CN116474840A - Spherical silicon-aluminum carrier and preparation method thereof - Google Patents

Abstract

The invention discloses a spherical silicon-aluminum carrier and a preparation method thereof. The preparation method of the spherical silicon-aluminum carrier comprises the following steps: adding a curing agent solution, an emulsifying agent, a polyol and an organic phase into the silicon-containing pseudo-boehmite sol respectively, stirring, adding water to prepare an oil-in-water (O/W) emulsion, dripping into an oil column for molding, washing, drying and roasting to obtain the spherical silicon-aluminum carrier. The spherical silicon-aluminum carrier prepared by the method has the characteristics of good roundness, low bulk density, high crushing strength and the like, can be used as a noble metal catalyst carrier, has no pollutant discharge, has no environmental pollution and is low in cost.

Description

A kind of spherical silica-alumina carrier and preparation method thereof

technical field

The invention relates to a spherical silica-alumina carrier and a preparation method thereof, in particular to a spherical silica-alumina carrier suitable for ebullating beds and noble metal catalysts and a preparation method thereof.

Background technique

The shape and size of the catalyst particles are generally determined according to the requirements of the reactor used in industrial production. At present, there are four types of reactors commonly used in industry: fixed bed, fluidized bed (ebullating bed), suspended bed and moving bed. Spherical, cylindrical, clover, four-leaf clover and sheet catalysts are commonly used in fixed bed reactors. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use spherical or strip-shaped catalysts with smaller particles.

The spherical catalyst has the advantages of good flow performance, high filling factor, uniform fluid distribution, low resistance, and small pressure drop, and is widely used in the technology of producing olefins from low-carbon alkanes by dehydrogenation.

At present, the catalysts for the dehydrogenation of light alkanes to olefins are mainly prepared by γ-Al ₂ O ₃ carrier supporting the active component Pt and other additives, such as EP100222A, CN1185994A and so on. However, because dehydrogenation reactions are reacted at a high temperature of about 600 ° C. The high reaction temperature often causes a large amount of carbon accumulation on the catalyst. As the catalyst uses time, it is necessary to perform multiple high-temperature charcoal regeneration treatment of catalysts. As a result, the γ-AL ₂ O ₃ carriers are prone to sintering and alpha-phase transformation, which greatly reduces the carrier than the surface area. Destruction, and then catalyst activity components gather, and the catalyst activity has severely decreased. Therefore, it is necessary to further modify the γ-Al ₂ O ₃ vehicles, so that the catalyst has higher thermal stability.

CN112973771A discloses a spherical catalyst carrier containing molecular sieve and alumina and its preparation and application. The catalyst carrier is a sol obtained by precipitating an inorganic aluminum salt through ammonia water and acidifying it, adding a mixed solution of ball-milled pseudoboehmite and molecular sieve and a sol modification aid to the sol, and then dropping balls into an oil ammonia column to form and age them, and finally washing, drying, and calcining to obtain composite pellets with high strength and large specific surface area. Doping with molecular sieves can also lead to a decrease in support strength.

CN105478100A discloses a method for preparing silicon-containing γ-Al ₂ O ₃ pellets.该方法是用拟薄水铝石干胶粉和去离子水搅拌并浆化，加入稀硝酸酸化，再加入尿素和预定量的硅酸钠溶液，搅拌5小时，加入煤油和脂肪醇聚氧乙烯醚搅拌5小时，在油氨柱内滴球成型，湿球在氨水中固化2 小时，然后过滤，用去离子水冲洗、干燥、焙烧，得含硅的γ-Al ₂ O ₃小球，该方法制备过程中硅源采用硅酸钠溶液，其Na ⁺很难洗涤，易作为杂质带入载体中，影响催化剂性能，同时其在油氨柱内滴球成型，湿球在氨水中固化也不利于操作，对环境造成污染。

CN104289220A discloses a preparation method and application of a high thermal stability low-carbon alkane dehydrogenation catalyst.该载体制备方法是将铝源加入至碱性水溶液中，搅拌，继续滴加碱性水溶液将混合溶液的pH调制7～14，过滤，去离子水洗涤后加入稀硝酸形成溶胶，再加入硅源，搅拌，过滤，陈化10～48小时，滴球成型，然后干燥、焙烧，得到含Si元素的γ-Al ₂ O ₃小球；或者是将铝源加入至碱性水溶液中，搅拌，继续滴加碱性水溶液将混合溶液的pH调制7～14，过滤，去离子水洗涤后加入稀硝酸形成溶胶，搅拌，过滤，陈化10～48小时，滴球成型，然后干燥、焙烧，得到γ-Al ₂ O ₃小球，然后将γ-Al ₂ O ₃小球在60～120℃下浸渍硅源的水溶液或乙醇溶液2～6小时，然后干燥、焙烧，得到含Si元素的γ-Al ₂ O ₃小球。 The disadvantage of this method is that the preparation cycle is long and the process is complicated. At the same time, if the inorganic silicon source used is difficult to wash, Na ⁺ is easily carried into the carrier as an impurity, affecting the performance of the catalyst, and the organic silicon source will pollute the environment.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a spherical silica-alumina carrier and a preparation method thereof. The spherical silica-alumina carrier prepared by the method has the characteristics of good roundness, low bulk density, high crushing strength, etc., and is suitable for being used as a noble metal catalyst carrier. The process has no discharge of pollutants, no environmental pollution, and low cost.

The first aspect of the present invention provides a method for preparing a spherical silica-alumina carrier, comprising:

Add curing agent solution, emulsifier, polyol and organic phase to silicon-containing pseudo-boehmite sol respectively, add water under stirring to prepare oil-in-water (O/W) emulsion, then drop into oil column to form, wash, dry and roast to obtain spherical silica-alumina carrier.

Further, the preparation method of the silicon-containing pseudo-boehmite sol includes:

(1) Add the first alkaline solution into the first reaction kettle, feed the mixed gas containing carbon dioxide to react, so that the pH value of the system is 2 to 4;

(2) adding bottom water in the second reaction kettle, heating to the reaction temperature, then the second alkaline solution and the material obtained in step (1) are fed into the second reaction kettle in parallel and reacted;

(3) Aging the slurry obtained after the reaction in step (2), filtering and washing after aging to obtain a silicon-containing pseudo-boehmite wet filter cake;

(4) adding water to the wet filter cake obtained in step (3) to make a slurry, and then adding a peptizer for peptization to obtain a silicon-containing pseudo-boehmite sol.

Further, in step (1), the first alkaline solution is a mixed solution of water glass and aluminum-containing alkaline solution; the aluminum-containing alkaline solution is one or both of sodium metaaluminate solution or potassium metaaluminate solution, preferably sodium metaaluminate solution. The modulus of the water glass is 2.5-3.0, and the caustic ratio of the sodium metaaluminate solution or potassium metaaluminate solution is 1.35-1.65.

Further, in step (1), the concentration of water glass in the first alkaline solution is 5-90 gSiO ₂ /L in terms of SiO ₂ , and the concentration of sodium metaaluminate and/or potassium meta-aluminate in the mixed solution is 10-30 gAl ₂ O ₃ /L in terms of Al ₂ O ₃ .

Further, in step (1), the volume of the first alkaline solution added to the first reactor is 2/3 to 3/4 of the volume of the first reactor; the volume fraction of carbon dioxide in the mixed gas containing carbon dioxide is 30% to 70%; the mixed gas containing carbon dioxide is a mixed gas of carbon dioxide and air.

Further, in step (1), the initial reaction temperature of introducing the mixed gas containing carbon dioxide for the reaction is 15-65°C. The reaction is an exothermic reaction, and the temperature of the system gradually rises. The whole reaction process does not need to be cooled to keep the temperature low. Generally, the temperature of the slurry is 40-75°C at the end of the reaction.

Further, in step (2), the second alkaline solution is one or both of sodium metaaluminate solution or potassium metaaluminate solution, preferably sodium metaaluminate solution; the concentration of the sodium metaaluminate solution and/or potassium _{metaaluminate} is 130-350 g Al ₂ O ₃ /L, preferably 150-250 g Al ₂ O 3 /L in terms of Al ₂ O ₃ . The caustic ratio of the second alkaline solution is 1.10-1.40, preferably 1.15-1.35.

Further, in step (2), the bottom water added to the second reactor is 1/10-1/5 of the volume of the second reactor.

Further, in the step (2), the materials obtained in the step (1) are added into the second reaction kettle, and the time for adding the materials is controlled to be 60-150 minutes.

Further, in step (2), the second alkaline solution and the material obtained in step (1) are fed into the second reaction kettle in parallel to react, and the pH value is controlled to be 7.5-9.0.

Further, in step (2), the reaction temperature of the reaction is 40°C-70°C, preferably 45°C-65°C.

Further, in step (2), the reaction is carried out under stirring.

Further, in step (3), the aging conditions are as follows: the temperature is 50° C. to 95° C., and the time is 30 minutes to 120 minutes.

Further, in step (3), the washing can be done using conventional washing methods in the art, preferably using deionized water at 50°C to 80°C until neutral.

Further, in step (3), the solid content of the obtained silicon-containing pseudo-boehmite wet filter cake is 35wt%-45wt%.

Further, in the step (4), the wet filter cake obtained in the step (3) is mixed with water and beaten to obtain a slurry; the peptizer is one or more of nitric acid, acetic acid, and citric acid, preferably nitric acid; the mass concentration of the peptizer is 50% to 70%.

Further, in step (4), the peptizing agent is added in an amount of 1 wt % to 10 wt %, preferably 2 wt % to 8 wt %, of the solid content of the silicon-containing pseudoboehmite wet filter cake.

Further, in step (4), the solid content of the silicon-containing pseudo-boehmite sol is 30wt%-35wt%.

Further, in the preparation method of the spherical silica-alumina carrier, the curing agent solution is a solution of one or more of hexamethylenetetramine and urea, preferably a hexamethylenetetramine solution; the mass concentration of the curing agent solution is 30% to 50%; the amount of the curing agent added is 1wt% to 15wt% of the solid content of the silicon-containing pseudoboehmite sol, preferably 2.5wt% to 12wt%.

Further, in the preparation method of the spherical silica-alumina carrier, the emulsifier is a non-ionic emulsifier, specifically selected from at least one of polyoxyethylene sorbitan monolaurates and fatty alcohol polyoxyethylene ethers; the hydrophilic-lipophilic balance (HLB) of the emulsifier is 13-20, preferably 15-18, and the amount of the emulsifier added is 0.2wt% to 2.0wt% of the solid content of the silicon-containing pseudo-boehmite sol, preferably 0.5wt %～1.5wt%.

Further, in the preparation method of the spherical silica-alumina carrier, the polyhydric alcohol is one or more of 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,2-propanediol, 1-pentanol, polyethylene glycol (400), and the addition amount of the polyhydric alcohol is 0.1wt% to 1.0wt% of the solid content of the silicon-containing pseudoboehmite sol, preferably 0.2wt% to 0.8wt%.

Further, in the preparation method of the spherical silica-alumina carrier, the organic phase is one or more of white oil or diesel oil; the amount of the organic phase added is 7.0wt% to 13.0wt% of the solid content in the silicon-containing pseudoboehmite sol, preferably 7.5wt% to 12.5wt%.

Further, in the preparation method of the spherical silica-alumina carrier, the mass of the water added is 0.5-1.5 times the solid content of the silicon-containing pseudo-boehmite sol.

Further, in the preparation method of the spherical silica-alumina carrier, the stirring speed is 1000-4000 rpm; the mass content of alumina in the oil-in-water (O/W) emulsion is 15%-25%.

Further, in the preparation method of the spherical silica-alumina carrier, the medium oil used in the oil column is one of white oil or diesel oil, preferably white oil, and the kinematic viscosity of the white oil at 40°C is 20-40 mm ² /s, preferably 25-35 mm ² /s; the molding temperature is 90°C-110°C, preferably 95°C-105°C.

Further, in the preparation method of the spherical silica-alumina carrier, the molding is carried out in an oil column, and the oil-in-water emulsion is dropped into the oil column, and the inner diameter of the dropper used is 0.4mm-2.0mm.

Further, in the preparation method of the spherical silica-alumina carrier, the washing is divided into two steps, that is, firstly, the molding material is washed with a mixed solution of at least one solvent selected from petroleum ether, cyclohexane or toluene and anhydrous ethanol at a volume ratio of 1: (1-3), to remove the medium oil of the molding material, and then washed with deionized water at a temperature of 70°C to 90°C to remove the mixed solution on the molding material.

Further, in the preparation method of the spherical silica-alumina carrier, the drying temperature is 100°C-150°C, and the drying time is 6-10 hours; the calcination temperature is 550°C-750°C, and the calcination time is 1-4 hours.

The second aspect of the present invention provides the spherical silica-alumina carrier obtained by the above preparation method.

Further, the properties of the spherical silica-alumina carrier are as follows: pore volume>0.68mL/g, preferably 0.70mL/g-0.95mL/g; specific surface area>180m²/g, preferably 185m²/g～240m²/g; pore distribution: the pore volume of pores with a pore diameter of <10nm accounts for less than 5.5% of the total pore volume, preferably less than 5.0%, and the pore volume of pores with a pore diameter>20nm accounts for less than 7.5% of the total pore volume, preferably less than 7.0%; the carrier particle diameter is 1.6-2.2mm, preferably 1.7-2.0mm, bulk density 0.60-0.68g/mL, crushing strength>50N/particle, preferably 55N /grain-75N/grain; the volume occupied by the fine spherical cavity is 10%-35% of the volume of the carrier.

Further, the mass content of SiO ₂ in the spherical silica-alumina carrier is 1.0-35.0%.

The third aspect of the present invention provides the application of the spherical silica-alumina carrier described in the second aspect as a catalyst carrier in the production of propylene from propane.

Compared with the prior art, the present invention has the advantages of:

(1) The silicon-containing pseudo-boehmite wet filter cake prepared by the present invention has low gibbsite, high crystallinity, and easy adjustment of silicon content, and the silicon-containing alumina obtained by roasting has a larger pore volume and pore diameter; meanwhile, the silicon-containing pseudo-boehmite wet filter cake prepared by the present invention has a high peptization index, which provides a guarantee for preparing a high lateral pressure strength carrier;

(2) In the preparation method of the present invention, the first alkaline solution first reacts with the mixed gas containing carbon dioxide, and adjusts the pH value of the system to a specific range, which is conducive to improving the crystallinity of the product, and in the co-current reaction with the second alkaline solution, the crystal grains formed after the reaction between the first alkaline solution and carbon dioxide can be used as crystal nuclei for the co-current reaction, so that the prepared silicon-containing pseudo-boehmite crystal grains increase, forming larger pore volume and suitable pore distribution;

(3) In the preparation method of the present invention, the first alkaline solution first reacts with the mixed gas containing carbon dioxide, and adjusts the pH value of the system to acidity, so that the ^Na in the water glass in the first alkaline solution is in a free state, and the precursor of silicon dioxide is combined with or adsorbed on the pseudo-boehmite crystal grains, so that subsequent Na ⁺ washing is easier and washing water is saved;

(4) The carrier raw material of the present invention is prepared into an oil-in-water (O/W) emulsion, and the organic phase is dispersed in the emulsion in the form of fine droplets. When forming, the emulsion droplets enter the medium oil and are automatically shrunk into a spherical shape under the action of surface tension. The gelling agent in the emulsion is decomposed by heat, and the released alkaline gas makes the emulsion solidify into small balls. At the same time, the stability of the emulsion is destroyed due to temperature. Shaped cavity, while the continuous phase silicon-containing aluminum hydroxide sol does not change, therefore, the bulk ratio is reduced, but the strength is not affected;

(5) Polyhydric alcohol is added in the process of preparing the oil-in-water (O/W) emulsion from the carrier raw material of the present invention, which improves the emulsifying ability of the emulsifier, and promotes the uniform dispersion of the organic phase to form fine droplets. At the same time, the size and number of the fine spherical cavity can be controlled by controlling the number of stirring revolutions and the amount of organic phase added;

(6) The preparation method of the present invention has simple process, easy operation and no pollution;

(7) The spherical silica-alumina carrier obtained by the preparation method of the present invention is used in the reaction of propane to propylene, has higher propane conversion rate and propylene selectivity, and the total carbon deposition amount of the catalyst after 35 hours of reaction is lower, and has better stability and good reaction performance.

Description of drawings

Fig. 1 is the SEM image of the spherical silica-alumina carrier prepared in Example 1 of the present invention;

Fig. 2 is the SEM image of the spherical silica-alumina carrier prepared in Example 3 of the present invention;

Fig. 3 is the SEM image of the spherical silica-alumina carrier prepared in Example 5 of the present invention;

Fig. 4 is the SEM image of the spherical silica-alumina carrier prepared in Comparative Example 1 of the present invention;

Fig. 5 is the SEM image of the spherical silica-alumina carrier prepared in Comparative Example 2 of the present invention;

FIG. 6 is an SEM image of the spherical silica-alumina carrier prepared in Comparative Example 3 of the present invention.

Detailed ways

The following examples will further illustrate the preparation method and effect of the spherical silica-alumina carrier in the present invention. Embodiments are carried out on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operation processes are provided, but the protection scope of the present invention is not limited to the following embodiments.

The experimental methods in the following examples are conventional methods in the art unless otherwise specified. The experimental materials used in the following examples were purchased from conventional biochemical reagent stores unless otherwise specified.

In the present invention, a Hitachi S-4700 field emission scanning electron microscope (SEM) from Japan was used to observe the morphology and particle size of the carrier.

In the present invention, the nitrogen adsorption-desorption curve of the sample is tested at -196° C. by using ASAP2020 automatic physical adsorption instrument of American Micromeritics Company, and the specific surface area, pore volume and pore size distribution are measured.

In the present invention, the crushing strength is tested by a ZQJ-Ⅲ intelligent particle strength testing machine manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical carriers is tested.

In the present invention, the bulk density is the solid weight of the spherical carrier loaded into a 100mL graduated cylinder.

In the present invention, the carrier fine spherical cavity volume test method is to prepare a solid spherical carrier with the same pore volume, particle size, and true density as the fine spherical cavity carrier. Measure 100 mL of the fine spherical cavity carrier and the solid spherical carrier with a 100 mL graduated cylinder respectively and weigh and measure. Then add deionized water to the 100 mL scale in the vector cylinder and measure the water volume. Then the total volume of the fine spherical cavity is the amount of deionized water added to the solid spherical carrier graduated cylinder minus 1 The difference between the total pore volume of 000mL solid spherical carrier and the amount of deionized water added to the fine spherical cavity carrier measuring cylinder minus the total pore volume of 100mL fine spherical cavity carrier.

Example 1

Add 3500mL of water glass with a modulus of 2.8 and a concentration of 50g SiO ₂ /L and a sodium metaaluminate mixed solution with a caustic ratio of 1.45 and a concentration of 25g Al ₂ O ₃ /L in the 5000mL first reaction kettle, and then feed a mixed gas of carbon dioxide and air containing 55% of the volume fraction of carbon dioxide to reduce the pH value of the system to 3.4, and the temperature of the material at the end of the reaction is 55°C;

Add 1500mL of bottom water to the 10000mL second reaction kettle, start the stirring and heating device, when the temperature rises to 65°C, add the above materials into the second reaction kettle at a flow rate of 35mL/min, and simultaneously add 180gAl₂o₃/L, a sodium metaaluminate solution with a caustic ratio of 1.25. By adjusting the flow rate of the sodium metaaluminate solution, the pH value of the slurry in the second reactor is controlled to be 8.0, while keeping the temperature of the slurry in the second reactor constant. After the above-mentioned materials are used up, the reaction is completed, and the slurry is aged at 90°C for 80 minutes. After the aging is completed, it is washed with deionized water at a temperature of 70°C until it is neutral. After filtering, a silicon-containing pseudo-boehmite wet cake with a solid content of 42% is obtained.

Take 238g of the above silicon-containing pseudo-boehmite filter cake, add 68.6g of deionized water to stir and beat evenly, then add 10.8g of nitric acid solution with a mass concentration of 60% for peptization, and finally make a silicon-containing pseudo-boehmite sol with a solid content of 31.5%;

Add 20 g of hexamethylenetetramine solution with a mass concentration of 40%, 0.8 g of polyoxyethylene sorbitan monolaurate (Tween 20) with an HLB value of 16.7, 0.6 g of 1,3-propanediol, and 9 g of white oil successively into the above-mentioned 317.5 g of silicon-containing pseudoboehmite sol, then add 128.3 g of deionized water, adjust the stirring speed to 3500 rpm for stirring, and make the final oil-in-water type (O/W) The solids content in the emulsion was 21%.

Using a dripper with an inner diameter of 0.8mm, the kinematic viscosity at 40°C is 28mm²The oil-in-water (O/W) emulsion mentioned above was added dropwise to white oil at a temperature of 95° C. for molding. The molding material was first washed with a mixed solution of petroleum ether and absolute ethanol at a volume ratio of 1:1 to remove the medium oil of the molding material, then washed with deionized water at a temperature of 85° C., dried at 130° C. for 8 hours, and roasted at 650° C. for 3 hours to obtain the spherical silicon-aluminum carrier A-1 of the present invention. The analysis results are shown in Table 1, and the SEM results are shown in Figure 1. It can be seen that the carrier of the present invention contains more uniform fine spherical cavities, which can effectively reduce the packing density of the carrier.

Example 2

Other conditions are the same as in Example 1, except that the concentration of SiO in the step mixed solution is changed to _75g /L, the concentration of _Al in the mixed solution is changed to _15g /L, the volume fraction of carbon dioxide in the mixed gas of carbon dioxide and air used is 45%, and the aging temperature is changed to 97°C to obtain the spherical silicon-aluminum carrier A-2 of the present invention. The analysis results are shown in Table 1. The SEM image is similar to Fig. 1.

Example 3

Other conditions are the same as in Example 1, except that the number of stirring revolutions during the preparation of the oil-in-water (O/W) emulsion is changed to 1500 revolutions/min to obtain the spherical silica-alumina carrier A-3 of the present invention. The analysis results are shown in Table 1, and the SEM results are shown in Figure 2.

Example 4

Other conditions are the same as in Example 1, except that the emulsifier is changed to 1.5 g of fatty alcohol polyoxyethylene ether (MOA-15) with an HLB value of 15.0, and 1,3-propanediol is changed to 1,3-butanediol to obtain the spherical silica-alumina carrier A-4 of the present invention, and the analysis results are shown in Table 1. The SEM image is similar to Fig. 1.

Example 5

In the 5000mL first reaction kettle, add 4000mL modulus to be 3.0, _SiO Concentration is the water glass of 35g/L and caustic ratio is 1.40, Al _{O Concentration} is the sodium metaaluminate mixed solution of 8g/L, then pass into the gaseous mixture that contains carbon dioxide and account for 45% carbon dioxide and air, make the system pH value drop to 2.5, the temperature of material is 40 ℃ when reaction finishes;

Add 1000mL of bottom water to the 10000mL second reaction kettle, start the stirring and heating device, when the temperature rises to 55°C, add the above materials into the second reaction kettle at a flow rate of 35mL/min, and simultaneously add the concentration of 210gAl₂o₃/L, a sodium metaaluminate solution with a caustic ratio of 1.18, by adjusting the flow rate of the sodium metaaluminate solution to control the pH value of the slurry in the second reactor to 8.8, while keeping the temperature of the slurry in the second reactor constant, after the above-mentioned materials are used up, the reaction is completed, and the slurry is aged at 80°C for 120min. After the aging is completed, it is washed with deionized water at a temperature of 75°C until it is neutral. After filtration, a silicon-containing pseudo-boehmite wet cake with a solid content of 37% is obtained.

Take 270g of the above silicon-containing pseudo-boehmite wet filter cake, add deionized water to stir and beat evenly, then add 6.2g of nitric acid solution with a mass concentration of 65% for peptization, and finally make a silicon-containing pseudo-boehmite sol with a silicon-alumina mass content of 34%;

To the above-mentioned 294.1g of silicon-containing pseudoboehmite sol, 23.4g of hexamethylenetetramine solution with a mass concentration of 32%, 1.2g of polyoxyethylene sorbitan monolaurate (Tween 20) with an HLB value of 16.7, 0.3g of 1,3-propylene glycol, and 7.5g of white oil were sequentially added to the above-mentioned 294.1g of silicon-containing pseudoboehmite sol, then deionized water was added, and the stirring speed was adjusted to 3500 rpm for stirring, so that the final prepared oil-in-water type ( O/W) The solids content in the emulsion was 18%.

Use a dropper with an inner diameter of 1.2 mm to drop the above oil-in-water (O/W) emulsion into white oil with a kinematic viscosity of 30 mm ² /s at 40 °C and a temperature of 105 °C for molding. The molding material is first washed with a mixed solution of cyclohexane and absolute ethanol at a volume ratio of 1:3 to remove the medium oil of the molding material, then washed with deionized water at a temperature of 75 °C, dried at 120 °C for 10 hours, and roasted at 700 °C for 2 hours to obtain The analysis results of the spherical silica-alumina carrier A-5 of the present invention are shown in Table 1, and the SEM results are shown in Figure 3.

Comparative example 1

Add 3500mL of water glass with a modulus of 2.8 and a concentration of 50g SiO ₂ /L and a sodium metaaluminate mixed solution with a caustic ratio of 1.45 and a concentration of 25g Al ₂ O ₃ /L in the 5000mL first reaction kettle, and then feed a mixed gas of carbon dioxide and air containing 55% of the volume fraction of carbon dioxide to reduce the pH value of the system to 3.4, and the temperature of the material at the end of the reaction is 55°C;

Add 1500mL of bottom water to the 10000mL second reaction kettle, start the stirring and heating device, when the temperature rises to 65°C, add the above-mentioned materials into the second reaction kettle at a flow rate of 35mL/min, and simultaneously add a concentration of 180gAl₂o₃/L, a sodium metaaluminate solution with a caustic ratio of 1.25. By adjusting the flow rate of the sodium metaaluminate solution, the pH value of the slurry in the second reactor is controlled to be 8.0, while keeping the temperature of the slurry in the second reactor constant. After the above-mentioned materials are used up, the reaction is completed, and the slurry is aged at 90°C for 80min. After the aging is completed, it is washed with deionized water at a temperature of 70°C until it is neutral. After filtration, a silicon-containing pseudoboehmite wet cake with a solid content of 42% is obtained.

Take 238g of the above silicon-containing pseudo-boehmite filter cake, add 227.4g of deionized water to stir and beat evenly, then add 10.8g of nitric acid solution with a mass concentration of 60% for peptization, and finally make a silicon-containing pseudo-boehmite sol with a solid content of 21%;

Use a dripper with an inner diameter of 0.8 mm to add the above oil-in-water (O/W) emulsion dropwise to white oil with a kinematic viscosity of 28 mm ² /s at 40 °C and a temperature of 95 °C for molding. The molding material is first washed with a mixed solution of petroleum ether and absolute ethanol at a volume ratio of 1:1 to remove the medium oil of the molding material, and then washed with deionized water at a temperature of 85 °C, dried at 130 °C for 8 hours, and roasted at 650 °C for 3 hours to obtain spherical silicon The analysis results of aluminum carrier D-1 are shown in Table 1, and the SEM results are shown in Figure 4.

Comparative example 2

Add 3500mL of water glass with a modulus of 2.8 and a concentration of 50g SiO ₂ /L and a sodium metaaluminate mixed solution with a caustic ratio of 1.45 and a concentration of 25g Al ₂ O ₃ /L in the 5000mL first reaction kettle, and then feed a mixed gas containing carbon dioxide and air with a volume fraction of 55% to reduce the pH value of the system to 3.4, and the temperature of the material at the end of the reaction is 55°C;

Add 1500mL of bottom water to the 10000mL second reaction kettle, start the stirring and heating device, when the temperature rises to 65°C, add the above materials into the second reaction kettle at a flow rate of 35mL/min, and simultaneously add 180gAl₂o₃/L, a sodium metaaluminate solution with a caustic ratio of 1.25. By adjusting the flow rate of the sodium metaaluminate solution, the pH value of the slurry in the second reactor is controlled to be 8.0, while keeping the temperature of the slurry in the second reactor constant. After the above-mentioned materials are used up, the reaction is completed, and the slurry is aged at 90°C for 80 minutes. After the aging is completed, it is washed with deionized water at a temperature of 70°C until it is neutral. After filtering, a silicon-containing pseudo-boehmite wet cake with a solid content of 42% is obtained.

Take 238g of the above silicon-containing pseudo-boehmite filter cake, add 68.6g of deionized water to stir and beat evenly, then add 10.8g of nitric acid solution with a mass concentration of 60% for peptization, and finally make a silicon-containing pseudo-boehmite sol with a solid content of 31.5%;

To the above-mentioned 317.5 g of silicon-containing pseudoboehmite sol, 20 g of hexamethylenetetramine solution with a mass concentration of 40%, 0.8 g of polyoxyethylene sorbitan monolaurate (Tween 20) with an HLB value of 16.7, and 9 g of white oil were successively added to the above-mentioned 317.5 g of silicon-containing pseudoboehmite sol, and then deionized water was added.

Use a dripper with an inner diameter of 0.8 mm to add the above oil-in-water (O/W) emulsion dropwise to white oil with a kinematic viscosity of 28 mm ² /s at 40 °C and a temperature of 95 °C for molding. The molding material is first washed with a mixed solution of petroleum ether and absolute ethanol at a volume ratio of 1:1 to remove the medium oil of the molding material, and then washed with deionized water at a temperature of 85 °C, dried at 130 °C for 8 hours, and roasted at 650 °C for 3 hours to obtain spherical silicon The analysis results of aluminum carrier D-2 are shown in Table 1, and the SEM results are shown in Figure 5.

Comparative example 3

Prepare 3500 mL of an aluminum sulfate mixed solution with a modulus of 2.8, a concentration calculated as SiO ₂ of 50 g/L and a concentration calculated as Al ₂ O ₃ of 25 g/L, for use.

Add 1500mL of bottom water to the 10000mL reactor, start the stirring and heating device, when the temperature rises to 65°C, add the obtained aluminum sulfate mixed solution into the reactor at a flow rate of 35mL/min, and simultaneously add 180g of Al₂o₃/L, a sodium metaaluminate solution with a caustic ratio of 1.25, by adjusting the flow rate of the sodium metaaluminate solution to control the pH value of the slurry in the reactor to 8.0, while keeping the temperature of the slurry in the reactor constant, the reaction is completed after the mixed solution is used up, and the slurry is aged at 90 ° C for 80 minutes. After aging, it is washed with deionized water at a temperature of 70 ° C until it is neutral. After filtration, a silicon-containing pseudo-boehmite wet cake with a solid content of 42% is obtained.

Take 238g of the above silicon-containing pseudo-boehmite filter cake, add deionized water to stir and beat evenly, then add 10.8g of nitric acid solution with a mass concentration of 60% for peptization, and finally make a silicon-containing pseudo-boehmite sol with a solid content of 31.5%;

To the above-mentioned 317.5 g of silicon-containing pseudoboehmite sol, 20 g of hexamethylenetetramine solution with a mass concentration of 40%, 0.8 g of polyoxyethylene sorbitan monolaurate (Tween 20) with an HLB value of 16.7, and 9 g of white oil were successively added to the above-mentioned 317.5 g of silicon-containing pseudoboehmite sol, and then deionized water was added.

Use a dripper with an inner diameter of 0.8 mm to add the above oil-in-water (O/W) emulsion dropwise to white oil with a kinematic viscosity of 28 mm ² /s at 40 °C and a temperature of 95 °C for molding. The molding material is first washed with a mixed solution of petroleum ether and absolute ethanol at a volume ratio of 1:1 to remove the medium oil of the molding material, and then washed with deionized water at a temperature of 85 °C, dried at 130 °C for 8 hours, and roasted at 650 °C for 3 hours to obtain spherical silicon The analysis results of aluminum carrier D-3 are shown in Table 1, and the SEM results are shown in Figure 6.

Example 6

The spherical silica-alumina carriers prepared in Examples 1, 3, 5 and Comparative Examples 1, 2, 3 were supersaturated and impregnated for 6 hours with an impregnation solution containing chloroplatinic acid, stannous chloride and hydrochloric acid, and the liquid/solid ratio was 2.0 mL/g. After impregnation, they were dried at 120°C for 12 hours, and then calcined at 600°C for 4 hours to obtain catalysts in the oxidation states of A _C -1, A _C -3, A _C -5 and DC _-1 , _DC -2, _DC -3. The metal content analysis results are shown in Table 2.

Load 10 ml of oxidized catalyst into the microreactor, and evaluate the catalyst activity after reducing it with hydrogen at 580°C for 4 hours. Using the mixed gas of hydrogen and propane as the raw material, the reaction was carried out at a reaction temperature of 625°C, a reaction pressure of 0.25MPa, a propane feed mass space velocity of 6.5h ^-1 , and a hydrogen/propane molar ratio of 0.5:1. The propane conversion and propylene selectivity of each catalyst at different reaction times are shown in Table 3.

The physical and chemical properties of the spherical silica-alumina carrier of table 1 embodiment and comparative example

Table 2 Catalyst metal content analysis results

serial number A _C -1 A _C -3 A _C -5 D _C -1 D _C -2 D _C -3 Pt, wt% 0.35 0.33 0.35 0.35 0.35 0.35 Sn, wt% 0.75 0.77 0.73 0.75 0.75 0.75

Table 3 Catalyst Evaluation Results

It can be seen from Table 3 that the catalyst prepared by the carrier of the present invention has higher propane conversion rate and propylene selectivity, the total carbon deposition amount of the catalyst is lower after 35 hours of reaction, and has better stability and good reaction performance.

Claims (14)

1. A preparation method for a spherical silica-alumina carrier, comprising the following steps: Add curing agent solution, emulsifier, polyol and organic phase to silicon-containing pseudo-boehmite sol respectively, add water under stirring to prepare oil-in-water (O/W) emulsion, then drop into oil column to form, wash, dry and roast to obtain spherical silica-alumina carrier. 2. the preparation method according to claim 1, is characterized in that, the preparation method of described silicon-containing pseudo-boehmite sol comprises: (1) Add the first alkaline solution into the first reaction kettle, feed the mixed gas containing carbon dioxide to react, so that the pH value of the system is 2 to 4; (2) adding bottom water in the second reaction kettle, heating to the reaction temperature, then the second alkaline solution and the material obtained in step (1) are fed into the second reaction kettle in parallel and reacted; (3) Aging the slurry obtained after the reaction in step (2), filtering and washing after aging to obtain a silicon-containing pseudo-boehmite wet filter cake; (4) adding water to the wet filter cake obtained in step (3) to make a slurry, and then adding a peptizer for peptization to obtain a silicon-containing pseudo-boehmite sol. 3. preparation method according to claim 2, is characterized in that, in step (1), described first alkaline solution is the mixed solution of water glass and aluminum-containing alkaline solution; Described aluminum-containing alkaline solution is one or both in sodium metaaluminate solution or potassium metaaluminate solution; The modulus of described water glass is 2.5～3.0, and the caustic ratio of described sodium metaaluminate solution or potassium metaaluminate solution is 1.35～1.65. 4. The preparation method according to claim 2, characterized in that, in step (1), the concentration of water glass in the first alkaline solution is 5-90 g SiO ₂ /L in terms of SiO ₂ , and the concentration of sodium metaaluminate and/or potassium meta-aluminate in the mixed solution is 10-30 g Al ₂ O ₃ /L in terms of Al ₂ O ₃ . 5. preparation method according to claim 2, it is characterized in that, in step (1), described in the first reactor, the volume that adds the first alkaline solution is 2/3～3/4 of the first reactor volume; In the described mixed gas containing carbon dioxide, the volume fraction of carbon dioxide is 30%～70%; The mixed gas containing carbon dioxide can be the mixed gas of carbon dioxide and air. 6. The preparation method according to claim 2, characterized in that, in step (2), the reaction temperature of the reaction is 40°C to 70°C; in step (3), the aging conditions are: the temperature is 50°C to 95°C, and the time is 30min to 120min. 7. according to the described preparation method of claim 1 and 2, it is characterized in that, described curing agent solution is one or more solutions in hexamethylenetetramine, urea; Described curing agent solution mass concentration is 30%～50%; Described curing agent add-on is 1wt%～15wt% of solid content in silicon-containing pseudo-boehmite sol. 8. The preparation method according to claim 1 or 2, wherein the emulsifier is a nonionic emulsifier, specifically selected from at least one of polyoxyethylene sorbitan monolaurates and fatty alcohol polyoxyethylene ethers; the hydrophilic-lipophilic balance value of the emulsifier is 13 to 20, and the amount of the emulsifier added is 0.2wt% to 2.0wt% of the solid content of the silicon-containing pseudoboehmite sol. 9. The preparation method according to claim 1 or 2, wherein the polyhydric alcohol is one or more of 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-propylene glycol, 1-pentanol, polyethylene glycol (400), and the addition amount of the polyhydric alcohol is 0.1wt% to 1.0wt% of the solid content in the silicon-containing pseudoboehmite sol. 10. The preparation method according to claim 1 or 2, wherein the organic phase is one or more of white oil or diesel oil; the amount of the organic phase added is 7.0wt% to 13.0wt% of the solid content in the silicon-containing pseudo-boehmite sol; the added quality of the water is 0.5 to 1.5 times the solid content in the silicon-containing pseudo-boehmite sol. 11. The preparation method according to claim 1 or 2, characterized in that, the stirring speed is 1000-4000 rpm; the mass content of alumina in the oil-in-water emulsion is 15%-25%; the medium oil used in the oil column is one of white oil or diesel oil, and the kinematic viscosity of the white oil at 40°C is ^20-40mm2 /s; the molding temperature is 90°C-110°C; The type emulsion is dripped into the oil column, and the inner diameter of the dripper used is 0.4mm to 2.0mm. 12. The spherical silica-alumina carrier obtained by the preparation method described in any one of claims 1-11. 13. The spherical silica-alumina carrier according to claim 12, characterized in that the properties of the spherical silica-alumina carrier are as follows: pore volume>0.68mL/g; specific surface area>180m2/g; pore distribution: the pore volume of pores with a diameter of <10nm accounts for less than 5.5% of the total pore volume, and the pore volume of pores with a diameter of> ^20nm accounts for less than 7.5% of the total pore volume; the particle diameter of the carrier is 1.6-2.2mm, and the bulk density is 0.60 ~0.68g/mL, crushing strength>50N/grain; the volume of fine spherical cavities is 10%-35% of the volume of the carrier. 14. The spherical silica-alumina carrier according to claim 12, characterized in that the mass content of SiO ₂ in the spherical silica-alumina carrier is 1.0-35.0%.