Catalyst carrier with customizable structure and preparation method

Abstract

The invention relates to a catalyst carrier with a customizable structure and a preparation method thereof. The invention discloses a method for customizing the pore diameter, pore volume and specific surface area structure of a catalyst carrier by using polyethylene oxide as a template and tetraethyl orthosilicate as a raw material. Comprising the following steps: preparing a solution from polyethylene oxide and an acid solution, adding tetraethyl orthosilicate, stirring, uniformly stirring, gelatinizing, dipping after gelatinizing, filtering, adding into an alkaline solution with a certain pH value, carrying out hydrolysis and condensation reaction, growing to form mesoporous silica, and subsequently washing, filtering, drying and calcining to obtain the mesoporous silica. By regulating and controlling the stirring time and speed, the pH value of ammonia water and the hydrolytic condensation reaction time, the specific surface area of the product mesoporous silica is regulated and controlled to be 500-1900m < 2 > / g, the pore volume is regulated and controlled to be 0.5-4ml / g, and the average pore size is regulated and controlled to be 5-30nm. The obtained mesoporous silica is very easy to perform surface modification or load active sites, the production cost is low, and industrial production can be realized. The catalyst can play a positive role in the fields of industrial catalysis, gas adsorption and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic nanomaterials, and specifically relates to an amorphous mesoporous silica and a preparation method for adjusting the specific surface area, pore diameter and pore volume thereof. Background Art

[0002] In industrial catalysts, the structure of the carrier, such as specific surface area, pore size, pore volume, etc., has a very important influence on the loading of the active sites of the catalyst, the contact area of ​​the reactants, and the adsorption and desorption behavior, which in turn affects the activity and service life of the catalyst. Mesoporous silica has attracted widespread attention due to its unique properties, such as adjustable specific surface area, pore size, pore volume and other structures. Mesoporous silica has a larger specific surface area and pore structure than alumina, and has a stronger adsorption capacity for carbon dioxide. Therefore, it has a wide range of applications in industrial catalysis, especially in the field of carbon dioxide conversion.

[0003] In the field of industrial catalysis, the specific surface area, pore size and pore volume of the catalyst carrier are key factors affecting its performance. The larger the specific surface area, the more active sites dispersed on its surface, and the better the catalyst activity. The size of the pore size and pore volume affects the activity of the catalyst. Too large or too small will lead to reduced activity. Therefore, the goal of industrial catalysts is to accurately control the pore size and pore volume of mesoporous silica materials while making the specific surface area as large as possible.

[0004] Mesoporous silica carrier is prepared using tetraethyl orthosilicate as raw material. The main method for preparing mesoporous silica at present is sol-gel method, which uses surfactants such as hexadecyl methyl ammonium bromide (CTAB) as mesopore directing agent, produces spherical mesoporous silica by condensation in alcohol / water system, or manufactures various structures by hydrothermal etching method, or uses pore expander to adjust pore size structure. However, these methods have certain problems, such as complex process, difficult control of specific surface area and mesopore size, certain pollution of pore expander used in production process, etc., which also limits the application of mesoporous silica in industrial field.

[0005] Therefore, the present invention proposes a new customizable catalyst carrier structure and a preparation method thereof, which can achieve rapid and large-scale preparation of amorphous mesoporous silica particles with controllable specific surface area, pore volume and pore size through a simple preparation process without using a mesopore expanding agent. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a customizable catalyst carrier structure and a preparation method thereof, which is safe, reliable and pollution-free, uses polyethylene oxide to construct a long-chain skeleton, uses tetraethyl orthosilicate as a silicon source raw material, and controls the growth rate of silicon dioxide crystals by adjusting the pH and reaction time. In this way, amorphous mesoporous silica particles with high specific surface area and controllable pore size and pore volume are prepared.

[0007] The method of the invention has a simple preparation process and can prepare mesoporous silica in batches on a large scale to realize the application of mesoporous silica in the field of industrial catalysis.

[0008] In order to achieve the above purpose, the technical solution adopted is:

[0009] Step 1: Dissolve polyethylene oxide in an acidic solution and stir evenly to obtain a polyethylene oxide solution.

[0010] Furthermore, in the polyethylene oxide solution in step 1, the mass ratio of polyethylene oxide to the acidic solution is 1:5-15;

[0011] Furthermore, the pH value of the acidic solution in step one is 0.08-0.15; the molecular weight of the polyethylene oxide is 100,000-3,000,000; the stirring is uniform, the stirring speed is 200-600 rpm, and the stirring time is 0.1-0.5 hours.

[0012] Step 2: Then add ethyl orthosilicate, stir evenly, seal and gel, and obtain a high molecular gel polymer;

[0013] Furthermore, the mass ratio of polyethylene oxide to tetraethyl orthosilicate in step 2 is 1:5-10; the gelation temperature is 40-80° C.; and the gelation time is 12-80 hours.

[0014] Furthermore, the stirring in step 2 is uniform, with a stirring speed of 200-600 rpm and a stirring time of 0.5-12 hours; or a stirring speed of 30000-50000 rpm and a stirring time of 0.5-3 minutes.

[0015] Step 3: soaking the high molecular gel polymer with deionized water for multiple times, and filtering out the remaining gel blocks;

[0016] Furthermore, the deionized water described in step three is immersed multiple times, and the ratio of gel volume to solution volume is 1:30-50; the total immersion time is 2-10 hours, the last immersion time is at least 1 hour, and the pH value of the immersion solution after the last immersion is 6.5-7.5.

[0017] Step 4: placing the gel block in an alkaline solution and sealing it, generating a copolymer of silica and gel after aging for a period of time, filtering and washing the copolymer;

[0018] Furthermore, the pH value of the alkaline solution in step 4 is 8-11; the aging refers to the slow reaction of the gel block under a suitable environment and temperature for a period of time, and the aging temperature is 40-80°C; the aging time is 12-120 hours, and the filtration and washing are performed, and the pH value of the filtered solution after washing is 6.5-7.5.

[0019] Step 5: drying and high-temperature calcining the filtered copolymer of silica and gel to obtain the high specific surface area mesoporous silica.

[0020] Furthermore, the drying method in step 5 is freeze drying for 12-24 hours; or the method is drying at a temperature of 40-120° C. for 12-48 hours;

[0021] Furthermore, in the high temperature calcination described in step five, the calcination temperature is 600-900 degrees, and the heating rate is 1-2 degrees Celsius per minute.

[0022] Compared with the prior art, the present invention is beneficial in that:

[0023] 1. The specific surface area of ​​the catalyst carrier prepared by the present invention is between 500-1900m2 / g, the pore volume is between 0.5-4ml / g, and the average pore diameter is between 5-30nm. The selection range is large, and the specific surface area, pore diameter and pore volume of the catalyst can be customized according to the stirring speed, stirring time, gelation time or pH value of the alkaline solution and drying conditions, so that the mesoporous silica with a suitable specific surface area can be prepared according to the needs.

[0024] The catalyst carrier prepared by the present invention has a complex pore structure and a high specific surface area, and silicon dioxide has a good adsorption effect on carbon dioxide. Using mesoporous silicon dioxide as a carrier can enhance the absorption and conversion of carbon dioxide by the catalyst. At the same time, the high specific surface area can effectively disperse the active sites of the catalyst, greatly increase the number of active sites of the catalyst with equal volume, and help to form active sites with a size of several nanometers or even single atomic level.

[0025] 2. The method used in the present invention is simple and has strong reproducibility. The equipment or raw materials used are easy to obtain, easy to scale up production, and have good industrialization potential. This catalyst carrier can be used in the fields of industrial catalysis, gas absorption, etc., and will have an important impact on environmental protection and carbon dioxide absorption and utilization.

[0026] 3. The shape or size of the mesoporous silica prepared by the present invention is not fixed. Its macroscopic structure can be changed using a mold during the gelation period according to the use requirements so that it has different sizes or shapes and can be applied to fluidized bed or fixed bed reactors.

[0027] 4. The mesoporous silica prepared by the present invention can be easily surface-modified by adding acidic or alkaline sites on the surface to improve the adsorption capacity of carbon dioxide or other substances, thereby increasing its application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a SEM image of amorphous mesoporous silica particles prepared in Example 1 of the present invention;

[0029] Figure 2 The nitrogen adsorption-desorption isotherm curve of the amorphous mesoporous silica particles prepared in Example 1 of the present invention;

[0030] Figure 3 The pore volume and pore size distribution curve of the amorphous mesoporous silica particles prepared in Example 1 of the present invention;

[0031] Figure 4 This is a pore volume and pore size distribution curve of the amorphous mesoporous silica particles prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The present invention provides a catalyst carrier with a customizable structure and a preparation method thereof, which is used to prepare various catalyst carriers in the catalytic industry, comprising the following steps: Step 1: dissolving polyethylene oxide in an acidic solution and stirring to obtain a polyethylene oxide solution; Step 2: Then add ethyl orthosilicate, stir evenly, seal and gel, and obtain a high molecular gel polymer; Step 3: soaking the obtained high molecular gel polymer with deionized water for multiple times, and filtering out the remaining gel blocks; Step 4: placing the gel block in an alkaline solution and sealing it, generating a copolymer of silica and gel after aging for a period of time, filtering and washing the copolymer; Step 5: The filtered silica and gel copolymer is dried and calcined at high temperature to obtain structure-adjustable mesoporous silica.

[0032] The present invention provides a catalyst carrier with a customizable structure and a preparation method thereof, wherein polyethylene oxide is used to prepare a gelled skeleton of a carrier pore structure, the method is simple, and the raw materials are readily available. At the same time, the fineness of the gel skeleton can be effectively controlled by adjusting the stirring speed and stirring time, the gelling time and temperature, or the molecular weight of polyethylene oxide, so as to finely control the specific surface area and pore structure of the mesoporous silica finally formed; in addition, by changing the solution pH value during the hydrolysis and condensation of ethyl orthosilicate, the time of hydrolysis and condensation, or the drying method, the pore size and pore volume of the prepared mesoporous silica carrier can be controlled; the present application solves the problem of preparing a catalyst carrier with a customizable structure at low cost, high efficiency and environmental protection.

[0033] It should be noted that, in the present invention, the solution components should be simple and free of impurities.

[0034] In the present invention, the aging time of the gelation or hydrolysis condensation needs to be adjusted by certain experiments, and the specific time is determined according to the desired carrier structure.

[0035] Preferably, the acidic solution in step 1 can be nitric acid or hydrochloric acid.

[0036] Preferably, the alkaline solution in step 4 can be aqueous ammonia or sodium hydroxide.

[0037] The present invention is further described below in conjunction with specific examples, but the protection scope of the present invention should not be limited.

[0038] Embodiment 1: First, 1 g of polyethylene oxide was dissolved in 10 g of nitric acid solution, the pH of the nitric acid solution was 0.10, the molecular weight of the polyethylene oxide was 200,000, and magnetic stirring was performed for 30 minutes at a stirring speed of 500 rpm.

[0039] In the second step, 8.125 g of tetraethyl silicate solution was added and magnetically stirred for 3 hours at a stirring speed of 600 rpm. The stirred solution was sealed and placed in an oven at 40 degrees for gelation for 60 hours.

[0040] The third step is to take out the high molecular gel polymer, break it into small pieces for later processing, and then use 350 ml of deionized water to soak the polymer three times, each time with an interval of 2 hours. The pH of the last soaking solution is measured at about 7.

[0041] In the fourth step, the high molecular gel polymer after soaking is filtered, sealed in an ammonia solution with a pH of 10, and aged in an oven at 40 degrees for 24 hours to generate silicon dioxide. Then, the silicon dioxide and gel copolymer in the ammonia solution are taken out and washed with deionized water until the pH of the washing water is 6.5-7.5.

[0042] The fifth step is to place the washed silica and gel copolymer in an oven at 40 degrees and dry them for 40 hours, and then place them in a muffle furnace and calcine them in air, raising the temperature from room temperature to 600 degrees at a heating rate of 1 degree per minute, and maintaining it at 600 degrees for 6 hours to remove the residual gel and impurities, and then slowly cool it to room temperature to obtain mesoporous silica.

[0043] Step 6. Crush the silica particles in a mortar and sieve them into 30-50 mesh sizes as needed.

[0044] The silica particles obtained in this example were measured to have a specific surface area of ​​1835 m2 / g, a pore volume of 1.99 ml / g, an average pore diameter of 6.79 nm, and a pore size distribution in which 67.86% of the pore volume belonged to pores of 2-10 nm and 32.14% of the pore volume belonged to pores of 10-50 nm.

[0045] Figure 1 This is a SEM image of the amorphous mesoporous silica prepared in Example 1 of the present invention. As can be seen from the image, its microscopic morphology is coral-like, and the mesopores are unevenly present on the surface of the particles.

[0046] Figure 2 This is a nitrogen adsorption-desorption isotherm of the amorphous mesoporous silica prepared in Example 1 of the present invention, which has a type II isotherm. It can be seen from the figure that the pore size of the silica prepared in the present invention is a mesoporous material.

[0047] Figure 3 This is a pore volume and pore size distribution curve of the amorphous mesoporous silica prepared in Example 1 of the present invention. It can be seen from the figure that the average pore size of the silica prepared in Example 1 of the present invention is 6.79 nm, the pore size distribution is relatively uniform, and the pore volume is 1.99 ml / g.

[0048] Example 2

[0049] The operation steps of Example 2 are the same as those of Example 1, except that freeze drying is used as the drying method.

[0050] The silica particles obtained in Example 2 were measured, and the specific surface area was 591m2 / g, the pore volume was 1.77ml / g, the average pore diameter was 19.01nm, and in the pore size distribution, 26.12% of the pore volume belonged to pores of 2-10nm, 33.79% of the pore volume belonged to pores of 10-50nm, and 40.08% of the pore volume belonged to pores of 50-80nm.

[0051] Figure 4This is a pore volume-level pore size distribution curve of the amorphous mesoporous silica prepared in Example 2 of the present invention. It can be seen from the figure that the average pore size of the silica prepared in Example 2 of the present invention is 19.01 nm, the pore size distribution is very uniform, and the pore volume is 1.76 ml / g.

[0052] This example demonstrates that the size and distribution of pores can be controlled by changing the drying conditions.

[0053] Example 3

[0054] The operating steps of Example 3 are the same as those of Example 1, except that the pH value of the ammonia water is 11.

[0055] The silica particles obtained in Example 3 were measured to have a specific surface area of ​​806.5 m2 / g, a pore volume of 2.31 ml / g, an average pore diameter of 16.95 nm, and a pore size distribution in which 24.22% of the pore volume belonged to pores of 2-10 nm and 75.78% of the pore volume belonged to pores of 10-50 nm.

[0056] This example demonstrates that the pore volume can be controlled by adjusting the pH of ammonia water.

[0057] Example 4

[0058] The operation steps of Example 4 are the same as those of Example 1, except that the gelation time is 1 day.

[0059] The silica particles obtained in Example 4 were measured, and the specific surface area was 599.6 m2 / g, the pore volume was 1.12 ml / g, the average pore diameter was 16.95 nm, and in the pore size distribution, 44.10% of the pore volume belonged to pores of 2-10 nm, 6.81% of the pore volume belonged to pores of 10-50 nm, and 49.09% of the pore volume belonged to pores of 50-200 nm.

[0060] This example demonstrates that the size and distribution of pores can be controlled by adjusting the gelation time.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A catalyst carrier with a customizable structure and a preparation method, characterized in that: The following steps are involved: Step 1: dissolving polyethylene oxide in an acidic solution and stirring to obtain a polyethylene oxide solution; Step 2: Then add ethyl orthosilicate, stir evenly, seal and gel, and obtain a high molecular gel polymer; Step 3: soaking the obtained high molecular gel polymer with deionized water for multiple times, and filtering out the remaining gel blocks; Step 4: placing the gel block in an alkaline solution and sealing it, generating a copolymer of silica and gel after aging for a period of time, filtering and washing the copolymer; Step 5: The filtered silica and gel copolymer is dried and calcined at high temperature to obtain structure-adjustable mesoporous silica.

2. The preparation method according to claim 1, characterized in that: The pH value of the acidic solution described in step 1 is 0.08-0.15; In the polyethylene oxide solution described in step 1, the mass ratio of polyethylene oxide to the acidic solution is 1:5-15; The polyethylene oxide described in step 1 has a molecular weight of 100,000-3,000,000; The mass ratio of polyethylene oxide to tetraethyl orthosilicate described in step 2 is 1:5-10.

3. The preparation method according to claim 1, characterized in that: The stirring described in step 1 is uniform, the stirring speed is 200-600 rpm, and the stirring time is 0.1-0.5 hours; The stirring in step 2 is uniform, with a stirring speed of 200-600 rpm and a stirring time of 0.5-12 hours, or a stirring speed of 30000-50000 rpm and a stirring time of 0.5-3 minutes.

4. The preparation method according to claim 1, characterized in that: The gelation temperature in step 2 is 40-80°C; The gelation time described in step 2 is 12-80 hours.

5. The preparation method according to claim 1, characterized in that: Multiple immersions in deionized water as described in step 3, with the volume ratio of gel to solution being 1:30-50; The total immersion time in step 3 is 2-10 hours, the last immersion time is at least 1 hour, and the pH value of the immersion solution after the last immersion is 6.5-7.

5.

6. The preparation method according to claim 1, characterized in that: The pH value of the alkaline solution described in step 4 is 8-11; The aging described in step 4 refers to the slow reaction of the gel block under a suitable environment and temperature for a period of time, and the aging temperature is 40-80°C; The aging time described in step 4 is 12-120 hours.

7. The preparation method according to claim 1, characterized in that: The filtration and washing described in step 4, the pH value of the filtered solution after washing is 6.5-7.

5.

8. The preparation method according to claim 1, characterized in that: The drying method in step 5 is freeze drying for 12-24 hours; The drying method in step 5 is drying at a temperature of 40-120° C. for 12-48 hours; The high temperature calcination described in step 5 has a calcination temperature of 600-900 degrees and a heating rate of 1-2 degrees Celsius per minute.

9. An amorphous mesoporous silica with adjustable specific surface area, pore size and pore volume, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. The mesoporous silica with adjustable specific surface area, pore diameter and pore volume according to claim 9, characterized in that: The specific surface area of ​​the mesoporous silica is 500-1900 m2 / g, the pore volume is 0.5-4 ml / g, and the average pore diameter is 5-30 nm.

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