CN109746029B

CN109746029B - Propane dehydrogenation catalyst, preparation method thereof and method for preparing propylene by propane dehydrogenation

Info

Publication number: CN109746029B
Application number: CN201711068975.8A
Authority: CN
Inventors: 亢宇; 刘红梅; 张明森
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2017-11-03
Filing date: 2017-11-03
Publication date: 2021-12-21
Anticipated expiration: 2037-11-03
Also published as: CN109746029A

Abstract

The invention relates to the field of catalysts, and discloses a propane dehydrogenation catalyst, a preparation method thereof and a method for preparing propylene by propane dehydrogenation. The propane dehydrogenation catalyst comprises a carrier and a Pt component, a Sn component and a Na component which are loaded on the carrier, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore structure and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 100-300m²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively. The propane dehydrogenation catalyst shows good catalytic performance when used for preparing propylene by propane dehydrogenation.

Description

Propane dehydrogenation catalyst, preparation method thereof and method for preparing propylene by propane dehydrogenation

Technical Field

The invention relates to the field of catalysts, in particular to a propane dehydrogenation catalyst, a preparation method thereof and a method for preparing propylene by propane dehydrogenation.

Background

Sepiolite belongs to orthorhombic or monoclinic system; the color is changeable, and is generally light white or grey white; have a silky luster, and sometimes a waxy luster; the streak is white, opaque, smooth in touch and sticky on the tongue; the Mohs hardness is between 2 and 2.5; the product has light weight and density of 1-2.2g/cm³(ii) a Low shrinkage, good plasticity and being soluble in hydrochloric acid. The chemical components of the sepiolite are silicon (Si) and magnesium (Mg); having a standard crystalline formula of Mg₈(H₂O)₄[Si₆O₁₆]₂(OH)₄·8H₂O, wherein SiO₂The content is generally between 54 and 60%, and the MgO content is more in the range of 21 to 25%. The sepiolite has strong adsorption, decoloration, dispersion and other performances, and also has high thermal stability, high temperature resistance up to 1500-.

Propylene is a basic raw material of petrochemical industry and is mainly used for producing polypropylene, acrylonitrile, acetone, propylene oxide, acrylic acid, butanol and octanol and the like. Half of the propylene supply comes from refinery by-products and about 45% from steam cracking, a few other alternative technologies. In recent years, the demand of propylene is increasing year by year, and the traditional propylene production can not meet the demand of the chemical industry for propylene, so that the propylene yield increase becomes a great hot point for research. The dehydrogenation of propane to propylene is one of the main technologies for increasing the yield of propylene. For more than 10 years, the dehydrogenation of propane to prepare propylene has become an important process for the industrial production of propylene. The main catalysts for propane dehydrogenation are the chromium oxide/alumina catalyst in the CYLofin process from ABB Lummus and the platinum tin/alumina catalyst in the Oleflex process from UOP. The chromium catalyst has lower requirements on raw material impurities and lower price compared with noble metals; however, the catalyst is easy to deposit carbon and deactivate, and is regenerated every 15 to 30 minutes, and the chromium in the catalyst is heavy metal, so that the environmental pollution is serious. The platinum-tin catalyst has high activity and good selectivity, the reaction period can reach several days, and the catalyst can bear harsh process conditions and is more environment-friendly; however, the noble metal platinum is expensive, so that the cost of the catalyst is high. The industrial production of the process for preparing propylene by propane dehydrogenation is over twenty years, and the research on dehydrogenation catalysts is more, but the current catalysts still have the defects of low propane conversion rate, easy inactivation and the like, and further improvement and perfection are needed. Therefore, it is of practical significance to develop a propane dehydrogenation catalyst having excellent performance. Much work has been done by researchers to improve the reaction performance of propane dehydrogenation catalysts. Such as: the molecular sieve carrier is adopted to replace the traditional gamma-Al 2O3 carrier, and the carrier has good effect and comprises MFI type microporous molecular sieves (CN104307555A, CN101066532A, CN101380587A and CN101513613A), mesoporous MCM-41 molecular sieves (CN102389831A), mesoporous SBA-15 molecular sieves (CN101972664A and CN101972664B) and the like. However, the pore diameter of the commonly used mesoporous material is small (average pore diameter is 6-9 nm), and if macromolecule catalytic reaction is carried out, the macromolecule is difficult to enter the pore channel, so that the catalytic effect is influenced. Therefore, the selection of a good carrier is an urgent problem to be solved in the field of propane dehydrogenation.

Disclosure of Invention

The propane dehydrogenation catalyst in the prior art usually takes Pt as a main metal active component and takes gamma-Al₂O₃As a carrier, the catalyst has the defects of poor dispersion of active components and poor catalytic activity and stability. The invention aims to overcome the defects that in the prior art, the mesoporous structure is unstable, the conversion rate of propane and the selectivity of propylene are not high, the catalyst is easy to inactivate and the like, and provides a propane dehydrogenation catalyst, a preparation method thereof and a method for preparing propylene by propane dehydrogenation.

In order to achieve the above object, the present invention provides a propane dehydrogenation catalyst, which comprises a carrier and a Pt component, a Sn component and a Na component supported on the carrier, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material having a two-dimensional hexagonal pore structure, and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10 to 60 μm, and the specific surface area is 100-²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the trimodal corresponds to the first most probable pore diameter and the second most probable pore diameterThe pore diameter and the third most probable pore diameter are respectively 1-5nm, 5-15nm and 10-40 nm.

The second aspect of the present invention provides a method for preparing the above propane dehydrogenation catalyst, comprising: carrying out thermal activation on a carrier, then carrying out impregnation treatment in a mixed solution containing a Pt component precursor, a Sn component precursor and a Na component precursor, and then sequentially carrying out solvent removal treatment, drying and roasting, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore channel structure and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area is 100-300 DEG F²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively.

In a third aspect, the present invention provides a propane dehydrogenation catalyst prepared by the above process.

In a fourth aspect of the present invention, there is provided a method for producing propylene by dehydrogenation of propane, the method comprising: and carrying out dehydrogenation reaction on propane in the presence of a catalyst and hydrogen, wherein the catalyst is the propane dehydrogenation catalyst provided by the invention or the propane dehydrogenation catalyst prepared by the method provided by the invention.

According to the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the advantages of a mesoporous molecular sieve material with a two-dimensional hexagonal pore channel distribution structure, sepiolite, silica gel and a spherical carrier are combined, so that the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is suitable for being used as a carrier of a supported catalyst, and is particularly suitable for being used as a carrier of a supported catalyst used in a reaction for preparing propylene by propane dehydrogenation.

In the supported catalyst of the invention, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material has the characteristics of porous structure, large specific surface area and large pore volume of mesoporous molecular sieve materials, combines the strong adsorption capacity of natural sepiolite due to large specific surface area and microporous structure, is favorable for the good dispersion of metal components on the surface of a carrier, and the carrier is also loaded with a Pt component, a Sn component and a Na component, so that the supported catalyst has the advantages of the supported catalyst such as high catalytic activity, less side reactions, simple post-treatment and the like, and has strong catalytic activity, so that the supported catalyst has better dehydrogenation activity and selectivity in the propane dehydrogenation reaction, the conversion rate of reaction raw materials is obviously improved, and particularly, in the reaction of preparing propylene by propane dehydrogenation by using the supported catalyst, the propane conversion rate can reach 33 percent, and the selectivity of the propylene can reach 86 percent.

And, when the supported catalyst is prepared by a spray-drying method, the supported catalyst can be recycled, and a high conversion rate of reaction raw materials can be still obtained during recycling.

In addition, the preparation method of the propane dehydrogenation catalyst adopts a co-impregnation method to replace the conventional step-by-step impregnation method, and has the advantages of simple preparation process, easily controlled conditions, low preparation cost, good economy and good product repeatability.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an X-ray diffraction pattern of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material of example 1;

FIG. 2 is an SEM scanning electron microscope picture of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material of example 1;

fig. 3 is a pore size distribution curve of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material of example 1.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a propane dehydrogenation catalyst which comprises a carrier, and a Pt component, a Sn component and a Na component which are loaded on the carrier, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore structure and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 100-300m²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively.

According to the invention, the carrier has a special two-dimensional hexagonal pore channel distribution structure, the limitation of one-dimensional pore channels on molecular transmission is broken through by the unique framework structure, the carrier is provided with spherical porous substances, the mesoporous pore channel structure of the carrier is uniform in distribution, proper in pore size, large in pore volume, good in mechanical strength and good in structural stability, and the special two-dimensional hexagonal ordered mesoporous pore channel distribution structure, the pore channel structure of sepiolite and silica gel are combined to be favorable for the good dispersion of metal components in the pore channels of the carrier. The supported catalyst obtained by loading the Pt component, the Sn component and the Na component has the advantages of high catalytic activity, less side reactions, simple post-treatment and the like, and has stronger catalytic activity and higher stability, so that the supported catalyst has better dehydrogenation activity and selectivity when being used for propane dehydrogenation reaction, and the conversion rate of reaction raw materials is obviously improved.

According to the invention, the average particle diameter of the particles of the support is determined using a laser particle size distribution instrument, and the specific surface area, pore volume and most probable pore diameter are determined according to a nitrogen adsorption method.

According to the invention, the structural parameters of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material are controlled within the range, so that the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is not easy to agglomerate, and the supported catalyst prepared by using the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material as a carrier can improve the conversion rate of reaction raw materials in the reaction process of preparing propylene by propane dehydrogenation. When the specific surface area of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is less than 100m²When the volume/g and/or pore volume is less than 0.7mL/g, the catalytic activity of the supported catalyst prepared by using the supported catalyst is remarkably reduced; when the specific surface area of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is more than 300m²When the volume/g and/or the pore volume is more than 1.3mL/g, the supported catalyst prepared by using the supported catalyst as the carrier is easy to agglomerate in the reaction process of preparing propylene by propane dehydrogenation, thereby influencing the conversion rate of the reaction raw materials in the reaction process of preparing propylene by propane dehydrogenation.

Preferably, the average particle diameter of the carrier is 10 to 50 μm, and the specific surface area is 150-250m²(iii) a pore volume of from 0.8 to 1.2mL/g, and a first mode pore size, a second mode pore size and a third mode pore size of from 2 to 4nm, from 5 to 12nm and from 15 to 38nm, respectively.

According to the present invention, the propane dehydrogenation catalyst comprises a carrier, and a Pt component, a Sn component, and a Na component supported on the carrier, wherein the Pt component is an active metal component, and the Sn component and the Na component are metal promoters.

According to the present invention, the carrier has a content of 97.5 to 99.3 wt%, the Pt component has a content of 0.2 to 0.5 wt% in terms of Pt element, the Sn component has a content of 0.2 to 1.2 wt% in terms of Sn element, and the Na component has a content of 0.3 to 0.8 wt% in terms of Na element, with respect to 100 parts by weight of the propane dehydrogenation catalyst.

Preferably, the propane dehydrogenation catalystThe average particle diameter is 10-50 μm, the specific surface area is 130-230m²(iii) a pore volume of from 0.7 to 1.1mL/g, and a first mode pore size, a second mode pore size and a third mode pore size of from 2 to 4nm, from 5 to 12nm and from 15 to 38nm, respectively.

According to the invention, the usage amount of the sepiolite, the mesoporous molecular sieve material with a two-dimensional hexagonal pore structure and the silica gel can adjust the pore structure of the carrier, and in order to enable the carrier to have better pore structure parameters, in the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material, the sepiolite content is 1-90 parts by weight, preferably 2-85 parts by weight, and the silica gel content is 1-90 parts by weight, preferably 2-85 parts by weight, relative to 100 parts by weight of the mesoporous molecular sieve material with a two-dimensional hexagonal pore structure.

The present invention also provides a method for preparing a propane dehydrogenation catalyst, the method comprising: carrying out thermal activation on a carrier, then carrying out impregnation treatment in a mixed solution containing a Pt component precursor, a Sn component precursor and a Na component precursor, and then sequentially carrying out solvent removal treatment, drying and roasting, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore channel structure and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area is 100-300 DEG F²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively.

According to the present invention, in order to remove hydroxyl groups and residual water in the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, a thermal activation treatment is first required to be performed before the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is loaded with metal components, and the conditions of the thermal activation treatment may include: in the presence of nitrogen, the carrier is calcined at the temperature of 300-900 ℃ for 7-10 h.

According to the invention, the metal component loaded on the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material can adopt an impregnation mode, the metal component enters the pore channel of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material by means of capillary pressure of the pore channel structure of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, and meanwhile, the metal component can be adsorbed on the surface of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material until the metal component reaches adsorption balance on the surface of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material. Preferably, the impregnation treatment is performed after the thermal activation treatment is performed on the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, and the impregnation treatment can be co-impregnation treatment or step-by-step impregnation treatment. In order to save the preparation cost and simplify the experimental process, the dipping treatment is preferably co-dipping treatment; further preferably, the conditions of the co-impregnation treatment include: mixing and contacting the thermally activated three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material in a solution containing a Pt component precursor, a Sn component precursor and a Na component precursor, wherein the impregnation temperature can be 25-50 ℃, and the impregnation time can be 2-6 h.

According to the present invention, the solutions of the Pt component precursor, the Sn component precursor, and the Na component precursor are not particularly limited as long as they are water-soluble, and may be conventionally selected in the art. For example, the Pt component precursor can be H₂PtCl₆The Sn component precursor may be SnCl₄The Na component precursor can be NaNO₃。

The concentration of the solution containing the Pt component precursor, the Sn component precursor, and the Na component precursor is not particularly limited in the present invention and may be conventionally selected in the art, for example, the concentration of the Pt component precursor may be 0.1 to 0.3mol/L, the concentration of the Sn component precursor may be 0.15 to 1mol/L, and the concentration of the Na component precursor may be 1 to 3.5 mol/L.

According to the present invention, the carrier, the Pt component precursor, the Sn component precursor, and the Na component precursor may be used in amounts such that the carrier has a content of 97.5 to 99.3 wt%, the Pt component has a content of 0.2 to 0.5 wt% in terms of Pt element, the Sn component has a content of 0.2 to 1.2 wt% in terms of Sn element, and the Na component has a content of 0.3 to 0.8 wt% in terms of Na element in the prepared propane dehydrogenation catalyst, based on the total weight of the propane dehydrogenation catalyst.

According to the present invention, the solvent removal treatment can be carried out by a method conventional in the art, for example, a rotary evaporator can be used to remove the solvent in the system.

According to the invention, the drying can be carried out in a drying oven and the baking can be carried out in a muffle furnace. The conditions for the drying and firing are also not particularly limited in the present invention, and may be conventionally selected in the art, for example, the conditions for the drying may include: the temperature is 110-150 ℃ and the time is 3-6 h; the conditions for the firing may include: the temperature is 600 ℃ and 650 ℃, and the time is 5-8 h.

According to the present invention, the method of forming the carrier includes the steps of:

(a) under the existence of a first template agent, trimethylpentane and ethanol, carrying out first contact on tetramethoxysilane and an acid agent, and sequentially carrying out first crystallization and filtration on a mixture obtained after the contact to obtain a No. 1 mesoporous molecular sieve filter cake; in the presence of a second template agent, carrying out second contact on a silicon source and an ammonia water solution, and carrying out second crystallization and filtration on a mixture obtained after the contact to obtain a No. 2 mesoporous molecular sieve filter cake;

(b) contacting water glass with inorganic acid, and filtering a product obtained after the contact to obtain a silica gel filter cake;

(c) and mixing and ball-milling the No. 1 mesoporous molecular sieve filter cake, the No. 2 mesoporous molecular sieve filter cake, the silica gel filter cake and the sepiolite, pulping solid powder obtained after ball-milling by using water, then carrying out spray drying, and removing the template agent from the obtained product.

In the formation process of the carrier, the No. 1 mesoporous molecular sieve filter cake is a mesoporous molecular sieve filter cake with a two-dimensional hexagonal pore channel distribution structure, and the No. 2 mesoporous molecular sieve filter cake is a mesoporous molecular sieve filter cake with a two-dimensional hexagonal pore channel distribution structure.

In the forming process of the carrier, the pore size distribution of the carrier is controlled to be trimodal distribution mainly by controlling the composition of a No. 1 mesoporous molecular sieve filter cake, a No. 2 mesoporous molecular sieve filter cake and a silica gel filter cake, so that the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material has a porous distribution structure, and the No. 1 mesoporous molecular sieve filter cake, the No. 2 mesoporous molecular sieve filter cake, the silica gel filter cake and the sepiolite are mixed and ball-milled by a control forming method, solid powder obtained after ball milling is slurried with water and then is subjected to spray drying, the template agent in the obtained product is removed, and the micro-morphology of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is controlled to be spherical.

According to the present invention, in the step (a), the process for preparing the filter cake of the mesoporous molecular sieve No. 1 may comprise: the first template, ethanol, trimethylpentane and tetramethoxysilane are subjected to first contact, and the resulting mixture is subjected to first crystallization and filtration. The order of the first contact is not particularly limited, and the first template, ethanol, trimethylpentane and tetramethoxysilane may be mixed simultaneously, or any two or three of them may be mixed, and then the other components may be added and mixed uniformly. According to a preferred embodiment, the first template, ethanol, acid and trimethylpentane are first mixed homogeneously and then tetramethoxysilane is added. The first contact mode is that the first template agent, ethanol and acid agent are mixed uniformly, the obtained mixture is placed in a water bath at 10-60 ℃, then the temperature is kept unchanged, trimethylpentane is slowly dripped into the mixture, the mixture is stirred and reacts for 5-20h, then the temperature is kept unchanged, tetramethoxysilane is slowly dripped into the mixture, and the mixture is stirred and reacts for 20-40 h. The dropping rate of the trimethylpentane can be 0.1-1g/min and the dropping rate of the tetramethoxysilane can be 0.1-1g/min based on 1g of the first template.

According to the invention, the dosage of each substance can be selected and adjusted in a wide range in the process of preparing the No. 1 mesoporous molecular sieve filter cake. For example, the first template, ethanol, trimethylpentane and tetramethoxysilane are used in a molar ratio of 1: 100-500: 200-500: 50-200, preferably 1: 200-400: 250-400: 70-150.

According to the present invention, in order to obtain the mesoporous filter cake No. 1 having the two-dimensional hexagonal pore distribution structure with the above pore size, the first template is preferably a triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene, and the first template can be obtained commercially (for example, from Aldrich company under the trade name P123 with the molecular formula of EO)₂₀PO₇₀EO₂₀And an average molecular weight Mn of 5800) can be obtained by various conventional methods. When the first template is polyoxyethylene-polyoxypropylene-polyoxyethylene, the number of moles of the template is calculated from the average molecular weight of polyoxyethylene-polyoxypropylene-polyoxyethylene.

According to the present invention, the acidic agent may be any of various substances or mixtures (e.g., solutions) conventionally used for adjusting pH. The acid agent is preferably used in the form of an aqueous solution, which may have a pH of 1 to 6, preferably 3 to 5. More preferably, the acid agent is acetic acid and sodium acetate buffer solution having a pH of 1-6 (more preferably 3-5).

According to the present invention, the conditions under which the tetramethoxysilane is first contacted with the acid agent may include: the temperature is 10-60 deg.C, the time is 10-72h, and the pH value is 1-7. In order to further facilitate uniform mixing between the respective substances, the first contact of the tetramethoxysilane with the acid agent is preferably performed under stirring conditions. The acid agent is preferably used in such an amount that the pH of the first contact reaction system of tetramethoxysilane and acid agent is 1 to 7.

According to the present invention, the conditions of the first crystallization may include: the temperature is 30-150 ℃ and the time is 10-72 h. Preferably, the conditions of the first crystallization include: the temperature is 40-100 ℃ and the time is 20-40 h. The first crystallization may be performed by a hydrothermal crystallization method.

According to the present invention, in the step (a), the process for preparing the filter cake of the mesoporous molecular sieve No. 2 may comprise: and carrying out second contact on a second template agent, a silicon source and an ammonia water solution, and carrying out second crystallization and filtration on a mixture obtained after the contact. The order of the second contacting is not particularly limited, and the second template, the silicon source and the aqueous ammonia solution may be mixed at the same time, or any two of them may be mixed, and then the other components may be added and mixed uniformly. According to a preferred embodiment, the second template agent and the silicon source are added into the ammonia water solution together and mixed uniformly. The second contact mode is that the second template agent and the silicon source are added into the ammonia water solution and mixed evenly, the obtained mixture is placed into a water bath with the temperature of 25-100 ℃ to be stirred until being dissolved, then the temperature is kept unchanged, and the mixture is stirred and reacted for 20-40 hours.

According to the invention, the dosage of each substance can be selected and adjusted in a wide range in the process of preparing the No. 2 mesoporous molecular sieve filter cake. For example, the molar ratio of the ammonia to the water in the silicon source, the second template agent and the ammonia water is 1: 0.1-1: 0.1-5: 100-200, preferably 1: 0.2-0.5: 1.5-3.5: 120-180.

According to the present invention, in order to make the obtained No. 2 mesoporous filter cake have the hexagonal pore distribution structure with the aforementioned pore size, the second template agent is preferably cetyl trimethyl ammonium bromide, the silicon source can be various silicon sources conventionally used in the art, preferably the silicon source is at least one of tetraethoxysilane, methyl orthosilicate, propyl orthosilicate, sodium orthosilicate and silica sol, and more preferably tetraethoxysilane.

According to the invention, the conditions under which the silicon source and the aqueous ammonia solution are subjected to the second contact may include: the temperature is 25-100 ℃, and the time is 10-72 h. In order to further facilitate uniform mixing of the materials, the second contacting of the silicon source, the second templating agent, and the aqueous ammonia is preferably performed under stirring conditions.

According to the present invention, the conditions of the second crystallization may include: the temperature is 30-150 ℃ and the time is 10-72 h. Preferably, the conditions of the second crystallization include: the temperature is 40-100 ℃ and the time is 20-40 h. The second crystallization may be performed by a hydrothermal crystallization method.

The conditions for contacting the water glass with the inorganic acid in the present invention are not particularly limited, and for example, in the step (b), the conditions for contacting the water glass with the inorganic acid generally include: the temperature can be 10-60 ℃, preferably 20-40 ℃; the time may be 1 to 5 hours, preferably 1.5 to 3 hours, and the pH value is 2 to 4. In order to further facilitate uniform mixing between the substances, the contact of the water glass with the mineral acid is preferably carried out under stirring conditions.

According to the invention, the water glass is an aqueous solution of sodium silicate conventional in the art, and its concentration may be 10 to 50% by weight, preferably 12 to 30% by weight.

According to the present invention, the kind of the inorganic acid may be conventionally selected in the art, and for example, may be one or more of sulfuric acid, nitric acid and hydrochloric acid. The inorganic acid may be used in a pure form or in the form of an aqueous solution thereof. The inorganic acid is preferably used in such an amount that the reaction system has a pH of 2 to 4 under the contact conditions of the water glass and the inorganic acid.

Further, in the above-described process for producing the filter cake of the mesoporous molecular sieve No. 1, the filter cake of the mesoporous molecular sieve No. 2, and the filter cake of silica gel, the process for obtaining the filter cake by filtration may include: after filtration, washing with distilled water was repeated (the number of washing may be 2 to 10), followed by suction filtration. Preferably, the washing during the preparation of the filter cake of the mesoporous molecular sieve No. 1 and the filter cake of the mesoporous molecular sieve No. 2 is such that the pH of the filter cake is 7, and the washing during the preparation of the silica gel filter cake is such that the sodium ion content is less than 0.02 wt%.

According to the present invention, in the step (c), the amount of the No. 1 mesoporous molecular sieve filter cake, the No. 2 mesoporous molecular sieve filter cake, the silica gel filter cake and the sepiolite may be selected according to the components of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material expected to be obtained, preferably, the sepiolite is used in an amount of 1 to 90 parts by weight, preferably 2 to 85 parts by weight, and the silica gel filter cake is used in an amount of 1 to 90 parts by weight, preferably 2 to 85 parts by weight, with respect to 100 parts by weight of the total amount of the No. 1 mesoporous molecular sieve filter cake and the No. 2 mesoporous molecular sieve filter cake; the weight ratio of the dosage of the No. 1 mesoporous molecular sieve filter cake to the dosage of the No. 2 mesoporous molecular sieve filter cake is 1: 0.5-2, preferably 1: 0.6-1.5. .

According to the present invention, the specific operation method and conditions of the ball milling are not particularly limited, subject to the principle that the structure of the mesoporous material is not destroyed or substantially destroyed and silica gel and sepiolite are allowed to enter the pore channels of the No. 1 mesoporous molecular sieve and the No. 2 mesoporous molecular sieve. One skilled in the art can select various suitable conditions to implement the present invention based on the above principles. Specifically, the ball milling is carried out in a ball mill, wherein the diameter of the milling balls in the ball mill can be 2-3 mm; the number of the grinding balls can be reasonably selected according to the size of the ball milling tank, and for the ball milling tank with the size of 50-150mL, 1 grinding ball can be generally used; the material of the grinding ball can be agate, polytetrafluoroethylene and the like, and agate is preferred. The ball milling conditions include: the rotation speed of the grinding ball can be 300-500r/min, the temperature in the ball milling tank can be 15-100 ℃, and the ball milling time can be 0.1-100 hours.

In the present invention, the process of slurrying the solid powder obtained after ball milling with water may be performed at 25 to 60 ℃. The weight ratio of solid powder to water used in the pulping process may be 1:0.5-5, preferably 1: 1-2.

In the present invention, the specific operation method and conditions of the spray drying are conventional in the art. Specifically, a slurry prepared from the solid powder and water is added into an atomizer and rotated at a high speed to realize spray drying. Wherein the spray drying conditions comprise: the temperature can be 100-300 ℃, and the rotating speed can be 10000-15000 r/min; preferably, the spray drying conditions include: the temperature is 150-250 ℃, and the rotating speed is 11000-13000 r/min; most preferably, the spray drying conditions include: the temperature is 200 ℃, and the rotating speed is 12000 r/min.

According to the invention, the method for removing the template agent is generally a calcination method. The conditions for removing the template agent may be selected conventionally in the art, and for example, the conditions for removing the template agent include: the temperature may be 500-700 deg.C, preferably 550-650 deg.C, and most preferably 600 deg.C; the time may be 10-40h, preferably 20-30h, most preferably 24 h.

The invention also provides a propane dehydrogenation catalyst prepared by the method.

The invention also provides a method for preparing propylene by propane dehydrogenation, which comprises the following steps: carrying out dehydrogenation reaction on propane in the presence of a catalyst and hydrogen, wherein the catalyst is the propane dehydrogenation catalyst.

According to the present invention, in order to improve the propane conversion and prevent the catalyst from coking, it is preferable that the molar ratio of the amount of propane to the amount of hydrogen is from 0.5 to 1.5: 1.

the conditions for the dehydrogenation reaction in the present invention are not particularly limited and may be conventionally selected in the art, and for example, the conditions for the dehydrogenation reaction may include: the reaction temperature is 600-650 ℃, the reaction pressure is 0.05-0.2MPa, the reaction time is 40-60h, and the propane mass space velocity is 2-5h^-1。

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples, polyoxyethylene-polyoxypropylene-polyoxyethylene, available from Aldrich, abbreviated as P123, and having the formula EO₂₀PO₇₀EO₂₀9003-11-6, average molecular weight 5800, of chemical abstracts in the United states;

in the following examples and comparative examples, X-ray diffraction analysis was carried out on an X-ray diffractometer, model D8Advance, available from Bruker AXS, Germany; scanning electron microscopy analysis was performed on a scanning electron microscope, model XL-30, available from FEI, USA; pore structure parameter analysis was performed on an ASAP2020-M + C type adsorber, available from Micromeritics, USA, and BET method was used for the specific surface area and pore volume calculation of the sample; the particle size distribution of the sample is carried out on a Malvern laser particle sizer; the rotary evaporator is produced by German IKA company, and the model is RV10 digital; the active component loading of the propane dehydrogenation catalyst was measured on a wavelength dispersive X-ray fluorescence spectrometer, model Axios-Advanced, available from parnacco, netherlands; analysis of the reaction product composition was performed on a gas chromatograph available from Agilent under model 7890A;

in the following experimental examples and experimental comparative examples, the conversion (%) of propane is ═ amount of propane-content of propane in the reaction product ÷ amount of propane used × 100%;

selectivity (%) of propylene ÷ actual yield of propylene ÷ theoretical yield of propylene × 100%.

Example 1

This example illustrates a propane dehydrogenation catalyst and a method for its preparation.

(1) Preparation of the support

Adding 1g of triblock copolymer P123 and 1.69g (0.037mol) of ethanol into 28ml of a buffer solution (pH 4.4) of acetic acid and sodium acetate, stirring at 15 ℃ until polyethylene glycol-polyglycerol-polyethylene glycol is completely dissolved, then adding 6g (0.053mol) of trimethylpentane into the solution, stirring at 15 ℃ for 8h, then adding 2.13g (0.014mol) of tetramethoxysilane into the solution, stirring at 15 ℃ for 20h, transferring the solution into a reaction kettle with a polytetrafluoroethylene lining, carrying out oven crystallization at 60 ℃ for 24h, carrying out suction filtration, washing for 4 times with deionized water until the pH is 7, and obtaining a No. 1 mesoporous molecular sieve filter cake X1 with a two-dimensional hexagonal pore structure;

adding hexadecyl trimethyl ammonium bromide and tetraethoxysilane into an ammonia water solution with the concentration of 25 weight percent, wherein the adding amount of the tetraethoxysilane is 1g, the feeding ratio of the massages is as follows: cetyl trimethylammonium bromide: ammonia (25%): deionized water 1: 0.37: 2.8: 142, stirring the mixture at the temperature of 80 ℃ until the mixture is dissolved, filtering the solution, washing the solution for 4 times by using deionized water until the pH value is 7, and obtaining a No. 2 mesoporous molecular sieve filter cake Y1 with a two-dimensional hexagonal pore channel structure;

mixing 15 wt% water glass and 12 wt% sulfuric acid solution in a weight ratio of 5:1, carrying out contact reaction at 30 ℃ for 1.5h, adjusting the pH value to 3 by using 98 wt% sulfuric acid, carrying out suction filtration on the obtained reaction material, and washing by using distilled water until the content of sodium ions is 0.02 wt% to obtain a silica gel filter cake B1.

And (2) putting 10g of the prepared filter cake X1, 10g of the prepared filter cake Y1, 20g of the prepared filter cake B1 and 20g of sepiolite into a 100ml ball milling tank, wherein the ball milling tank is made of polytetrafluoroethylene, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 400 r/min. Sealing the ball milling tank, and carrying out ball milling for 1 hour in the ball milling tank at the temperature of 60 ℃ to obtain 30g of solid powder; dissolving the solid powder in 30g of deionized water, and spray-drying at 200 ℃ at a rotating speed of 12000 r/min; calcining the product obtained after spray drying in a muffle furnace at 500 ℃ for 24 hours, and removing the template agent to obtain 30g of a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material C1 with a two-dimensional hexagonal pore channel distribution structure.

(2) Preparation of propane dehydrogenation catalyst

Calcining 30g of the spherical sepiolite mesoporous molecular sieve silica gel composite material C1 with three holes obtained in the step (1) at 400 ℃ for 10h under the protection of nitrogen for thermal activation treatment, and removing hydroxyl and residual moisture of the spherical aluminum-containing mesoporous molecular sieve silica gel composite material C1;

0.08g H₂PtCl₆·6H₂O、0.207g SnCl₄·5H₂O and 0.185g NaNO₃Dissolving the mixture in 100ml of deionized water to obtain a mixture solution, soaking the mixture solution in the mixture solution for 5h at 25 ℃, evaporating solvent water in the system by using a rotary evaporator to obtain a solid product, placing the solid product in a drying oven at 120 ℃, drying for 3h, then placing the dried product in a muffle furnace at 600 ℃, and roasting for 6h to obtain the propane dehydrogenation catalyst Cat-1 (the content of the Pt component is 0.3 wt% based on the Pt element, the content of the Sn component is 0.7 wt% based on the Sn element, the content of the Na component is 0.5 wt% based on the Na element, and the balance is a carrier).

The three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material C1 and the propane dehydrogenation catalyst Cat-1 are characterized by an XRD, a scanning electron microscope and an ASAP2020-M + C type adsorption instrument;

fig. 1 is an X-ray diffraction (XRD) spectrum of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite C1, wherein the abscissa is 2 θ and the ordinate is intensity, and the XRD spectrum of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite C1 has a two-dimensional hexagonal cavity structure specific to a mesoporous material, as can be seen from a small-angle spectrum peak appearing in the XRD spectrum;

fig. 2 is an SEM scanning electron microscope image of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1, and it can be seen from the image that the microscopic morphology of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1 is microspheres with a particle size of 10-60 μm, and the monodispersity thereof is good;

fig. 3 is a pore size distribution diagram of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1, and it can be seen from the diagram that the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1 is in porous distribution.

Table 1 shows the pore structure parameters of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1 and the propane dehydrogenation catalyst Cat-1.

TABLE 1

*: the first most probable aperture, the second most probable aperture, and the third most probable aperture are separated by commas: the first most probable aperture, the second most probable aperture and the third most probable aperture are arranged in the order from left to right.

As can be seen from the data in table 1, the specific surface area and pore volume of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1 used as a carrier were reduced after loading the main active Pt component, the auxiliary Sn component and the auxiliary Na component, which indicates that the main active Pt component, the auxiliary Sn component and the auxiliary Na component enter the interior of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C1 during the loading reaction.

Comparative example 1

This comparative example serves to illustrate a reference propane dehydrogenation catalyst and a method of making the same.

The carrier and the propane dehydrogenation catalyst were prepared according to the method of example 1, except that a mesoporous molecular sieve material having a two-dimensional hexagonal pore structure was not added in the process of preparing the carrier, thereby preparing the carrier D1 and the propane dehydrogenation catalyst Cat-D-1, respectively.

Comparative example 2

A carrier and a propane dehydrogenation catalyst were prepared according to the method of example 1, except that no silica gel was added during the preparation of the carrier, thereby preparing a carrier D2 and a propane dehydrogenation catalyst Cat-D-2, respectively.

Comparative example 3

A support and a propane dehydrogenation catalyst were prepared according to the method of example 1, except that sepiolite was not added during the preparation of the support, thereby preparing the support D3 and the propane dehydrogenation catalyst Cat-D-3, respectively.

Comparative example 4

A carrier and a propane dehydrogenation catalyst were prepared according to the method of example 1, except that during the impregnation process for preparing the propane dehydrogenation catalyst, NaNO was not added₃Addition of only 0.133g H₂PtCl₆·6H₂O and 0.295g SnCl₄·5H₂And O, loading an active component Pt and a metal auxiliary agent Sn on the spherical aluminum-containing mesoporous molecular sieve silica gel composite material serving as the carrier after thermal activation by a co-impregnation method to prepare the propane dehydrogenation catalyst Cat-D-4, wherein the content of the Pt component in terms of Pt element is 0.5 wt%, the content of the Sn component in terms of Sn element is 1 wt% and the balance is the carrier, based on the total weight of the propane dehydrogenation catalyst Cat-D-4).

Comparative example 5

A carrier and a propane dehydrogenation catalyst were prepared according to the method of example 1, except that there was no spray-drying step in the preparation of the carrier, and a Pt component, a Sn component, and a Na component were supported on a spherical aluminum-containing mesoporous molecular sieve silica gel composite as a carrier only by the impregnation method, thereby preparing a propane dehydrogenation catalyst Cat-D-5.

Example 2

(1) Preparation of the support

Adding 1g of triblock copolymer P123 and 1.84g (0.04mol) of ethanol into 28ml of buffer solution (pH is 5) of acetic acid and sodium acetate, stirring at 15 ℃ until polyethylene glycol-polyglycerol-polyethylene glycol is completely dissolved, then adding 9.12g (0.08mol) of trimethylpentane into the solution, stirring at 15 ℃ for 8h, then adding 3.04g (0.02mol) of tetramethoxysilane into the solution, stirring at 25 ℃ for 15h, transferring the solution into a polytetrafluoroethylene-lined reaction kettle, oven-crystallizing at 100 ℃ for 10h, then performing suction filtration, washing with deionized water for 4 times until the pH is 7, and obtaining No. 1 mesoporous molecular sieve filter cake X2 with a two-dimensional hexagonal pore structure;

adding hexadecyl trimethyl ammonium bromide and tetraethoxysilane into an ammonia water solution with the concentration of 25 weight percent, wherein the adding amount of the tetraethoxysilane is 1g, the feeding ratio of the massages is as follows: cetyl trimethylammonium bromide: ammonia (25%): deionized water 1: 0.5: 3.5: 150, stirring the mixture at the temperature of 80 ℃ until the mixture is dissolved, filtering the solution, washing the solution for 4 times by using deionized water until the pH value is 7, and obtaining a No. 2 mesoporous molecular sieve filter cake Y2 with a two-dimensional hexagonal pore channel structure;

mixing 15 wt% water glass and 12 wt% sulfuric acid solution in a weight ratio of 4:1, reacting at 40 deg.c for 1.5 hr, regulating the pH value to 2 with 98 wt% sulfuric acid, suction filtering the obtained reaction material, and washing with distilled water to sodium ion content of 0.02 wt% to obtain silica gel filter cake B2.

And (2) putting 10g of the prepared filter cake X2, 10g of the prepared filter cake Y2, 10g of the prepared filter cake B2 and 8g of sepiolite into a 100ml ball milling tank, wherein the ball milling tank is made of polytetrafluoroethylene, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 300 r/min. Sealing the ball milling tank, and carrying out ball milling for 0.5 hour in the ball milling tank at the temperature of 80 ℃ to obtain 38g of solid powder; dissolving the solid powder in 20g of deionized water, and spray-drying at 250 ℃ at the rotating speed of 11000 r/min; calcining the product obtained after spray drying in a muffle furnace at 500 ℃ for 15 hours, and removing the template agent to obtain 35g of a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material C2 with a two-dimensional hexagonal pore channel distribution structure.

(2) Preparation of propane dehydrogenation catalyst

Calcining 35g of the spherical sepiolite mesoporous molecular sieve silica gel composite material C2 with three holes obtained in the step (1) at 400 ℃ for 10h under the protection of nitrogen for thermal activation treatment, and removing hydroxyl and residual moisture of the spherical aluminum-containing mesoporous molecular sieve silica gel composite material C2;

0.08g H₂PtCl₆·6H₂O、0.207g SnCl₄·5H₂O and 0.185g NaNO₃Dissolving the mixture in 100ml of deionized water to obtain a mixture solution, soaking the mixture solution in the mixture solution for 5h at 25 ℃, evaporating solvent water in the system by using a rotary evaporator to obtain a solid product, placing the solid product in a drying oven at 120 ℃, drying for 3h, then placing the dried product in a muffle furnace at 600 ℃, and roasting for 6h to obtain the propane dehydrogenation catalyst Cat-2 (the content of the Pt component is 0.3 wt% based on the Pt element, the content of the Sn component is 0.7 wt% based on the Sn element, the content of the Na component is 0.5 wt% based on the Na element, and the balance is a carrier).

Table 2 shows the pore structure parameters of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C2 and the propane dehydrogenation catalyst Cat-2.

TABLE 2

As can be seen from the data in table 2, the specific surface area and pore volume of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C2 used as a carrier were reduced after loading the main active Pt component, the auxiliary Sn component and the auxiliary Na component, which indicates that the main active Pt component, the auxiliary Sn component and the auxiliary Na component enter the interior of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C2 during the loading reaction.

Example 3

(1) Preparation of the support

Adding 1g of triblock copolymer P123 and 2.76g (0.06mol) of ethanol into 28ml of a buffer solution (pH 3) of acetic acid and sodium acetate, stirring at 15 ℃ until polyethylene glycol-polyglycerol-polyethylene glycol is completely dissolved, then adding 5.7g (0.05mol) of trimethylpentane into the solution, stirring at 15 ℃ for 8 hours, then adding 2.13g (0.014mol) of tetramethoxysilane into the solution, stirring at 40 ℃ for 10 hours, transferring the solution into a polytetrafluoroethylene-lined reaction kettle, oven-crystallizing at 40 ℃ for 40 hours, performing suction filtration, washing with deionized water for 4 times until the pH is 7, and obtaining No. 1 mesoporous molecular sieve filter cake X3 with a two-dimensional hexagonal pore structure;

adding hexadecyl trimethyl ammonium bromide and tetraethoxysilane into an ammonia water solution with the concentration of 25 weight percent, wherein the adding amount of the tetraethoxysilane is 1g, the feeding ratio of the massages is as follows: cetyl trimethylammonium bromide: ammonia (25%): deionized water 1: 0.4: 3: 130, stirring at the temperature of 60 ℃ until the solution is dissolved, filtering the solution, washing for 4 times by using deionized water until the pH value is 7, and obtaining a No. 2 mesoporous molecular sieve filter cake Y3 with a two-dimensional hexagonal pore structure;

mixing 15 wt% water glass and 12 wt% sulfuric acid solution in the weight ratio of 6:1, contacting and reacting at 20 deg.c for 3 hr, regulating the pH value to 4 with 98 wt% sulfuric acid, suction filtering the obtained reaction material, and washing with distilled water to sodium ion content of 0.02 wt% to obtain silica gel filter cake B3.

And (3) putting 10g of the prepared filter cake X3, 10g of the prepared filter cake Y3, 30g of the prepared filter cake B3 and 12g of sepiolite into a 100ml ball milling tank, wherein the ball milling tank is made of polytetrafluoroethylene, grinding balls are made of agate, the diameter of each grinding ball is 3mm, the number of the grinding balls is 1, and the rotating speed is 550 r/min. Sealing the ball milling tank, and carrying out ball milling for 10 hours in the ball milling tank at the temperature of 40 ℃ to obtain 55g of solid powder; dissolving the solid powder in 30g of deionized water, and spray-drying at 150 ℃ at the rotating speed of 13000 r/min; calcining the product obtained after spray drying in a muffle furnace at 500 ℃ for 24 hours, and removing the template agent to obtain 53g of a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material C3 with a two-dimensional hexagonal pore channel distribution structure.

(2) Preparation of propane dehydrogenation catalyst

Calcining 53g of the spherical sepiolite mesoporous molecular sieve silica gel composite material C3 with three holes obtained in the step (1) at 400 ℃ for 10h under the protection of nitrogen for thermal activation treatment, and removing hydroxyl and residual moisture of the spherical aluminum-containing mesoporous molecular sieve silica gel composite material C3;

0.08g H₂PtCl₆·6H₂O、0.207g SnCl₄·5H₂O and 0.185g NaNO₃Dissolving the mixture in 100ml of deionized water to obtain a mixture solution, soaking the mixture solution in the mixture solution for 5h at 25 ℃, evaporating solvent water in the system by using a rotary evaporator to obtain a solid product, placing the solid product in a drying oven at 120 ℃, drying for 3h, then placing the dried product in a muffle furnace at 600 ℃, and roasting for 6h to obtain the propane dehydrogenation catalyst Cat-3 (the content of the Pt component is 0.3 wt% based on the Pt element, the content of the Sn component is 0.7 wt% based on the Sn element, the content of the Na component is 0.5 wt% based on the Na element, and the balance is a carrier).

Table 3 shows the pore structure parameters of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C3 and the propane dehydrogenation catalyst Cat-3.

TABLE 3

As can be seen from the data in table 3, the specific surface area and pore volume of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C3 as a carrier were reduced after loading the main active Pt component, the auxiliary Sn component and the auxiliary Na component, which indicates that the main active Pt component, the auxiliary Sn component and the auxiliary Na component enter the interior of the three-pore spherical sepiolite mesoporous molecular sieve silica gel composite material C3 during the loading reaction.

Experimental example 1

This example is intended to illustrate the preparation of propylene using the propane dehydrogenation catalyst of the present invention

0.5g of propane dehydrogenation catalyst Cat-1 was charged into a fixed bed quartz reactor, the reaction temperature was controlled at 610 ℃, the reaction pressure was 0.1MPa, and the molar ratio of propane: the molar ratio of hydrogen is 1:1, the reaction time is 50h, and the mass space velocity of propane is 3h^-1. Propane conversion and propylene selectivity are shown in table 4.

Experimental examples 2 to 3

Propane dehydrogenation was carried out to produce propylene in accordance with the procedure of experimental example 1, except that the propane dehydrogenation catalyst Cat-1 was replaced with the propane dehydrogenation catalyst Cat-2 and the propane dehydrogenation catalyst Cat-3, respectively. Propane conversion and propylene selectivity are shown in table 4.

Experimental comparative examples 1 to 5

Propane dehydrogenation was carried out to produce propylene in accordance with the procedure of Experimental example 1, except that the propane dehydrogenation catalyst Cat-D-1, the propane dehydrogenation catalyst Cat-D-2, the propane dehydrogenation catalyst Cat-D-3, the propane dehydrogenation catalyst Cat-D-4 and the propane dehydrogenation catalyst Cat-D-5 were used in place of the propane dehydrogenation catalyst Cat-1, respectively. Propane conversion and propylene selectivity are shown in table 4.

TABLE 4

	Dehydrogenation catalyst	Conversion of propane	Propylene selectivity
				Experimental example 1	Cat-1	33％	86％
Experimental example 2	Cat-2	32.4％	85.7％
				Experimental example 3	Cat-3	32.8％	85.2％
Experimental comparative example 1	Cat-D-1	10.2％	22.1％
				Experimental comparative example 2	Cat-D-2	7.3％	25.2％
Experimental comparative example 3	Cat-D-3	13.1％	41.3％
				Experimental comparative example 4	Cat-D-4	12.2％	42.3％
Experimental comparative example 5	Cat-D-5	11.9％	51.1％

It can be seen from table 4 that, when the propane dehydrogenation catalyst prepared by using the spherical sepiolite mesoporous molecular sieve silica gel composite material with three pores of the invention is used in the reaction for preparing propylene by propane dehydrogenation, higher propane conversion rate and propylene selectivity can still be obtained after 50 hours of reaction, which indicates that the propane dehydrogenation catalyst of the invention not only has better catalytic performance, but also has excellent stability.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. The propane dehydrogenation catalyst is characterized by comprising a carrier and a Pt component, a Sn component and a Na component loaded on the carrier, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore structure and silica gel, and the three-hole spherical sepiolite is characterized by comprising a support, a Pt component, a Sn component and a Na component which are loaded on the support, wherein the support is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite materialThe average particle size of the sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area is 100-300m²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively;

wherein the forming method of the carrier comprises the following steps:

2. The propane dehydrogenation catalyst of claim 1, wherein the support is present in an amount of 97.5 to 99.3 wt.%, the Pt component is present in an amount of 0.2 to 0.5 wt.% as Pt element, the Sn component is present in an amount of 0.2 to 1.2 wt.% as Sn element, and the Na component is present in an amount of 0.3 to 0.8 wt.% as Na element, based on the total weight of the propane dehydrogenation catalyst;

and/or the average particle size of the carrier is 10-50 mu m, and the specific surface area is 150-250m²(iii) a pore volume of from 0.8 to 1.2mL/g, and a trimodal distribution corresponding to a first mode pore size, a second mode pore size and a third mode pore size of from 2 to 4nm, from 5 to 12nm and from 15 to 38nm, respectively.

3. The propane dehydrogenation catalyst according to claim 1, wherein the sepiolite is contained in an amount of 1 to 90 parts by weight and the silica gel is contained in an amount of 1 to 90 parts by weight, relative to 100 parts by weight of the mesoporous molecular sieve material having a two-dimensional hexagonal pore structure.

4. The propane dehydrogenation catalyst according to claim 3, wherein the sepiolite is contained in an amount of 2 to 85 parts by weight and the silica gel is contained in an amount of 2 to 85 parts by weight, relative to 100 parts by weight of the mesoporous molecular sieve material having a two-dimensional hexagonal pore structure.

5. A process for preparing a propane dehydrogenation catalyst, the process comprising: carrying out immersion treatment on a carrier after thermal activation in a mixed solution containing a Pt component precursor, a Sn component precursor and a Na component precursor, and then sequentially carrying out solvent removal treatment, drying and roasting, wherein the carrier is a three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material, the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material contains sepiolite, a mesoporous molecular sieve material with a two-dimensional hexagonal pore structure and silica gel, the average particle size of the three-hole spherical sepiolite mesoporous molecular sieve silica gel composite material is 10-60 mu m, and the specific surface area is 100-300 m-²The pore volume is 0.7-1.3mL/g, the pore diameter is in trimodal distribution, and the first most probable pore diameter, the second most probable pore diameter and the third most probable pore diameter corresponding to the trimodal distribution are 1-5nm, 5-15nm and 10-40nm respectively;

wherein the forming method of the carrier comprises the following steps:

6. The method according to claim 5, wherein the support, the Pt component precursor, the Sn component precursor and the Na component precursor are used in amounts such that the propane dehydrogenation catalyst is prepared in which the support is contained in an amount of 97.5 to 99.3% by weight, the Pt component is contained in an amount of 0.2 to 0.5% by weight in terms of Pt element, the Sn component is contained in an amount of 0.2 to 1.2% by weight in terms of Sn element, and the Na component is contained in an amount of 0.3 to 0.8% by weight in terms of Na element, based on the total weight of the propane dehydrogenation catalyst;

and/or the average particle size of the carrier is 10-50 mu m, and the specific surface area is 150-250m²(ii)/g, pore volume is 0.8-1.2mL/g, first most probable pore diameter, second most probable pore diameter and third most probable pore diameter corresponding to trimodal distribution are 2-4nm, 5-12nm and 15-38nm, respectively;

and/or, the conditions of thermal activation include: the temperature is 300-900 ℃ and the time is 7-10 h; the conditions of the impregnation treatment include: the temperature is 25-50 ℃ and the time is 2-6 h.

7. The method of claim 5, wherein in step (a), the first template, ethanol, trimethylpentane and tetramethoxysilane are used in a molar ratio of 1: 100-500: 200-500: 50-200 parts of; the molar ratio of the ammonia to the water in the silicon source, the second template agent and the ammonia water is 1: 0.1-1: 0.1-5: 100-;

and/or, the first template agent comprises triblock copolymers of polyoxyethylene-polyoxypropylene-polyoxyethylene P123 and F127, and the acid agent is acetic acid and sodium acetate buffer solution with the pH value of 1-6; the second template agent is hexadecyl trimethyl ammonium bromide, and the silicon source comprises at least one of tetraethoxysilane, methyl orthosilicate, propyl orthosilicate, sodium metasilicate and silica sol;

and/or, the conditions of the first contacting comprise: the temperature is 10-60 ℃, the time is 10-72h, the pH value is 1-7, and the first crystallization conditions comprise: the temperature is 30-150 ℃, and the time is 10-72 h; the conditions of the second contacting include: the temperature is 25-100 ℃, and the time is 10-72 h; the conditions of the second crystallization include: the temperature is 30-150 ℃ and the time is 10-72 h.

8. The method of claim 7, wherein in step (a), the first template, ethanol, trimethylpentane and tetramethoxysilane are used in a molar ratio of 1: 200-400: 250-400: 70-150; the molar ratio of the ammonia to the water in the silicon source, the second template agent and the ammonia water is 1: 0.2-0.5: 1.5-3.5: 120-180;

the silicon source is tetraethoxysilane.

9. The production method according to claim 5, wherein in the step (b), the conditions under which the water glass is contacted with the inorganic acid include: the temperature is 10-60 ℃, the time is 1-5 hours, and the pH value is 2-4; the inorganic acid is one or more of sulfuric acid, nitric acid and hydrochloric acid;

and/or, in the step (c), the sepiolite is used in an amount of 1-90 parts by weight and the silica gel filter cake is used in an amount of 1-90 parts by weight, relative to 100 parts by weight of the total amount of the No. 1 mesoporous molecular sieve filter cake and the No. 2 mesoporous molecular sieve filter cake; the weight ratio of the dosage of the No. 1 mesoporous molecular sieve filter cake to the dosage of the No. 2 mesoporous molecular sieve filter cake is 1:0.5 to 2;

and/or the template agent removing process comprises the following steps: calcining at 500-700 deg.c for 10-40 hr.

10. The preparation method according to claim 9, wherein, in the step (c), the sepiolite is used in an amount of 2 to 85 parts by weight and the silica gel cake is used in an amount of 2 to 85 parts by weight, relative to 100 parts by weight of the total amount of the filter cake of the mesoporous molecular sieve No. 1 and the filter cake of the mesoporous molecular sieve No. 2; the weight ratio of the dosage of the No. 1 mesoporous molecular sieve filter cake to the dosage of the No. 2 mesoporous molecular sieve filter cake is 1: 0.6-1.5.

11. A propane dehydrogenation catalyst prepared by the process of any of claims 5-10.

12. A method for producing propylene by propane dehydrogenation, comprising: the dehydrogenation of propane in the presence of a catalyst and hydrogen, characterized in that the catalyst is a propane dehydrogenation catalyst according to any one of claims 1 to 4 and 11.

13. The process according to claim 12, wherein the molar ratio of the amount of propane to the amount of hydrogen is between 0.5 and 1.5: 1;

and/or, the dehydrogenation reaction conditions include: the reaction temperature is 600-650 ℃, the reaction pressure is 0.05-0.2MPa, the reaction time is 40-60h, and the propane mass space velocity is 2-5h^-1。