selectivity. CN112206814a discloses an isomerism catalyst using a modified ZSM-48 molecular sieve as a carrier and a preparation method thereof, wherein the molecular sieve is subjected to post-treatment by organic alkali or acid to obtain mesopores, the framework structure of the molecular sieve is corroded in the treatment process, and the stability of the catalyst in the reaction is reduced.
In order to realize the wide application of the ZSM-48 zeolite molecular sieve in the petrochemical industry as soon as possible, how to realize the preparation of the zeolite molecular sieve with abundant mesopores or external specific surface pores on the premise of ensuring low silicon-aluminum ratio, and the increase of the synthesis yield of the molecular sieve becomes a key point. In summary, it has been found that the following disadvantages exist regardless of how the synthetic method is improved: (1) the silicon-aluminum ratio of the synthesized ZSM-48 molecular sieve is higher, and more acid sites are not exposed; (2) when the mesoporous structure is constructed, acid or alkali is needed to be used for carrying out aftertreatment on the molecular sieve, so that a framework structure is corroded, and the stability of the catalyst is reduced.
Disclosure of Invention
The invention aims to provide a synthesis method of a ZSM-48 molecular sieve with a mesoporous and microporous cascade structure, which is characterized in that a mesoporous structuring agent is added in the process of synthesizing the ZSM-48 molecular sieve with a low silicon-aluminum ratio by using a seed crystal auxiliary method, the mesoporous number is increased by adjusting the proportion of the mesoporous structuring agent, the diffusion limit in the hydroisomerization reaction of n-hexadecane is reduced, and the isomerism selectivity is improved.
The technical scheme of the invention is as follows:
a preparation method of a high-performance hydroisomerization catalyst ZSM-48 molecular sieve with a mesoporous step structure comprises the following steps:
sequentially adding a silicon source, an aluminum source, an alkali source, water, a template agent, a mesoporous structuring agent and a seed crystal, stirring until a gel system is formed, uniformly stirring, and crystallizing for 1-4d under the condition of hydrothermal autogenous pressure at 180 ℃ to obtain the ZSM-48 molecular sieve with the mesoporous step structure and low silicon-aluminum ratio; wherein, the mol ratio range of each material is: (1.40-4.50) Na 2 O：60SiO 2 ：(0.60-1.00)Al 2 O 3 : (0.80-2.40) template agent: (1000-2800) H 2 O: (0.03-0.10) mesoporous structurant, seed crystal addition amount and SiO 2 The mass ratio of (2) is 0.01-7.00%; filtering, washing and drying the product obtained after the hydrothermal crystallization, and roasting at 500-650 ℃ for 3-5 hours to finally obtain the ZSM-48 molecular sieve with the meso-microporous cascade structure.
The mesoporous construction agent is polyacrylamide, polyvinylpyrrolidone and tetramethyl ammonium chloride.
The aluminum source is one or more than two of aluminum nitrate, aluminum sulfate, sodium metaaluminate and aluminum isopropoxide.
The silicon source is one or more than two of fumed silica, silica sol and tetraethoxysilane.
The template agent is hexamethyldiammonium bromide.
The seed crystal is Beta.
The alkali source is sodium hydroxide.
The invention has the beneficial effects that: the ZSM-48 molecular sieve with a mesoporous step structure is successfully synthesized in situ by adopting a method of adding the mesoporous constructor, and the mesoporous number of the molecular sieve is changed by adjusting the adding proportion of the mesoporous constructor. Compared with the traditional ZSM-48 catalyst, the conversion rate is increased to about 99wt%, the isomerism selectivity is increased to about 93wt%, the selectivity of the single branched product is increased to about 86wt%, the selectivity of the double branched product is increased to about 31wt%, the yield of the three branched product is increased to about 10wt%, the maximum cracking conversion rate is not more than 13wt% at a low reaction temperature, and the cracking conversion rate is only 42wt% at 340 ℃.
Drawings
FIG. 1 is an XRD diffraction pattern of a ZSM-48 standard sample prepared in example 1.
FIG. 2 is an SEM image of a ZSM-48 standard prepared in example 1.
FIGS. 3, 5, 7 and XRD diffraction patterns for ZSM-48 having a meso-microporous hierarchical structure were prepared for example 2, in which the polyacrylamide addition ratios were varied.
FIGS. 4, 6, 8 and 10 are SEM pictures of ZSM-48 having a mesoporous and microporous ladder structure prepared in example 2 in which the polyacrylamide addition ratios are different.
FIG. 9 is an XRD diffraction pattern for ZSM-48 having a meso-microporous hierarchical structure prepared in example 3.
FIG. 10 is an SEM image of ZSM-48 having a mesoporous step structure prepared in example 3.
FIG. 11 is an XRD diffraction pattern for ZSM-48 having a meso-microporous hierarchical structure prepared in example 4.
FIG. 12 is an SEM image of ZSM-48 having a mesoporous step structure prepared in example 4.
FIG. 13 is an XRD diffraction pattern for ZSM-48 having a meso-microporous hierarchical structure prepared in example 4.
FIG. 14 is an SEM image of ZSM-48 having a mesoporous step structure prepared in example 4.
Detailed Description
The present invention will be described in detail by way of examples, but the present invention is not limited to these examples.
Example 1
According to the mole ratio of each component: 3.95Na 2 O：60SiO 2 ：0.75Al 2 O 3 :1.2 template agent: 1500H 2 O, sequentially adding 0.64g of sodium hydroxide, 0.31g of sodium metaaluminate, 1.09g of hexamethyldiammonium bromide and 9g of fumed silica into 67.5g of deionized water, uniformly stirring and mixing for 0.5h to obtain white gel, adding 0.018g of beta molecular sieve as heterogeneous seed crystal, continuously stirring and uniformly mixing, transferring to a 100mL hydrothermal kettle, placing into a 180 ℃ oven, and crystallizing for 24h at the rotating speed of 60 r/min. The obtained product is filtered, washed, and the filter cake is placed in an oven at 80 ℃ for drying for 12 hours, and then is baked for 6 hours at 550 ℃ to obtain the ZSM-48 molecular sieve. The XRD diffraction of this sample was shown in FIG. 1, and the crystallinity was 100% using this sample as a standard.
Example 2
According to the mole ratio of each component: 3.95Na 2 O：60SiO 2 ：0.75Al 2 O 3 :1.2 template agent: 1500H 2 O: 0.64g of sodium hydroxide, 0.31g of sodium metaaluminate, 1.09g of hexamethyldiammonium bromide, 0.3195g (X=0.03)/0.5325 g (X=0.05)/0.7455 g (X=0.07)/1.065 g (X=0.10) of polyacrylamide and 9g of fumed silica are sequentially added into 67.5g of deionized water, uniformly stirred and mixed for 0.5h to obtain white gel, 0.018g of Beta molecular sieve is added as heterogeneous seed crystal, continuously stirred and uniformly mixed, transferred into a 100mL hydrothermal kettle, and put into an oven at 180 ℃ for crystallization for 48h at the rotating speed of 60 r/min. And filtering and washing the obtained product, drying a filter cake in an oven at 80 ℃ for 12 hours, and roasting at 550 ℃ for 6 hours to obtain the ZSM-48 molecular sieve with the mesoporous step structure. When x=0.03, the XRD spectrum of the molecular sieve ZSM-48 having a meso-microporous cascade structure was obtained, which was similar to that of fig. 3, the relative crystallinity was about 102%, and the needle-like crystals were observed under a scanning electron microscope in fig. 4. When x=0.05, the XRD spectrum is similar to that of fig. 5, the relative crystallinity is about 98%, and fig. 6 is a needle-like crystal as viewed under a scanning electron microscope. When x=0.07, the XRD spectrum is similar to that of fig. 7, the relative crystallinity is about 90%, and fig. 8 is a more loose needle-like crystal as viewed under a scanning electron microscope. XRD spectrum when x=0.1Similar to FIG. 9, not crystallized to ZSM-48, FIG. 10 was observed as amorphous material (SiO 2 ). As the proportion of polyacrylamide is increased, the crystallinity of the synthesized mesoporous step structure molecular sieve ZSM-48 is reduced, and when the proportion is too large, the molecular sieve cannot be synthesized.
Example 3
According to the mole ratio of each component: 3.95Na 2 O：60SiO 2 ：0.75Al 2 O 3 :1.2 template agent: 1200H 2 O: adding 0.7822g of sodium hydroxide, 0.3757g of sodium metaaluminate, 1.3280g of hexamethyl diammonium bromide, 1.0175g of polyvinylpyrrolidone and 11g of fumed silica into 67.5g of deionized water in sequence, stirring and mixing uniformly for 0.5h to obtain white gel, adding 0.022g of Beta molecular sieve as heterogeneous seed crystal, continuously stirring and mixing uniformly, transferring into a 100mL hydrothermal kettle, placing into a 180 ℃ oven at the rotating speed of 60r/min, crystallizing for 48h, filtering and washing the obtained product, placing the filter cake into the 80 ℃ oven for drying for 12h, and roasting for 6h at 550 ℃ to obtain the ZSM-48 molecular sieve with the mesoporous step structure. The XRD spectrum of the molecular sieve ZSM-48 with the mesoporous and microporous cascade structure is similar to that of FIG. 11, the relative crystallinity is about 95%, but impurity peaks appear, and the molecular sieve is a corolla crystal as observed under a scanning electron microscope in FIG. 12, and is similar to a standard sample.
Example 4
According to the mole ratio of each component: 3.95Na 2 O：60SiO 2 ：0.75Al 2 O 3 :1.2 template agent: 1500H 2 O:0.05 tetramethyl ammonium chloride, sequentially adding 0.64g sodium hydroxide, 0.31g sodium metaaluminate, 1.09g hexamethyl diammonium bromide, 0.8220g tetramethyl ammonium chloride and 9g fumed silica into 67.5g deionized water, stirring and mixing uniformly for 0.5h to obtain white gel, adding 0.018g Beta molecular sieve as heterogeneous seed crystal, continuously stirring and mixing uniformly, transferring to a 100mL hydrothermal kettle, placing in a 180 ℃ oven at the rotating speed of 60r/min, crystallizing for 48h, filtering and washing the obtained product, placing the filter cake in the 80 ℃ oven for drying for 12h, and roasting at 550 ℃ for 6h to obtain the ZSM-48 molecular sieve with the mesoporous step structure. Obtaining the mesoporous stepThe XRD spectrum of the molecular sieve ZSM-48 was similar to that of FIG. 13, the relative crystallinity was about 43%, and the structure was observed as a needle-like crystal under a scanning electron microscope in FIG. 14.
Example 5
The standard sample obtained in example 1 and the ZSM-48 molecular sieve having a mesoporous step structure obtained by X=0.03 in example 2 were weighed into 3g of sample, 90ml of 0.5mol/L ammonium nitrate solution was weighed into a flask, and NH was performed at 80 ℃ 4 + Exchanging and stirring for two hours, repeating the NH 4 + Exchanging twice, filtering, washing, and drying the filter cake in an oven at 80 ℃ for 8 hours. Taking out the sample, soaking 0.5wt% of Pt, steaming in a rotary way, putting into a baking oven for drying, putting into a tube furnace, and roasting for 3 hours at 400 ℃ in an oxygen atmosphere to obtain the Pt/ZSM-48 dual-function catalyst. The hydroisomerization of n-hexadecane was carried out in a fixed bed reactor, the catalyst was first reduced under a hydrogen atmosphere at 400 ℃ for 3 hours, and the reaction was started after cooling to 220 ℃. The reaction temperature is 220-360 ℃, the reaction pressure is 4MPa, and the volume ratio of hydrogen to n-hexadecane is 300:1. Table 1 below shows the results of hydroisomerization of n-hexadecane by the catalyst having a standard sample in this example, and Table 2 below shows the results of hydroisomerization of n-hexadecane by the catalyst having a meso-porous cascade structure in this example, and it can be seen from a comparison of the two tables that the conversion of the catalyst having a meso-porous cascade structure increases with increasing temperature and has a very high selectivity at a lower temperature, with a conversion of about 99wt% and a highest isomerization selectivity of about 15wt% compared to the conventional ZSM-48 catalyst, wherein the selectivity of the single branched product increases by about 10wt%, the selectivity of the double branched product increases by about 5wt%, the yield of the triple branched product increases by about 3wt%, and the cracking conversion is reduced by about 13wt% at the highest (corresponding 340 ℃ C.). The data show that the in-situ synthesized mesoporous step structure ZSM-48 not only improves the selectivity of the n-hexadecane hydroisomerization reaction, but also greatly reduces the cracking yield in the reaction process, greatly improves the isomerism yield, and proves that the catalyst has excellent isomerism performance.
TABLE 1
TABLE 2
Claims (7)
1. A preparation method of a high-performance hydroisomerization catalyst ZSM-48 molecular sieve with a mesoporous step structure is characterized by comprising the following steps:
sequentially adding a silicon source, an aluminum source, an alkali source, water, a template agent, a mesoporous structuring agent and a seed crystal, stirring until a gel system is formed, uniformly stirring, and crystallizing for 1-4d under the condition of hydrothermal autogenous pressure at 180 ℃ to obtain the ZSM-48 molecular sieve with the mesoporous step structure and low silicon-aluminum ratio; wherein, the mol ratio range of each material is: (1.40-4.50) Na 2 O：60SiO 2 ：(0.60-1.00)Al 2 O 3 : (0.80-2.40) template agent: (1000-2800) H 2 O: (0.03-0.10) mesoporous structurant, seed crystal addition amount and SiO 2 The mass ratio of (2) is 0.01-7.00%; filtering, washing and drying the product obtained after the hydrothermal crystallization, and roasting at 500-650 ℃ for 3-5 hours to finally obtain the ZSM-48 molecular sieve with the meso-microporous cascade structure.
2. The method according to claim 1, wherein the mesoporous structurant is polyacrylamide, polyvinylpyrrolidone, or tetramethyl ammonium chloride.
3. The method according to claim 1, wherein the aluminum source is one or a mixture of two or more of aluminum nitrate, aluminum sulfate, sodium metaaluminate and aluminum isopropoxide.
4. The method according to claim 1, wherein the silicon source is one or a mixture of two or more of fumed silica, silica sol and ethyl orthosilicate.
5. The method of claim 1, wherein the template agent is hexamethyldiammonium bromide.
6. The method of claim 1, wherein the seed crystal is Beta.
7. The method of claim 1, wherein the alkali source is sodium hydroxide.
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