CN111847471A - Hierarchical pore titanium silicalite molecular sieve for encapsulating active metal and preparation method thereof - Google Patents

Hierarchical pore titanium silicalite molecular sieve for encapsulating active metal and preparation method thereof Download PDF

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CN111847471A
CN111847471A CN201910346379.4A CN201910346379A CN111847471A CN 111847471 A CN111847471 A CN 111847471A CN 201910346379 A CN201910346379 A CN 201910346379A CN 111847471 A CN111847471 A CN 111847471A
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pore volume
molecular sieve
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pore
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CN111847471B (en
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王宝荣
彭欣欣
林民
朱斌
夏长久
罗一斌
舒兴田
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • C01B37/005—Silicates, i.e. so-called metallosilicalites or metallozeosilites
    • 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
    • B01J29/89—Silicates, aluminosilicates or borosilicates of titanium, zirconium or hafnium
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/19—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with organic hydroperoxides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
    • 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
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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
    • Y02P20/584—Recycling of catalysts

Abstract

The invention relates to a hierarchical pore titanium silicalite molecular sieve for encapsulating active metal and a preparation method thereof, wherein the active metal content of the molecular sieve is 0.1-10 wt% calculated by metal oxide and based on the dry basis weight of the molecular sieve, and the active metal is one of VIB group metals; the specific surface area of the molecular sieve is 650-1000 m2(ii) a total pore volume of 0.3 to 0.65m3(g) the mesoporous volume is 0.2-0.46 m3The pore volume of pores with the pore diameter of less than 2nm accounts for 15-60% of the total pore volume, the pore volume of pores with the pore diameter of 2-10 nm accounts for 31-85% of the total pore volume, and the pore volume of pores with the pore diameter of more than 10nm accounts for less than 10% of the total pore volume. The molecular sieve has the advantages ofHigh crystallinity and excellent co-oxidation activity, can be used for catalyzing the co-oxidation reaction of macromolecular raw materials and effectively improves the conversion rate of the raw materials and the selectivity of target products.

Description

Hierarchical pore titanium silicalite molecular sieve for encapsulating active metal and preparation method thereof
Technical Field
The disclosure relates to the field of catalysis, in particular to a hierarchical pore titanium silicalite molecular sieve for encapsulating active metal and a preparation method thereof
Background
The co-oxidation is a process for generating corresponding organic alcohol and epoxy compound by oxidizing organic matters with air/oxygen to generate organic peroxide and then transferring the organic peroxide and olefin through oxygen under the action of a catalyst, and the process is one of main industrial production methods of propylene oxide. Isobutane, ethylbenzene, and cumene are commonly used organic feedstocks that are oxidized to form t-butyl hydroperoxide (TBHP), ethylbenzene hydroperoxide (EBHP), and Cumene Hydroperoxide (CHP), respectively. Under the action of homogeneous molybdenum-containing catalyst or solid-phase titanium-based catalyst, TBHP, EBHP and CHP react with propylene to co-produce tert-butyl alcohol, phenethyl alcohol, dimethyl benzyl alcohol and propylene oxide.
The prior co-oxidation process has longer flow and higher energy consumption. In addition, homogeneous molybdenum-containing catalysts, although having a high epoxidation activity, are difficult to separate and recover; the solid phase titanium-based catalyst mainly comprises silanized Ti-HMS, silanized Ti-SBA-15, silanized Ti-MCM-41, silanized Ti-MCM-48 and silanized Ti-containing porous SiO2Etc. although the titanium-containing catalyst can make the conversion rate of organic peroxide and the selectivity of propylene oxide reach above 90% and 95% respectively under optimized conditions, the amorphous property of the catalyst material surface has better performance than that of the catalyst material surface because HMS, SBA-15, MCM-41, MCM-48 and porous silicon material are all amorphous The catalyst has more surface hydroxyl groups and stronger acidity, so the activity and the propylene oxide selectivity of the catalyst need to be improved by reducing the amount of the surface hydroxyl groups and the number of acid centers through silanization, but the activity stability and the regeneration performance of the catalyst are influenced.
The titanium silicalite TS-1 is a heteroatom molecular sieve with an MFI topological structure and a four-coordination framework titanium, and has the advantages of mild reaction conditions, green and environment-friendly oxidation process, good selectivity of oxidation products and the like in the oxidation reaction of organic matters. Currently, TS-1 has been widely used in reactions such as alkane oxidation, olefin epoxidation, phenol hydroxylation, cyclohexanone ammoximation and oxidative desulfurization. Among them, the epoxidation of propylene, the hydroxylation of phenol and the ammoximation of cyclohexanone have already been realized in industrial production.
Although TS-1 has excellent selective oxidation performance and wider application field, TS-1 can only react with H due to the limitation of the pore channel structure2O2And the oxides with small molecular size are combined to catalyze organic matters with smaller size to perform oxidation reaction. Aiming at the defect, a mesoporous or even macroporous structure can be introduced into the TS-1 to prepare the titanium silicalite molecular sieve with multi-stage pore diameter, thereby improving the performance of the TS-1 when applied to macromolecular oxides and reactants.
According to different synthesis methods, the synthesis of the hierarchical pore TS-1 mainly comprises a skeleton atom removing method, a double template agent synthesis ordered micro-mesoporous composite molecular sieve method, a hard template method, a dry glue conversion method, a silanization method and the like. Under proper conditions, a precursor of the molecular sieve is treated by using a silylation reagent, and then the precursor is hydrothermally synthesized, so that a rich secondary pore structure can be efficiently constructed in crystal grains of the molecular sieve.
Cheneviere et al (J Catal,2010,269:161-168.) with [ 3-trimethoxysilylpropyl ]]Research carried out by using dimethyl octadecane ammonium bromide as a silanization reagent shows that the hierarchical pore TS-1 has more surface hydroxyl groups and stronger hydrophilic performance. Thus, in the epoxidation of cyclohexene, H2O2The cyclohexene conversion rate catalyzed by the hierarchical porous TS-1 is only 19.0 percent, and the oxidation system formed by the tert-butyl hydroperoxide and the hierarchical porous TS-1 can convert 43.0 percent of cyclohexene into oxidation products. Serrano (Chem)Commun,2009,11: 1407-. Compared with the conventional TS-1, the hierarchical pore titanium silicalite molecular sieve has stronger hydrophilicity, and organic peroxide is a more suitable oxidant; tert-butyl hydroperoxide is used as an oxidant, the conversion rates of cyclohexene and 1-octene can respectively reach 85% and 42%, and the selectivity of the oxidation product is kept at 100%; in addition, the multi-stage hole TS-1 has better oxidative desulfurization activity. Although this method can improve the selective oxidation performance of the titanium silicalite molecular sieve, the silylation agent can also interact with the Ti active sites and reduce the catalytic activity of the molecular sieve.
In order to solve the problems of the prior co-oxidation catalyst, a catalytic material with better hydrothermal stability and regeneration performance needs to be further developed. The titanium silicalite TS-1 has excellent oxygen transfer activity and better stability, and is an ideal choice for a co-oxidation catalyst. However, the molecular size of organic peroxides is usually large, while the pore size of conventional TS-1 is only about 0.55nm, and it is still necessary to improve the co-oxidation activity by constructing hierarchical pores within the TS-1 crystal grains. But the olefin epoxidation activity of the multi-stage pore TS-1 still has room for improvement. Therefore, it is necessary to further modify the hierarchical pore TS-1 to prepare a catalytic material with better co-oxidation activity and stability.
Disclosure of Invention
The purpose of the present disclosure is to provide a hierarchical pore titanium silicalite molecular sieve for encapsulating active metals and a preparation method thereof, wherein the molecular sieve has high crystallinity and high co-oxidation activity, and can be used for catalyzing co-oxidation reaction of macromolecular raw materials.
To achieve the above object, a first aspect of the present disclosure: the provided hierarchical pore titanium silicalite molecular sieve for encapsulating active metal is calculated by metal oxide and based on the dry basis weight of the molecular sieve, the active metal content of the molecular sieve is 0.1-10 wt%, and the active metal is VIB group metal One of (1); the specific surface area of the molecular sieve is 650-1000 m2(ii) a total pore volume of 0.3 to 0.65m3(g) the mesoporous volume is 0.2-0.46 m3The pore volume of pores with the pore diameter of less than 2nm accounts for 15-60% of the total pore volume, the pore volume of pores with the pore diameter of 2-10 nm accounts for 31-85% of the total pore volume, and the pore volume of pores with the pore diameter of more than 10nm accounts for less than 10% of the total pore volume.
Optionally in said molecular sieve29In the SiNMR structure spectrogram, Q4/Q3 is 1-15, wherein Q4 represents Si- (O-Si) in the molecular sieve4The peak area of the resonance peak generated by the structure, Q3 represents HO-Si- (O-Si) in the molecular sieve3Peak area of formants generated by the structure.
Optionally, the molecular sieve has an active metal content of 0.2 to 6 wt%, preferably 0.4 to 2.5 wt%, calculated as metal oxide and based on the weight of the molecular sieve on a dry basis; and/or the presence of a gas in the gas,
the active metal is molybdenum, tungsten or chromium.
In a second aspect of the present disclosure: there is provided a process for preparing an active metal encapsulated multigraded pore titanium silicalite molecular sieve according to the first aspect of the disclosure, the process comprising the steps of:
a. mixing a silicon source, a structure directing agent, an active metal source, a titanium source and water to obtain a first mixture;
b. Directly adding a silanization reagent into the first mixture obtained in the step a or adding the silanization reagent into the first mixture obtained in the step a after the first mixture is pre-crystallized at the temperature of 30-90 ℃ for 0.1-48 h to obtain a second mixture;
c. and c, transferring the second mixture obtained in the step b into a pressure-resistant closed container, crystallizing for 1-240 hours at 110-230 ℃ under autogenous pressure, and recovering a crystallized product.
Optionally, in step a, the molar ratio of the first mixture is SiO2：R：TiO2：M：H2O is 1: (0.001-5): (0.0001-0.1): (0.0001-0.1): (5-400); preferably, the molar ratio of the first mixture is SiO2：R：TiO2：Mo：H2O＝1: (0.005-3): (0.0005-0.05): (0.0005-0.04): (10-200); further preferably, the molar ratio of the first mixture is SiO2：R：TiO2：M：H2O is 1: (0.01-2): (0.001-0.03): (0.001-0.02): (15-100); wherein R represents the number of moles of structure directing agent and M represents the number of moles of active metal in terms of simple substance.
Optionally, in step a, the silicon source is methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, silica gel, white carbon black or silica sol, or a combination of two or three of them.
Optionally, in step a, the titanium source is titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, or tetrabutyl titanate, or a combination of two or three thereof.
Optionally, in step a, the structure directing agent is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof.
Optionally, in step a, the active metal source is ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, molybdenum hexacarbonyl, molybdenum acetylacetonate, sodium tungstate, tungstic acid, ammonium tungstate, sodium phosphotungstate, silicotungstic acid, tungsten hexachloride, potassium chromate, ammonium chromate, potassium dichromate, chromium chloride or chromium nitrate, or a combination of two or three thereof.
Optionally, in step b, the silylating agent is dimethyldichlorosilane, methyltrichlorosilane, trimethylchlorosilane, 1, 7-dichlorooctylmethyltetrasiloxane, [ 3-trimethoxysilylpropyl ] dimethyloctadecylammonium bromide, N-phenyl-3-aminopropyltrimethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, methyltriethoxysilane, tert-butyldimethylchlorosilane, hexadecyltrimethoxysilane, or octyltriethoxysilane, or a combination of two or three thereof; preferably, the silylating agent is phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisiloxane or methyltriethoxysilane, or a combination of two or three thereof.
Optionally, in step b, the molar ratio of the silylating agent in the second mixture is SiO2: w is 1: (0.001 to 0.5), preferably SiO2: w is 1: (0.005-0.3), wherein W represents the mole number of the silanization reagent.
Optionally, in the step b, the temperature of the pre-crystallization is 40-80 ℃, and the time is 0.5-32 hours.
Optionally, in the step c, the crystallization temperature is 120-190 ℃ and the crystallization time is 2-192 h.
Optionally, the method further comprises: c, drying and roasting the crystallization product recovered in the step c; the drying conditions include: the temperature is 60-150 ℃, and the time is 0.5-24 h; the roasting conditions comprise: the temperature is 400-900 ℃, and the time is 1-16 h.
Through the technical scheme, the hierarchical pore titanium silicalite molecular sieve for encapsulating the active metal has high crystallinity and excellent co-oxidation activity, can be used for catalyzing the co-oxidation reaction of macromolecular raw materials, and effectively improves the conversion rate of the raw materials and the selectivity of target products.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:
FIG. 1 is a TEM photograph of a molybdenum-encapsulating, hierarchical pore titanium silicalite TS-1 prepared in example 1.
FIG. 2 is a pore distribution plot of the molybdenum-encapsulating hierarchical pore titanium silicalite TS-1 prepared in example 1.
FIG. 3 is a molybdenum-encapsulating, hierarchical pore titanium silicalite molecular sieve prepared in example 129And (3) a SiNMR structure spectrogram.
FIG. 4 is a TEM photograph of the multi-stage pore titanium silicalite TS-1 prepared in comparative example 1.
FIG. 5 is a pore distribution plot of a hierarchical pore titanium silicalite TS-1 prepared in comparative example 1.
FIG. 6 is a hierarchical pore titanium silicalite molecular sieve prepared in comparative example 129And (3) a SiNMR structure spectrogram.
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
The first aspect of the disclosure: providing a hierarchical pore titanium silicalite molecular sieve for encapsulating active metal, wherein the active metal content of the molecular sieve is 0.1-10 wt% based on metal oxide and the dry basis weight of the molecular sieve, and the active metal is one of VIB group metals; the specific surface area of the molecular sieve is 650-1000 m2(ii) a total pore volume of 0.3 to 0.65m3(g) the mesoporous volume is 0.2-0.46 m 3The pore volume of pores with the pore diameter of less than 2nm accounts for 15-60% of the total pore volume, the pore volume of pores with the pore diameter of 2-10 nm accounts for 31-85% of the total pore volume, and the pore volume of pores with the pore diameter of more than 10nm accounts for less than 10% of the total pore volume.
Compared with the existing hierarchical pore titanium silicalite molecular sieve, the hierarchical pore titanium silicalite molecular sieve for encapsulating the active metal has higher crystallinity and excellent co-oxidation activity, can be used for catalyzing the co-oxidation reaction of macromolecular raw materials and effectively improves the conversion rate of the raw materials and the selectivity of target products.
Further, in the molecular sieve29In the SiNMR structure spectrogram, Q4/Q3 can be 1-15, wherein Q4 represents Si- (O-Si) in the molecular sieve4The peak area of the formant generated by the structure, namely the peak area of the formant generated by the structure formed by connecting the silicon atom with four silicon atoms through a silicon-oxygen bond; q3 represents HO-Si- (O-Si) in molecular sieve3The peak area of the resonance peak generated by the structure, namely the peak area of the resonance peak generated by the structure formed by connecting a silicon atom with three silicon atoms through a silicon-oxygen bond and connecting a hydroxyl group. The molecular sieve of the present disclosure has a strong Q4 signal, but almost no Q3 signal, which indicates that the molecular sieve of the present disclosure has almost no framework defects, with high junctions And (4) crystallinity.
In accordance with the present disclosure, the molecular sieve preferably has an active metal content of from 0.2 to 6 weight percent, more preferably from 0.4 to 2.5 weight percent, based on the metal oxide and based on the dry weight of the molecular sieve.
According to the present disclosure, the active metal is preferably molybdenum, tungsten or chromium.
In a second aspect of the present disclosure: there is provided a process for preparing an active metal encapsulated multigraded pore titanium silicalite molecular sieve according to the first aspect of the disclosure, the process comprising the steps of:
a. mixing a silicon source, a structure directing agent, an active metal source, a titanium source and water to obtain a first mixture;
b. directly adding a silanization reagent into the first mixture obtained in the step a or adding the silanization reagent into the first mixture obtained in the step a after the first mixture is pre-crystallized at the temperature of 30-90 ℃ for 0.1-48 h to obtain a second mixture;
c. and c, transferring the second mixture obtained in the step b into a pressure-resistant closed container, crystallizing for 1-240 hours at 110-230 ℃ under autogenous pressure, and recovering a crystallized product.
The method simultaneously introduces a titanium source and an active metal source into a system for synthesizing the hierarchical pore molecular sieve by silanization, thereby preparing the hierarchical pore titanium silicalite molecular sieve for encapsulating the active metal,
According to the disclosure, in the step a, the molar ratio of the first mixture may be SiO2：R：TiO2：M：H2O is 1: (0.001-5): (0.0001-0.1): (0.0001-0.1): (5-400); wherein R represents the number of moles of structure directing agent and M represents the number of moles of active metal in terms of simple substance. In order to further improve the catalytic activity of the prepared molecular sieve, the molar ratio of the first mixture is preferably SiO2：R：TiO2：M：H2O is 1: (0.005-3): (0.0005-0.05): (0.0005-0.04): (10-200). Further preferably, the molar ratio of the first mixture is SiO2：R：TiO2：M：H2O＝1：(0.01～2)：(0.001～0.03)：(0.001～0.02)：(15～100)。
According to the present disclosure, in step a, the silicon source may be a silicon source commonly used for synthesizing titanium silicalite molecular sieves, which is well known to those skilled in the art, and the present disclosure has no particular limitation thereto, for example, the silicon source may be a silicon ester (organosilicate), a solid silica gel, a silica white, or a combination of two or three thereof. In order to avoid the possible influence of the heteroatom in the silicon source, such as trivalent heteroatom like boron or aluminum, on the crystallization of the titanium-silicon molecular sieve, the silicon source is preferably silicone ester, solid silica gel or white carbon black with high silicon dioxide content and low impurity content, or a combination of two or three of the above; more preferably a silicone ester. Wherein the general formula of the silicon ester is shown as formula I:
Figure BDA0002042401830000081
In the formula I, R1、R2、R3And R4Each independently may be C1-C4Alkyl of (2) including C1-C4Straight chain alkyl of (2) and C3-C4Branched alkyl groups such as: r1、R2、R3And R4Each independently may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, with R being preferred1、R2、R3And R4Each independently being methyl or ethyl, i.e. the silicon ester is preferably methyl, ethyl, propyl or butyl orthosilicate, or a combination of two or three thereof.
In accordance with the present disclosure, in step a, the titanium source may be a titanium source commonly used by those skilled in the art for synthesizing titanium silicalite molecular sieves, and the present disclosure has no particular limitation thereto, for example, the titanium source may be titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, or tetrabutyl titanate, or a combination of two or three thereof.
According to the disclosure, in step a, the structure directing agent may be a structure directing agent commonly used in the synthesis of titanium silicalite molecular sieves, and the invention has no special relation to the structure directing agentFor example, the structure directing agent can be a quaternary ammonium base, an aliphatic amine, or an aliphatic alcohol amine, or a combination of two or three thereof; wherein the quaternary ammonium base can be organic quaternary ammonium base, and the aliphatic amine can be NH 3In which at least one hydrogen is substituted with an aliphatic hydrocarbon group (e.g., an alkyl group), which may be a variety of NH3Wherein at least one hydrogen is substituted with a hydroxyl-containing aliphatic group (e.g., an alkyl group).
Specifically, the structure directing agent can be a quaternary ammonium base represented by formula II, an aliphatic amine represented by formula III, or an aliphatic alcohol amine represented by formula IV, or a combination of two or three of them.
Figure BDA0002042401830000082
In the formula II, R5、R6、R7And R8Each independently may be C1-C4Alkyl of (2) including C1-C4Straight chain alkyl of (2) and C3-C4Branched alkyl groups of (a), for example: r5、R6、R7And R8Each independently may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.
R9(NH2)n(formula III)
In the formula III, n is an integer of 1 or 2. When n is 1, R9Is C1-C6Alkyl of (2) including C1-C6Straight chain alkyl of (2) and C3-C6Such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl or n-hexyl. When n is 2, R9Is C1-C6Alkylene of (2) including C1-C6Linear alkylene of (A) and (C)3-C6Such as methylene, ethylene, n-propylene, n-butylene, n-pentylene or n-hexylene.
(HOR10)mNH(3-m)(formula IV)
In the formula IV, m are R10May be the same or different and each independently may be C1-C4Alkylene of (2) including C1-C4Linear alkylene of (A) and (C)3-C4A branched alkylene group of (a), such as methylene, ethylene, n-propylene or n-butylene; m is 1, 2 or 3.
Preferably, the structure directing agent is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (including various isomers of tetrapropylammonium hydroxide, such as tetra-n-propylammonium hydroxide and tetra-i-propylammonium hydroxide), or tetrabutylammonium hydroxide (including various isomers of tetrabutylammonium hydroxide, such as tetra-n-butylammonium hydroxide and tetra-i-butylammonium hydroxide), or a combination of two or three thereof. Most preferably, the structure directing agent is tetrapropylammonium hydroxide.
According to the present disclosure, in step a, the active metal source may be a compound containing the active metal, for example, the active metal source may be ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, molybdenum hexacarbonyl, molybdenum acetylacetonate, sodium tungstate, tungstic acid, ammonium tungstate, sodium phosphotungstate, silicotungstic acid, tungsten hexachloride, potassium chromate, ammonium chromate, potassium dichromate, chromium chloride or chromium nitrate, or a combination of two or three thereof.
According to the present disclosure, in step a, the water may be water commonly used in the synthesis of molecular sieves, and in order to avoid the introduction of heteroatoms, deionized water is preferred in the present disclosure.
According to the disclosure, in step a, the silicon source, the structure directing agent, the active metal source, the titanium source and the water may be uniformly mixed according to a conventional method to obtain the first mixture. In a preferred embodiment of the present disclosure, the silicon source, the structure directing agent and the water may be mixed uniformly at a temperature of 20 to 100 ℃, and more preferably 30 to 90 ℃, and then the active metal source and the titanium source may be added and mixed uniformly.
According to the present disclosure, in step b, the addition of the silylation agent is performed in two ways. In a first embodiment, a silylating agent is added directly to the first mixture obtained in step a to obtain the second mixture. The second implementation mode is that the first mixture obtained in the step a is pre-crystallized at the temperature of 30-90 ℃ for 0.1-48 h, and then a silanization reagent is added to obtain a second mixture. Compared with the first embodiment, the second embodiment, namely, the first mixture is pre-crystallized and then the silylation reagent is added for crystallization, is more favorable for improving the stability of the prepared molecular sieve.
According to the present disclosure, in step b, the silylating agent may be dimethyldichlorosilane, methyltrichlorosilane, trimethylchlorosilane, 1, 7-dichlorooctylmethyltetrasiloxane, [ 3-trimethoxysilylpropyl ] dimethyloctadecylammonium bromide, N-phenyl-3-aminopropyltrimethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, methyltriethoxysilane, tert-butyldimethylchlorosilane, hexadecyltrimethoxysilane, or octyltriethoxysilane, or a combination of two or three thereof. Preferably, the silanization reagent is phenyl triethoxysilane, hexamethyldisilazane, hexamethyldisiloxane or methyl triethoxysilane, or a combination of two or three of them, and the silanization reagent has appropriate reactivity and molecular size, which is more beneficial for preparing molecular sieves with high catalytic activity.
According to the disclosure, in step b, the molar ratio of the silylating agent in the second mixture is SiO2: w is 1: (0.001-0.5), wherein W represents the mole number of the silylation agent. In order to further improve the catalytic activity of the prepared molecular sieve, the molar ratio of the silylating agent in the second mixture is preferably SiO 2：W＝1：(0.005～0.3)。
According to the present disclosure, in step b, the conditions of the pre-crystallization are preferably: the temperature of the pre-crystallization is 40-80 ℃, and the time is 0.5-32 h.
According to the present disclosure, in step c, the crystallization conditions are preferably: the crystallization temperature is 120-190 ℃, and the crystallization time is 2-192 h.
According to the present disclosure, in step c, the crystallization may be performed under static conditions or under dynamic stirring conditions; in order to ensure that the crystallization system is uniformly mixed and a uniform crystallization product is obtained, the crystallization process is optimized to be carried out under the condition of dynamic stirring; more preferably, the dynamic crystallization is carried out at a stirring speed of 100 to 800 r/min.
According to the present disclosure, the method may further comprise: and c, drying and roasting the crystallization product recovered in the step c. The conditions for drying and calcining may be conventional in the art, for example, the conditions for drying may include: the temperature is 60-150 ℃, and the time is 0.5-24 h; the conditions for the firing may include: the temperature is 400-900 ℃, and the time is 1-16 h.
The present disclosure will be described in further detail below by way of examples.
In each of the following examples and comparative examples, Transmission Electron Microscope (TEM) results were determined using JEOL JEM-2100, test methods were: dispersing a molecular sieve sample in an ethanol solution, placing the sample on a sample net, and drying the sample net at an accelerating voltage of 200 kV. The specific surface area SBET is the static N of the sample measured at liquid nitrogen temperature (77.4K) using an ASAP2405J static nitrogen adsorption apparatus from Micromeritics 2After adsorption and desorption curves, P/P is adjusted0The adsorption curve is obtained by BET fitting in the range of 0.05-0.35. The pore volume was measured according to the method described in RIPP 151-90 of "petrochemical analysis methods" written in Ponkui et al.29Characterization of the Si NMR spectra was determined using a Varian INOVA model 300 NMR spectrometer under the following test conditions: the resonance frequency spectrum is 59.588MHz, and the magic angle rotating speed is 3 kHz.29The Q4 signal in Si NMR refers to Si- (O-Si) in molecular sieves4A formant generated by the structure, namely a formant generated by the structure formed by connecting silicon atoms with four silicon atoms through silicon-oxygen bonds; the Q3 signal refers to HO-Si- (O-Si) in the molecular sieve3The resonance peak generated by the structure is that the silicon atom is connected with three silicon atoms through silicon oxygen bonds and is connected with one hydroxyl group. To pair29After the Si NMR resonance peak spectrogram is subjected to peak-splitting fitting, an integration method is adopted to calculate the ratio of peak areas of Q4 and Q3This is the Q4/Q3 value.
Example 1
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, molybdenum acetylacetonate and deionized water to obtain SiO2: structure directing agent: TiO 22：Mo：H2O is 1: 0.2: 0.025: 0.01: 50; then according to SiO 2: silylation reagent ═ 1: 0.12, adding phenyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, and roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 1.4 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2,29si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm is 18% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm is 75% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm is 7% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 2
Under the condition of stirring, mixing methyl orthosilicate, tetramethyl ammonium hydroxide, titanium tetrachloride, ammonium molybdate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 0.02: 0.005: 0.001: 20, a first mixture; then according to SiO2: silylation reagent ═ 1: 0.01, adding hexamethyldisilazane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 160 ℃ under stirring and crystallizing under autogenous pressure for 12 h. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 0.4 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2, 29Si NMR junctionSimilar to FIG. 3, the pore volume of pores with a pore diameter of less than 2nm accounted for 25% of the total pore volume, the pore volume of pores with a pore diameter of 2 to 10nm accounted for 69% of the total pore volume, the pore volume of pores with a pore diameter of greater than 10nm accounted for 6% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 3
Under the condition of stirring, mixing n-butyl silicate, tetraethyl ammonium hydroxide, titanium nitrate, phosphomolybdic acid and deionized water to obtain SiO with the molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 2: 0.03: 0.02: 100 of a first mixture; then according to SiO2: silylation reagent ═ 1: 0.3, adding methyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 190 ℃ under stirring and crystallizing for 6h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 2.5 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of 1 to 2nm accounted for 38% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounted for 55% of the total pore volume, and the pore volume of pores having a pore diameter of greater than 10nm accounted for 7% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 4
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, sodium tungstate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：W：H2O is 1: 1.2: 0.01: 0.01: 40; then according to SiO2: silylation reagent ═ 1: 0.2, adding phenyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, returningCollecting crystallized product, drying at 110 deg.C for 6h, calcining at 550 deg.C for 4h to obtain hierarchical pore titanium silicalite TS-1 with tungsten content of 1.5 wt%, TEM result similar to that in FIG. 1 and pore distribution similar to that in FIG. 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm is 31% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm is 64% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm is 5% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 5
Mixing silica gel, tetrapropylammonium hydroxide, tetrapropyltitanate, phosphomolybdic acid and deionized water under the condition of stirring to obtain SiO in the molar ratio 2: structure directing agent: TiO 22：Mo：H2O is 1: 3: 0.05: 0.025: 150; then according to SiO2: silylation reagent ═ 1: 0.25 mol ratio, adding phenyltriethoxysilane into the first mixture, stirring uniformly, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 150 ℃ for 2h, roasting at 650 ℃ for 8h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 3.0 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounted for 48% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounted for 43% of the total pore volume, and the pore volume of pores having a pore diameter of greater than 10nm accounted for 9% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 6
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, molybdenum acetylacetonate and deionized water to obtain SiO2: structure directing agent: TiO 2 2：Mo：H2O is 1: 0.005: 0.0005: 0.0005: 10; then according to SiO2: silylation reagent ═ 1: 0.12 mol ratio of phenyl triethoxysilaneAdding the mixture into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 0.3 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm is 45% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm is 52% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm is 3% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 7
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, molybdenum acetylacetonate and deionized water to obtain SiO2: structure directing agent: TiO 22：Mo：H2O is 1: 0.001: 0.0001: 0.0001: 5; then according to SiO 2: silylation reagent ═ 1: 0.001, adding methyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, and roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 0.2 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2,29si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm was 56% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm was 39% of the total pore volume, and the pore volume of pores having a pore diameter of more than 10nm was 5% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 8
Mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, ammonium molybdate and deionized water under the condition of stirring to obtain the productTo the molar ratio of SiO2: structure directing agent: TiO 22：Mo：H2O is 1: 5: 0.1: 0.1: 400; then according to SiO2: silylation reagent ═ 1: 0.5, adding hexamethyldisilazane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, and roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 5.8 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2, 29Si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm was 48% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm was 48% of the total pore volume, and the pore volume of pores having a pore diameter of more than 10nm was 4% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 9
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, ammonium molybdate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 0.2: 0.025: 0.01: 50; then according to SiO2: silylation reagent ═ 1: 0.12, adding N-phenyl-3-aminopropyltrimethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, and roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 1.4 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2,29si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm is 42% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm is 50% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm is 8% of the total pore volume, and the specific surface area is The pore volumes and Q4/Q3 values are listed in Table 1.
Example 10
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, ammonium molybdate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 0.2: 0.025: 0.01: 50; then according to SiO2: silylation reagent ═ 1: 0.12, adding phenyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 230 ℃ under stirring and crystallizing for 200h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 1.4 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounted for 38% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounted for 56% of the total pore volume, and the pore volume of pores having a pore diameter of greater than 10nm accounted for 6% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 11
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, ammonium molybdate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 0.5: 0.015: 0.005: 30 of a first mixture; pre-crystallizing the first mixture at 50 deg.C for 16h, and mixing with SiO2: silylation reagent ═ 1: adding phenyl triethoxysilane according to the molar ratio of 0.1, uniformly stirring, and transferring the obtained second mixture to a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, and roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 0.8 wt%, the TEM result is similar to that in figure 1, and the pore distribution isIn a manner similar to that of figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounted for 16% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounted for 80% of the total pore volume, and the pore volume of pores having a pore diameter of more than 10nm accounted for 4% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 12
Under the condition of stirring, mixing white carbon black, tetrapropylammonium hydroxide, tetrabutyl titanate, molybdenum acetylacetonate and deionized water to obtain SiO2: structure directing agent: TiO 22：Mo：H2O is 1: 0.01: 0.005: 0.015: 15; pre-crystallizing the first mixture at 40 deg.C for 32h, and mixing with SiO2: silylation reagent ═ 1: adding hexamethyldisiloxane in a molar ratio of 0.01, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 190 ℃ under stirring and crystallizing under autogenous pressure for 192 h. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 180 ℃ for 0.5h, and then roasting at 800 ℃ for 2h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 1.8 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2,29si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm was 26% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm was 65% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm was 9% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 13
Under the condition of stirring, silica sol, tetrapropylammonium hydroxide, tetrabutyl titanate, sodium molybdate and deionized water are mixed to obtain SiO with the molar ratio 2: structure directing agent: TiO 22：Mo：H2O is 1: 2.5: 0.04: 0.04: 160; pre-crystallizing the first mixture at 80 deg.C for 4 hr, and mixing with SiO2: silylation reagent ═ 1: adding methyl triethoxysilane according to the molar ratio of 0.3, uniformly stirring, and transferring the obtained second mixture to a pressure-resistant stainless steel reaction kettle; heating to 150 deg.C under stirringAnd crystallized under autogenous pressure for 72 h. After the stainless steel pressure-resistant reaction kettle is cooled to room temperature, recovering crystallized products, drying at 60 ℃ for 24h, roasting at 400 ℃ for 16h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 3.4 wt%, the TEM result is shown in figure 1, the pore distribution is shown in figure 2,29si NMR results are shown in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounted for 38% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounted for 57% of the total pore volume, and the pore volume of pores having a pore diameter of greater than 10nm accounted for 5% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 14
Under the condition of stirring, mixing the white carbon black, the tetrapropylammonium hydroxide, the tetraethyl titanate, the ammonium molybdate and the deionized water to obtain SiO with the molar ratio2: structure directing agent: TiO 2 2：Mo：H2O is 1: 4: 0.08: 0.08: 300 of a homogeneous mixture; pre-crystallizing the first mixture at 70 deg.C for 1 hr, and mixing with SiO2: silylation reagent ═ 1: adding hexamethyldisilazane in a molar ratio of 0.4, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 190 ℃ under stirring and crystallizing for 24h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 130 ℃ for 4h, roasting at 550 ℃ for 6h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 5.5 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounts for 26% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounts for 69% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm accounts for 5% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 15
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, potassium chromate and deionized water to obtain SiO with the molar ratio2: structure directing agent: TiO 22：Cr：H2O is 1: 1.2: 0.016: 0.008: 36; will be provided with Pre-crystallizing the first mixture at 70 deg.C for 1 hr, and mixing with SiO2: silylation reagent ═ 1: adding hexamethyldisilazane in a molar ratio of 0.012, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 190 ℃ under stirring and crystallizing for 24h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 130 ℃ for 4h, roasting at 550 ℃ for 6h to obtain the chromium-encapsulated hierarchical pore titanium silicalite TS-1, wherein the chromium content is 1.9 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm accounts for 33% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm accounts for 59% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm accounts for 8% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Example 16
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate, ammonium molybdate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：Mo：H2O is 1: 0.5: 0.015: 0.005: 30 of a first mixture; pre-crystallizing the first mixture at 90 deg.C for 0.1h, and mixing with SiO 2: silylation reagent ═ 1: adding phenyl triethoxysilane according to the molar ratio of 0.1, uniformly stirring, and transferring the obtained second mixture to a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. After the stainless steel pressure-resistant reaction kettle is cooled to the room temperature, recovering the crystallized product, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the molybdenum-encapsulated hierarchical pore titanium silicalite TS-1, wherein the molybdenum content is 1.1 wt%, the TEM result is similar to that in figure 1, the pore distribution is similar to that in figure 2,29si NMR results are similar to those in FIG. 3, in which the pore volume of pores having a pore diameter of less than 2nm is 58% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm is 38% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm is 4% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
Comparative example 1
Under the condition of stirring, mixing ethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate and deionized water to obtain SiO in molar ratio2: structure directing agent: TiO 22：H2O is 1: 0.2: 0.025: 50; then according to SiO2: silylation reagent ═ 1: 0.12, adding phenyltriethoxysilane into the first mixture, uniformly stirring, and transferring the obtained second mixture into a pressure-resistant stainless steel reaction kettle; heating to 170 ℃ under stirring and crystallizing for 8h under autogenous pressure. Recovering crystallized product after the stainless steel pressure-resistant reaction kettle is cooled to room temperature, drying at 110 ℃ for 6h, roasting at 550 ℃ for 4h to obtain the hierarchical pore titanium silicalite TS-1, wherein the TEM result is shown in figure 4, the pore distribution is shown in figure 5, 29Si NMR results are shown in FIG. 6, in which the pore volume of pores having a pore diameter of less than 2nm was 12% of the total pore volume, the pore volume of pores having a pore diameter of 2 to 10nm was 54% of the total pore volume, the pore volume of pores having a pore diameter of more than 10nm was 34% of the total pore volume, and the specific surface area, pore volume and Q4/Q3 values are shown in Table 1.
TABLE 1
Figure BDA0002042401830000201
Figure BDA0002042401830000211
Test examples
The molecular sieves obtained in the examples and the comparative examples are used for catalyzing the co-oxidation reaction of cyclohexene, and the reaction conditions are as follows: cyclohexene and tert-butyl hydroperoxide are mixed according to a molar ratio of 1: 1 was mixed and contacted with the molecular sieve prepared in example in an amount of 10% by weight of cyclohexene, and reacted at 100 ℃ for 2 hours, and the conversion of cyclohexene and the selectivity of cyclohexene oxide were calculated according to the following formulas, and the results are shown in Table 2.
Cyclohexene conversion (%). The amount of cyclohexene converted/initial amount of cyclohexene X100%
Selectivity to cyclohexene oxide (%). corresponds to the amount of cyclohexene oxide/amount of cyclohexene converted × 100%
TABLE 2
Figure BDA0002042401830000212
Figure BDA0002042401830000221
As can be seen from table 2, the molecular sieve of the present disclosure can effectively increase the conversion rate of cyclohexene and the selectivity of cyclohexene oxide.
The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (14)

1. The hierarchical pore titanium silicalite molecular sieve for encapsulating active metal is characterized in that the active metal content of the molecular sieve is 0.1-10 wt% based on the metal oxide and the dry basis weight of the molecular sieve, and the active metal is one of VIB group metals; the specific surface area of the molecular sieve is 650-1000 m2(ii) a total pore volume of 0.3 to 0.65m3(g) the mesoporous volume is 0.2-0.46 m3The pore volume of the pores with the pore diameter of less than 2nm accounts for 15-60% of the total pore volume, the pore volume of the pores with the pore diameter of 2-10 nm accounts for 31-85% of the total pore volume, and the pore volume of the pores with the pore diameter of more than 10nm accounts for 10% of the total pore volume to form the molecular sieveThe following steps.
2. The molecular sieve of claim 1, wherein the molecular sieve is 29In the SiNMR structure spectrogram, Q4/Q3 is 1-15, wherein Q4 represents Si- (O-Si) in the molecular sieve4The peak area of the resonance peak generated by the structure, Q3 represents HO-Si- (O-Si) in the molecular sieve3Peak area of formants generated by the structure.
3. The molecular sieve of claim 1, wherein the molecular sieve has an active metal content of from 0.2 to 6 wt.%, preferably from 0.4 to 2.5 wt.%, calculated as metal oxide and based on the weight of the molecular sieve on a dry basis; and/or the presence of a gas in the gas,
the active metal is molybdenum, tungsten or chromium.
4. The method of preparing the active metal-encapsulated hierarchical pore titanium silicalite molecular sieve of any one of claims 1 to 3, comprising the steps of:
a. mixing a silicon source, a structure directing agent, an active metal source, a titanium source and water to obtain a first mixture;
b. directly adding a silanization reagent into the first mixture obtained in the step a or adding the silanization reagent into the first mixture obtained in the step a after the first mixture is pre-crystallized at the temperature of 30-90 ℃ for 0.1-48 h to obtain a second mixture;
c. and c, transferring the second mixture obtained in the step b into a pressure-resistant closed container, crystallizing for 1-240 hours at 110-230 ℃ under autogenous pressure, and recovering a crystallized product.
5. The method of claim 4, wherein the molar ratio of the first mixture in step a is SiO2：R：TiO2：M：H2O is 1: (0.001-5): (0.0001-0.1): (0.0001-0.1): (5-400); preferably, the molar ratio of the first mixture is SiO2：R：TiO2：Mo：H2O＝1：(0.005～3)：(0.0005～0.05)：(0.0005～0.04)：(10～200) (ii) a Further preferably, the molar ratio of the first mixture is SiO2：R：TiO2：M：H2O is 1: (0.01-2): (0.001-0.03): (0.001-0.02): (15-100); wherein R represents the number of moles of structure directing agent and M represents the number of moles of active metal in terms of simple substance.
6. The method according to claim 4, wherein in step a, the silicon source is methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, silica gel, white carbon black or silica sol, or a combination of two or three of them.
7. The method of claim 4, wherein in step a, the titanium source is titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, or tetrabutyl titanate, or a combination of two or three thereof.
8. The method of claim 4, wherein in step a, the structure directing agent is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof.
9. The process of claim 4, wherein in step a, the active metal source is ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, molybdenum hexacarbonyl, molybdenum acetylacetonate, sodium tungstate, tungstic acid, ammonium tungstate, sodium phosphotungstate, silicotungstic acid, tungsten hexachloride, potassium chromate, ammonium chromate, potassium dichromate, chromium chloride, or chromium nitrate, or a combination of two or three thereof.
10. The process of claim 4, wherein in step b, the silylating agent is dimethyldichlorosilane, methyltrichlorosilane, trimethylchlorosilane, 1, 7-dichlorooctylmethyltetrasiloxane, [ 3-trimethoxysilylpropyl ] dimethyloctadecylammonium bromide, N-phenyl-3-aminopropyltrimethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisiloxane, methyltriethoxysilane, tert-butyldimethylchlorosilane, hexadecyltrimethoxysilane, or octyltriethoxysilane, or a combination of two or three thereof; preferably, the silylating agent is phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisiloxane or methyltriethoxysilane, or a combination of two or three thereof.
11. The process according to claim 4, wherein in step b, the molar ratio of the silylating agent in the second mixture is SiO2: w is 1: (0.001 to 0.5), preferably SiO2: w is 1: (0.005-0.3), wherein W represents the mole number of the silanization reagent.
12. The method according to claim 4, wherein in the step b, the temperature of the pre-crystallization is 40-80 ℃ and the time is 0.5-32 h.
13. The method of claim 4, wherein in the step c, the crystallization temperature is 120-190 ℃ and the crystallization time is 2-192 h.
14. The method of claim 4, wherein the method further comprises: c, drying and roasting the crystallization product recovered in the step c; the drying conditions include: the temperature is 60-150 ℃, and the time is 0.5-24 h; the roasting conditions comprise: the temperature is 400-900 ℃, and the time is 1-16 h.
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