CN112844454A - ZSM-5 catalyst and preparation method and application thereof - Google Patents

ZSM-5 catalyst and preparation method and application thereof Download PDF

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CN112844454A
CN112844454A CN201911102456.8A CN201911102456A CN112844454A CN 112844454 A CN112844454 A CN 112844454A CN 201911102456 A CN201911102456 A CN 201911102456A CN 112844454 A CN112844454 A CN 112844454A
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catalyst
zsm
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李猛
杨文书
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Wison Engineering Ltd
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Wison Engineering Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • 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
    • B01J29/005—Mixtures of molecular sieves comprising at least one molecular sieve which is not an aluminosilicate zeolite, e.g. from groups B01J29/03 - B01J29/049 or B01J29/82 - B01J29/89
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
    • C07C2/862—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms
    • C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
    • 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
    • B01J2229/30—After treatment, characterised by the means used
    • B01J2229/32—Reaction with silicon compounds, e.g. TEOS, siliconfluoride
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2529/00—Catalysts comprising molecular sieves
    • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
    • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • 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
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention provides a ZSM-5 catalyst and a preparation method and application thereof, wherein the preparation method comprises the following steps: 1) mixing a ZSM-5 molecular sieve with a binder silicon dioxide, forming, drying and roasting; 2) carrying out hydrothermal crystallization on the catalyst obtained in the step 1) in an aqueous solution containing a template agent quaternary ammonium salt and an additive, washing, drying and roasting; 3) and (3) carrying out chemical vapor deposition on the catalyst obtained in the step 2) and a cyclohexane solution containing silicon ester, and roasting to obtain the ZSM-5 catalyst. The preparation method disclosed by the invention is simple in process, the prepared ZSM-5 catalyst is good in crystallization, the problems of reduction of the effective specific surface area of the catalyst and insufficient acid modification of the outer surface caused by introduction of the binder are solved, the preparation method has obvious advantages in shape-selective catalytic reaction, and particularly has great industrial application potential in the field of preparation of p-xylene through toluene and methanol alkylation.

Description

ZSM-5 catalyst and preparation method and application thereof
Technical Field
The invention relates to the field of preparation of molecular sieves, in particular to a ZSM-5 catalyst and a preparation method and application thereof.
Background
The ZSM-5 molecular sieve has two-dimensional ten-membered ring channels, one is a straight ten-membered ring channel, and the other is a ten-membered ring channel with a Zigzag shape: the channel structure is 0.51 nm × 0.55 nm ([100] direction) and 0.53 nm × 0.56 nm ([010] direction). The method has wide application in shape-selective reactions such as preparation of p-xylene by toluene disproportionation, preparation of p-xylene by toluene alkylation with methanol and the like. Due to the size of the pore canal, the kinetic diameter of paraxylene molecules in dimethylbenzene is smaller, and the paraxylene molecules can be more easily diffused out of the pore canal. The diffused p-xylene is isomerized into m-xylene and o-xylene under the action of external surface acidity, so that the selectivity of the target product p-xylene is reduced. Therefore, elimination of the external surface acidity becomes a critical step in the preparation of shape selective catalytic reaction catalysts.
The actual industrial catalyst needs a binder to bind the molecular sieve together and process the molecular sieve into a large-particle catalyst so as to be applied to the fixed bed reactor. And mesoporous channels with the pore diameter larger than that of micropores of the molecular sieve are formed between the molecular sieve crystal particles and the binder, so that the function of conveying reactants and products is played, and the performance of the catalyst is greatly influenced. However, the adhesive is introduced to cover part of the surface of the molecular sieve with the adhesive, part of the pore channels are blocked, the effective specific surface area is reduced, the diffusion of reactants and products is influenced, and the influence cannot be removed by subsequent organic silicon modification, so that the activity of the catalyst is reduced.
The acidic modification of the outer surface of the molecular sieve is commonly carried out by silicon ester deposition modification, metal oxide modification, acid treatment and the like. However, the shaped catalyst introduces more ineffective specific surface area, and the single modification method is not enough to effectively modify the acidity of the outer surface of the catalyst.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a ZSM-5 catalyst, a method for preparing the same and use thereof, the method comprising the steps of: 1) mixing a ZSM-5 molecular sieve with a binder silicon dioxide, forming, drying and roasting; 2) carrying out hydrothermal crystallization on the catalyst obtained in the step 1) in an aqueous solution containing a template agent quaternary ammonium salt and an additive, washing, drying and roasting; 3) and (3) carrying out chemical vapor deposition on the catalyst obtained in the step 2) and a cyclohexane solution containing silicon ester, and roasting to obtain the ZSM-5 catalyst. The preparation method disclosed by the invention is simple in process, the prepared ZSM-5 catalyst is good in crystallization, pore channel blockage caused by excessive silicon ester loading is not needed, the binder is converted into the molecular sieve, the effective specific surface area is improved, the problems that the effective specific surface area of the catalyst is reduced and the outer surface is insufficiently modified by acidity caused by the introduction of the binder are solved, the preparation method has obvious advantages in shape-selective catalytic reaction, and particularly has great industrial application potential in the fields of toluene shape-selective disproportionation reaction and toluene methanol alkylation for preparing p-xylene.
To achieve the above objects and other related objects, the present invention is achieved by the following technical solutions.
The invention provides a preparation method of a ZSM-5 catalyst, which comprises the following steps:
1) mixing a ZSM-5 molecular sieve with a binder silicon dioxide, forming, drying and roasting;
2) carrying out hydrothermal crystallization on the catalyst obtained in the step 1) in an aqueous solution containing a template agent quaternary ammonium salt and an additive, washing, drying and roasting;
3) and (3) carrying out chemical vapor deposition on the catalyst obtained in the step 2) and a cyclohexane solution containing silicon ester, and roasting to obtain the ZSM-5 catalyst.
Preferably, step 1) further comprises at least one of the following technical features:
1) silica-alumina molar ratio SiO of ZSM-5 molecular sieve2/Al2O325 to 2000, such as 25 to 100, 100 to 300, 300 to 450, or 450 to 2000;
2) the mass fraction of the silicon dioxide is 5-50%, such as 5-8%, 8-10%, 10-20% or 20-50%;
3) the adhesive silicon dioxide is selected from one or more of silica sol and white carbon black;
4) the calcination temperature is 500-550 deg.C, such as 500-525 deg.C or 525-550 deg.C.
More preferably, in feature 1), the ZSM-5 molecular sieve has a silica-alumina molar ratio of SiO2/Al2O3Is 100 to 450, such as 100 to 300 or 300 to 450.
Preferably, step 2) further comprises at least one of the following technical features:
1) the template agent quaternary ammonium salt is selected from one or more of tetrapropyl ammonium hydroxide and tetrapropyl ammonium bromide;
2) the additive is selected from one or more of ammonium fluoride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride;
3) the mass fraction of the template agent quaternary ammonium salt in the catalyst obtained in the step 1) is 1-50%, such as 1-20% or 20-50%;
4) the additive accounts for 0.5-20% of the mass fraction of the catalyst obtained in the step 1), such as 0.5-10% or 10-20%;
5) the mass fraction of the water in the catalyst obtained in the step 1) is 100-1000%, such as 100-460% or 460-1000%;
6) the hydrothermal crystallization temperature is 160-180 ℃, such as 160-170 ℃ or 170-180 ℃;
7) the hydrothermal crystallization time is 3-48 hours, such as 3-24 hours or 24-48 hours;
8) the calcination temperature is 500-550 deg.C, such as 500-525 deg.C or 525-550 deg.C.
Preferably, in the step 3), the silicon ester is selected from one or more of ethyl orthosilicate and methyl orthosilicate.
Preferably, in step 3), the concentration of the silicone ester is 0.1 to 2.0 mol/L, such as 0.1 to 1.0 mol/L or 1.0 to 2.0 mol/L.
Preferably, in the step 3), the volume of the cyclohexane solution containing the silicon ester added to every 1 g of the catalyst obtained in the step 2) is 0.6-1.2 ml, for example, the volume of the cyclohexane solution containing the silicon ester added to every 1 g of the catalyst obtained in the step 2) is 0.6-0.8 or 0.8-1.2 ml.
Preferably, step 3) further comprises at least one of the following technical features:
1) the temperature of the chemical vapor deposition reaction is 160-180 ℃, such as 160-170 ℃ or 170-180 ℃;
2) the reaction time of chemical vapor deposition is 3-48 hours, such as 3-24 hours or 24-48 hours;
3) the calcination temperature is 500-550 deg.C, such as 500-525 deg.C or 525-550 deg.C.
The invention provides a ZSM-5 catalyst which is prepared by the preparation method.
In a third aspect, the invention provides the use of the above ZSM-5 catalyst for the alkylation of toluene with methanol to produce paraxylene or toluene disproportionation.
According to the invention, through the processes of binder conversion crystallization, silicon ester chemical reaction deposition and the like, the strength of the formed catalyst can be better maintained by adding the additive conversion crystallization, the silicon dioxide binder can be more effectively converted and crystallized along the epitaxy of the molecular sieve, meanwhile, the utilization efficiency of the silicon ester is improved through high-temperature chemical vapor deposition, and the problems of insufficient acid modification on the outer surface of the formed catalyst and reduction of the effective specific surface area caused by introduction of the binder in the prior art are solved. Aiming at the problems of reduced effective specific surface area and insufficient external surface acid modification caused by introduction of a formed catalyst binder, the invention forms silica and a ZSM-5 molecular sieve, performs binder crystal transformation in a quaternary ammonium salt aqueous solution, and carries silicon ester modification by a chemical deposition method to prepare the binder-free catalyst for removing the external surface acidity. The catalyst obtained by the method does not need to be loaded with excessive silicon ester to cause pore channel blockage, and simultaneously, the binder is converted into the molecular sieve, so that the effective specific surface area is improved. Has obvious advantages in shape-selective catalytic reaction, and particularly has great industrial application potential in the fields of toluene shape-selective disproportionation and toluene methanol alkylation for preparing p-xylene. The ZSM-5 catalyst prepared by the preparation method has good and controllable modification effect, and particularly for the nano ZSM-5 catalyst, the problems of pore channel blockage and great reduction of activity caused by multiple silicon ester modification by the traditional modification method are solved.
Drawings
FIG. 1 is a scanning electron micrograph of a sample A formed by the nano ZSM-5 molecular sieve and the silica sol as the binder in example 1.
FIG. 2 is a scanning electron micrograph of sample B after crystallization of a quaternary ammonium salt in example 1.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
Example 1
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; adding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium fluoride and 40 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ to perform chemical vapor deposition, taking out and drying the sample B, and roasting the dried sample B for 4 hours at 550 ℃ to obtain the binder-free ZSM-5 catalyst A1 with the acidity of the outer surface removed.
FIG. 1 is a scanning electron micrograph of a sample A formed by the nano ZSM-5 molecular sieve and the silica sol as the binder in example 1. FIG. 2 is a scanning electron micrograph of sample B after crystallization of a quaternary ammonium salt in example 1. It can be seen that the amorphous binder is converted to a well crystallized molecular sieve.
Example 2
Weighing SiO in molar ratio2/Al2O3100 g of 100-size 300 nanometer ZSM-5 molecular sieve and 25 g of white carbon black are uniformly mixed, extruded and molded, and calcined at the high temperature of 550 ℃ for 4 hours after being dried to obtain a sample A; adding 5 g of tetrapropylammonium bromide, 0.05 g of ammonium nitrate and 10 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into a solution, carrying out hydrothermal crystallization at 160 ℃ for 48 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 6 ml of 0.1 mol/L cyclohexane solution of tetramethyl orthosilicate, reacting for 48 hours at 160 ℃, performing chemical vapor deposition, taking out, drying, and roasting for 4 hours at 550 ℃ to obtain the binder-free ZSM-5 catalyst A2 with the acid outer surface removed.
Example 3
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of a 450-size 300 nanometer ZSM-5 molecular sieve and 5.3 g of white carbon black, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; adding 0.1 g of tetrapropylammonium bromide, 2 g of ammonium carbonate and 100 g of water into a reaction kettle, uniformly mixing, putting 10 g of sample A into the solution, carrying out hydrothermal crystallization at 180 ℃ for 3 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 3 ml of 2.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 3 hours at 180 ℃, performing chemical vapor deposition, taking out, drying, and roasting at 550 ℃ for 4 hours to obtain the binder-free ZSM-5 catalyst A3 with the acid outer surface removed.
Example 4
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; adding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium bicarbonate and 40 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; 5 g of sample B are weighed into a reaction vessel, 4 ml of 1.0 mol/l tetraethyl orthosilicate are addedAnd (3) reacting the cyclohexane solution at 170 ℃ for 24 hours to perform chemical vapor deposition, taking out and drying the solution, and roasting the dried solution at 550 ℃ for 4 hours to obtain the binder-free ZSM-5 catalyst A4 with the outer surface acidity removed.
Example 5
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; adding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium sulfate and 40 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ to perform chemical vapor deposition, taking out and drying the sample B, and roasting the dried sample B for 4 hours at 550 ℃ to obtain the binder-free ZSM-5 catalyst A5 with the acidity of the outer surface removed.
Example 6
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; adding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium chloride and 40 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ to perform chemical vapor deposition, taking out and drying the sample B, and roasting the dried sample B for 4 hours at 550 ℃ to obtain the binder-free ZSM-5 catalyst A6 with the acidity of the outer surface removed.
Example 7
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 25-sized 300-nanometer ZSM-5 molecular sieve and 100 g of white carbon black, extruding and molding, drying, and roasting at the high temperature of 500 ℃ for 4 hours to obtain a sample A; 8 g of 25% tetra was added to the reactorUniformly mixing a propyl ammonium hydroxide aqueous solution, 1 g of ammonium fluoride and 40 g of water, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing and drying, and roasting at 500 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ to perform chemical vapor deposition, taking out and drying the sample B, and roasting the dried sample B for 4 hours at 500 ℃ to obtain the binder-free ZSM-5 catalyst A7 with the acidity of the outer surface removed.
Example 8
Weighing SiO in molar ratio2/Al2O3100 g of a 2000-size 300-nanometer ZSM-5 molecular sieve and 11 g of white carbon black are uniformly mixed, extruded and molded, and calcined at the high temperature of 525 ℃ for 4 hours after being dried to obtain a sample A; adding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium fluoride and 40 g of water into a reaction kettle, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 525 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, placing the sample B into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ to perform chemical vapor deposition, taking out and drying the sample B, and roasting the dried sample B for 4 hours at 525 ℃ to obtain the binder-free ZSM-5 catalyst A8 with the acidity of the outer surface removed.
Comparative example 9
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; weighing 5 g of the sample A, placing the sample A into a reaction kettle, adding 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, reacting for 24 hours at 170 ℃ for chemical vapor deposition, taking out and drying, and roasting at 550 ℃ for 4 hours to obtain the ZSM-5 catalyst A9.
Comparative example 10
Weighing SiO in molar ratio2/Al2O3Uniformly mixing 100 g of 300-sized 300-nanometer ZSM-5 molecular sieve and 37 g of silica sol with the mass fraction of 30%, extruding and molding, drying, and roasting at the high temperature of 550 ℃ for 4 hours to obtain a sample A; reaction kettleAdding 8 g of 25% tetrapropyl ammonium hydroxide aqueous solution, 1 g of ammonium fluoride and 40 g of water, uniformly mixing, putting 10 g of the sample A into the solution, carrying out hydrothermal crystallization at 170 ℃ for 24 hours, washing, drying, and roasting at 550 ℃ for 4 hours to obtain a sample B; weighing 5 g of sample B, soaking the sample B in 4 ml of 1.0 mol/L cyclohexane solution of tetraethyl orthosilicate, drying the sample B at 120 ℃ for 30 minutes, cooling the dried sample B to room temperature, taking the dried sample out, and roasting the cooled sample B at 550 ℃ for 4 hours to obtain the ZSM-5 catalyst A10.
Example 11
The catalysts prepared in examples and comparative examples were evaluated for their reaction performance by alkylating toluene with methanol as a probe. And (3) crushing the ZSM-5 catalyst into 20-40 meshes by adopting an evaluation mode of a fixed bed. The specific evaluation conditions were: 4.0g of catalyst is filled, the reaction temperature is 460.0 ℃, and the weight hourly space velocity of the raw material of the benzene alcohol is 4.0h-1The molar ratio of benzene alcohol was 2.0, the molar ratio of water/benzene alcohol was 3.0, the molar ratio of hydrogen/benzene alcohol was 2.0, the pressure was atmospheric, and the reaction product was sampled and analyzed after 4 hours of reaction, and the results are shown in Table 1.
TABLE 1 toluene methanol alkyl reaction Performance of the example and comparative catalysts
Catalyst and process for preparing same Toluene conversion (mol%) Selectivity to p-xylene (% by mol)
Example 1-A1 18.6 91.3
Example 2-A2 19.0 88.7
Example 3-A3 19.7 79.1
Example 4-A4 19.3 80.4
Example 5-A5 18.1 87.9
Example 6-A6 20.2 76.7
Example 7-A7 26.4 48.1
Example 8-A8 14.8 90.2
Comparative examples 9 to A9 25.8 28.1
Comparative example 10-A10 23.7 43.7
The results of the selectivity to p-xylene in table 1 show that, by adopting the method of the present invention, the acid center on the outer surface of the molecular sieve can be effectively eliminated, the selectivity to p-xylene in the product reaches 91.3%, for nano ZSM-5, the PX selectivity can be greatly improved by one-time silicone ester modification, and meanwhile, amorphous components caused by the introduction of the binder are solved, and the amorphous components are crystallized into the molecular sieve to improve the diffusibility of the product and reactants.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (10)

1. A preparation method of a ZSM-5 catalyst comprises the following steps:
1) mixing a ZSM-5 molecular sieve with a binder silicon dioxide, forming, drying and roasting;
2) carrying out hydrothermal crystallization on the catalyst obtained in the step 1) in an aqueous solution containing a template agent quaternary ammonium salt and an additive, washing, drying and roasting;
3) and (3) carrying out chemical vapor deposition on the catalyst obtained in the step 2) and a cyclohexane solution containing silicon ester, and roasting to obtain the ZSM-5 catalyst.
2. The preparation method according to claim 1, characterized in that step 1) further comprises at least one of the following technical features:
1) silica-alumina molar ratio SiO of ZSM-5 molecular sieve2/Al2O325 to 2000;
2) the mass fraction of the silicon dioxide is 5-50%;
3) the adhesive silicon dioxide is selected from one or more of silica sol and white carbon black;
4) the roasting temperature is 500-550 ℃.
3. The process according to claim 2, wherein in the case of the characteristic 1), ZSM-5 is usedThe mole ratio of Si to Al of the sub-sieve SiO2/Al2O3Is 100 to 450.
4. The preparation method according to claim 1, wherein the step 2) further comprises at least one of the following technical characteristics:
1) the template agent quaternary ammonium salt is selected from one or more of tetrapropyl ammonium hydroxide and tetrapropyl ammonium bromide;
2) the additive is selected from one or more of ammonium fluoride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride;
3) the template agent quaternary ammonium salt accounts for 1-50% of the mass fraction of the catalyst obtained in the step 1);
4) the additive accounts for 0.5-20% of the mass fraction of the catalyst obtained in the step 1);
5) the mass fraction of water in the catalyst obtained in the step 1) is 100-1000%;
6) the hydrothermal crystallization temperature is 160-180 ℃;
7) the hydrothermal crystallization time is 3-48 hours;
8) the roasting temperature is 500-550 ℃.
5. The preparation method according to claim 1, wherein in the step 3), the silicon ester is selected from one or more of ethyl orthosilicate and methyl orthosilicate.
6. The method according to claim 1, wherein the concentration of the silicone ester in the step 3) is 0.1 to 2.0 mol/l.
7. The method according to claim 1, wherein the volume of the cyclohexane solution containing the silicon ester added in the step 3) is 0.6 to 1.2 ml per 1 g of the catalyst obtained in the step 2).
8. The preparation method according to claim 1, wherein the step 3) further comprises at least one of the following technical features:
1) the temperature of the chemical vapor deposition reaction is 160-180 ℃;
2) the reaction time of chemical vapor deposition is 3-48 hours;
3) the roasting temperature is 500-550 ℃.
9. A ZSM-5 catalyst, characterized by being obtained by the preparation method of any one of claims 1 to 8.
10. The catalyst of claim 9 used in a p-xylene or toluene disproportionation reaction by toluene alkylation with methanol.
CN201911102456.8A 2019-11-12 2019-11-12 ZSM-5 catalyst and preparation method and application thereof Pending CN112844454A (en)

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