Spherical Esterification Catalyst, Its Preparation Method and Application in the Synthesis Reaction of n-Butyl Acetate

Abstract

The present invention relates to the field of fine chemicals, and discloses a spherical esterification catalyst, a preparation method thereof, and an application thereof in the synthesis reaction of n-butyl acetate. The spherical esterification catalyst comprises a spherical composite carrier, alumina and MCM-22 molecular sieve supported on the spherical composite carrier, and based on the total weight of the spherical esterification catalyst, the content of the spherical composite carrier is 40-80% by weight, and the content of the phosphotungstate is 20-60% by weight. When this catalyst is used in the synthesis reaction of n-butyl acetate, a higher acetic acid conversion rate and n-butyl acetate selectivity can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of fine chemicals, and specifically, to a spherical esterification catalyst, a preparation method thereof, and an application thereof in the synthesis reaction of n-butyl acetate. Background Art

[0002] N-butyl acetate is an important organic chemical product and has good solubility in ethyl cellulose, polyvinyl acetate, polyvinyl chloride, chlorinated rubber, gutta-percha, polyacrylate, polymethyl methacrylate, and many natural resins such as rosin, tannin extract, Manila gum, dammar resin, etc. N-butyl acetate can not only be used as an excellent organic solvent and is widely used in fields such as collodion, nitrocellulose, varnish, artificial leather, medicine, and plastic processing, but also can be used as an industrial fragrance or food flavor. With the enhancement of people's environmental protection awareness, acetate esters have gradually become substitutes for organic solvents such as benzene, toluene, and methyl ethyl ketone. The traditional process for producing n-butyl acetate industrially is to use concentrated sulfuric acid as a catalyst to catalyze the esterification reaction of acetic acid and n-butanol to produce n-butyl acetate. The concentrated sulfuric acid catalyst has the advantage of low price, but using concentrated sulfuric acid as a catalyst causes serious environmental pollution, requires high equipment material requirements, has many side reactions, many by-products, and it is relatively difficult to separate and purify the obtained product. Therefore, the use of inorganic acid catalysts in esterification reactions has gradually been phased out. In recent years, the production process of acetate esters in China has been continuously developed, and the production capacity of acetate esters has been continuously improved. The use of solid acids or cation exchange resins as catalysts for the synthesis reaction of n-butyl acetate has been greatly developed and has also been widely applied in industrial production. Solid catalysts exhibit advantages such as good stability, high selectivity, low cost, and easy separation in esterification reactions. However, the reaction rate of such catalysts is relatively slow, and the ester yield is relatively low. Cation exchange resins exhibit advantages such as good stability, high selectivity, low cost, and easy separation in esterification reactions. However, cation exchange resins themselves have poor heat resistance (generally applicable to esterification reactions at temperatures below 150°C), relatively small specific surface area and pore volume, and cation exchange resins are prone to swelling, and their reaction activity as esterification catalysts is poor, and the ester yield is relatively low.

[0003] Compared with resin catalysts, hydrogen-type zeolite molecular sieves (such as: Hβ molecular sieves) have a certain pore structure and surface acidity and are suitable for catalyzing the esterification reaction of small molecules. However, the pore size of zeolite molecular sieves is relatively small (0.5 - 0.7 nm), and the diffusion of macromolecular products may be inhibited during the reaction; moreover, the number of acid sites on the surface of zeolite molecular sieves is relatively small, and the efficiency of catalyzing the esterification reaction is relatively low. Therefore, it is also unrealistic to directly apply hydrogen-type zeolite molecular sieve materials to the synthesis reaction of n-butyl acetate. With the increasing demand for n-butyl acetate, the prospect of synthesizing n-butyl acetate by a green and environmentally friendly process is broad. For researchers, developing excellent catalysts for the synthesis reaction of n-butyl acetate, improving the reaction efficiency, and inhibiting the generation of by-products are important future work directions. Summary of the Invention

[0004] The object of the present invention is to overcome the problems existing in the prior art, such as excessive side reactions of inorganic acid catalysts used in the production process of n-butyl acetate and serious environmental pollution, as well as poor catalytic activity and low ester selectivity of solid acid catalysts and acidic cation exchange resin catalysts. A spherical esterification catalyst, a preparation method thereof, and an application thereof in the synthesis reaction of n-butyl acetate are provided. When the catalyst is used in the synthesis reaction of n-butyl acetate, higher acetic acid conversion rate and n-butyl acetate selectivity can be obtained.

[0005] To achieve the above object, in the first aspect of the present invention, a spherical esterification catalyst is provided, wherein the spherical esterification catalyst comprises a spherical composite support and phosphotungstate supported on the spherical composite support, and based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 40 - 80% by weight, and the content of the phosphotungstate is 20 - 60% by weight.

[0006] In the second aspect of the present invention, a preparation method of the aforementioned spherical esterification catalyst is provided, wherein the preparation method comprises:

[0007] (S1) After contacting the spherical composite support with an aqueous solution of a metal salt for a first reaction, a solid product is obtained through a first separation. After drying and first calcination of the solid product, a catalyst intermediate is obtained;

[0008] (S2) After contacting the catalyst intermediate with an aqueous solution of phosphotungstic acid for a second reaction, a solid product is obtained through a second separation. After washing, drying, and second calcination of the solid product, a spherical esterification catalyst is obtained.

[0009] In the third aspect of the present invention, an application of the aforementioned spherical esterification catalyst in the synthesis reaction of n-butyl acetate is provided.

[0010] Through the above technical solutions, the technical solutions of the present invention have the following advantages:

[0011] (1) The spherical esterification catalyst provided by the present invention is spherical, with uniform size, smooth surface, high mechanical strength, stable structure, good high-temperature resistance, and does not deform or swell during the reaction process.

[0012] (2) The raw materials of the spherical esterification catalyst provided by the present invention are easily available, the preparation method has a simple process, the conditions are easy to control, and the product has good repeatability.

[0013] (3) When the spherical esterification catalyst provided by the present invention is used in the acetic acid ester synthesis reaction, the process conditions are mild, and the requirements for the reaction device are not high. The acetic acid conversion rate is high, and the acetic acid ester selectivity is high.

[0014] Other features and advantages of the present invention will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the XRD pattern of the spherical composite support A prepared in Example 1 of the present invention;

[0016] Figure 2 is a picture of the spherical composite support A prepared in Example 1. SPECIFIC EMBODIMENTS

[0017] The endpoints and any values disclosed in this text are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this text.

[0018] As described above, the first aspect of the present invention provides a spherical esterification catalyst. Among them, the spherical esterification catalyst includes a spherical composite support and phosphotungstate supported on the spherical composite support. Based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 40-80% by weight, and the content of the phosphotungstate is 20-60% by weight.

[0019] The inventors of the present invention found that: in the prior art, the esterification catalysts used for producing n-butyl acetate are divided into two categories: homogeneous and heterogeneous. Among them, homogeneous catalysts mainly include inorganic acid solutions and organic acids, and heterogeneous catalysts mainly include solid acids and cation exchange resins. The advantages of homogeneous catalysts are low price and good catalytic activity. However, due to the difficulties in separating the product from the catalyst, many side reactions, and easy corrosion of equipment, etc., they have been gradually phased out. Although solid acid esterification catalysts solve the problems of difficult product separation and serious equipment corrosion, they are rarely used in industrial production due to disadvantages such as poor catalytic activity, high reaction temperature, and low product selectivity. Compared with the above catalysts, resin catalysts have the advantages of high selectivity, low cost, and easy separation. However, the ester yield is relatively low during the synthesis reaction of n-butyl acetate, and the high-temperature resistance performance is also poor. Resin is an organic polymer material, which is easily swollen in organic solvents and deformed or even decomposed in a high-temperature environment. This is the main reason for the poor high-temperature resistance performance of resin catalysts.

[0020] Phosphotungstate is a good esterification catalyst. It not only has a stable structure, is not easy to absorb moisture, is easy to store, convenient to use, and has a low price, but also does not corrode equipment during use, making it a very promising green esterification catalyst. However, phosphotungstate tends to agglomerate during the catalytic esterification reaction, resulting in a decrease in catalytic efficiency. If a suitable carrier can be selected to disperse the phosphotungstate catalyst well, the above problems can be solved and the efficiency of the catalyst can be improved. Compared with resin catalysts, MCM-22 zeolite has a certain pore structure and surface acidity, which is suitable for catalyzing the esterification reaction of small molecules. However, the pore size of this type of zeolite is relatively small, and the diffusion of macromolecular products may be inhibited during the reaction; moreover, the number of acid sites on the surface of MCM-22 zeolite is small, and the efficiency of catalyzing the esterification reaction is low, so it is not suitable to directly act as a catalyst for the synthesis reaction of n-butyl acetate. In addition, in industrial production, solid-phase esterification catalysts need to be formed before application. For example, resin catalysts are generally spherical. Spherical catalysts have the advantages of high bulk density, large loading capacity, low abrasion, little dust during loading, fast mass transfer, and high reaction efficiency.

[0021] During the development of esterification catalysts, the inventors of the present invention found that if MCM-22 zeolite is mixed with an aluminum-containing material with good viscosity in a certain proportion and prepared into a spherical alumina-MCM-22 composite support through a unique forming method. This support belongs to an inorganic structure and not only will not swell and deform in organic solvents, but also has good heat resistance. After loading phosphotungstate on the spherical composite support, an esterification catalyst with good mechanical strength can be obtained. This catalyst can exhibit good catalytic activity and n-butyl acetate selectivity when used in the acetic acid esterification reaction.

[0022] According to the present invention, preferably, based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 48-73% by weight, and the content of the phosphotungstate is 27-52% by weight; more preferably, based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 58.5-66.3% by weight, and the content of the phosphotungstate is 33.7-41.5% by weight. In the present invention, by using the foregoing specific contents of the spherical composite support and phosphotungstate, the prepared catalyst can have better catalytic activity and ester selectivity when used in the acetic acid esterification reaction.

[0023] According to the present invention, the phosphotungstate is an alkali metal salt of phosphotungstic acid, preferably one or more of potassium phosphotungstate, rubidium phosphotungstate, and cesium phosphotungstate.

[0024] According to the present invention, the specific surface area of the spherical composite support is 400-900m 2 / g, the pore volume is 0.3 - 0.9 ml / g, the pore size distribution is bimodal, and the first most probable pore size corresponding to the bimodality is 0.3 - 1 nm, and the second most probable pore size is 8 - 25 nm; the average particle diameter is 1.0 - 3.0 mm, and the average particle strength is 20 - 70 N; preferably, the specific surface area of the spherical composite support is 450 - 750 m 2 / g, the pore volume is 0.4 - 0.7 ml / g, the pore size distribution is bimodal, and the first most probable pore size corresponding to the bimodality is 0.4 - 0.8 nm, and the second most probable pore size is 10 - 20 nm; the average particle diameter is 1.2 - 2.7 mm, and the average particle strength is 25 - 60 N; more preferably, the specific surface area of the spherical composite support is 508 - 634 m 2 / g, the pore volume is 0.51 - 0.62 ml / g, the average particle diameter is 1.5 - 2.4 mm, the pore size distribution is bimodal, and the first most probable pore size corresponding to the bimodality is 0.5 - 0.7 nm, and the second most probable pore size is 12 - 16 nm; the average particle strength is 28.1 - 52.6 N. In the present invention, by using the spherical composite support with the foregoing specific parameters, the prepared catalyst can have better catalytic activity and ester selectivity when used in the acetic acid esterification reaction.

[0025] According to the present invention, the preparation method of the spherical composite support includes:

[0026] (1) Mixing an alumina precursor, MCM-22 molecular sieve, acidic aqueous solution, and extrusion aid to obtain a mixture, and subjecting the mixture to pelletizing to obtain a spherical alumina-MCM-22 precursor;

[0027] (2) Drying and calcining the spherical alumina-MCM-22 precursor to obtain a spherical alumina-MCM-22 composite support.

[0028] In the present invention, the pseudo-boehmite can be obtained by commercial purchase or preparation. Specifically, in the present invention, the pseudo-boehmite includes: German original imported pseudo-boehmite powder of model SB (purchased from Beijing Yatai Aohua Chemical Auxiliary Co., Ltd., with a specific surface area of 241 m 2 / g, pore volume of 0.53 cm 3 / g), pseudo-boehmite powder of model P-DF-09-LSi (produced by Shandong Aluminum Co., Ltd., with a specific surface area of 286 m 2 / g, pore volume of 1.08 cm 3 / g) and macroporous pseudo-boehmite powder of model PB-0101 (produced by Zibo Hengqi Powder New Materials Co., Ltd., with a specific surface area of 327 m 2 / g, pore volume of 1.02 cm3 one or more of those in / g).

[0029] According to the present invention, in step (1), the MCM-22 molecular sieve can be selected from one or several of MCM-22 molecular sieves with different silica-alumina ratios, preferably the MCM-22 molecular sieve with a low silica-alumina ratio; the molar ratio of SiO2 to Al2O3 of the MCM-22 molecular sieve with a low silica-alumina ratio is 10-50:1. In the present invention, the MCM-22 molecular sieve (500m 2 / g, SiO2 / Al2O3 = 25) is purchased from Nanjing Xianfeng Nano Technology Materials Co., Ltd.

[0030] According to the present invention, the acidic aqueous solution can be an organic acid aqueous solution or an inorganic acid aqueous solution. Preferably, the acidic aqueous solution is selected from one or more of formic acid aqueous solution, acetic acid aqueous solution, citric acid aqueous solution, nitric acid aqueous solution and hydrochloric acid aqueous solution. More preferably, the acidic aqueous solution is nitric acid aqueous solution or citric acid aqueous solution; in the present invention, the mass concentration of the acidic aqueous solution is 1-20%, preferably 2-10%.

[0031] According to the present invention, the extrusion aid is selected from one or more of sesbania powder, polyethylene glycol, polyvinyl alcohol, polyacrylamide and cellulose; preferably, the extrusion aid is sesbania powder.

[0032] Preferably, the weight ratio of the alumina precursor, the MCM-22 molecular sieve, the extrusion aid and the acidic aqueous solution is 1:(0.2-1):(0.02-0.5):(0.2-5); preferably, the weight ratio of the alumina precursor, the MCM-22 molecular sieve, the extrusion aid and the acidic aqueous solution is 1:(0.3-0.5):(0.07-0.12):(0.6-0.8).

[0033] According to the present invention, in step (1), the alumina precursor, the MCM-22 molecular sieve, the acidic aqueous solution and the extrusion aid are mixed. The conditions for the mixing include: the stirring rate is 50-300 r / min, the temperature is 20-60 °C, and the time is 0.5-6 h; preferably, the stirring rate is 150-250 r / min, the temperature is 20-40 °C, and the time is 0.5-1 h.

[0034] According to the present invention, in step (2), the conditions for drying include: the temperature is 70-150 °C, and the time is 3-24 h; preferably, the temperature is 100-130 °C, and the time is 6-12 h.

[0035] According to the present invention, in step (2), the conditions for roasting include: the temperature is 400 - 700 °C, and the time is 2 - 30 h; preferably, the temperature is 550 - 700 °C, and the time is 12 - 15 h.

[0036] According to the present invention, in step (1), the method for making pellets includes:

[0037] (1 - 1) Extruding the mixture into strips, and then cutting and extruding into raw material balls;

[0038] (1 - 2) Shaping the raw material balls to obtain standard spherical balls;

[0039] (1 - 3) Screening the standard spherical balls to obtain spherical precursors.

[0040] According to the present invention, in step (1 - 1), after uniformly mixing the alumina precursor, the MCM - 22 molecular sieve, the acidic aqueous solution, and the extrusion aid, the obtained mixture is transferred to a micro - pelletizer to extrude a long strip with a circular cross - section, and then cut and extruded into raw material balls; wherein, the conditions for extruding into strips include: the extrusion speed is 0.5 - 5 m / min, and the diameter of the circular cross - section of the long strip is 1.0 - 3.0 mm; the conditions for cutting include: the cutting speed is 100 - 3500 pieces / minute.

[0041] According to the present invention, in step (1 - 2), the raw material balls are put into a micro - pellet shaper for shaping to make them into standard spherical shapes; wherein, the conditions for shaping include: the rolling time is 0.5 - 10 minutes / time, the number of rolling times is 1 - 5 times, and the rotational speed of the sample chamber is 50 - 1400 r / min.

[0042] According to the present invention, in step (1 - 3), the standard spherical balls are put into a micro - pellet screening machine to screen out spherical precursors of suitable sizes.

[0043] The second aspect of the present invention provides a method for preparing the aforementioned spherical esterification catalyst, wherein the preparation method includes:

[0044] (S1) Contacting the spherical composite support with an aqueous solution of a metal salt for a first reaction, and after the first separation, obtaining a solid product. After drying and the first roasting of the solid product, a catalyst intermediate is obtained;

[0045] (S2) Contacting the catalyst intermediate with an aqueous solution of phosphotungstic acid for a second reaction, and after the second separation, obtaining a solid product. After washing, drying, and the second roasting of the solid product, a spherical esterification catalyst is obtained.

[0046] According to the present invention, in step (S1), the metal salt is selected from one or more of carbonates, chlorides, sulfates, and nitrates of alkali metals; preferably, the alkali metal is selected from one or several of potassium, rubidium, and cesium.

[0047] According to the present invention, the concentration of the aqueous solution of the metal salt is 0.05 - 2.0 mol / L, preferably 0.1 - 1.0 mol / L.

[0048] According to the present invention, the weight ratio of the spherical composite support to the aqueous solution of the metal salt is 1:(2 - 100), preferably 1:(5 - 50).

[0049] According to the present invention, the conditions for the first reaction of the spherical composite support with the aqueous solution of the metal salt include: the reaction temperature can be 30 - 120 °C, preferably 40 - 90 °C; the time can be 0.5 - 20 h, preferably 2 - 10 h. Preferably, in order to achieve a better mixing effect, rapid stirring or ultrasonic means can be used during the contact reaction of the spherical composite support and the aqueous metal salt solution to improve the reaction efficiency.

[0050] According to the present invention, the conditions for the first calcination include: the temperature is 250 - 400 °C and the time is 3 - 10 h.

[0051] According to the present invention, in step (S1), there are no special requirements for the first separation method, and it can be a method well-known in the art, for example: using a rotary evaporator or heating and evaporating water during stirring.

[0052] According to the present invention, in step (S2), the concentration of the aqueous solution of phosphotungstic acid is 1 - 30%, preferably 5 - 20%.

[0053] According to the present invention, the weight ratio of the spherical composite support to the aqueous solution of phosphotungstic acid is 1:(5 - 50), preferably 1:(10 - 30).

[0054] According to the present invention, the conditions for the second reaction of the catalyst intermediate with the aqueous solution of the metal salt include: the reaction temperature can be 30 - 120 °C, preferably 40 - 90 °C; the time can be 0.5 - 20 h, preferably 2 - 10 h. Preferably, in order to achieve a better contact reaction effect, rapid stirring or ultrasonic means can be used during the contact reaction of the catalyst intermediate and the aqueous metal salt solution to improve the contact reaction efficiency.

[0055] According to the present invention, there are no special requirements for the separation method in step (S2), for example: filtration or suction filtration can be used to remove the liquid to obtain a solid product.

[0056] According to the present invention, in step (S2), there is no particular requirement for the method of washing the solid product. For example, deionized water can be used to wash the solid product, the volume ratio of deionized water to the solid product can be 5-20, and the number of washing times can be 2-8 times.

[0057] According to the present invention, in steps (S1) and (S2), the conditions for drying the solid product are preferably: the drying temperature is 80-130°C, and the drying time is 3-20 hours.

[0058] According to the present invention, the conditions for the second calcination include: the temperature is 250-400°C, and the time is 3-10 h; the conditions for the first calcination and the second calcination can be the same or different.

[0059] The third aspect of the present invention provides an application of the aforementioned spherical esterification catalyst in the synthesis reaction of n-butyl acetate.

[0060] Among them, the application method of the catalyst includes: acetic acid and n-butanol are simultaneously contacted with the spherical esterification catalyst.

[0061] In the present invention, the contact conditions of acetic acid and n-butanol with the catalyst include: the contact temperature can be 50-160°C, preferably 70-130°C; the contact pressure can be 0.01-5.0 MPa, preferably 0.1-3.0 Mpa; the mass space velocity of acetic acid can be 0.01-30 h -1 , preferably 0.1-10 h -1 ; the molar ratio of acetic acid to n-butanol is 1:0.1-20, preferably 1:0.5-10.

[0062] The present invention will be described in detail below through examples.

[0063] In the following examples and comparative examples:

[0064] The XRD test of the sample was carried out on a Philips X'Pert MPD type X-ray powder diffractometer in the Netherlands, with a Cu Kα target and a scanning range of 2θ = 5-90°.

[0065] The pore structure parameter analysis of the sample was carried out on an ASAP2020-M+C type adsorption instrument produced by Micromeritics in the United States. Before the sample was measured, it was vacuum degassed at 350°C for 4 hours. The BET method was used to calculate the specific surface area of the sample, and the BJH model was used to calculate the pore volume.

[0066] The elemental analysis experiment of the sample was carried out on an EagleⅢ energy dispersive X-ray fluorescence spectrometer produced by EDAX in the United States.

[0067] The rotary evaporator is produced by IKA Company in Germany, and the model is RV10 digital.

[0068] The drying oven is produced by Shanghai Yiheng Scientific Instrument Co., Ltd., and the model is DHG-9030A.

[0069] The muffle furnace is produced by CARBOLITE Company, and the model is CWF1100.

[0070] The kneader is the FN-NH2 type kneader produced by Tianshui Huayuan Pharmaceutical Equipment Technology Co., Ltd.; the micro ball making machine is the HWJ-100 type micro ball making machine produced by Tianshui Huayuan Pharmaceutical Equipment Technology Co., Ltd.; the micro pellet shaping machine is the FN-XZXJ type micro pellet shaping machine produced by Tianshui Huayuan Pharmaceutical Equipment Technology Co., Ltd.; the micro pellet screening machine is the SWP-1200 type micro pellet screening machine produced by Tianshui Huayuan Pharmaceutical Equipment Technology Co., Ltd.

[0071] Example 1

[0072] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0073] (1) Preparation of spherical alumina-MCM-22 composite support

[0074] Mix 120 g of pseudo-boehmite powder with the model number P-DF-09-LSi, 50 g of MCM-22 molecular sieve (SiO2 / Al2O3 = 25), 85 g of 5% dilute nitric acid and 10 g of sesbania powder, and transfer them to a kneader for stirring and mixing evenly. The kneading temperature is 35 °C, the main shaft rotation speed of the kneader is 150 r / min, and the kneading time is 1 h. Put the evenly mixed raw materials into the hopper of the micro ball making machine, select an extrusion die with a pore diameter of 2.1 mm, adjust the extrusion speed to 2 m / min, and the cutting speed to 1200 grains / minute, and extrude and cut the raw materials into round small particles. Put the above round small particles into the micro pellet shaping machine for shaping, and the shaping conditions are as follows: the rolling time is 3 minutes / time, the rolling times are 3 times, and the rotation speed of the sample chamber is 300 r / min. Put the standard round spherical raw material balls obtained after shaping into the micro pellet screening machine to screen out spherical precursors with a size of 2.1 mm. Dry the spherical precursors at 110 °C for 8 h, and then calcine them at 600 °C for 15 h to obtain spherical alumina-MCM-22 composite support A.

[0075] The alumina content in spherical alumina-MCM-22 composite support A is 62.7 wt%, and the MCM-22 molecular sieve content is 37.3 wt%.

[0076] Characterize spherical alumina-MCM-22 composite support A, and its structural parameters are listed in Table 1.

[0077] Figure 1It is the XRD pattern of spherical alumina-MCM-22 composite support A. Figure 1 It is the XRD pattern of spherical composite support A. As shown in the pattern, the main X-ray diffraction angles of this sample are: 2θ = 7.2°, 8.1°, 10.0°, 12.8°, 14.4°, 15.9°, 20.2°, 21.7°, 22.6°, 23.7°, 24.9°, 25.9°, 27.0°, 33.5°, 37.4°, 39.5°, 45.8°, and 66.8°. Among them, the fourteen diffraction signals at 2θ = 7.2°, 8.1°, 10.0°, 12.8°, 14.4°, 15.9°, 20.2°, 21.7°, 22.6°, 23.7°, 24.9°, 25.9°, 27.0°, and 33.5° coincide with the diffraction pattern of MCM-22 molecular sieve; the four diffraction signals at 2θ = 37.4°, 39.5°, 45.8°, and 66.8° coincide with the diffraction pattern of γ-Al2O3, indicating that the crystal phase of MCM-22 molecular sieve in spherical alumina-MCM-22 composite support A has not changed significantly after calcination at 600 °C, and the pseudo-boehmite presents a typical γ-Al2O3 crystal phase after dehydration.

[0078] Figure 2 It is a picture of spherical alumina-MCM-22 composite support A. It can be seen that the appearance of this support is white spherical, with good sphericity, smooth spherical surface, and uniform particle size.

[0079] (2) Preparation of spherical esterification catalyst

[0080] Mix 10 g of spherical alumina-MCM-22 composite support A with 260 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L, and stir and react at 70 °C for 6 h. After the reaction, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 175 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stir and react at 70 °C for 6 h. After the reaction, filter to remove the liquid to obtain a solid product. Wash the solid product 4 times with distilled water, then dry the solid product at 100 °C for 12 h, and then calcine at 320 °C for 6 h to obtain spherical esterification catalyst A.

[0081] Based on the total weight of catalyst A, the content of spherical alumina-MCM-22 composite support A is 61.3 wt%, and the content of potassium phosphotungstate is 38.7 wt%.

[0082] (3) Evaluation of catalyst reaction performance

[0083] The esterification performance of catalyst A was evaluated on a fixed-bed reaction apparatus. 5.0 g of the catalyst was loaded into a stainless-steel fixed-bed reactor with an inner diameter of 8 mm. The reaction temperature was 110 °C, the reaction pressure was adjusted to 0.3 MPa using nitrogen, and the weight hourly space velocity of acetic acid was 3.0 h -1 -1, the molar ratio of n-butanol to acetic acid was 5:1, and the reaction time was 20 h. After the product was cooled, it was analyzed using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and a flame ionization detector (FID). Programmed temperature rise was used, and quantitative analysis was performed using a correction factor. The conversion rate of acetic acid was 96.8%, and the selectivity of n-butyl acetate was 99.6%.

[0084] Example 2

[0085] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0086] (1) Preparation of the spherical composite support

[0087] 100 g of pseudo-boehmite powder of model SB, 50 g of MCM-22 molecular sieve (SiO2 / Al2O3 = 25), 80 g of acetic acid aqueous solution with a concentration of 10%, and 12 g of sesbania powder were mixed and transferred to a kneader for stirring and mixing evenly. The kneading temperature was 35 °C, the main shaft rotation speed of the kneader was 150 r / min, and the kneading time was 1 h. The uniformly mixed raw materials were put into the hopper of a micro ball-making machine. A bar extrusion die with a pore diameter of 1.6 mm was selected, the bar extrusion speed was adjusted to 5 m / min, and the cutting speed was 2000 grains / min. The raw materials were extruded into bars and then extruded and cut into small round particles. The above-mentioned round particles were put into a pellet shaping machine for shaping. The shaping conditions were as follows: the rolling time was 0.5 min / time, the rolling times were 2 times, and the sample chamber rotation speed was 500 r / min. The standard round raw material balls obtained after shaping were put into a pellet screening machine to screen out spherical precursors with a size of 1.6 mm. The spherical precursors were dried at 130 °C for 6 h and then calcined at 700 °C for 12 h to obtain a spherical alumina-MCM-22 composite support B.

[0088] The alumina content in the spherical alumina-MCM-22 composite support B was 60.0 wt%, and the MCM-22 molecular sieve content was 40.0 wt%.

[0089] The spherical alumina-MCM-22 composite support B was characterized, and its structural parameters are listed in Table 1.

[0090] (2) Preparation of the spherical esterification catalyst

[0091] Mix 10 g of spherical alumina-MCM-22 composite support B with 515 g of an aqueous cesium carbonate solution with a concentration of 0.2 mol / L, and stir and react at 90 °C for 2 h. After the reaction ends, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 130 °C for 3 h and calcined at 280 °C for 8 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 310 g of an aqueous phosphotungstic acid solution with a concentration of 5%, and stir and react at 90 °C for 2 h. After the reaction ends, filter to remove the liquid to obtain a solid product. After washing the solid product 4 times with distilled water, dry the solid product at 130 °C for 5 h, and then calcine at 380 °C for 4 h to obtain a short rod-shaped catalyst B supported on a silica mesoporous material.

[0092] Based on the total weight of catalyst B, the content of spherical alumina-MCM-22 composite support B is 58.5% by weight, and the content of cesium phosphotungstate is 41.5% by weight.

[0093] (3) Catalyst reaction performance evaluation

[0094] Carry out the esterification reaction performance test of catalyst B according to the method in step (3) of Example 1. The acetic acid conversion rate is 97.0%, and the selectivity of n-butyl acetate is 99.4%.

[0095] Example 3

[0096] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0097] (1) Preparation of spherical composite support

[0098] Mix 130 g of pseudo-boehmite powder of model PB-0101, 40 g of MCM-22 molecular sieve (SiO2 / Al2O3 = 25), 85 g of an aqueous citric acid solution with a concentration of 20%, and 8 g of talc powder, and transfer them to a kneader for stirring and mixing evenly. The kneading temperature is 20 °C, the main shaft rotation speed of the kneader is 200 r / min, and the kneading time is 0.5 h. Put the uniformly mixed raw materials into the hopper of a micro ball-making machine, select an extrusion die with a pore diameter of 2.5 mm, adjust the extrusion speed to 1 m / min, and the cutting speed to 500 grains / minute, and extrude and cut the raw materials into round small particles. Put the above round small particles into a pill shaping machine for shaping, and the shaping conditions are as follows: the rolling time is 2 minutes / time, the rolling times are 4 times, and the sample chamber rotation speed is 200 r / min. Put the standard round spherical raw material balls obtained after shaping into a pill screening machine to screen out spherical precursors with a size of 2.5 mm. Dry the spherical precursors at 90 °C for 10 h, and then calcine at 500 °C for 30 h to obtain spherical alumina-MCM-22 composite support C.

[0099] The spherical alumina-MCM-22 composite support C contains 71.0 wt% of alumina and 29.0 wt% of MCM-22 molecular sieve.

[0100] The spherical alumina-MCM-22 composite support C was characterized, and its structural parameters are listed in Table 1.

[0101] (2) Preparation of spherical esterification catalyst

[0102] 10 g of spherical alumina-MCM-22 composite support C and 115 g of an aqueous potassium carbonate solution with a concentration of 1.0 mol / L were mixed and stirred at 40 °C for 10 h. After the reaction ended, the stirring was stopped, and the solvent water was removed using a rotary evaporator to obtain a solid product. The solid product was dried at 80 °C for 20 h and calcined at 300 °C for 6 h to obtain a catalyst intermediate. The above catalyst intermediate was mixed with 75 g of an aqueous phosphotungstic acid solution with a concentration of 20% and stirred at 60 °C for 8 h. After the reaction ended, the liquid was removed by suction filtration to obtain a solid product. After washing the solid product 4 times with distilled water, the solid product was dried at 80 °C for 20 h and then calcined at 350 °C for 4 h to obtain a short rod-shaped catalyst C supported on all-silica mesoporous material.

[0103] Based on the total weight of catalyst C, the content of spherical alumina-MCM-22 composite support C is 66.3 wt%, and the content of potassium phosphotungstate is 33.7 wt%.

[0104] (3) Evaluation of catalyst reaction performance

[0105] The esterification reaction performance of catalyst C was tested according to the method in step (3) of Example 1. The conversion rate of acetic acid was 96.5%, and the selectivity of n-butyl acetate was 99.7%.

[0106] Table 1

[0107]

[0108] Example 4

[0109] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0110] A spherical esterification catalyst D was prepared according to the same method as in Example 1, except that the preparation conditions of the catalyst in step (2) of Example 1 were changed. Specifically:

[0111] Mix 10 g of spherical alumina-MCM-22 composite support A with 170 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L, and stir and react at 70 °C for 6 h. After the reaction is completed, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 114 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stir and react at 70 °C for 6 h. After the reaction is completed, filter to remove the liquid to obtain a solid product. Wash the solid product 4 times with distilled water, then dry the solid product at 100 °C for 12 h and calcine at 320 °C for 6 h to obtain spherical esterification catalyst D.

[0112] Based on the total weight of catalyst D, the content of spherical alumina-MCM-22 composite support A is 70.7% by weight, and the content of potassium phosphotungstate is 29.3% by weight.

[0113] Test the catalytic performance of catalyst D according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate is 95.7%, and the selectivity for n-butyl acetate is 99.0%.

[0114] Example 5

[0115] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0116] Prepare spherical esterification catalyst E according to the same method as in Example 1, the difference is: change the preparation conditions of the catalyst in step (2) of Example 1, specifically:

[0117] Mix 10 g of spherical alumina-MCM-22 composite support A with 446 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L, and stir and react at 70 °C for 6 h. After the reaction is completed, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 300 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stir and react at 70 °C for 6 h. After the reaction is completed, filter to remove the liquid to obtain a solid product. Wash the solid product 4 times with distilled water, then dry the solid product at 100 °C for 12 h and calcine at 320 °C for 6 h to obtain spherical esterification catalyst E.

[0118] Based on the total weight of catalyst E, the content of spherical alumina-MCM-22 composite support A is 48% by weight, and the content of potassium phosphotungstate is 52% by weight.

[0119] Test the catalytic performance of catalyst E according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate is 95.4%, and the selectivity for n-butyl acetate is 98.7%.

[0120] Example 6

[0121] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0122] The spherical esterification catalyst F was prepared by the same method as in Example 1, except that: the preparation conditions of the catalyst in step (2) of Example 1 were changed. Specifically:

[0123] 10 g of spherical alumina-MCM-22 composite support A and 136 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L were mixed and stirred at 70 °C for 6 h. After the reaction ended, the stirring was stopped, and the solvent water was removed using a rotary evaporator to obtain a solid product. The solid product was dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. The above catalyst intermediate was mixed with 91 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stirred at 70 °C for 6 h. After the reaction ended, the liquid was removed by suction filtration to obtain a solid product. After washing the solid product 4 times with distilled water, the solid product was dried at 100 °C for 12 h and then calcined at 320 °C for 6 h to obtain the spherical esterification catalyst F.

[0124] Based on the total weight of catalyst F, the content of spherical alumina-MCM-22 composite support A was 75.1% by weight, and the content of potassium phosphotungstate was 24.9% by weight.

[0125] According to the esterification reaction performance evaluation method in step (3) of Example 1, the catalytic performance of catalyst F was tested. The acetic acid conversion rate was 94.2%, and the selectivity of n-butyl acetate was 98.1%.

[0126] Example 7

[0127] This example is used to illustrate the spherical esterification catalyst prepared by the present invention.

[0128] The spherical esterification catalyst G was prepared by the same method as in Example 1, except that: the preparation conditions of the catalyst in step (2) of Example 1 were changed. Specifically:

[0129] Mix 10 g of spherical alumina-MCM-22 composite support A with 618 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L, and stir and react at 70 °C for 6 h. After the reaction is completed, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 415 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stir and react at 70 °C for 6 h. After the reaction is completed, filter to remove the liquid to obtain a solid product. After washing the solid product 4 times with distilled water, dry the solid product at 100 °C for 12 h, and then calcine at 320 °C for 6 h to obtain spherical esterification catalyst G.

[0130] Based on the total weight of catalyst G, the content of spherical alumina-MCM-22 composite support A is 40% by weight, and the content of potassium phosphotungstate is 60% by weight.

[0131] Test the catalytic performance of catalyst G according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate is 93.9%, and the selectivity of n-butyl acetate is 97.8%.

[0132] Comparative Example 1

[0133] Prepare spherical esterification catalyst D1 according to the same method as in Example 1, the difference is: change the preparation conditions of the catalyst in step (2) of Example 1, specifically:

[0134] Mix 10 g of spherical alumina-MCM-22 composite support A with 52 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L, and stir and react at 70 °C for 6 h. After the reaction is completed, stop stirring, and use a rotary evaporator to remove the solvent water to obtain a solid product. The solid product is dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. Mix the above catalyst intermediate with 35 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stir and react at 70 °C for 6 h. After the reaction is completed, filter to remove the liquid to obtain a solid product. After washing the solid product 4 times with distilled water, dry the solid product at 100 °C for 12 h, and then calcine at 320 °C for 6 h to obtain spherical esterification catalyst D1.

[0135] Based on the total weight of catalyst D1, the content of spherical alumina-MCM-22 composite support A is 88.8% by weight, and the content of potassium phosphotungstate is 11.2% by weight.

[0136] Test the catalytic performance of catalyst D1 according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate is 73.2%, and the selectivity of n-butyl acetate is 92.9%.

[0137] Comparative Example 2

[0138] The spherical esterification catalyst D2 was prepared in the same manner as in Example 1, except that: step (1) in Example 1 was cancelled, and the "spherical alumina-MCM-22 composite support A" in step (2) of Example 1 was replaced with "commercially available silica (purchased from Qingdao Hailang Silica Gel Desiccant Factory, specific surface area 329 m 2 / g, average particle diameter 1.5 mm)", to obtain catalyst D2.

[0139] Based on the total weight of catalyst D2, the content of commercially available silica was 61.3% by weight, and the content of potassium phosphotungstate was 38.7% by weight.

[0140] The catalytic performance of catalyst D2 was tested according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate was 87.6%, and the selectivity to n-butyl acetate was 95.3%.

[0141] Comparative Example 3

[0142] The spherical esterification catalyst D3 was prepared in the same manner as in Example 1, except that: step (1) in Example 1 was cancelled, and the "10 g of spherical alumina-MCM-22 composite support A" in step (2) of Example 1 was replaced with "14 g of pseudo-boehmite of model P-DF-09-LSi", to obtain catalyst D3.

[0143] Based on the total weight of catalyst D3, the content of alumina was 61.3% by weight, and the content of potassium phosphotungstate was 38.7% by weight.

[0144] The catalytic performance of catalyst D3 was tested according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate was 90.1%, and the selectivity to n-butyl acetate was 95.1%.

[0145] Comparative Example 4

[0146] The spherical esterification catalyst D4 was prepared in the same manner as in Example 1, except that: step (1) in Example 1 was cancelled, and the "10 g of spherical alumina-MCM-22 composite support A" in step (2) of Example 1 was replaced with "10 g of MCM-22 molecular sieve", to obtain catalyst D4.

[0147] Based on the total weight of catalyst D4, the content of MCM-22 molecular sieve was 61.3% by weight, and the content of potassium phosphotungstate was 38.7% by weight.

[0148] The catalytic performance of catalyst D4 was tested according to the esterification reaction performance evaluation method in step (3) of Example 1. The acetic acid conversion rate was 92.8%, and the selectivity to n-butyl acetate was 96.4%.

[0149] Comparative Example 5

[0150] The esterification catalyst D5 was prepared according to the same method as in Example 1, except that: in step (1), 70 g of pseudo-boehmite powder of model P-DF-09-LSi and 98 g of MCM-22 molecular sieve were used to obtain catalyst D5.

[0151] Based on the total weight of catalyst D5, the content of the spherical composite support was 61.3 wt%, and the content of potassium phosphotungstate was 38.7 wt%.

[0152] The catalytic performance of catalyst D5 was tested according to the esterification reaction performance evaluation method in step (3) of Example 1. The conversion rate of acetic acid was 93.1%, and the selectivity of n-butyl acetate was 97.3%.

[0153] Comparative Example 6

[0154] The esterification catalyst D6 was prepared according to the same method as in Example 1, except that: the preparation conditions of the catalyst in step (2) of Example 1 were changed, specifically:

[0155] 10 g of spherical alumina-MCM-22 composite support A and 1060 g of an aqueous potassium carbonate solution with a concentration of 0.6 mol / L were mixed and stirred at 70 °C for 6 h. After the reaction ended, stirring was stopped, and the solvent water was removed using a rotary evaporator to obtain a solid product. The solid product was dried at 100 °C for 8 h and calcined at 320 °C for 6 h to obtain a catalyst intermediate. The above catalyst intermediate was mixed with 713 g of an aqueous phosphotungstic acid solution with a concentration of 10%, and stirred at 70 °C for 6 h. After the reaction ended, the liquid was removed by suction filtration to obtain a solid product. The solid product was washed 4 times with distilled water, dried at 100 °C for 12 h, and then calcined at 320 °C for 6 h to obtain spherical esterification catalyst D6.

[0156] Based on the total weight of catalyst D6, the content of spherical alumina-MCM-22 composite support A was 28 wt%, and the content of potassium phosphotungstate was 72 wt%.

[0157] The catalytic performance of catalyst D6 was tested according to the esterification reaction performance evaluation method in step (3) of Example 1. The conversion rate of acetic acid was 74.3%, and the selectivity of n-butyl acetate was 93.5%.

[0158] It can be seen from the above results that the spherical esterification catalyst provided by the present invention can directly convert acetic acid and n-butanol to generate n-butyl acetate, obtaining a relatively high conversion rate of acetic acid and selectivity of n-butyl acetate.

[0159] In Comparative Example 1, the content of the spherical alumina-MCM-22 composite support A was too high. Due to the low content of the active component phosphotungstate on the catalyst and the insufficient active sites during the reaction process, the conversion rate of acetic acid was low and the selectivity of n-butyl acetate was low.

[0160] In Comparative Example 2, instead of using the spherical composite support specifically defined in the present invention, commercially available silica was used. Due to the irregular pore structure of the commercially available silica and the uneven dispersion of the active component on the support surface, the conversion rate of acetic acid was low and the selectivity of n-butyl acetate was low.

[0161] In Comparative Example 3, instead of using the spherical composite support specifically defined in the present invention, a single alumina support was used. Due to the uneven pore size distribution of alumina, which is not conducive to the dispersion of the active component on the support surface and also not conducive to the diffusion of raw materials and products during the reaction process, the conversion rate of acetic acid was low and the selectivity of n-butyl acetate was low.

[0162] In Comparative Example 4, instead of using the spherical composite support specifically defined in the present invention, a single MCM-22 molecular sieve was used. Due to the small pore size of the MCM-22 molecular sieve, the surface was uneven after being prepared into a catalyst, and the dispersion of the active component was poor, resulting in a low conversion rate of acetic acid and a low selectivity of n-butyl acetate.

[0163] In Comparative Example 5, the weight ratio of the content of alumina and MCM-22 molecular sieve in the spherical composite support was 1:2 (because the pseudo-boehmite of model P-DF-09-LSi contains about 30% water, and only 70% of the weight of alumina is obtained after being made into a finished product). The content of MCM-22 molecular sieve was too high. Since the proportion of MCM-22 molecular sieve in the spherical composite support was not within the specific range required by the present invention, the prepared catalyst had poor strength, uneven surface, and poor dispersion of the active component, thus resulting in a low conversion rate of acetic acid and a low selectivity of n-butyl acetate.

[0164] In Comparative Example 6, the content of the spherical alumina-MCM-22 composite support A was too low. Due to the too high content of the active component phosphotungstate on the catalyst and the uneven dispersion of the active component on the support, and the low utilization efficiency of the active center during the reaction process, the conversion rate of acetic acid was low and the selectivity of n-butyl acetate was low.

[0165] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. Application of a spherical esterification catalyst in the synthesis reaction of n-butyl acetate, characterized in that, The applications described include: acetic acid and n-butanol are simultaneously contacted with a spherical esterification catalyst in a fixed-bed reactor. Among them, the spherical esterification catalyst includes a spherical composite support and phosphotungstate supported on the spherical composite support. The spherical composite support includes alumina and MCM-22 molecular sieve. Based on the total weight of the spherical composite support, the content of alumina is 50-80% by weight, and the content of MCM-22 molecular sieve is 20-50% by weight; the specific surface area of the spherical composite support is 400-900m 2 / g, the pore volume is 0.3-0.9 mL / g, the pore size distribution is bimodal, and the first most probable pore size corresponding to the bimodality is 0.3-1 nm, and the second most probable pore size is 8-25 nm; the average particle diameter is 1.0-3.0 mm, and the average particle strength is 20-70 N; and based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 40-80% by weight, and the content of the phosphotungstate is 20-60% by weight.

2. The application according to claim 1, wherein, Based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 48 - 73% by weight, and the content of the phosphotungstate is 27 - 52% by weight.

3. The application according to claim 2, wherein Based on the total weight of the spherical esterification catalyst, the content of the spherical composite support is 58.5 - 66.3% by weight, and the content of the phosphotungstate is 33.7 - 41.5% by weight.

4. The application according to claim 1, wherein, The phosphotungstate is an alkali metal salt of phosphotungstic acid.

5. The application according to claim 4, wherein, The phosphotungstate is selected from one or more of potassium phosphotungstate, rubidium phosphotungstate, and cesium phosphotungstate.

6. The application according to claim 1, wherein The specific surface area of the spherical composite carrier is 450-750m 2 / g, the pore volume is 0.4-0.7 mL / g, the pore size distribution is bimodal, and the first most probable pore size corresponding to the bimodality is 0.4-0.8 nm, and the second most probable pore size is 10-20 nm; the average particle diameter is 1.2-2.7 mm, and the average particle strength is 25-60 N.

7. The application according to claim 6, wherein, The specific surface area of the spherical composite carrier is 508-634 m 2 / g, the pore volume is 0.51-0.62 mL / g, the pore size distribution is bimodal, the first most probable pore size corresponding to the bimodality is 0.5-0.7 nm, the second most probable pore size is 12-16 nm; the average particle diameter is 1.5-2.4 mm, and the average particle strength is 28.1-52.6 N.

8. The application according to claim 1, wherein Based on the total weight of the spherical composite support, the content of alumina is 60 - 71% by weight, and the content of MCM-22 molecular sieve is 29 - 40% by weight.

9. The application according to any one of claims 1-8, wherein The method for preparing the spherical composite support includes: (1) Mixing an alumina precursor, an MCM-22 molecular sieve, an acidic aqueous solution, and an extrusion aid to obtain a mixture, and subjecting the mixture to pelletizing to obtain a spherical alumina-MCM-22 precursor; (2) Drying and calcining the spherical alumina-MCM-22 precursor to obtain a spherical alumina-MCM-22 composite support.

10. The application according to claim 9, wherein, The alumina precursor is selected from one or more of pseudoboehmite, aluminum hydroxide gel, aluminum sol, gibbsite, and boehmite; and / or, the specific surface area of the MCM-22 molecular sieve is 400-600 m 2 / g, and the pore volume is 0.4-0.7 cm 3 / g; and / or, the weight ratio of the alumina precursor, the MCM-22 molecular sieve, the extrusion aid, and the acidic aqueous solution is 1:(0.2 - 1):(0.02 - 0.5):(0.2 - 5).

11. The application according to any one of claims 1-3, wherein, The method for preparing the spherical esterification catalyst includes: (S1) Contacting the spherical composite support with an aqueous solution of a metal salt for a first reaction, followed by a first separation to obtain a solid product, and drying and first calcining the solid product to obtain a catalyst intermediate; (S2) Contacting the catalyst intermediate with an aqueous solution of phosphotungstic acid for a second reaction, followed by a second separation to obtain a solid product, and washing, drying, and second calcining the solid product to obtain a spherical esterification catalyst.

12. The application according to claim 11, wherein, The metal salt is selected from one or more of carbonates, chlorides, sulfates, and nitrates of alkali metals; and / or, the concentration of the aqueous solution of the metal salt is 0.05 - 2.0 mol / L; and / or, the weight ratio of the spherical composite support to the aqueous solution of the metal salt is 1:(2 - 100); and / or, the conditions of the first reaction include: temperature of 30 - 120°C, time of 0.5 - 20 h; and / or, the conditions of the first calcination include: temperature of 250 - 400°C, time of 3 - 10 h.

13. The application according to claim 11, wherein, The concentration of the aqueous solution of phosphotungstic acid is 1 - 30%; and / or, the weight ratio of the spherical composite support to the aqueous solution of phosphotungstic acid is 1:(5 - 50); and / or, the conditions of the second reaction include: temperature of 30 - 120°C, time of 0.5 - 20 h; and / or, the conditions of the second calcination include: temperature of 250 - 400°C, time of 3 - 10 h.

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