CN118005032A - Hierarchical porous titanium-silicon molecular sieve containing framework titanium and anatase, and preparation method and application thereof - Google Patents

Hierarchical porous titanium-silicon molecular sieve containing framework titanium and anatase, and preparation method and application thereof Download PDF

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CN118005032A
CN118005032A CN202211330131.7A CN202211330131A CN118005032A CN 118005032 A CN118005032 A CN 118005032A CN 202211330131 A CN202211330131 A CN 202211330131A CN 118005032 A CN118005032 A CN 118005032A
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titanium
molecular sieve
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carbon atoms
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张鹏
夏长久
彭欣欣
邢恩会
张晓昕
罗一斌
舒兴田
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Sinopec Petrochemical Research Institute Co ltd
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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Abstract

The present disclosure relates to a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase, a preparation method and applications thereof. The titanium-silicon molecular sieve has the following Ti 2p 3/2 XPS characteristics: the titanium silicalite molecular sieve has spectral peaks at positions N 1 and N 2; wherein N 1 is 459.2 +/-0.2 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 1 is recorded as A 1; the N 2 is 460.5+/-0.5 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 2 is recorded as A 2; x 1 as defined by the following formula (1) is any number between 0.8 and 2.2 ev: x 1＝N2-N1 formula (1); x 2 as defined by the following formula (2) is any number between 0.1 and 0.8: x 2＝A2/A1 formula (2). The method can exert the synergistic effect of framework titanium and anatase, can effectively improve the cyclohexanone oxime conversion rate and the caprolactam selectivity in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, and prolongs the service life of the catalyst.

Description

Hierarchical porous titanium-silicon molecular sieve containing framework titanium and anatase, and preparation method and application thereof
Technical Field
The present disclosure relates to the field of titanium-silicon molecular sieve preparation, and in particular relates to a hierarchical pore titanium-silicon molecular sieve containing framework titanium and anatase, and a preparation method and application thereof.
Background
Since the development of the titanium silicalite molecular sieve in the eighties of the twentieth century, a series of titanium silicalite molecular sieves with different framework structures such as titanium-containing heteroatom molecular sieve TS-1 with MFI structure, heteroatom molecular sieve TS-2 with MEL structure, ti-beta with BEA structure, TS-48 with macroporous structure, MCM-41 with MWW structure and the like have been developed successively. TS-1 can catalyze the partial oxidation of alkane, the epoxidation of alkene, the oxidation of alcohol, the hydroxylation of phenol and benzene, the ammoximation of cyclohexanone, and the like. Wherein, the epoxidation of propylene, the hydroxylation of phenol and the ammoximation of cyclohexanone have been realized in industrial production.
Caprolactam is an important monomer for synthesizing nylon-6, is widely used for producing important downstream products such as engineering plastics, nylon-6 fibers, industrial cord fabrics and the like, and can also be used in the fields of coating, medicines, fine chemicals and the like. At present, more than 95% of caprolactam production adopts a cyclohexanone oxime liquid-phase Beckmann rearrangement reaction process, uses concentrated sulfuric acid (or fuming sulfuric acid) as a catalyst and a solvent, has serious problems of equipment corrosion, environmental pollution and the like, uses liquid ammonia to neutralize waste sulfuric acid after the reaction is finished, and generates a large amount of low-value ammonium sulfate byproducts (1.9 t ammonium sulfate/t caprolactam), so that the technical economy of the route is poor.
Therefore, a cyclohexanone oxime gas phase Beckmann rearrangement process based on a molecular sieve catalyst is highly valued in academia and industry. Compared with the traditional liquid phase method, the process avoids the use of ammonia gas and fuming sulfuric acid from the source, has the atomic utilization rate of 100 percent, and is an environment-friendly caprolactam green production process. The pure silicon molecular sieve with the MFI topological structure shows excellent catalytic performance, and the industrial experiment of cyclohexanone oxime gas-phase Beckmann rearrangement is carried out by adopting the pure silicon molecular sieve in succession by Japanese Sumitomo and China petrochemical industry in the beginning of the century. Because the silicon hydroxyl active center of the pure silicon molecule is unstable, and the silicon hydroxyl active center is easily deactivated by heated and alkaline byproducts, a new active center needs to be introduced to enhance the deactivation resistance of the catalyst.
Baojun Li (RSC adv.,2013,3,20811-20815) adds S-1 and TS-1 molecular sieves as seed crystals during crystallization of the molecular sieves, and synthesizes titanium-silicon molecular sieves with different particle sizes for the cyclohexanone oxime gas phase beckmann rearrangement reaction, the conversion rate of the molecular sieves is reduced to 95% at 6h, the selectivity is stabilized at 86%, and the reaction effect is not ideal. Ferdi Sch uth et al (Microporous and Mesoporous Materials,2009,117,228-232) added 1, 7-dichloro-octamethyl-tetraoxy-silylating agent during the synthesis of titanium silicalite to perform pore-forming to obtain a titanium silicalite molecular sieve with multi-stage pores, which was reacted for 30 hours with a caprolactam yield of 1.6mmol CPL g -1cat h-1.
Therefore, when the titanium-silicon molecular sieve synthesized by the prior art is used for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, the caprolactam selectivity and the catalyst life improving effect are not ideal, and a certain gap is reserved between the titanium-silicon molecular sieve and the industrial production requirement.
Disclosure of Invention
The invention aims to provide a hierarchical porous titanium-silicon molecular sieve containing skeleton titanium and anatase, a preparation method and application thereof, which exert the synergistic effect of the skeleton titanium and the anatase, can effectively improve the cyclohexanone oxime conversion rate and the selectivity of caprolactam in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, and prolong the service life of a catalyst.
To achieve the above object, a first aspect of the present disclosure provides a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase, the titanium silicalite molecular sieve having the following Ti 2p 3/2 XPS characteristics: the titanium silicalite molecular sieve has spectral peaks at the positions of N 1 and N 2; wherein N 1 is 459.2 +/-0.2 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 1 is recorded as A 1; the N 2 is 460.5+/-0.5 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 2 is recorded as A 2; x 1 as defined by the following formula (1) is any number between 0.8 and 2.2 ev: x 1＝N2-N1 formula (1); x 2 as defined by the following formula (2) is any number between 0.1 and 0.8: x 2＝A2/A1 formula (2).
Optionally, the value of X 1 is any value between 1.0 and 2.0 ev; the value of X 2 is any value between 0.2 and 0.5.
Optionally, the molar ratio of silicon atoms to titanium atoms in the titanium-silicon molecular sieve is (6-145): 1, preferably (8 to 130): 1, a step of;
Optionally, the configuration of the titanium silicalite molecular sieve is selected from one or more of MFI topology, MEL topology, BEA topology and SVR topology; preferably an MFI topology.
Optionally, the titanium silicalite molecular sieve has a plurality of cavity structures in the crystal; wherein the size of the single cavity structure is 4-105 nm, preferably 6-80 nm;
Preferably, the volume of all the cavity structures accounts for 25-85% of the total volume of the molecular sieve, and more preferably 30-75%;
Optionally, the shape of the cavity structure is selected from one or more of spherical, cubic, ellipsoidal and irregular cubic.
Optionally, the titanium silicalite molecular sieve comprises molecular sieve particles composed of single crystal grains and/or molecular sieve particles composed of a plurality of crystal grains in an aggregation mode;
Alternatively, the molecular sieve particles have an average particle size of 0.22 to 0.85 μm, preferably 0.26 to 0.60 μm; BET specific surface area of 275 to 575m 2/g, preferably 295 to 560m 2/g; the specific surface area of the micropores is 235-520 m 2/g, preferably 250-495 m 2/g; the total pore volume is 0.25-0.65 cm 3/g, preferably 0.28-0.55 cm 3/g; the volume of the mesoporous is 0.12-0.55 cm 3/g, preferably 0.15-0.45 cm 3/g;
Optionally, a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of the low-temperature nitrogen adsorption of the titanium silicalite molecular sieve; preferably, the hysteresis loop exhibits an initial relative pressure (P/P 0) of 0.30 to 0.55, preferably 0.33 to 0.48.
A second aspect of the present disclosure provides a method of preparing a hierarchical pore titanium silicalite molecular sieve comprising framework titanium and anatase, comprising the steps of:
S1, mixing a first titanium source, a silicon source, a first template agent, water, a silanization reagent and a structural filler to obtain a reaction mixture;
S2, sequentially carrying out first hydrothermal crystallization treatment and first roasting treatment on the reaction mixture to obtain a first molecular sieve intermediate;
S3, mixing the first molecular sieve intermediate, a second template agent and water, and then sequentially carrying out second hydrothermal crystallization treatment and second roasting treatment to obtain a second molecular sieve intermediate;
S4, mixing the second molecular sieve intermediate with a second titanium source, and then performing third roasting treatment.
Optionally, in step S1, the first titanium source: silicon source: a first template agent: water: the molar ratio of the silylation agent is (0.005-4): 1: (0.02-6): (3-90): (0.02-4); preferably (0.008 to 2.5): 1: (0.03-4): (6-40): (0.03-2.5); the weight ratio of SiO 2 to structural filler is (4-75) based on SiO 2: 1, preferably (6 to 55): 1.
Optionally, in step S1, the silicon source is at least one selected from the group consisting of silicone grease, solid silica gel, white carbon black, and silica sol; preferably at least one selected from the group consisting of silicone grease, solid silica gel and white carbon black;
further preferred is a silicone grease having a structure represented by the following formula (A):
wherein R a、Rb、Rc、Rd is each independently selected from alkyl groups having 1 to 6 carbon atoms, said alkyl groups being branched or straight chain alkyl groups; preferably, R a、Rb、Rc、Rd is each independently selected from a straight chain alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 to 4 carbon atoms; further preferably, each R a、Rb、Rc、Rd is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; further preferably, the organic silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate and dimethyl diethyl silicone grease.
Optionally, the first template in step S1 and the second template in step S3 are organic bases; and each independently is preferably at least one selected from the group consisting of quaternary ammonium bases, aliphatic amines, and aliphatic alcohol amines;
further preferably, the first template and the second template are each independently selected from at least one of quaternary ammonium bases having a structure represented by the following formula (B):
r 1、R2、R3 and R 4 are each selected from one or more of an alkyl group having 1 to 4 carbon atoms, preferably a straight chain alkyl group having 1 to 4 carbon atoms and a branched alkyl group having 3 to 4 carbon atoms, further preferably R 1、R2、R3 and R 4 are each selected from one or more of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group and a tert-butyl group;
Further preferably, the first template and the second template are each independently tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide;
Alternatively, the first and second templates may be the same or different; preferably the same.
Optionally, the first titanium source in step S1 and the second titanium source in step S4 are each independently selected from one or more of an organic titanium source and an inorganic titanium source;
The organic titanium source is titanium-containing organic acid ester and is selected from at least one of structures shown in the following formula (C):
Wherein R 5、R6、R7 and R 8 are each selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, preferably straight chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms, further preferably R 5、R6、R7 and R 8 are each selected from the group consisting of straight chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms; alternatively, R 5、R6、R7 and R 8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl; preferably, each is independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl;
the inorganic titanium source is selected from one or more of titanium chloride, titanium nitrate and titanium sulfate;
Preferably, the first titanium source and the second titanium source are each independently selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate;
wherein the first titanium source and the second titanium source may be the same or different; preferably the same.
Optionally, in step S1, the silylating agent is selected from the group consisting of a general formula of R eSi(Rf)(Rg)Rh, wherein R e、Rf、Rg、Rh is each independently halogen, alkyl, alkoxy, aryl, mercapto, or amine, and at least one of R e、Rf、Rg、Rh is alkyl, alkoxy, aryl, mercapto, or amine; the carbon atoms of the alkyl, alkoxy, mercapto and amino groups are each independently C 1～C18;
preferably, the silylating agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyl trimethoxysilane, phenyl trimethoxysilane, 1, 7-dichlorooctanethyltetrasiloxane, hexadecyl trimethoxysilane, octyl triethoxysilane, 3-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane; further preferably one or more selected from the group consisting of N-phenyl-3-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane.
Optionally, in step S1, the structural filler is selected from one or more of an amphiphilic surfactant and a hard template;
Preferably, the amphiphilic surfactant is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, branched sodium dodecyl benzene sulfonate, alpha-olefin sulfonate with 14-16 carbon atoms and sodium secondary alkyl sulfonate;
preferably, the hard template agent is selected from one or more of PEO-PPO-PEO block copolymer, mesoporous carbon, natural fiber, polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyvinyl alcohol;
Further preferably, the structural filler is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, PEO-PPO-PEO block copolymer, mesoporous carbon and natural cellulose.
Optionally, step S1 includes:
a. Mixing a first titanium source, a silicon source, a first template agent and water to obtain a silicon hydrolytic sol;
b. adding a silanization reagent and a structural filler into the hydrolytic sol of silicon, and mixing to obtain a reaction mixture;
optionally, the conditions under which the mixing in step a is performed include: stirring for 6-12 h at 40-90 ℃;
Optionally, the conditions under which mixing is performed in step b include: stirring for 2-4 h at 20-50 ℃;
Preferably, the silicon source is organic silicone grease, and in the step a, after mixing the first titanium source, the silicon source, the first template agent and water, hydrolysis alcohol removal treatment is further included, so that a hydrolysis sol of the silicon is obtained;
Optionally, the conditions of the hydrolysis alcohol expelling treatment include: stirring and hydrolyzing for 6-12 h at 40-90 ℃; preferably at 60-85 deg.C for 8-10 hr.
Alternatively, the conditions of the first hydrothermal crystallization process in step S2 and the second hydrothermal crystallization process in step S3 each independently include: the hydrothermal crystallization time is 5-175 h, and the hydrothermal crystallization temperature is 120-235 ℃; preferably, the hydrothermal crystallization time is 6-85 h, and the hydrothermal crystallization temperature is 135-190 ℃; the pressure is autogenous pressure;
The conditions of the first firing treatment in step S2 and the second firing treatment in step S3 each independently include: the roasting temperature is 280-700 ℃ and the roasting time is 1-16 h; preferably, the roasting temperature is 330-600 ℃ and the roasting time is 2-5 h.
Optionally, in step S3, the second template agent: water: the weight ratio of the first molecular sieve intermediate is (0.03-6): (1-50): 1, a step of; preferably (0.08 to 4.5): (3-35): 1.
Optionally, in step S4, the second titanium source: the molar ratio of the silicon source is (0.004-3.5): 1, preferably (0.006 to 3): 1, a step of;
Optionally, the conditions of the third firing treatment include: the roasting temperature is 270-650 ℃, preferably 290-570 ℃; the roasting time is 0.3-5 h, preferably 0.5-3.5 h.
A third aspect of the present disclosure provides a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase prepared according to the method of the second aspect of the present disclosure.
A fourth aspect of the present disclosure provides a process for preparing caprolactam from cyclohexanone oxime, comprising: contacting cyclohexanone oxime with a catalyst to perform a vapor phase Beckmann rearrangement reaction, wherein the catalyst comprises a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase according to the first and third aspects of the present disclosure.
Through the technical scheme, the present disclosure provides a hierarchical pore titanium-silicon molecular sieve containing skeleton titanium and anatase, and a preparation method and application thereof, wherein the titanium-silicon molecular sieve has abundant skeleton titanium and non-skeleton titanium species, and has a large number of nest hydroxyl active centers; in addition, the titanium-silicon molecular sieve has a multi-stage pore structure comprising macropores, micropores and mesopores, a large intra-crystal cavity structure, a large specific surface area and a large pore volume, and has high caprolactam selectivity and long reaction life in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:
FIG. 1 is a Ti 2p 3/2 XPS spectrum of a hierarchical pore titanium silicalite molecular sieve obtained in example 1;
FIG. 2 is an XRD spectrum of a molecular sieve of hierarchical porous titanium silicon obtained in example 1;
FIG. 3 is a TEM electron microscope image of the hierarchical porous titanium-silicon molecular sieve obtained in example 1;
FIG. 4 is an SEM image of the hierarchical porous titanium silicon molecular sieve obtained in example 1;
FIG. 5 is a graph showing the adsorption and desorption of nitrogen from the molecular sieve of hierarchical pore titanium silicalite obtained in example 1;
FIG. 6 is an infrared hydroxyl spectrum of the molecular sieve of the hierarchical pore titanium silicalite obtained in example 1;
FIG. 7 is an XRD spectrum of a molecular sieve of hierarchical porous titanium silicon obtained in example 10;
FIG. 8 is an XRD spectrum of a molecular sieve of hierarchical porous titanium silicon obtained in example 11.
Detailed Description
The following describes specific embodiments of the present disclosure in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
The first aspect of the present disclosure provides a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase, the titanium silicalite molecular sieve having the following Ti 2p 3/2 XPS characteristics:
Wherein N 1 is 459.2 +/-0.2 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 1 is recorded as A 1; the N 2 is 460.5+/-0.5 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 2 is recorded as A 2;
x 1 as defined by the following formula (1) is any number between 0.8 and 2.2 ev:
x 1＝N2-N1 formula (1);
X 2 as defined by the following formula (2) is any number between 0.1 and 0.8:
X 2＝A2/A1 formula (2).
The present disclosure provides a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase, which has both abundant framework titanium and non-framework titanium species, and has a large number of nested hydroxyl active centers; in addition, the titanium-silicon molecular sieve has a multi-level pore structure comprising macropores, micropores and mesopores, a large intra-crystal cavity structure, a large specific surface area and a large pore volume, and has high caprolactam selectivity and long reaction life in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction.
In the present disclosure, ti 2p 3/2 XPS test can employ test instruments and test methods conventional in the art, and employ conventional processing software and methods to perform peak splitting, integration, and the like on the spectrum peaks.
In a preferred embodiment, the value of X 1 is any number between 1.0 and 2.0 ev; the value of X 2 is any value between 0.2 and 0.5. When the values of X 1 and X 2 of the titanium silicalite molecular sieve are within the range of the present embodiment, the titanium silicalite molecular sieve has higher cyclohexanone oxime conversion and caprolactam selectivity in the cyclohexanone oxime gas phase beckmann rearrangement reaction, and the catalytic stability of the molecular sieve is better under the long-term reaction condition.
In one embodiment, the molar ratio of silicon atoms to titanium atoms in the titanium silicalite molecular sieve is (6-145): 1, preferably (8 to 130): 1. the present disclosure obtains the molar ratio of titanium atoms to silicon atoms in a molecular sieve by an X-ray fluorescence spectroscopy analysis method.
In a preferred embodiment, the titanium silicon molecular sieve has a plurality of cavity structures in the crystal; wherein the size of the individual cavity structures is 4-105 nm, preferably 6-80 nm. The titanium silicon molecular sieve provided by the disclosure is internally provided with a large-size multi-cavity structure, and the cavity structure is internally provided with active centers containing abundant silicon hydroxyl groups, and the multi-cavity structure provides a large number of independent reaction units; in addition, the large-size cavity structure meets the requirement of macromolecular reaction, and reaction products flow out of the catalyst more easily, so that the phenomenon of reduced catalytic activity of the catalyst caused by pore channel blockage is avoided.
In the present disclosure, the cavity structure in the molecular sieve and its size are obtained by transmission electron microscopy. In the present disclosure, the size of the cavity structure refers to the length between two positions on the cavity wall passing through the center of the cavity structure in a transmission electron micrograph of the molecular sieve; for example, a "single cavity structure having a size of 4 to 105nm" means that the length between two positions on the cavity wall passing through the center of the cavity structure in any one cavity structure in the molecular sieve is in the range of 4 to 105 nm.
In a preferred embodiment, the total cavity structure accounts for 30-85% of the total volume of the molecular sieve, and more preferably 35-75%;
Optionally, the shape of the cavity structure is selected from one or more of spherical, cubic, ellipsoidal and irregular cubic.
In one embodiment, the titanium silicalite molecular sieve comprises molecular sieve particles composed of single grains and/or molecular sieve particles composed of a plurality of grains in an aggregation mode;
Alternatively, the molecular sieve particles have an average particle size of 0.22 to 0.85 μm, preferably 0.26 to 0.60 μm; BET specific surface area of 275 to 575m 2/g, preferably 295 to 560m 2/g; the specific surface area of the micropores is 235-520 m 2/g, preferably 250-495 m 2/g; the total pore volume is 0.25-0.65 cm 3/g, preferably 0.28-0.55 cm 3/g; the mesoporous volume is 0.12-0.55 cm 3/g, preferably 0.15-0.45 cm 3/g.
In a preferred embodiment, a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low temperature nitrogen adsorption of the titanium silicalite.
In one embodiment, the hysteresis loop exhibits an initial relative pressure (P/P 0) of 0.30 to 0.55, preferably 0.33 to 0.48.
In a specific embodiment, the configuration of the titanium-silicon molecular sieve with the hierarchical pore structure is one or more selected from an MFI topological structure, an MEL topological structure, a BEA topological structure and an SVR topological structure; further preferred is the MFI topology.
A second aspect of the present disclosure provides a method of preparing a hierarchical pore titanium silicalite molecular sieve comprising framework titanium and anatase, comprising the steps of:
S1, mixing a first titanium source, a silicon source, a first template agent, water, a silanization reagent and a structural filler to obtain a reaction mixture;
S2, sequentially carrying out first hydrothermal crystallization treatment and first roasting treatment on the reaction mixture to obtain a first molecular sieve intermediate;
S3, mixing the first molecular sieve intermediate, a second template agent and water, and then sequentially carrying out second hydrothermal crystallization treatment and second roasting treatment to obtain a second molecular sieve intermediate;
S4, mixing the second molecular sieve intermediate with a second titanium source, and then performing third roasting treatment.
The present disclosure provides a method for preparing a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase, wherein a silylation agent and a structural filler are introduced into a molecular sieve synthesis raw material, which can produce a molecular sieve support layer pore-expanding effect, and prepare a molecular sieve material with an open pore channel; then adding a template agent for dissolution and recrystallization to prepare the hierarchical porous titanium-silicon molecular sieve with rich framework titanium species; and loading anatase species to finally obtain the intra-crystal multi-cavity multi-stage pore titanium-silicon molecular sieve with the synergistic effect of skeleton titanium and non-skeleton titanium.
In the present disclosure, the hydrolytic condensation of the silicon hydroxyl groups of the silylation agent with the silicon hydroxyl groups of the organosilicon source produces stable Si-O-Si bonds, thereby ensuring realization of the expanding effect of the support layer. In addition, the long carbon chain of the silylation agent and the structural filler of the amphiphilic surfactant can form a stable and controllable structural unit (the long carbon chain of the silylation agent and the hydrophobic group of the surfactant are close to each other and interact with van der Waals force), so that fine adjustment effect on expanding the support layer is achieved; or the space filling function is realized by using a hard template agent with controllable size. So that the finally obtained molecular sieve has ordered mesoporous structure with controllable pore diameter (controlled by the chain length of the alkyl chain of the silylating agent). And then introducing a template agent into the molecular sieve with open pores, and obtaining the titanium-silicon molecular sieve with a hierarchical pore structure by utilizing a dissolution and recrystallization mechanism of the template agent. Finally, uniformly dispersing anatase species by utilizing a multi-cavity structure, and roasting to enable skeleton titanium and non-skeleton titanium species to generate a synergistic effect to obtain the intra-crystal multi-cavity hierarchical pore titanium silicon molecular sieve.
In one embodiment, in step S1, the first titanium source: silicon source: a first template agent: water: the molar ratio of the silylation agent is (0.005-4): 1: (0.02-6): (3-90): (0.02-4); the weight ratio of SiO 2 to structural filler is (4-75) based on SiO 2: 1.
In a preferred embodiment, in step S1, the first titanium source: silicon source: a first template agent: water: the molar ratio of the silylation agent is (0.008-2.5): 1: (0.03-4): (6-40): (0.03-2.5); the weight ratio of SiO 2 to structural filler is (6-55) calculated by SiO 2: 1. the titanium silicalite molecular sieve prepared according to the embodiment has higher catalytic activity and catalytic stability.
In one embodiment, in step S1, the silicon source is at least one selected from the group consisting of silicone grease, solid silica gel, white carbon black, and silica sol; preferably at least one selected from the group consisting of silicone grease, solid silica gel and white carbon black;
further preferred is a silicone grease having a structure represented by the following formula (A):
Wherein R a、Rb、Rc、Rd is each independently selected from alkyl groups having 1 to 6 carbon atoms, said alkyl groups being branched or straight chain alkyl groups; preferably, R a、Rb、Rc、Rd is each independently selected from a straight chain alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 to 4 carbon atoms; further preferably, each R a、Rb、Rc、Rd is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.
In a preferred embodiment, the silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate and dimethyl diethyl silicone grease.
In one embodiment, in step S1, the first template is an organic base, preferably at least one selected from the group consisting of quaternary ammonium bases, aliphatic amines, and aliphatic alcohol amines.
In a specific embodiment, the first template is selected from at least one of quaternary ammonium bases having a structure represented by the following formula (B):
R 1、R2、R3 and R 4 are each selected from one or more of an alkyl group having 1 to 4 carbon atoms, preferably a straight chain alkyl group having 1 to 4 carbon atoms and a branched alkyl group having 3 to 4 carbon atoms, and further preferably R 1、R2、R3 and R 4 are each selected from one or more of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group and a tert-butyl group.
In a preferred embodiment, the first template is tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide.
In one embodiment, step S1 includes:
a. Mixing a first titanium source, a silicon source, a first template agent and water to obtain a silicon hydrolytic sol;
b. Adding a silanization reagent and a structural filler into the hydrolytic sol of silicon respectively, and mixing to obtain a reaction mixture;
optionally, the conditions under which the mixing in step a is performed include: stirring for 6-12 h at 40-90 ℃;
optionally, the conditions under which mixing is performed in step b include: stirring at 20-50 deg.c for 2-4 hr.
In a specific embodiment, the silicon source is organic silicone grease, and in the step a, after mixing the first titanium source, the silicon source, the first template agent and water, hydrolysis alcohol removal treatment is further included, so that a hydrolysis sol of the silicon is obtained;
optionally, the conditions of the hydrolysis alcohol expelling treatment include: stirring and hydrolyzing for 6-12 h at 40-90 ℃; preferably at 60-85 deg.C for 8-10 hr. Preferably, the hydrolysis alcohol-expelling treatment is performed so that the mass content of alcohol produced by hydrolysis of the obtained silicone grease in the silica hydrolysis sol is 10ppm or less.
In one embodiment, in step S1, the first titanium source is selected from one or more of an organic titanium source and an inorganic titanium source;
wherein the organic titanium source is organic acid ester containing titanium atom element and is selected from at least one of structures shown in the following formula (C):
Wherein R 5、R6、R7 and R 8 are each selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, preferably straight chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms, further preferably R 5、R6、R7 and R 8 are each selected from the group consisting of straight chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms; alternatively, R 5、R6、R7 and R 8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl; preferably, each is independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl;
The inorganic titanium source is selected from one or more of titanium chloride, titanium nitrate and titanium sulfate.
In a preferred embodiment, the first titanium source is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.
In one embodiment, in step S1, the silylating agent is selected from the group consisting of R eSi(Rf)(Rg)Rh, wherein R e、Rf、Rg、Rh is each independently halogen, alkyl, alkoxy, aryl, mercapto, or amine, and at least one of R e、Rf、Rg、Rh is alkyl, alkoxy, aryl, mercapto, or amine; the carbon atoms of the alkyl, alkoxy, mercapto and amino groups are each independently C 1～C18.
In a preferred embodiment, the silylating agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyl trimethoxysilane, phenyl trimethoxysilane, 1, 7-dichlorooctanethyltetrasiloxane, hexadecyltrimethoxysilane, octyltriethoxysilane, 3-aminopropyl trimethoxysilane, N- β - (aminoethyl) - γ -aminopropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane; further preferably one or more selected from the group consisting of N-phenyl-3-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane.
In one embodiment, in step S1, the structural filler is selected from one or more of an amphiphilic surfactant and a hard template agent;
Preferably, the amphiphilic surfactant is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, branched sodium dodecyl benzene sulfonate, alpha-olefin sulfonate with 14-16 carbon atoms and sodium secondary alkyl sulfonate;
Preferably, the hard template agent is selected from one or more of PEO-PPO-PEO block copolymer, mesoporous carbon, natural fiber, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyvinyl alcohol.
In a preferred embodiment, the structural filler is selected from one or more of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, PEO-PPO-PEO block copolymers, mesoporous carbon and natural cellulose.
Reagents referred to in this disclosure may all be purchased from common sources or prepared by methods known in the art.
In one embodiment, the conditions of the first hydrothermal crystallization treatment in step S2 include: the hydrothermal crystallization time is 5-175 h, and the hydrothermal crystallization temperature is 120-235 ℃; the pressure is autogenous pressure;
The conditions of the first baking process in step S2 include: the roasting temperature is 280-700 ℃ and the roasting time is 1-16 h.
In a preferred embodiment, the conditions of the first hydrothermal crystallization treatment in step S2 include: the hydrothermal crystallization time is 6-85 h, and the hydrothermal crystallization temperature is 135-190 ℃; the pressure is autogenous pressure;
the conditions of the first baking process in step S2 include: the roasting temperature is 330-600 ℃ and the roasting time is 2-5 h. The titanium silicalite molecular sieve prepared according to the embodiment has better catalytic activity.
In a specific embodiment, after the first hydrothermal crystallization treatment, the method further includes a step of subjecting a product of the first hydrothermal crystallization treatment to a first filtration treatment and a first drying treatment, and then subjecting the product to the first baking treatment. Wherein the temperature of the first drying treatment is 50-120 ℃ and the time is 1-12 h.
In one embodiment, in step S3, the second template agent: water: the weight ratio of the first molecular sieve intermediate is (0.03-6): (1-50): 1, a step of; preferably (0.08 to 4.5): (3-35): 1.
In the present disclosure, the selection range of the second template is the same as that of the first template, and thus will not be described herein. And the first and second templates may be the same or different; preferably the same kind of templating agent.
In the present disclosure, the selection range of the second titanium source is the same as that of the first titanium source, and thus will not be described herein. And the first titanium source and the second titanium source may be the same or different; preferably the same titanium source reagent.
In one embodiment, the conditions of the second hydrothermal crystallization treatment in step S3 include: the hydrothermal crystallization time is 5-175 h, and the hydrothermal crystallization temperature is 120-235 ℃; the pressure is autogenous pressure;
The conditions of the second baking process in step S3 include: the roasting temperature is 280-700 ℃ and the roasting time is 1-16 h.
In a preferred embodiment, the conditions of the second hydrothermal crystallization treatment in step S3 include: the hydrothermal crystallization time is 6-85 h, and the hydrothermal crystallization temperature is 135-190 ℃; the pressure is autogenous pressure;
The conditions of the second baking process in step S3 include: the roasting temperature is 330-600 ℃ and the roasting time is 2-5 h. The titanium silicalite molecular sieve prepared according to the embodiment has better catalytic activity.
In a specific embodiment, after the second hydrothermal crystallization treatment, the method further includes a step of performing a second filtration treatment and a second drying treatment on the product of the second hydrothermal crystallization treatment, and then performing the second baking treatment. Wherein the temperature of the second drying treatment is 50-120 ℃ and the time is 1-12 h.
In a more preferred embodiment, in step S4, the second titanium source: the molar ratio of the silicon source is (0.004-3.5): 1, preferably (0.006 to 3): 1. according to the embodiment, the second titanium source is introduced, so that the molecular sieve with better performance can be obtained. In this disclosure, "second titanium source: the molar ratio of the silicon source "the number of moles of the silicon source is calculated on the basis of the molecular weight 60 of pure silicon (SiO 2) according to the mass/60 of the addition of the second molecular sieve intermediate.
In a specific embodiment, in step S4, the conditions of the third baking treatment include: the roasting temperature is 270-650 ℃, preferably 290-570 ℃; the roasting time is 0.3-5 h, preferably 0.5-3.5 h.
A third aspect of the present disclosure provides a hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase prepared according to the method of the second aspect of the present disclosure.
A fourth aspect of the present disclosure provides a process for preparing caprolactam by vapor phase beckmann rearrangement of cyclohexanone oxime, comprising: contacting cyclohexanone oxime with a catalyst to react, wherein the catalyst comprises the hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase according to the first aspect and the third aspect of the present disclosure.
In a specific embodiment, the cyclohexanone oxime gas phase Beckmann rearrangement reaction conditions comprise: the reaction temperature is 350-400 ℃, the reaction pressure is 0-0.2 MPa, and the molar ratio of nitrogen to cyclohexanone oxime is 0.1-30: 1, the cyclohexanone oxime accounts for 5 to 50 weight percent of the total amount of the cyclohexanone oxime and the solvent, and the weight airspeed of the cyclohexanone oxime is 1 to 10h -1.
The present disclosure is described in detail below by way of examples.
Ti 2p 3/2 XPS characterization of the sample was measured on an esclab 250X-ray photoelectron spectrometer with monochromatic alkαx-rays, energy 1486.6eV, power 150W, and charge displacement corrected with carbon-contaminated C1s peak (284.8 eV).
The X-ray diffraction (XRD) phase diagram of the sample is measured on a Siemens D5005 type X-ray diffractometer, the radiation source is K alpha (Cu), and the testing range 2 theta is 0.5-70 degrees.
Transmission electron microscopy TEM of the samples was obtained on a Tecnai G2F20S-TWIN transmission electron microscope from FEI company. The cavity structure and the size thereof are obtained according to TEM electron microscope test. The volume content of the cavity structure in the sample accounting for the total volume of the molecular sieve is obtained by a method for measuring a Transmission Electron Microscope (TEM) photo: the volume of each cavity in the molecular sieve particles is measured according to TEM photo (the intermediate value of the sum of the maximum length and the minimum length passing through the center of the cavity structure is calculated according to the sphere shape to be taken as the sphere shape diameter, the sphere shape radius is further obtained, the sum of the volumes of all the cavities is calculated to be the percentage of the total volume of the molecular sieve particles, and the average value is obtained after calculating the volume fraction of the cavity structure of 50 molecular sieve particles).
SEM images of the samples were obtained on a high resolution cold field emission scanning electron microscope in hitachi S4800. The average particle size of the sample was measured by measuring SEM electron microscopy (average after measuring particle sizes of 50 molecular sieves).
The total specific surface area and total pore volume of the samples were measured on a Micromeritics company ASAP245 static nitrogen adsorber according to ASTM D4222-98 standard method. The determination of the adsorption and desorption isotherms for low temperature nitrogen adsorption of the sample was performed according to ASTM D4222-98 standard method.
The infrared hydroxyl spectrogram (IR-OH) of the sample was measured on a Nicolet 8210 type Fourier infrared spectrometer, with a test range of 400-4000 cm -1.
X-ray analysis of the sample (determination of the molar ratio of Si to Ti in the molecular sieve) was performed by using an instrument of Japanese motor Co 3013 type, tungsten target, excitation voltage of 40kV, excitation current of 250mA.
The reagents used in the examples and comparative examples below were all purchased through conventional sources.
Example 1
(1) 3G of tetrabutyl titanate (0.0088 mol), 104g of tetraethyl silicate (0.5 mol), 65g of tetrapropylammonium hydroxide (TPAOH) with concentration of 25 wt%, 0.08 mol) and 140g of water are sequentially added into a 500mL beaker, placed on a magnetic stirrer with heating and stirring functions to be uniformly mixed, stirred for 5 hours at 60 ℃, and evaporated water is periodically supplemented to obtain colorless transparent titanium silica gel solution;
(2) 9g N-phenyl-3-aminopropyl trimethoxysilane (PHAPTMS, 0.035 mol) and 3gPEO-PPO-PEO triblock copolymer (P123, purchased from enoKai, weight average molecular weight 5800) were added to the mixture of step (1) and stirred for 2 hours;
(3) Transferring the mixture obtained in the step (2) into a stainless steel closed reaction kettle, crystallizing at the constant temperature of 170 ℃ for 24 hours to obtain a sample, filtering and washing the obtained sample, drying at the temperature of 110 ℃ for 3 hours, and roasting at the temperature of 550 ℃ for 3 hours in a muffle furnace to obtain an intermediate product TS-1-T (first molecular sieve intermediate);
(4) Uniformly mixing 10g of TS-1-T sample, 20g of tetrapropylammonium hydroxide (TPAOH) aqueous solution with the concentration of 25 wt% and 40g of water (the weight ratio of the second template agent to the first molecular sieve intermediate is 0.5:5.5:1), transferring the mixture into a stainless steel closed reaction kettle, crystallizing the mixture at the constant temperature of 170 ℃ for 24 hours to obtain a sample, filtering and washing the obtained sample, drying the sample at 110 ℃ for 3 hours, and roasting the sample at 550 ℃ in a muffle furnace for 3 hours to obtain the sample TS-1-T-C (second molecular sieve intermediate).
(5) 0.2G of titanium tetrachloride (0.001 mol) was dissolved in 3g of absolute ethanol, and gradually added dropwise to 4.84g of TS-1-T-C molecular sieve (the mole number of the intermediate of the second molecular sieve was calculated as pure silica, namely, 4.84/60= 0.08067mol; the mole ratio of the second titanium source to the silicon source was 0.0124), and after grinding uniformly, the mixture was calcined in a muffle furnace at 550℃for 3 hours to obtain sample STS-1.
The results of characterization of the structural parameters of sample STS-1 are shown in Table 2;
The Ti 2p 3/2 XPS spectrum of the sample STS-1 is shown in figure 1, and as can be seen from the figure, the sample STS-1 has obvious spectrum peaks of non-framework titanium (N 1 = 459.2 ev) and framework titanium (N 2 =460.8 ev), and the X 1 =1.6 ev is obtained by calculation of the formula (1); the peak area A 1 of non-framework titanium is 2909, the peak area A 2 of framework titanium is 969, and the peak area A 1 of non-framework titanium is calculated by a formula (2) to obtain X 2 =0.33;
The XRD spectrum of the sample STS-1 is shown in figure 2, which shows that the titanium-silicon molecular sieve sample has an MFI topological structure;
the TEM electron microscope photograph of the sample STS-1 is shown in FIG. 3, and the molecular sieve is in a multi-stage pore structure with multiple cavities in the crystal; and the size of the single cavity structure is 15-75 nm;
the SEM electron micrograph of sample STS-1 is shown in FIG. 4, and as can be seen from the figure, the molecular sieve is uniform ellipsoidal particles;
The BET plot of sample STS-1 is shown in FIG. 5, from which it can be seen that there is a distinct hysteresis loop between the nitrogen adsorption and desorption curves in the plot, which hysteresis loop occurs at an initial relative pressure (P/P 0) of 0.45;
The infrared hydroxyl spectrum of the sample STS-1 is shown in FIG. 6, and obvious silicon hydroxyl active center can be seen, wherein the spectrum peak at the position 3740cm -1 is terminal hydroxyl, which represents the side reaction center; the spectrum peak at the -1 position of 3690cm is ortho-hydroxyl; the peak at 3550cm -1 is the nest type silicon hydroxyl group and represents the main reaction center.
Comparative example 1
This comparative example is different from example 1 in the preparation method of reference example 1: without addition of silylating agent (N-phenyl-3-aminopropyl trimethoxysilane) and structural filler (P123), the product was designated D-1; the preparation conditions are shown in Table 1, and the characterization results of the obtained molecular sieves are shown in Table 2.
Comparative example 2
This comparative example was prepared according to the prior art method to produce conventional titanium silicalite molecular sieves (Zeolite, 1992, vol.12, pages 943-950).
22.5G of tetraethyl silicate and 7.0g of tetrapropylammonium hydroxide are mixed, 59.8g of deionized water is added for uniform mixing; then hydrolyzing at 60 ℃ for 1.0h to obtain a hydrolysis solution of the tetraethyl silicate. Then, a solution of 1.1g of tetrabutyl titanate and 5.0g of isopropyl alcohol was slowly dropped into the above solution under the vigorous stirring, and the mixture was stirred at 75℃for 3 hours to give a clear and transparent colloid. And transferring the colloid into a stainless steel closed reaction kettle, crystallizing at a constant temperature of 170 ℃ for 3 days to obtain the conventional TS-1 molecular sieve which is marked as D-2.
Comparative example 3
This comparative example was prepared as in comparative example 2, except that a silylating agent and a structural filler were added, specifically comprising the steps of:
(1) 22.5g of tetraethyl silicate and 7.0g of tetrapropylammonium hydroxide are mixed, 59.8g of deionized water is added for uniform mixing; then hydrolyzing at 60 ℃ for 1.0h to obtain a hydrolysis solution of the tetraethyl silicate. Then, a solution of 1.1g of tetrabutyl titanate and 5.0g of isopropyl alcohol was slowly dropped into the above solution under the vigorous stirring, and the mixture was stirred at 75℃for 3 hours to give a clear and transparent colloid.
(2) To the mixture of step (1) was added 1.9g of N-phenyl-3-aminopropyl trimethoxysilane (PHAPTMS) and 0.65g of PEO-PPO-PEO triblock copolymer (P123, purchased from Inoki, weight average molecular weight 5800) and stirred for 2 hours;
(3) And transferring the colloid into a stainless steel closed reaction kettle, crystallizing at a constant temperature of 170 ℃ for 3 days to obtain the reamed TS-1 molecular sieve, which is marked as D-3. The preparation conditions are shown in Table 1, and the characterization results of the obtained molecular sieves are shown in Table 2.
Examples 2 to 9
A titanium silicalite molecular sieve was prepared as in example 1, except that in example 1: the mixture ratio and the synthesis conditions are changed, and the obtained titanium-silicon molecular sieve samples are marked as STS-2 to STS-9; the preparation conditions are shown in Table 1, and the characterization results of the obtained molecular sieves are shown in Table 2.
Example 10
The titanium silicalite molecular sieve of MEL structure was prepared by the method of example 1, differing from example 1 in that: changing a template agent, wherein the template agent is tetrabutylammonium hydroxide (TBAOH), and the obtained titanium silicalite molecular sieve sample is marked as STS-10; the preparation conditions are shown in Table 1, and the characterization results of the obtained molecular sieves are shown in Table 2. XRD of STS-10 is shown in FIG. 7, indicating that STS-10 is of MEL structure.
Example 11
A hierarchical pore beta molecular sieve was prepared according to the method of example 1, differing from example 1 in that: changing the proportion and the template agent, wherein the template agent is tetraethylammonium hydroxide (TEAOH), preparing BEA topological structure, and obtaining a titanium-silicon molecular sieve sample which is marked as STS-11; the preparation conditions are shown in Table 1, and the characterization results of the obtained molecular sieves are shown in Table 2. XRD of STS-11 is shown in FIG. 8, indicating that STS-11 has the BEA structure.
Example 12
A titanium silicalite molecular sieve was prepared as in example 1, except that in example 1:
The temperature of the first hydrothermal crystallization treatment is 120 ℃ and the time is 96 hours; the temperature of the first roasting treatment is 280 ℃ and the time is 8 hours;
the temperature of the second hydrothermal crystallization treatment is 120 ℃ and the time is 96 hours; the temperature of the second roasting treatment is 280 ℃ and the time is 8 hours;
The temperature of the third roasting treatment is 270 ℃ and the time is 0.3h;
the obtained titanium-silicon molecular sieve sample is marked as STS-12; the characterization results of the resulting molecular sieves STS-12 are shown in Table 2.
TABLE 1
In table 1, TPAOH is tetrapropylammonium hydroxide, TBAOH is tetrabutylammonium hydroxide, TEAOH is tetraethylammonium hydroxide; PHAPTMS is N-phenyl-3-aminopropyl trimethoxysilane, APTMS is 3-aminopropyl triethoxysilane, GCPMS is 3-glycidoxypropyl (dimethoxy) methylsilane, TOMS is methyltrimethoxysilane; p123 is PEO-PPO-PEO triblock copolymer and CTAB is cetyl trimethylammonium bromide. Reagents employed in the present disclosure may be obtained through conventional purchase channels.
The water in the "water/silicon source" calculation in table 1 also includes water from the first aqueous templating agent solution; "Water: the water in the first molecular sieve intermediate calculation also includes water from the second aqueous template solution.
TABLE 2
From the data in table 2 above, it can be seen that: compared with the molecular sieves D-1 to D-3 prepared in comparative examples 1 to 3, the molecular sieves STS-1 to STS-12 prepared by the method provided by the disclosure have larger total volume percentage of the total cavity structure of the molecular sieves.
Test case
The molecular sieves prepared in the above examples and comparative examples were evaluated, the prepared molecular sieves were tabletted and then crushed, and particles of 20 to 60 mesh were taken as a catalyst to perform a cyclohexanone oxime vapor phase Beckmann rearrangement reaction, and the catalytic performance of the obtained molecular sieves was evaluated under the following conditions:
The evaluation device was a constant pressure continuous flow fixed bed reactor, the inside diameter of the reactor was 5mm, and the loading amount of the catalyst was 2g. After loading the catalyst, the catalyst was pretreated for 3 hours under nitrogen atmosphere at 350 ℃. The concentration of the raw material cyclohexanone oxime was 35% by weight, the solvent was methanol, and the reaction conditions included: the cyclohexanone oxime weight space velocity (WHSV, flow rate of cyclohexanone oxime in the feed/weight of catalyst in the reactor) was 2h -1, the reaction temperature was 380 ℃, the nitrogen flow rate was 4 liter/h, and the reaction times were 24h and 200h, respectively.
The cooled reaction product was collected, and the concentration of each substance was quantitatively analyzed by gas chromatography using a model 6890 gas chromatograph manufactured by Agilent corporation, and the analytical column was an HP-5 column. The test conditions included: the temperature of the vaporization chamber is 250 ℃, the temperature of the detection chamber is 230 ℃, the column temperature is programmed, the temperature is kept constant for 8 minutes at 110 ℃, the temperature is increased to 230 ℃ at 15 ℃/min, and the temperature is kept for 14 minutes; the results are shown in Table 3 below.
Wherein the conversion (mol%) of cyclohexanone oxime = (molar content of cyclohexanone oxime in the feed-molar content of cyclohexanone oxime in the product)/molar content of cyclohexanone oxime in the feed x 100%;
caprolactam selectivity (mol%) =mole% caprolactam in product/(mole% cyclohexanone oxime in 100-product) ×100%;
Cyclohexanone oxime conversion reduction (%) = (24 h cyclohexanone conversion-200 h cyclohexanone conversion)/24 h cyclohexanone conversion x 100%;
caprolactam selectivity reduction (%) = (24 h caprolactam selectivity-200 h caprolactam selectivity)/24 h caprolactam selectivity x 100%.
TABLE 3 Table 3
From the data in table 3 above, it can be seen that:
Compared with the molecular sieves D-1-D-3 prepared in comparative examples 1-3, the molecular sieves STS-1-STS-12 prepared by the method disclosed in the disclosure have the Ti 2p 3/2 XPS characteristics that X 1 is in the range of 0.8-2.2 ev, X 2 is in the range of 0.1-0.8, the molecular sieves STS-1-STS-12 have higher catalytic activity in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, the cyclohexanone oxime conversion rate and caprolactam selectivity are higher, and the catalytic stability under the long-time reaction condition (200 h) is higher.
Further, X 1 of the molecular sieves STS-1 to STS-8 and STS-10 to STS-11 prepared in the examples is in the range of 1.0 to 2.0ev, X 2 is in the range of 0.2 to 0.5, and compared with the molecular sieves STS-9 and STS-12, the cyclohexanone oxime conversion rate and caprolactam selectivity in the reaction of the molecular sieves STS-1 to STS-8 and STS-10 to STS-11 are higher, and the catalytic stability under the long-time reaction condition (200 h) is higher.
Comparing example 1 with example 9, example 1 prepared molecular sieve according to the raw material addition ratio in the preferred embodiment, the obtained molecular sieve STS-1 has higher cyclohexanone oxime conversion rate and caprolactam selectivity in the catalytic reaction, and has higher catalytic stability under the long-term reaction condition (200 h).
Comparing example 1 with example 12, example 1 performs molecular sieve preparation according to the reaction conditions in the preferred embodiment, and the resulting molecular sieve STS-1 has higher cyclohexanone oxime conversion and caprolactam selectivity in the catalytic reaction and higher catalytic stability under long-term reaction conditions (200 h).
The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (18)

1. A hierarchical pore titanium silicalite molecular sieve comprising framework titanium and anatase, wherein the titanium silicalite molecular sieve has the following Ti 2p 3/2 XPS characteristics:
The titanium silicalite molecular sieve has spectral peaks at the positions of N 1 and N 2;
Wherein N 1 is 459.2 +/-0.2 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 1 is recorded as A 1; the N 2 is 460.5+/-0.5 ev, and the spectrum peak area of the titanium silicalite molecular sieve at the position of the binding energy N 2 is recorded as A 2;
x 1 as defined by the following formula (1) is any number between 0.8 and 2.2 ev:
x 1＝N2-N1 formula (1);
X 2 as defined by the following formula (2) is any number between 0.1 and 0.8:
X 2＝A2/A1 formula (2).
2. The titanium silicalite molecular sieve according to claim 1, wherein said X 1 has any value between 1.0 and 2.0 ev; the value of X 2 is any value between 0.2 and 0.5.
3. The titanium silicalite molecular sieve according to claim 1, wherein the molar ratio of silicon atoms to titanium atoms in the titanium silicalite molecular sieve is (6-145): 1, preferably (8 to 130): 1, a step of;
Optionally, the configuration of the titanium silicalite molecular sieve is selected from one or more of MFI topology, MEL topology, BEA topology and SVR topology; preferably an MFI topology.
4. The titanium silicalite of claim 1, wherein the titanium silicalite has a plurality of cavity structures within the crystals; wherein the size of the single cavity structure is 4-105 nm, preferably 6-80 nm;
Preferably, the volume of all the cavity structures accounts for 25-85% of the total volume of the molecular sieve, and more preferably 30-75%;
Optionally, the shape of the cavity structure is selected from one or more of spherical, cubic, ellipsoidal and irregular cubic.
5. The titanium silicalite molecular sieve according to claim 1, wherein the titanium silicalite molecular sieve comprises molecular sieve particles of single crystallite composition, and/or molecular sieve particles of multiple crystallite aggregates;
Alternatively, the molecular sieve particles have an average particle size of 0.22 to 0.85 μm, preferably 0.25 to 0.60 μm; BET specific surface area of 275 to 575m 2/g, preferably 295 to 560m 2/g; the specific surface area of the micropores is 235-520 m 2/g, preferably 250-495 m 2/g; the total pore volume is 0.25-0.65 cm 3/g, preferably 0.28-0.55 cm 3/g; the volume of the mesoporous is 0.12-0.55 cm 3/g, preferably 0.15-0.45 cm 3/g;
Optionally, a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of the low-temperature nitrogen adsorption of the titanium silicalite molecular sieve; preferably, the hysteresis loop exhibits an initial relative pressure (P/P 0) of 0.30 to 0.55, preferably 0.33 to 0.48.
6. A method for preparing a hierarchical pore titanium silicalite molecular sieve comprising framework titanium and anatase comprising the steps of:
S1, mixing a first titanium source, a silicon source, a first template agent, water, a silanization reagent and a structural filler to obtain a reaction mixture;
S2, sequentially carrying out first hydrothermal crystallization treatment and first roasting treatment on the reaction mixture to obtain a first molecular sieve intermediate;
S3, mixing the first molecular sieve intermediate, a second template agent and water, and then sequentially carrying out second hydrothermal crystallization treatment and second roasting treatment to obtain a second molecular sieve intermediate;
S4, mixing the second molecular sieve intermediate with a second titanium source, and then performing third roasting treatment.
7. The method of claim 6, wherein in step S1, the first titanium source: silicon source: a first template agent: water: the molar ratio of the silylation agent is (0.005-4): 1: (0.02-6): (3-90): (0.02-4); preferably (0.008 to 2.5): 1: (0.03-4): (6-40): (0.03-2.5); the weight ratio of SiO 2 to structural filler is (4-75) based on SiO 2: 1, preferably (6 to 55): 1.
8. The method of claim 6, wherein in step S1, the silicon source is selected from at least one of silicone grease, solid silica gel, white carbon, and silica sol; preferably at least one selected from the group consisting of silicone grease, solid silica gel and white carbon black;
further preferred is a silicone grease having a structure represented by the following formula (A):
wherein R a、Rb、Rc、Rd is each independently selected from alkyl groups having 1 to 6 carbon atoms, said alkyl groups being branched or straight chain alkyl groups; preferably, R a、Rb、Rc、Rd is each independently selected from a straight chain alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 to 4 carbon atoms; further preferably, each R a、Rb、Rc、Rd is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; further preferably, the organic silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate and dimethyl diethyl silicone grease.
9. The method of claim 6, wherein the first templating agent in step S1 and the second templating agent in step S3 are organic bases; and each independently is preferably at least one selected from the group consisting of quaternary ammonium bases, aliphatic amines, and aliphatic alcohol amines;
further preferably, the first template and the second template are each independently selected from at least one of quaternary ammonium bases having a structure represented by the following formula (B):
r 1、R2、R3 and R 4 are each selected from one or more of an alkyl group having 1 to 4 carbon atoms, preferably a straight chain alkyl group having 1 to 4 carbon atoms and a branched alkyl group having 3 to 4 carbon atoms, further preferably R 1、R2、R3 and R 4 are each selected from one or more of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group and a tert-butyl group;
Further preferably, the first template and the second template are each independently tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide;
Alternatively, the first and second templates may be the same or different; preferably the same.
10. The method of claim 6, wherein the first titanium source in step S1 and the second titanium source in step S4 are each independently selected from one or more of an organic titanium source and an inorganic titanium source;
The organic titanium source is titanium-containing organic acid ester and is selected from at least one of structures shown in the following formula (C):
Wherein R 5、R6、R7 and R 8 are each selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, preferably straight chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms, further preferably R 5、R6、R7 and R 8 are each selected from the group consisting of straight chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms; alternatively, R 5、R6、R7 and R 8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl; preferably, each is independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl;
the inorganic titanium source is selected from one or more of titanium chloride, titanium nitrate and titanium sulfate;
Preferably, the first titanium source and the second titanium source are each independently selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate;
wherein the first titanium source and the second titanium source may be the same or different; preferably the same.
11. The method of claim 6, wherein in step S1, the silylating agent is selected from the group consisting of R eSi(Rf)(Rg)Rh, wherein R e、Rf、Rg、Rh is each independently halogen, alkyl, alkoxy, aryl, mercapto, or amine, and at least one of R e、Rf、Rg、Rh is alkyl, alkoxy, aryl, mercapto, or amine; the carbon atoms of the alkyl, alkoxy, mercapto and amino groups are each independently C 1～C18;
preferably, the silylating agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyl trimethoxysilane, phenyl trimethoxysilane, 1, 7-dichlorooctanethyltetrasiloxane, hexadecyl trimethoxysilane, octyl triethoxysilane, 3-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane; further preferably one or more selected from the group consisting of N-phenyl-3-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane.
12. The method according to claim 6, wherein in step S1, the structural filler is selected from one or more of an amphiphilic surfactant and a hard template;
Preferably, the amphiphilic surfactant is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, branched sodium dodecyl benzene sulfonate, alpha-olefin sulfonate with 14-16 carbon atoms and sodium secondary alkyl sulfonate;
preferably, the hard template agent is selected from one or more of PEO-PPO-PEO block copolymer, mesoporous carbon, natural fiber, polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyvinyl alcohol;
Further preferably, the structural filler is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, PEO-PPO-PEO block copolymer, mesoporous carbon and natural cellulose.
13. The method according to claim 6, wherein step S1 comprises:
a. Mixing a first titanium source, a silicon source, a first template agent and water to obtain a silicon hydrolytic sol;
b. adding a silanization reagent and a structural filler into the hydrolytic sol of silicon, and mixing to obtain a reaction mixture;
optionally, the conditions under which the mixing in step a is performed include: stirring for 6-12 h at 40-90 ℃;
Optionally, the conditions under which mixing is performed in step b include: stirring for 2-4 h at 20-50 ℃;
Preferably, the silicon source is organic silicone grease, and in the step a, after mixing the first titanium source, the silicon source, the first template agent and water, hydrolysis alcohol removal treatment is further included, so that a hydrolysis sol of the silicon is obtained;
Optionally, the conditions of the hydrolysis alcohol expelling treatment include: stirring and hydrolyzing for 6-12 h at 40-90 ℃; preferably at 60-85 deg.C for 8-10 hr.
14. The method according to claim 6, wherein the conditions of the first hydrothermal crystallization process in step S2 and the second hydrothermal crystallization process in step S3 each independently include: the hydrothermal crystallization time is 5-175 h, and the hydrothermal crystallization temperature is 120-235 ℃; preferably, the hydrothermal crystallization time is 6-85 h, and the hydrothermal crystallization temperature is 135-190 ℃; the pressure is autogenous pressure;
The conditions of the first firing treatment in step S2 and the second firing treatment in step S3 each independently include: the roasting temperature is 280-700 ℃ and the roasting time is 1-16 h; preferably, the roasting temperature is 330-600 ℃ and the roasting time is 2-5 h.
15. The method of claim 6, wherein in step S3, the second templating agent: water: the weight ratio of the first molecular sieve intermediate is (0.03-6): (1-50): 1, a step of; preferably (0.08 to 4.5): (3-35): 1.
16. The method of claim 6, wherein in step S4, the second titanium source: the molar ratio of the silicon source is (0.004-3.5): 1, preferably (0.006 to 3): 1, a step of;
Optionally, the conditions of the third firing treatment include: the roasting temperature is 270-650 ℃, preferably 290-570 ℃; the roasting time is 0.3-5 h, preferably 0.5-3.5 h.
17. A hierarchical pore titanium silicalite molecular sieve comprising framework titanium and anatase prepared according to the method of any one of claims 6 to 16.
18. A process for preparing caprolactam by a vapor phase beckmann rearrangement of cyclohexanone oxime comprising: contacting cyclohexanone oxime with a catalyst to react, wherein the catalyst comprises the hierarchical pore titanium silicalite molecular sieve containing framework titanium and anatase according to any one of claims 1 to 5 and 17.
CN202211330131.7A 2022-10-27 2022-10-27 Hierarchical porous titanium-silicon molecular sieve containing framework titanium and anatase, and preparation method and application thereof Pending CN118005032A (en)

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