Preparation method of silica gel microspheres used as catalyst carrier

Abstract

The invention relates to a preparation method of silica gel microspheres used as a catalyst carrier, which comprises the following steps of: adjusting the speed of converting acidified water glass into gel by means of controlling material temperature and material concentration, multiple times of acidification and the like, so that the acidified water glass is atomized to form liquid drops, and then the liquid drops are quickly converted into the gel; and carrying out aging, acid washing, water washing, supercritical carbon dioxide drying, roasting in an atmosphere furnace and the like to prepare the silica gel microspheres with high specific surface area and large pore volume. Compared with the prior art, the specific surface area of the obtained silica gel can reach 250-450 m < 2 > / g, the pore volume can reach 1.5-3.0 cm < 3 > / g, and the silica gel has good strength and fluidity.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation and relates to a method for preparing silica gel microspheres used as catalyst carriers. Background Art

[0002] Silica gel has a wide range of uses. Among them, microsphere silica gel with large pore volume, large pore diameter and high specific surface area is particularly suitable for polyolefin catalyst supports, especially metallocene catalyst supports, because of its suitable pore volume, pore diameter, specific surface area and good fluidity.

[0003] There are many methods for preparing silica microspheres. The most common method is to use silicate and inorganic acid as raw materials, react at a certain pH value to form gel, and then undergo aging, acid washing, water washing, drying or spray molding, roasting and other steps to obtain silica microspheres. Patent documents CN113754798A, CN110732341A, CN106622378B and other existing technologies all prepare gel raw materials first, then crush them into slurry, and then spray dry them to obtain silica microspheres.

[0004] However, this traditional method of preparing silica microsphere carriers has two shortcomings: (1) It is difficult for existing silica microspheres to achieve both high specific area and large pore volume, and the specific surface area is often sacrificed for large pore volume. (2) The spray drying process affects the strength of silica microspheres. Silica powder forms a microsphere structure through the action of the adhesive. Due to the different thermal expansion coefficients between the adhesive and the silica powder, when the silica microspheres are heated or cooled, they are prone to collapse and cracking.

[0005] Therefore, new methods must be used to prepare silica gel microspheres with high specific surface area, high pore volume, good strength and fluidity to meet the requirements of catalyst supports. Summary of the invention

[0006] The purpose of the present invention is to overcome at least one of the defects of the above-mentioned prior art and to provide a method for preparing silica gel microspheres used as catalyst carriers, so as to obtain silica gel microspheres with high specific surface area, high pore volume, good strength and fluidity.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing silica gel microspheres used as catalyst carriers, comprising the following steps:

[0009] (1) adding beta molecular sieve modified powder to water glass solution and stirring thoroughly to obtain mixed solution A; and mixing the mixed solution with sulfuric acid solution B at high speed to obtain mixed solution D;

[0010] (2) The mixed liquid D precooled to -4 to 0°C is rapidly mixed with another sulfuric acid solution B precooled to -4 to 0°C, and the obtained material d is rapidly mixed with the acid salt solution C. The obtained mixed liquid e is sheared by a high-pressure airflow to obtain atomized droplets E; the droplets are collected and filtered using a flowing organic solvent to obtain particles F;

[0011] (3) Particles F are dispersed in an aqueous solution of n-butanol and then aged to obtain gel-aged particles G, which are dispersed in an aqueous solution of oxalic acid, stirred, heated to 50-70° C., treated for 1-2 hours, and filtered to obtain particles H;

[0012] (4) dispersing the particles H in deionized water, stirring, washing, and filtering to raise the pH value of the washing water to above 5.5 to obtain washed particles I;

[0013] (5) dispersing particle I in low-carbon alcohol, stirring for 24 hours, filtering to obtain particle J, drying with supercritical carbon dioxide, and sieving to select particles with a diameter of 10 to 150 μm to obtain particle K;

[0014] (6) calcining the particles K in a gradient temperature increasing manner to obtain silica gel microspheres.

[0015] Furthermore, the modified beta molecular sieve powder described in step (1) is prepared by the following method:

[0016] The beta molecular sieve is soaked in an oxalic acid solution, heated to 50-70°C, stirred for 0.5-2 hours, and filtered; the above process is repeated multiple times; the obtained acid-treated beta molecular sieve is washed until the washing solution is nearly neutral, and then dried and calcined to obtain the beta molecular sieve modified powder.

[0017] Further, the beta molecular sieve is a commercially available beta molecular sieve having a silicon-aluminum ratio (n(SiO2) / n(Al2O3), molar ratio) of 25 to 80:1 and a particle size of less than 1 micron;

[0018] The mass concentration of the oxalic acid solution is 0.5-2%.

[0019] The washed beta molecular sieve has a drying temperature of 100-140°C, a calcination temperature of 450-550°C, and a calcination time of 1-3h.

[0020] Furthermore, the water glass solution in step (1) is prepared by adding high-purity water glass to deionized water, wherein the amount of deionized water is 3 to 4 times the mass of the high-purity water glass;

[0021] The high-purity water glass has a modulus of 3.1 to 3.7, a silicon dioxide mass fraction of 25% to 29%, wherein the impurity iron oxide mass fraction is less than 0.005%, and the impurity aluminum oxide mass fraction is less than 0.07%.

[0022] Furthermore, the amount of the modified beta molecular sieve powder in the mixed solution A is 1% to 15% of the mass of the water glass;

[0023] The mass fraction of the sulfuric acid solution B is 5% to 10%;

[0024] The mass fraction of the acid salt solution C is 5% to 10%;

[0025] The acid salt used in the acid salt solution C is selected from sodium bicarbonate, ammonium bicarbonate, sodium bisulfate, ammonium bisulfate or a mixture thereof.

[0026] Since the process of converting water glass into gel by adding acid is very rapid, if the acid is added too quickly, gelation can be completed within a few seconds, resulting in an uneven reaction system. To achieve that water glass is sprayed out to form droplets in a very short time after adding acid, and then the droplets are quickly converted into gel, extremely high requirements are placed on the pH control, temperature control, and rapid mixing of the reaction system. Therefore, the present invention adopts a step-by-step acid addition method to adjust the pH value of the system in stages, thereby ensuring that the system is always in a uniform reaction state and ensuring that the microstructure is adjustable and controllable.

[0027] Furthermore, the mixed solution A and the sulfuric acid solution B in step (1) are continuously introduced into a first high-speed stirring mixer with a cooling jacket at a mass flow ratio of 100:25 to 100:50, and are stirred and mixed at high speed for 2 to 10 minutes; the pH of the mixed solution D is 11 to 13.

[0028] Furthermore, the mixed solution D and the sulfuric acid solution B in step (2) are continuously introduced into a second high-speed stirring mixer at a mass flow ratio of 100:10 to 100:25, and mixed rapidly for 15 to 60 seconds, and the pH of the mixed material is 10 to 12;

[0029] Water glass continuously produces metasilicic acid during the acidification process. Metasilicic acid can form a network structure by polycondensation of silanols under strong alkalinity (pH 10-14) or strong acidity (pH 1-4) and above room temperature. When networking is improved to a certain degree, it becomes a gel, and the system loses fluidity. If acidification is continued, there will inevitably be uneven mixing, and the situation of inconsistent local pH environment will cause inconsistent microstructure. As a catalyst carrier, it will affect the catalyst reaction activity. Moreover, the reaction of sulfuric acid and water glass belongs to a strong exothermic reaction, and the reaction heat must be removed quickly. After sulfuric acid is added to a certain degree, the heat transfer ability of the reaction system decreases sharply. For this reason, the present invention realizes continuous preparation by reasonably controlling the acid-adding step and finely regulating the acid-adding process.

[0030] The material d and the acid salt solution C are continuously introduced into a high-speed stirring mixer (3) at a mass flow ratio of 100:10 to 100:25, and mixed rapidly for 15 to 60 seconds. The pH value of the obtained mixed solution e is 8 to 10, and the mixed solution is sprayed out from the bottom nozzle of the high-speed stirring mixer (3) to obtain atomized droplets E under the shearing action of high-pressure airflow.

[0031] Furthermore, the nozzle is a two-fluid nozzle, and the high-pressure airflow is a mixture of nitrogen and carbon dioxide at 2 to 8 bar, wherein the carbon dioxide content is 20% to 100%.

[0032] The organic solvent for collecting the atomized droplets E is n-butanol or isobutanol containing water, wherein the mass fraction of water is 0.5% to 7%.

[0033] Furthermore, in step (3), the mass fraction of the aqueous solution of n-butanol is 0% to 5%;

[0034] The aging process is: firstly heating to 50-70°C for 15-18 hours, then heating to 80-90°C for 3-6 hours;

[0035] The mass fraction of oxalic acid in the oxalic acid aqueous solution is 0.1-1%, and the amount of the oxalic acid aqueous solution used is 16-20 times the mass of the gel-aged particles G.

[0036] The low-carbon alcohol described in step (4) is ethanol, isopropanol or n-butanol, and the amount of the low-carbon alcohol used is 15 to 25 times the mass of the water-washed particles I.

[0037] The supercritical carbon dioxide drying in step (5) is performed at a pressure of 10 to 20 MPa, a temperature of 40 to 120° C., a carbon dioxide flow rate of 10 to 20 g of carbon dioxide per gram of particles J per hour, and a processing time of 2 to 4 hours.

[0038] Furthermore, the gradient heating method of step (6) is to stay at 300-400°C for 0.5-1.5 hours, 500-600°C for 1-3 hours, and 600-700°C for 3-6 hours, respectively, and the heating rate and cooling rate are controlled at 0.5-1.5°C / min;

[0039] The calcination is carried out in an air atmosphere, and the air flow rate is 0.2 to 2 L of air per gram of particle K per hour;

[0040] The silica gel microspheres have a SiO2 mass fraction greater than 99.9%, an Al2O3 mass fraction less than 0.05%, and a Na2O mass fraction less than 0.01%.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The method of the present invention can prepare a pore volume of 1.5 to 3.0 cm 3 / g, specific surface area 250~450m 2 / g, spherical silica gel with a diameter of 10 to 150 microns; prepare micron-sized silica gel carriers, the reaction system is uniform, and the surface tension of the atomized liquid is used to form the particles naturally. The formed particles have good sphericity and good fluidity.

[0043] (2) Beta molecular sieve has a pore structure of a three-dimensional twelve-membered ring straight channel system, a wide adjustable range of silicon-aluminum ratio, a high specific surface area, acid catalytic properties and hydrothermal stability, and is widely used as a catalyst carrier in the chemical industry. The present invention organically combines Beta molecular sieve with a high-performance silica gel carrier, which is conducive to further expanding the application performance of the silica gel carrier.

[0044] The beta molecular sieve skeleton has a pore size of 0.75 nm. After acid treatment, part of the aluminum in the skeleton is removed to form a mesoporous structure with a pore size of 2 to 6 nm. The gel encapsulating the beta molecular sieve will be transformed into a mesoporous structure with a pore size of 15 to 25 nm. These three structures are combined to form a microsphere carrier with a multi-level pore structure. Among them, the microporous structure provides a high specific surface area, and the mesoporous structure provides a high pore volume. As a result, the silica gel microspheres prepared by the present invention have a high specific surface area while maintaining a high pore volume.

[0045] After the beta molecular sieve is treated with acid, silanol (Si-OH) groups are generated on the surface. In the subsequent gel condensation process, not only the silanol groups in the gel will condense to form Si-O-Si bonds, but also the silanol groups on the surface of the beta molecular sieve will condense with the silanol groups in the gel to form Si-O-Si bonds. Therefore, the silica gel microspheres prepared by the present invention have good strength and are not easy to collapse after being soaked in liquid, which is beneficial to the loading process of the catalyst.

[0046] (3) During the atomization process, carbon dioxide gas diffuses into the droplets to replenish acid, so that the outer layer of the droplets is converted into a gel layer. When the droplets enter the flowing organic solvent, the droplets maintain a dispersed state, and the inside further solidifies into a gel. Therefore, the silica gel microspheres prepared by the present invention have a smooth surface, good sphericity, and good fluidity.

[0047] (4) The present invention divides the acid addition process into four steps: adding acid in the first high-speed stirring mixer, adding acid in the second high-speed stirring mixer, adding acid salt in the third high-speed stirring mixer, and diffusing carbon dioxide gas into the droplets to supplement acid during the atomization process. In the first step, the heat release is large, the viscosity is low, the system is easy to transfer heat, and the temperature is controlled by the cooling jacket; in the second step, the viscosity of the system is greatly improved, the heat transfer capacity is weakened, and the reaction raw materials are pretreated at low temperature to control the temperature rise and avoid gelation; in the third step, the acid salt is used to further slowly reduce the pH value of the system; in the fourth step, the droplets are atomized, and carbon dioxide promotes the formation of atomized particles; in the fifth step, the water absorption effect of n-butanol (or isobutanol) is used to promote further solidification of the microsphere gel; in the sixth step, the acid salt is used, combined with aging and other operation steps, to further deepen the internal pH value adjustment. The entire process control window period is extended, the control difficulty is reduced, and it is easy to achieve industrialization. By finely controlling the pH value and combining high-speed stirring to achieve uniform ingredients, it is ensured that the system is always in a uniform state, and the purpose of microstructure homogenization is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A system for preparing silica gel microspheres used as catalyst carriers in the present invention;

[0049] In the figure, the symbols are: 1 is a mixed solution A storage tank, 2 is a solution B storage tank, 3 is a first metering pump, 4 is a second metering pump, 5 is a first high-speed stirring mixer, 6 is a third metering pump, 7 is a solution D storage tank, 8 is a fourth metering pump, 9 is a second high-speed stirring mixer, 10 is a second solution B storage tank, 11 is a fifth metering pump, 12 is a sixth metering pump, 13 is a third high-speed stirring mixer, 14 is a solution C storage tank, 15 is a seventh metering pump, 16 is an eighth metering pump, 17 is an atomizing nozzle, 18 is a first gas flow controller, 19 is a second gas flow controller, 20 is a gas mixer, and 21 is a container;

[0050] Figure 2 This is an electron microscope photo of a smooth-surfaced silica microsphere prepared according to the method of the present invention, with a magnification of 2000;

[0051] Figure 3 This is an electron microscope photo of commercially available silica microspheres, with a magnification of 300. DETAILED DESCRIPTION

[0052] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0053] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0054] In view of the shortcomings of the traditional method for preparing silica microsphere carriers, the present invention provides a new method for preparing silica microspheres with high specific surface area, high pore volume, good strength and fluidity to meet the requirements of catalyst carriers. Figure 1 The system shown includes a mixed liquid A storage tank 1 and a first solution B storage tank 2. The mixed liquid A storage tank 1 and the first solution B storage tank 2 are respectively connected to a first high-speed stirring mixer 5 through pipelines, and a first metering pump 3 and a second metering pump 4 are respectively provided on the connecting pipelines. The first high-speed stirring mixer 5 is sequentially connected to a third metering pump 6, a solution D storage tank 7, a fourth metering pump 8, and a second high-speed stirring mixer 9 through pipelines. The second solution B storage tank 10 is connected to the second high-speed stirring mixer 9 through a pipeline, and a fifth metering pump 11 is provided on the pipeline. The second high-speed stirring mixer 9 is sequentially connected to a sixth metering pump 12 and a third high-speed stirring mixer 13 through a pipeline. The third high-speed stirring mixer 13 is also connected to a solution C storage tank 14, and a seventh metering pump 15 is provided on the connecting pipeline. The bottom of the third high-speed stirring mixer 13 is connected to an atomizing nozzle 17 through an eighth metering pump 16, and the atomizing nozzle 17 is also connected to a gas mixer 20. The gas mixer 20 is respectively connected to compressed nitrogen through a first gas flow controller 18 and to compressed carbon dioxide through a second gas flow controller 19.

[0055] The method for preparing silica gel microspheres used as catalyst carriers using the above system comprises the following steps:

[0056] (1) Preparation of beta molecular sieve modified powder:

[0057] 11) Soak a commercially available beta molecular sieve having a silicon-aluminum ratio (n(SiO2) / n(Al2O3), molar ratio) of 25-80 and a particle size of less than 1 micron in a 0.5-2% oxalic acid solution, heat to 50-70° C., stir for 0.5-2 hours, and filter; repeat the above process twice;

[0058] 12) Wash the acid-treated beta molecular sieve with deionized water until the washing solution is nearly neutral (pH 6-7);

[0059] 13) Dry the washed beta molecular sieve at 100-140°C and calcine at 450-550°C for more than 1-3 hours.

[0060] (2) High-purity water glass is diluted with deionized water to prepare a dilute water glass solution, and beta molecular sieve modified powder is added thereto, and the mixture is stirred thoroughly to prepare a mixed solution A, which is placed in a mixed solution A storage tank 1 with a cooling device. Sulfuric acid is diluted with deionized water to prepare a sulfuric acid solution B, which is divided into two parts, one of which is placed in a first solution B storage tank 2 with a cooling device, and the other is placed in a second solution B storage tank 10 with a cooling device. Acid salt is dissolved in deionized water to prepare an acid salt solution C, which is placed in a solution C storage tank 14 with a cooling device.

[0061] The amount of the modified beta molecular sieve powder is 1% to 15% of the mass of the high-purity water glass; the sulfuric acid is analytically pure, and the mass fraction of sulfuric acid in the sulfuric acid solution B is 5% to 10%; the acid salt is one of sodium bicarbonate, ammonium bicarbonate, sodium bisulfate, ammonium bisulfate, etc. or a mixture thereof, and the mass fraction of the acid salt in the acid salt solution C is 5% to 10%;

[0062] (3) The mixed solution A and the sulfuric acid solution B in the first solution B storage tank 2 are continuously introduced into the first high-speed stirring mixer 5 with a cooling jacket at a mass flow ratio of 100:25 to 100:50, and are rapidly mixed. After staying for 2 to 10 minutes, the mixed solution is withdrawn from the first high-speed stirring mixer 5 to obtain a mixed solution D. The pH of the mixed solution D is 11 to 13, and the mixed solution D is placed in a solution D storage tank 7 with a cooling device.

[0063] (4) The mixed solution D precooled to -4 to 0°C in the solution D storage tank 7 and the sulfuric acid solution B precooled to -4 to 0°C in the second solution B storage tank 10 are continuously introduced into the second high-speed stirring mixer 9 at a mass flow ratio of 100:10 to 100:25, and are rapidly mixed. After staying for 15 to 60 seconds, the pH value of the obtained material d is 10 to 12, and it flows out to the third high-speed stirring mixer 13 with a cooling device, and is rapidly mixed with the acid salt solution C output from the solution C storage tank 14. The material d and the acid salt solution C flow into the third high-speed stirring mixer 13 at a mass flow ratio of 100:10 to 100:25, and stay for 15 to 60 seconds; the pH value of the obtained mixed solution e is 8 to 10, and it is sprayed from the atomizing nozzle 17 at the bottom of the third high-speed stirring mixer 13, and a high-pressure airflow is sprayed into the atomizing nozzle 17 through the gas mixer 20. Under the shearing action of the high-pressure airflow, atomized droplets E are obtained and placed in a container 21 for receiving the droplets. The atomizing nozzle is a two-fluid nozzle, and the high-pressure airflow is a mixture of nitrogen and carbon dioxide at 2 to 8 bar, wherein the carbon dioxide content is 20% to 100%.

[0064] The container 21 is filled with an organic solvent, and the flowing organic solvent is used to collect and filter the particles F. The organic solvent for collecting the atomized droplets E is water-containing n-butanol or isobutanol, wherein the mass fraction of water is 0.5% to 7%.

[0065] (5) Disperse particles F in an aqueous solution containing n-butanol (mass fraction of n-butanol 0% to 5%), heat to 50 to 70°C, and treat for 15 to 18 hours. Heat to 80 to 90°C, and treat for 3 to 6 hours. Filter to obtain gel-aged particles G. Disperse them in an aqueous solution of oxalic acid with a mass fraction of 0.1 to 1%, the amount of oxalic acid aqueous solution used is 16 to 20 times the mass of gel-aged particles G, stir, heat to 50 to 70°C, and treat for 1 to 2 hours. Repeat this process for more than 3 times, filter, and obtain particles H.

[0066] (6) Disperse the particles H in deionized water, stir, wash, and filter. Repeat this process for more than 6 times until the pH value of the washing water rises to above 5.5, thereby obtaining washed particles I.

[0067] (7) Dispersing the particles I in a low-carbon alcohol, stirring for 24 hours, and filtering to obtain particles J. The low-carbon alcohol is ethanol, isopropanol or n-butanol, and the amount of the low-carbon alcohol is 15 to 25 times the mass of the washed particles I.

[0068] (8) Particles J are dried using supercritical carbon dioxide and sieved using a standard sieve. Particles with a diameter of 10 to 150 μm are selected to obtain particles K. The supercritical carbon dioxide drying pressure is 10 to 20 MPa, the temperature is 40 to 120° C., the carbon dioxide flow rate is 10 to 20 g of carbon dioxide per gram of particle J per hour, and the processing time is 2 to 4 hours.

[0069] (9) Calcination of the particles K by gradient heating: dwelling at 300-400°C for 0.5-1.5 hours, 500-600°C for 1-3 hours, and 600-700°C for 3-6 hours, respectively, with the heating rate and cooling rate controlled at 0.5-1.5°C / min; calcination is carried out in an air atmosphere with an air flow rate of 0.2-2 L of air per gram of particles K per hour; silica gel microspheres are obtained.

[0070] The mass fraction of SiO2 in the obtained silica gel microspheres is greater than 99.9%, the mass fraction of Al2O3 is less than 0.05%, and the mass fraction of Na2O is less than 0.01%.

[0071] The following describes it in detail through specific embodiments.

[0072] Example 1

[0073] (1) Soak a commercially available beta molecular sieve with a silicon-aluminum ratio (n(SiO2) / n(Al2O3), molar ratio) of 28 and a particle size of less than 1 micron in an oxalic acid solution with a mass concentration of 1%, heat to 60°C, stir for 1 hour, and filter; repeat the above process twice. Wash the acid-treated beta molecular sieve with deionized water until the washing solution is nearly neutral (pH 6-7). Dry the washed beta molecular sieve at 120°C and calcine at 500°C for 2 hours to obtain a modified beta molecular sieve powder, and the silicon-aluminum ratio after modification is increased to 60.

[0074] (2) Select high-purity water glass (silicon dioxide mass fraction 29%) with a modulus of 3.1, add 4 times the mass of deionized water to prepare a water glass solution, add 5% of the total mass of the water glass solution to the beta molecular sieve modified powder, put it into the mixed liquid A storage tank 1, stir it continuously to make the materials mixed evenly, and cool it to -2°C to obtain a mixed liquid A.

[0075] Analytical pure sulfuric acid was diluted with deionized water to a mass fraction of 8%, stirred continuously, and cooled to -2°C to obtain sulfuric acid solution B.

[0076] Sodium bicarbonate is dissolved in deionized water to prepare an acid salt solution C with a mass concentration of 8%, which is stored in a solution C storage tank 14 .

[0077] (3) Mixed solution A flows into the first high-speed stirring mixer 5 through the first metering pump 3 at a mass flow rate of 500 g / min; sulfuric acid solution B flows into the first high-speed stirring mixer 5 through the second metering pump 4 at a mass flow rate of 200 g / min; high-speed stirring is performed to fully and continuously mix the mixed solution A and sulfuric acid solution B in the first high-speed stirring mixer 5 to obtain a mixed solution D. The first high-speed stirring mixer 5 is equipped with a cooling device to control the temperature of the mixed solution D to -2°C.

[0078] (4) After the mixed liquid D stays in the first high-speed stirring mixer 5 for 5 minutes, it flows into the solution D storage tank 7 through the third metering pump 6 for temporary storage. The solution D storage tank 7 is equipped with a cooling device to control the temperature of the mixed liquid D to -2°C. The mixed liquid D flows into the second high-speed stirring mixer 9 through the fourth metering pump 8, with a mass flow rate of 700g / min. The sulfuric acid solution B in the second solution B storage tank 10 (cooled to -2°C) flows into the second high-speed stirring mixer 9 through the fifth metering pump 11, with a mass flow rate of 70g / min. The mixed liquid D and the sulfuric acid solution B are stirred and mixed at a high speed in the second high-speed stirring mixer 9. The second high-speed stirring mixer 9 is equipped with a cooling device to control the temperature of the obtained material d to -2°C.

[0079] After the mixed solution D and the mixed material d of the sulfuric acid solution B stay in the second high-speed stirring mixer 9 for 15 seconds, it flows into the third high-speed stirring mixer 13 through the sixth metering pump 12, with a mass flow rate of 770 g / min. The acid salt solution C flows into the third high-speed stirring mixer 13 through the seventh metering pump 15, with a mass flow rate of 77 g / min, and the two are stirred and mixed at a high speed in the third high-speed stirring mixer 13. The third high-speed stirring mixer 13 is equipped with a cooling device, and the temperature is controlled to be -2°C.

[0080] After the mixed liquid stays in the third high-speed stirring mixer 13 for 15 seconds, it enters the atomizing nozzle 17 through the eighth metering pump 16, and under the shearing action of the mixed airflow of 2 bar, atomized droplets E are obtained. The flow rate of the eighth metering pump 16 is 847 g / min. The molar fraction of nitrogen in the mixed airflow is 40%, and the molar fraction of carbon dioxide is 60%.

[0081] n-Butanol with a water content of 5 wt% is placed in a container 21 to receive atomized droplets E. The n-Butanol is continuously stirred and flowed to prevent the droplets from coalescing. After collecting the droplets for 10 minutes, the spraying is stopped. The droplets are stirred in the n-Butanol for 30 minutes to form gel particles F.

[0082] (5) Filter and collect the gel particles F, and disperse them in an aqueous solution containing n-butanol (mass fraction of n-butanol 0% to 5%), and stir. The mass of the aqueous solution is 16 times the mass of the gel particles F. Use dilute sulfuric acid to adjust the pH to 7 to 9, heat to 65°C, and treat for 16 hours. Use dilute sulfuric acid to adjust the pH to 7 to 9 again, heat to 80°C, and treat for 4 hours.

[0083] Filter and collect the gel-aged particles G. Disperse them in a 0.5% oxalic acid aqueous solution (the mass of the oxalic acid aqueous solution is 16 times the mass of the particles F), stir, heat to 65°C, treat for 1 hour, and filter. Repeat the above oxalic acid soaking treatment process twice. Acid-treated particles H are obtained.

[0084] (6) Disperse the acid-treated particles H in deionized water (the mass of the deionized water is 16 times the mass of the particles H), stir, wash, and filter. Repeat this process for more than 6 times until the pH of the washed water rises to above 5.5. Washed particles I are obtained.

[0085] (7) Disperse the washed particles I in isopropanol (the mass of isopropanol is 20 times the mass of the washed particles I), stir for 24 hours, and filter to obtain alcohol foam particles J.

[0086] (8) The alcohol bubble particles J are dried using supercritical carbon dioxide to remove water and organic solvents from the particles. The supercritical carbon dioxide drying pressure is 20 MPa, the temperature is 100°C, the carbon dioxide flow rate is 10 g of carbon dioxide per gram of particles J per hour, and the treatment time is 4 hours. Screening is performed to select particles with a mesh size of 10 to 150 to obtain dry particles K.

[0087] (9) The particles K were dried by calcining in a gradient heating manner: 350°C for 1 hour, 550°C for 2 hours, and 750°C for 4 hours. The heating rate and cooling rate were controlled at 1°C / min. The air flow rate was 0.2L of air per gram of particles K per hour. The desired silica gel microspheres were obtained.

[0088] The test results of specific surface area, pore volume, silica content, etc. are shown in Table 1.

[0089] Example 2

[0090] Immerse commercially available beta molecular sieves with a silicon-aluminum ratio (n(SiO2) / n(Al2O3), molar ratio) of 80 and a particle size of less than 1 micron in a 1% oxalic acid solution, heat to 60°C, stir for 1 hour, and filter; repeat the above process twice. Wash the acid-treated beta molecular sieve with deionized water until the washing solution is nearly neutral (pH 6-7). Dry the washed beta molecular sieve at 120°C and calcine at 500°C for 2 hours to obtain a modified beta molecular sieve powder, and the silicon-aluminum ratio after modification is increased to 100.

[0091] Select high-purity water glass (silicon dioxide mass fraction 25%) with a modulus of 3.5, add 3.5 times the mass of deionized water to prepare a water glass solution, add 15% of the total mass of the water glass solution beta molecular sieve modified powder, put it into mixed liquid A storage tank 1, stir it continuously to make the materials mix evenly, and cool it to -4°C to obtain mixed liquid A.

[0092] Analytical pure sulfuric acid was diluted with deionized water to a mass fraction of 10%, stirred sufficiently and continuously, and cooled to -4°C to obtain sulfuric acid solution B.

[0093] Ammonium bisulfate is dissolved in deionized water to prepare an acid salt solution C with a mass concentration of 10%, which is stored in a solution C storage tank 14 .

[0094] The mixed solution A flows into the first high-speed stirring mixer 5 through the first metering pump 3 at a mass flow rate of 500 g / min; the sulfuric acid solution B flows into the first high-speed stirring mixer 5 through the second metering pump 4 at a mass flow rate of 250 g / min; the mixed solution A and the sulfuric acid solution B are stirred at high speed to be fully and continuously mixed in the first high-speed stirring mixer 5 to obtain a mixed solution D. The first high-speed stirring mixer 5 is equipped with a cooling device to control the temperature of the mixed solution D to -4°C.

[0095] After the mixed liquid D stays in the first high-speed stirring mixer 5 for 2 minutes, it flows into the solution D storage tank 7 through the third metering pump 6 for temporary storage. The solution D storage tank 7 is equipped with a cooling device to control the temperature of the mixed liquid D to -4°C. The mixed liquid D flows into the second high-speed stirring mixer 9 through the fourth metering pump 8, with a mass flow rate of 750g / min. The sulfuric acid solution B in the second solution B storage tank 10 flows into the second high-speed stirring mixer 9 through the fifth metering pump 11, with a mass flow rate of 75g / min. The mixed liquid D and the sulfuric acid solution B are stirred and mixed at a high speed in the second high-speed stirring mixer 9. The second high-speed stirring mixer 9 is equipped with a cooling device to control the temperature of the obtained material d to -4°C.

[0096] After the mixed solution D and the mixed material d of the sulfuric acid solution B stay in the second high-speed stirring mixer 9 for 60 seconds, it flows into the third high-speed stirring mixer 13 through the sixth metering pump 12, with a mass flow rate of 825 g / min. The acid salt solution C flows into the third high-speed stirring mixer 13 through the seventh metering pump 15, with a mass flow rate of 206 g / min, and the two are stirred and mixed at a high speed in the third high-speed stirring mixer 13. The third high-speed stirring mixer 13 is equipped with a cooling device, and the temperature is controlled to be -4°C.

[0097] After the mixed liquid stays in the third high-speed stirring mixer 13 for 60 seconds, it enters the atomizing nozzle 17 through the eighth metering pump 16, and under the shearing action of the mixed airflow of 8 bar, atomized droplets E are obtained. The flow rate of the eighth metering pump 16 is 1031 g / min. The molar fraction of nitrogen in the mixed airflow is 80%, and the molar fraction of carbon dioxide is 20%.

[0098] Isobutanol with a water content of 7 wt% was used to receive the droplets E. The isobutanol was continuously stirred and flowed to prevent the droplets from coalescing. After collecting the droplets for 10 minutes, the spraying was stopped. The droplets were stirred in the isobutanol for 30 minutes to form gel particles F.

[0099] Filter and collect gel particles F, and disperse them in an aqueous solution containing n-butanol (mass fraction of n-butanol 0% to 5%), and stir. The mass of the aqueous solution is 16 times the mass of gel particles F. Use dilute sulfuric acid to adjust the pH to 7-9, and heat to 50°C for 16 hours. Use dilute sulfuric acid to adjust the pH to 7-9 again, and heat to 90°C for 4 hours.

[0100] Filter and collect the gel-aged particles G. Disperse them in a 0.5% oxalic acid aqueous solution (the mass of the oxalic acid aqueous solution is 20 times the mass of the particles F), stir, heat to 50°C, treat for 2 hours, and filter. Repeat the above oxalic acid soaking treatment process twice. Acid-treated particles H are obtained.

[0101] The acid-treated particles H are dispersed in deionized water (the mass of the deionized water is 16 times the mass of the particles G), stirred, washed, and filtered. This process is repeated for more than 6 times until the pH of the washed water rises to above 5.5. Washed particles I are obtained.

[0102] The washed particles I were dispersed in ethanol (the mass of ethanol was 20 times the mass of particles H), stirred for 24 hours, and filtered to obtain alcohol foam particles I.

[0103] The alcohol bubble particles I are dried using supercritical carbon dioxide to remove water and organic solvents from the particles. The supercritical carbon dioxide drying pressure is 10 MPa, the temperature is 120°C, the carbon dioxide flow rate is 10 g of carbon dioxide per gram of particles I per hour, and the processing time is 2 hours. Use a standard sieve for sieving. Select particles with a diameter between 10 and 150 microns to obtain dry particles J.

[0104] Particles J were dried by calcining in a gradient heating manner: 350°C for 1 hour, 550°C for 2 hours, and 750°C for 4 hours. The heating rate and cooling rate were controlled at 1°C / min. The air flow rate was 2L of air per gram of silica gel particles per hour. The desired silica gel microspheres were obtained.

[0105] The test results of specific surface area, pore volume, silica content, etc. are shown in Table 1.

[0106] Example 3

[0107] Select high-purity water glass with a modulus of 3.7, add 3 times the mass of deionized water, add 1% of the total mass of the water glass solution beta molecular sieve modified powder (the treatment method is the same as Example 2), put it into the mixed liquid A storage tank 1, stir it continuously to make the materials mix evenly, and cool it to 0°C to obtain a mixed liquid A.

[0108] Analytical pure sulfuric acid was diluted with deionized water to a mass fraction of 9%, stirred sufficiently and continuously, and cooled to 0° C. to obtain sulfuric acid solution B.

[0109] Sodium bisulfate is dissolved in deionized water to prepare an acid salt solution C with a mass concentration of 10%, which is stored in a solution C storage tank 14 .

[0110] The mixed solution A flows into the first high-speed stirring mixer 5 through the first metering pump 3 at a mass flow rate of 500 g / min; the sulfuric acid solution B flows into the first high-speed stirring mixer 5 through the second metering pump 4 at a mass flow rate of 220 g / min; the mixed solution A and the sulfuric acid solution B are stirred at high speed to be fully and continuously mixed in the first high-speed stirring mixer 5 to obtain a mixed solution D. The first high-speed stirring mixer 5 is equipped with a cooling device to control the temperature of the mixed solution D to be 0°C.

[0111] After the mixed liquid D stays in the first high-speed stirring mixer 5 for 10 minutes, it flows into the solution D storage tank 7 through the third metering pump 6 for temporary storage. The solution D storage tank 7 is equipped with a cooling device to control the temperature of the mixed liquid D to 0°C. The mixed liquid D flows into the second high-speed stirring mixer 9 through the fourth metering pump 8, with a mass flow rate of 720g / min. The sulfuric acid solution B (cooled to 0°C) in the second solution B storage tank 10 flows into the second high-speed stirring mixer 9 through the fifth metering pump 11, with a mass flow rate of 180g / min. The mixed liquid D and the sulfuric acid solution B are stirred and mixed at a high speed in the second high-speed stirring mixer 9. The second high-speed stirring mixer 9 is equipped with a cooling device to control the temperature of the obtained material d to 0°C.

[0112] After the mixed solution D and the mixed material d of the sulfuric acid solution B stay in the second high-speed stirring mixer 9 for 15 seconds, it flows into the third high-speed stirring mixer 13 through the sixth metering pump 12, with a mass flow rate of 900 g / min. The acid salt solution C flows into the third high-speed stirring mixer 13 through the seventh metering pump 15, with a mass flow rate of 225 g / min, and the two are stirred and mixed at a high speed in the third high-speed stirring mixer 13. The third high-speed stirring mixer 13 is equipped with a cooling device, and the temperature is controlled to be 0°C.

[0113] After the mixed liquid stays in the third high-speed stirring mixer 13 for 15 seconds, it enters the atomizing nozzle 17 through the eighth metering pump 16, and under the shearing action of the mixed airflow at 3 bar, atomized droplets E are obtained. The flow rate of the eighth metering pump 16 is 1125 g / min. The molar fraction of nitrogen in the mixed airflow is 0%, and the molar fraction of carbon dioxide is 100%.

[0114] n-Butanol with a water content of 5 wt% is placed in a container 21 to receive the droplets E. The n-Butanol is continuously stirred and flowed to prevent the droplets from coalescing. After collecting the droplets for 10 minutes, the spraying is stopped. The droplets are stirred in the n-Butanol for 30 minutes to form gel particles F.

[0115] Filter and collect gel particles F. Disperse them in an aqueous solution containing n-butanol (mass fraction of n-butanol 0% to 5%) and stir. The mass of deionized water is 16 times the mass of gel particles F. Use dilute sulfuric acid to adjust the pH to 7-9, heat to 70°C, and treat for 16 hours. Use dilute sulfuric acid to adjust the pH to 7-9 again, heat to 90°C, and treat for 4 hours.

[0116] Filter and collect the gel-aged particles G. Disperse them in a 0.5% oxalic acid aqueous solution (the mass of the oxalic acid aqueous solution is 20 times the mass of the particles G), stir, heat to 70°C, treat for 2 hours, and filter. Repeat the above oxalic acid soaking treatment process twice. Acid-treated particles H are obtained.

[0117] The acid-treated particles H are dispersed in deionized water (the mass of the deionized water is 16 times the mass of the particles G), stirred, washed, and filtered. This process is repeated for more than 6 times until the pH of the washed water rises to above 5.5. Washed particles I are obtained.

[0118] The washed particles I were dispersed in isopropanol (the mass of isopropanol was 20 times the mass of particles I), stirred for 24 hours, and filtered to obtain alcohol foam particles J.

[0119] The alcohol bubble particles J were dried using supercritical carbon dioxide to remove water and organic solvents from the particles. The supercritical carbon dioxide drying pressure was 15 MPa, the temperature was 110°C, the carbon dioxide flow rate was 5 g of carbon dioxide per gram of particles J per hour, and the treatment time was 3 hours. Screening was performed to select particles with mesh sizes of 10 to 150 to obtain dried particles K.

[0120] Particle K was calcined and dried in a gradient heating method: 350°C for 1 hour, 550°C for 2 hours, and 750°C for 4 hours. The heating rate and cooling rate were controlled at 1°C / min. The air flow rate was 1L of air per gram of silica gel particles per hour. The desired silica gel microspheres were obtained. The test results of specific surface area, pore volume, silica content, etc. are shown in Table 1.

[0121] Example 4

[0122] Immerse commercially available beta molecular sieves with a silicon-aluminum ratio (n(SiO2) / n(Al2O3), molar ratio) of 50 and a particle size of less than 1 micron in a 1% oxalic acid solution, heat to 60°C, stir for 1 hour, and filter; repeat the above process twice. Wash the acid-treated beta molecular sieve with deionized water until the washing solution is nearly neutral (pH 6-7). Dry the washed beta molecular sieve at 120°C and calcine at 500°C for 2 hours to obtain a modified beta molecular sieve powder, and the silicon-aluminum ratio after modification is increased to 80.

[0123] Select high-purity water glass (silicon dioxide mass fraction 27.6%) with a modulus of 3.5, add 4 times the mass of deionized water, add 8% mass of beta molecular sieve modified powder, put it into mixed liquid A storage tank 1, stir it continuously to mix the materials evenly, and cool it to -3°C to obtain mixed liquid A.

[0124] Analytical pure sulfuric acid was diluted with deionized water to a mass fraction of 8%, stirred continuously, and cooled to -3°C to obtain sulfuric acid solution B.

[0125] Ammonium bicarbonate is dissolved in deionized water to prepare an acid salt solution C with a mass concentration of 10%, which is stored in a solution C storage tank 14 .

[0126] The mixed solution A flows into the first high-speed stirring mixer 5 through the first metering pump 3 at a mass flow rate of 400 g / min; the sulfuric acid solution B flows into the first high-speed stirring mixer 5 through the second metering pump 4 at a mass flow rate of 200 g / min; the mixed solution A and the sulfuric acid solution B are stirred at high speed to be fully and continuously mixed in the first high-speed stirring mixer 5 to obtain a mixed solution D. The first high-speed stirring mixer 5 is equipped with a cooling device to control the temperature of the mixed solution D to -3°C.

[0127] After the mixed solution D stays in the first high-speed stirring mixer 5 for 5 minutes, it flows into the solution D storage tank 7 through the third metering pump 6 for temporary storage. The solution D storage tank 7 is equipped with a cooling device to control the temperature of the mixed solution D to -3°C. The mixed solution D flows into the second high-speed stirring mixer 9 through the fourth metering pump 8, with a mass flow rate of 600g / min. The sulfuric acid solution B in the second solution B storage tank 10 flows into the second high-speed stirring mixer 9 through the fifth metering pump 11, with a mass flow rate of 60g / min. The mixed solution D and the sulfuric acid solution B are stirred and mixed at a high speed in the second high-speed stirring mixer 9. The second high-speed stirring mixer 9 is equipped with a cooling device to control the temperature to -3°C.

[0128] After the mixed solution D and the mixed material d of the sulfuric acid solution B stay in the second high-speed stirring mixer 9 for 15 seconds, it flows into the third high-speed stirring mixer 13 through the sixth metering pump 12, with a mass flow rate of 660 g / min. The acid salt solution C flows into the third high-speed stirring mixer 13 through the seventh metering pump 15, with a mass flow rate of 140 g / min, and the two are stirred and mixed at a high speed in the third high-speed stirring mixer 13. The third high-speed stirring mixer 13 is equipped with a cooling device, and the temperature is controlled to be -3°C.

[0129] After the mixed liquid stays in the third high-speed stirring mixer 13 for 15 seconds, it enters the nozzle through the eighth metering pump 16 and is sheared by the mixed airflow at 6 bar to obtain atomized droplets E. The flow rate of the eighth metering pump 16 is 800 g / min. The molar fraction of nitrogen in the mixed airflow is 50%, and the molar fraction of carbon dioxide is 50%.

[0130] n-Butanol with a water content of 1 wt% is placed in a container 21 to receive the droplets E. The n-Butanol is continuously stirred and flowed to prevent the droplets from coalescing. After collecting the droplets for 10 minutes, the spraying is stopped. The droplets are stirred in the n-Butanol for 30 minutes to form gel particles F.

[0131] Filter and collect gel particles F. Disperse them in an aqueous solution containing n-butanol (mass fraction of n-butanol 0% to 5%) and stir. The mass of deionized water is 16 times the mass of gel particles F. Use dilute sulfuric acid to adjust the pH to 7 to 9, heat to 60°C, and treat for 16 hours. Use dilute sulfuric acid to adjust the pH to 7 to 9 again, heat to 85°C, and treat for 4 hours.

[0132] Filter and collect the gel-aged particles G. Disperse them in a 0.5% oxalic acid aqueous solution (the mass of the oxalic acid aqueous solution is 18 times the mass of the particles G), stir, heat to 60°C, treat for 2 hours, and filter. Repeat the above oxalic acid soaking treatment process twice. Acid-treated particles H are obtained.

[0133] The acid-treated particles H are dispersed in deionized water (the mass of the deionized water is 16 times the mass of the particles H), stirred, washed, and filtered. This process is repeated for more than 6 times until the pH of the washed water rises to above 5.5. Washed particles I are obtained.

[0134] The washed particles I were dispersed in isopropanol (the mass of isopropanol was 20 times the mass of particles I), stirred for 24 hours, and filtered to obtain alcohol foam particles J.

[0135] The alcohol bubble particles J were dried with supercritical carbon dioxide to remove water and organic solvents from the particles. The supercritical carbon dioxide drying pressure was 15 MPa, the temperature was 100°C, the carbon dioxide flow rate was 2 g of carbon dioxide per gram of particles J per hour, and the treatment time was 4 hours. Screening was performed to select particles with mesh sizes of 10 to 150 to obtain dried particles K.

[0136] Particles K were dried by roasting in a gradient heating method. They were kept at 350°C for 1 hour, 550°C for 2 hours, and 750°C for 4 hours. The heating rate and cooling rate were controlled at 1°C / min. The air flow rate was 0.5L of air per gram of silica gel particles per hour. The desired silica gel microspheres were obtained.

[0137] The test results of specific surface area, pore volume, silica content, etc. are shown in Table 1.

[0138] Comparative Example 1

[0139] The process is the same as in Example 1, except that the organic solvent n-butanol used to collect the atomized droplets E in the container 21 in step 4 is replaced with deionized water. The pore volume of the obtained silica microspheres decreases significantly. See Table 1 for details.

[0140] Comparative Example 2

[0141] The process is the same as in Example 1, except that step 7 is omitted, and the washed silica gel particles I are directly dried and calcined with supercritical carbon dioxide. The pore volume of the obtained silica gel microspheres decreases significantly. See Table 1 for details.

[0142] Comparative Example 3

[0143] The process is the same as in Example 1, except that the supercritical carbon dioxide drying in step 8 is replaced by conventional oven drying. The pore volume of the obtained silica gel microspheres is greatly reduced. See Table 1 for details.

[0144] Comparative Example 4

[0145] Commercially available silica gel microspheres are selected from the commercially available silica gel model Davison 955 produced by Grace Company.

[0146] Table 1 Silica gel carrier physical property test data

[0147]

[0148] The specific surface area, pore volume, SiO2 content and abrasion rate in Table 1 are measured according to the reference standard "Silica gel test method HG / T2765.5-2005".

[0149] It can be seen from the above table that the silica gel microspheres prepared in Examples 1-4 all have a high specific surface area while maintaining a high pore volume.

[0150] In comparative example 1, after the organic solvent n-butanol for collecting the atomized droplets E in Example 1 was replaced with deionized water, the pore volume of the obtained silica gel microspheres was greatly reduced, resulting in a smaller average pore size, which would affect the subsequent mass transfer performance inside the catalyst particles.

[0151] Comparative Examples 2 and 3 omitted a certain step of the present invention, and both resulted in a significant decrease in the pore volume of the obtained silica microspheres, which proves that each step of the present invention is very important and can work synergistically to obtain silica microspheres having both a high specific surface area and a high pore volume.

[0152] The electron microscope photo of the silica microspheres obtained in Example 1 is shown in Figure 2 As can be seen from the figure, the surface of the silica gel microspheres prepared by the method of the present invention is smooth. Figure 3 ), it can be seen that the silica gel microspheres prepared by the method of the present invention still show a smooth surface when magnified 2000 times, while the commercially available silica gel microspheres can still be seen to have a rough surface even when magnified 300 times. It can be seen that the silica gel microspheres prepared by the present invention have a smooth surface, good sphericity, good fluidity, and good particle strength (a small wear rate represents a high strength).

[0153] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing silica gel microspheres used as catalyst carriers, characterized in that: The following steps are involved: (1) adding beta molecular sieve modified powder to water glass solution and stirring thoroughly to obtain mixed solution A; and mixing the mixed solution with sulfuric acid solution B at high speed to obtain mixed solution D; (2) The mixed liquid D precooled to -4 to 0°C is rapidly mixed with another sulfuric acid solution B precooled to -4 to 0°C, and the obtained material d is rapidly mixed with the acid salt solution C. The obtained mixed liquid e is sheared by a high-pressure airflow to obtain atomized droplets E; the droplets are collected and filtered using a flowing organic solvent to obtain particles F; (3) Particles F are dispersed in an aqueous solution of n-butanol and then aged to obtain gel-aged particles G, which are dispersed in an aqueous solution of oxalic acid, stirred, heated to 50-70° C., treated for 1-2 hours, and filtered to obtain particles H; (4) dispersing the particles H in deionized water, stirring, washing, and filtering to raise the pH value of the washing water to above 5.5 to obtain washed particles I; (5) dispersing particle I in low-carbon alcohol, stirring for 24 hours, filtering to obtain particle J, drying with supercritical carbon dioxide, and sieving to select particles with a diameter of 10 to 150 μm to obtain particle K; (6) calcining the particles K in a gradient temperature increasing manner to obtain silica gel microspheres.

2. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The beta molecular sieve modified powder described in step (1) is prepared by the following method: The beta molecular sieve is soaked in an oxalic acid solution, heated to 50-70°C, stirred for 0.5-2 hours, and filtered; the above process is repeated multiple times; the obtained acid-treated beta molecular sieve is washed until the washing solution is nearly neutral, and then dried and calcined to obtain the beta molecular sieve modified powder.

3. The method for preparing silica gel microspheres used as catalyst carriers according to claim 2, characterized in that: The beta molecular sieve is a commercially available beta molecular sieve with a silicon-aluminum ratio of 25 to 80:1 and a particle size of less than 1 micron; The mass concentration of the oxalic acid solution is 0.5-2%; The washed beta molecular sieve has a drying temperature of 100-140°C, a calcination temperature of 450-550°C, and a calcination time of 1-3h.

4. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The water glass solution described in step (1) is prepared by adding high-purity water glass to deionized water, wherein the amount of deionized water is 3 to 4 times the mass of the high-purity water glass; The high-purity water glass has a modulus of 3.1 to 3.7, a silicon dioxide mass fraction of 25% to 29%, wherein the impurity iron oxide mass fraction is less than 0.005%, and the impurity aluminum oxide mass fraction is less than 0.07%.

5. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The amount of modified beta molecular sieve powder in the mixed solution A is 1% to 15% of the mass of water glass; The mass fraction of the sulfuric acid solution B is 5% to 10%; The mass fraction of the acid salt solution C is 5% to 10%; The acid salt used in the acid salt solution C is selected from sodium bicarbonate, ammonium bicarbonate, sodium bisulfate, ammonium bisulfate or a mixture thereof.

6. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The mixed solution A and the sulfuric acid solution B in step (1) are continuously introduced into a first high-speed stirring mixer (5) with a cooling jacket at a mass flow ratio of 100:25 to 100:50, and are stirred and mixed at high speed for 2 to 10 minutes; the pH of the mixed solution D is 11 to 13.

7. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The mixed solution D and the sulfuric acid solution B in step (2) are continuously introduced into the second high-speed stirring mixer (9) at a mass flow ratio of 100:10 to 100:25, and mixed rapidly for 15 to 60 seconds, and the pH of the mixed material is 10 to 12; The material d and the acid salt solution C are continuously introduced into a high-speed stirring mixer (3) at a mass flow ratio of 100:10 to 100:25, and mixed rapidly for 15 to 60 seconds. The pH value of the obtained mixed solution e is 8 to 10, and the mixed solution is sprayed out from an atomizing nozzle at the bottom of the high-speed stirring mixer (3) to obtain atomized droplets E under the shearing action of a high-pressure airflow.

8. The method for preparing silica gel microspheres used as catalyst carriers according to claim 7, characterized in that: The atomizing nozzle is a two-fluid nozzle, and the high-pressure gas flow is a mixture of nitrogen and carbon dioxide at 2 to 8 bar, wherein the carbon dioxide content is 20% to 100%; The organic solvent for collecting the atomized droplets E is n-butanol or isobutanol containing water, wherein the mass fraction of water is 0.5% to 7%.

9. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: Step (3) The mass fraction of the aqueous solution of n-butanol is 0% to 5%; The aging process is: firstly heating to 50-70°C for 15-18 hours, then heating to 80-90°C for 3-6 hours; The mass fraction of oxalic acid in the oxalic acid aqueous solution is 0.1-1%, and the amount of the oxalic acid aqueous solution is 16-20 times the mass of the gel-aged particles G; The low-carbon alcohol described in step (4) is ethanol, isopropanol or n-butanol, and the amount of the low-carbon alcohol used is 15 to 25 times the mass of the water-washed particles I. The supercritical carbon dioxide drying in step (5) is performed at a pressure of 10 to 20 MPa, a temperature of 40 to 120° C., a carbon dioxide flow rate of 10 to 20 g of carbon dioxide per gram of particles J per hour, and a processing time of 2 to 4 hours.

10. The method for preparing silica gel microspheres used as catalyst carriers according to claim 1, characterized in that: The gradient heating method of step (6) is to stay at 300-400°C for 0.5-1.5 hours, 500-600°C for 1-3 hours, and 600-700°C for 3-6 hours, respectively, and the heating rate and cooling rate are controlled at 0.5-1.5°C / min; The calcination is carried out in an air atmosphere, and the air flow rate is 0.2 to 2 L of air per gram of particle K per hour; The silica gel microspheres have a SiO2 mass fraction greater than 99.9%, an Al2O3 mass fraction less than 0.05%, and a Na2O mass fraction less than 0.01%.

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