Hydrophobic modifier / metal oxide / beta molecular sieve composite adsorbent for methanol-dimethyl carbonate azeotrope separation and preparation method thereof

Abstract

The invention belongs to the technical field of adsorption materials, and particularly relates to a hydrophobic modifier / metal oxide / beta molecular sieve composite adsorbent for methanol-dimethyl carbonate azeotrope separation and a preparation method of the hydrophobic modifier / metal oxide / beta molecular sieve composite adsorbent. The hydrophobic modifier / metal oxide / beta molecular sieve composite adsorbent is prepared by sequentially carrying out acid treatment, metal loading, calcination and hydrophobic modifier treatment on a beta molecular sieve, the pH value of a solution does not need to be adjusted, a precipitant is not used, the preparation process does not involve chemical reaction, the operation is simple, and the adsorbent is safe and efficient. Wherein a back-mixing impregnation method is adopted for metal loading, a large number of metal oxides are loaded on the small-pore-diameter beta molecular sieve, and the problem of local particle accumulation caused by a high-concentration metal salt solution is solved. The hydrophobic modifier is adopted for treatment, the interaction between dimethyl carbonate and the surface of the adsorbent is reduced, meanwhile, the adsorption performance of the composite adsorbent on methanol is remarkably improved, and the problems that a methanol-dimethyl carbonate separation adsorbent at the present stage is low in adsorption capacity and selectivity are effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorption materials, and particularly relates to a hydrophobic modifier / metal oxide / beta molecular sieve composite adsorbent for separating methanol-dimethyl carbonate azeotrope and a preparation method thereof. Background Art

[0002] Dimethyl carbonate is a chemical raw material with low toxicity and excellent environmental performance. It is known as the "new cornerstone" of the chemical synthesis industry in the 21st century. Among them, lithium battery electrolyte is one of the main downstream demands of dimethyl carbonate. Dimethyl carbonate can not only improve fuel power and reduce pollutant gas emissions, but also play an indispensable role in improving battery performance and extending battery life. The rapid growth of the new energy industry has intensified the market demand for dimethyl carbonate. As of September 2024, the total output of power batteries and other batteries in my country was 101.3GWh, a year-on-year increase of 36.8%. At the same time, the annual growth rate of dimethyl carbonate demand for lithium battery electrolytes exceeded 40%. Although the domestic dimethyl carbonate production capacity has increased by 2 million tons in the past three years, it is still facing a situation of supply exceeding demand. The current mainstream electrolyte solvent is battery-grade dimethyl carbonate, which has high product purity requirements (>99.95%), high process difficulty, and high technical barriers. In the industrial production of dimethyl carbonate, excess methanol is used as a raw material to improve the reaction conversion rate and product yield, and the resulting products are all azeotropes of methanol and dimethyl carbonate (mass ratio is 7:3). Therefore, efficient separation of methanol-dimethyl carbonate azeotropes is one of the key steps in the preparation of battery-grade dimethyl carbonate.

[0003] At present, the separation methods of methanol-dimethyl carbonate azeotrope mainly include pressure swing distillation, extractive distillation, membrane separation and adsorption separation. Among them, the adsorption separation method has the characteristics of simple process, low energy consumption and mild conditions, which can effectively reduce the separation cost and simplify the complex separation process, and has unique application and research value in the separation of azeotropes. The key to the adsorption separation of methanol-dimethyl carbonate azeotrope is to prepare an adsorbent with excellent performance, which needs to have high selectivity and adsorption capacity, good structural strength, stable chemical properties, low price, etc. β molecular sieve is a crystal composed of an aluminum silicate skeleton. Its unique topological structure gives it excellent heat resistance, acid and alkali resistance and hydrothermal stability. In addition, the β molecular sieve has a large number of uniform and neatly arranged pores in its structure. It can screen molecules while adsorbing substances, so it has a certain adsorption capacity and selectivity. However, the adsorption mechanism of molecular sieves is mainly physical adsorption, so the overall adsorption capacity is low. In addition, although there is a difference in molecular size between single methanol and single dimethyl carbonate, the azeotrope formed by the two usually exists in a macromolecular cluster structure, and the adjustable pore size in the β molecular sieve is difficult to achieve efficient molecular screening. Therefore, its selectivity for methanol-dimethyl carbonate azeotrope is low. Adsorbent modification is an effective way to improve adsorption capacity and selectivity, mainly including acid modification, ultrasonic modification, load modification, organic modification, etc. Among them, load modification increases the types and number of chemical active sites on the surface by loading active components (mainly metal oxides) on the carrier, while organic modification is to introduce organic matter into the surface or inside of the material to change the surface charge, polarity, hydrophilicity and hydrophobicity, so as to achieve the purpose of increasing adsorption capacity and selectivity. It is currently the most commonly used and effective modification method. Mechanism studies have shown that methanol molecules can form strong chemical bonds with metal active sites on the surface of metal oxides, while dimethyl carbonate can only form weak hydrogen bonds with hydroxyl oxygen atoms on the surface. Therefore, metal oxides show extremely high selectivity for methanol in methanol-dimethyl carbonate azeotrope. In addition, the role of chemical bonds can also break the cluster structure of azeotropes, decompose them into small molecules, and promote the molecular sieving effect of pore size. On the other hand, if the hydroxyl groups on the adsorbent surface can be reduced through organic modification, especially hydrophobic modification, the dimethyl carbonate adsorbed by hydrogen bonding can be effectively reduced, thereby further improving the selectivity of the adsorbent for methanol.

[0004] Chemical coprecipitation, sol-gel and impregnation are important preparation methods for modified adsorbents. In the chemical coprecipitation method, a modified material containing metal oxides and organic matter is obtained by adding an appropriate precipitant and reacting in the solution. In the sol-gel method, a compound containing a modified component is used as a precursor, and a modified material is prepared through steps such as hydrolysis, condensation, aging and drying. In the impregnation method, a carrier is immersed in a solution containing a modified component, and the modified material is obtained through stirring, filtering and drying. Compared with the other two preparation methods, the impregnation method has the significant advantages of simple operation and high efficiency and speed, but the maximum loading amount of the active component is limited by the pore size and pore volume of the carrier. When the pore volume of the carrier is low, it is difficult for the prepared impregnation solution to reach the required active component concentration; when the pore size of the carrier is small, the active component particles are very easy to accumulate on the surface of the carrier, resulting in uneven loading in the pores. Therefore, using β molecular sieve as a carrier, adopting metal modification and organic modification, introducing a large number of chemically active sites through an improved impregnation method while reducing the surface hydrophilicity can effectively solve the dilemma of low adsorption capacity and selectivity faced by the current methanol-dimethyl carbonate separation adsorbent. Summary of the invention

[0005] The problem in the prior art is that the organic modifier / metal oxide / β molecular sieve adsorbent obtained by the conventional impregnation method has the problems of few chemical active sites, surface particle accumulation and uneven loading of active components, resulting in a small adsorption capacity for methanol-dimethyl carbonate azeotrope and low separation selectivity. In view of the above problems, the present invention provides an azeotrope separation composite adsorbent, and its preparation method comprises the following steps:

[0006] (1) Preparing a β molecular sieve carrier: dispersing the β molecular sieve in a hydrochloric acid solution with a concentration of 1 to 3 mol / L, stirring at room temperature for 1 to 2 hours to remove impurities inside the molecular sieve and dredge the pores; filtering, washing the filter cake with deionized water until the filtrate is neutral, placing the pretreated β molecular sieve in a constant temperature forced air drying oven at 100 to 110° C. for 8 to 12 hours to obtain dry β molecular sieve particles; sieving the dry β molecular sieve particles through 100 to 120 meshes to obtain a β molecular sieve carrier;

[0007] (2) Preparation of metal oxide / β molecular sieve material: placing a metal salt solution in a stirred tank, then immersing the β molecular sieve carrier obtained in step (1) in the metal salt solution, stirring at room temperature for 1 to 2 hours, filtering to obtain a solid filter cake, and then drying at 100 to 110° C. for 4 to 6 hours, sieving through 100 to 120 mesh, and then returning the obtained solid particles to the stirred tank, remixing with the residual metal salt solution in the tank, continuing to stir at room temperature for 1 to 2 hours, and filtering by suction. The filter cake is dried at 100 to 110° C. for 4 to 6 hours, sieving through 100 to 120 mesh, and then calcining at 300 to 350° C. for 2 to 4 hours to obtain a metal oxide / β molecular sieve material;

[0008] (3) preparing a hydrophobic modifier / metal oxide / β molecular sieve composite material: immersing the metal oxide / β molecular sieve material obtained in step (2) in an aqueous solution of a hydrophobic modifier, stirring at 50-60° C. for 1-2 h, filtering with suction, washing the filter cake with deionized water, drying at 100-110° C. for 8-12 h, and sieving through 100-120 mesh to obtain a hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent;

[0009] Preferably, the metal salt includes at least one of aluminum chloride, ferric chloride, ferrous chloride, manganese chloride and ammonium metatungstate.

[0010] Preferably, the hydrophobic modifier includes at least one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and polycarboxylate ammonium salt dispersants.

[0011] Preferably, in step (1), the ratio of the β molecular sieve carrier to the aqueous hydrochloric acid solution is 0.8-1.5 g: 10-15 mL.

[0012] Preferably, the concentration of the metal salt solution in step (2) is 0.05 to 3 mol / L.

[0013] Preferably, in step (2), the mass ratio of the β molecular sieve carrier to the metal salt is 1:1 to 1:10.

[0014] Preferably, the concentration of the aqueous solution of the hydrophobic modifier in step (3) is 0.1 to 0.5 mol / L.

[0015] Preferably, in step (3), the mass ratio of metal oxide / β molecular sieve to hydrophobic modifier is 1:0.1 to 1:2.5.

[0016] A hydrophobic modifier / metal oxide / beta molecular sieve composite material prepared by the method.

[0017] The above hydrophobic modifier / metal oxide / β molecular sieve composite material is applied to the separation of methanol-dimethyl carbonate azeotrope, and the specific steps are as follows:

[0018] The hydrophobic modifier / metal oxide / β molecular sieve adsorbent is mixed with the methanol-dimethyl carbonate azeotrope solution, placed in a conical flask, and placed in a constant temperature oscillator for azeotrope adsorption separation.

[0019] Preferably, the mass ratio of methanol:dimethyl carbonate:DMF in the methanol-dimethyl carbonate azeotrope solution is (14-56):(6-24):(20-80).

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) In the process of preparing the adsorbent, the present invention adopts the back-mixing impregnation method to uniformly load a large amount of metal oxides on the β molecular sieve carrier, which not only increases the types and number of chemically active sites on the surface, but also avoids the accumulation and uneven distribution of active components.

[0022] (2) In the process of preparing the adsorbent, the present invention uses a hydrophobic modifier to modify the surface of the adsorbent, which effectively reduces the number of hydroxyl groups on the surface of the adsorbent, thereby reducing the dimethyl carbonate adsorbed by hydrogen bonding, and further improving the selectivity of the adsorbent for methanol.

[0023] (3) Compared with the commonly used chemical co-precipitation method, this preparation method does not require adjusting the pH value of the solution, does not use a precipitant, and the preparation process does not involve chemical reactions. The preparation operation is simple, safe, and efficient. The prepared hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent is used for the separation of methanol-dimethyl carbonate azeotropes, with a large adsorption capacity and a good separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the preparation of the composite adsorbent of Example 1;

[0025] Figure 2 The static adsorption separation performance of the composite adsorbent prepared by using different metal salts for azeotropic simulated solution in Examples 1-5;

[0026] Figure 3 The static adsorption separation performance of the composite adsorbents prepared by different hydrophobic modifiers in Examples 1 and 6-9 on azeotropic simulated solutions.

[0027] Figure 4 The static adsorption separation performance of the composite adsorbent prepared by using dodecyltrimethylammonium bromide of different concentrations for azeotropic simulated solution in Examples 1 and 10-13 is shown.

[0028] Figure 5 The static adsorption separation performance of the composite adsorbent prepared in Examples 14-17 for simulated solutions with different azeotropic concentrations. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0030] Example 1

[0031] (1) Preparation of β molecular sieve carrier: First, 5 g of β molecular sieve (analytical grade, purchased from Aladdin Biochemical Technology Co., Ltd.) was dispersed in 50 mL of 2 mol / L hydrochloric acid aqueous solution, stirred at room temperature for 2 h, and then the mixed solution was washed with deionized water until neutral; then the acid-activated β molecular sieve was placed in an oven at 105° C. and dried for 8 h, and ground and sieved through 100 mesh to obtain β molecular sieve carrier powder.

[0032] (2) Preparation of metal oxide / β molecular sieve material: Take 34.73g aluminum chloride hexahydrate, add 50mL deionized water, and stir at room temperature for 5min to make it dissolve evenly. Place the aluminum chloride hexahydrate salt solution in a stirring tank, then immerse the 5g β molecular sieve carrier obtained in step (1) in the aluminum chloride hexahydrate salt solution, stir at room temperature for 2h, filter to obtain a solid filter cake, and then dry it at 105°C for 6h, sieve 100 mesh, and then return the obtained solid particles to the stirring tank, remix with the residual liquid of the metal salt solution in the tank, continue to stir at room temperature for 2h, filter, dry the filter cake at 105°C for 6h, sieve 100 mesh, and then calcine at 350°C for 4h to obtain Al2O3 / β molecular sieve material, wherein the mass ratio of metal oxide to molecular sieve in the Al2O3 / β molecular sieve material is 15:85;

[0033] (3) Preparation of hydrophobic modifier / metal oxide / β molecular sieve composite material: Take 1.54g dodecyltrimethylammonium bromide as a modifier, add 50mL deionized water, stir at room temperature for 5min to fully dissolve it, and prepare a hydrophobic modifier aqueous solution with a concentration of 0.1mol / L. Then add 5g of the prepared Al2O3 / β molecular sieve material, gradually heat to 50℃ and continue stirring for 2h, filter and wash several times, dry in an oven at 105℃ for 8h, grind and sieve 100 mesh, and obtain dodecyltrimethylammonium bromide / Al2O3 / β molecular sieve composite adsorbent.

[0034] Static adsorption experiments were conducted, and N,N-dimethylformamide (DMF) was used as an inert solvent to prepare an azeotrope simulation solution, in which the mass ratio of methanol: dimethyl carbonate: DMF was 35:15:50. 0.50g of dodecyltrimethylammonium bromide / Al2O3 / β molecular sieve adsorbent was weighed as an adsorbent, mixed with 10mL of azeotrope simulation solution, placed in a conical flask, and placed in a constant temperature oscillator for azeotrope adsorption separation. Oscillate until adsorption equilibrium is reached, and the upper clear liquid is taken after standing to determine the concentration of the equilibrium liquid after adsorption. The saturated adsorption capacity for methanol is calculated to be 1901.06mg / g, the saturated adsorption capacity for dimethyl carbonate is 519.23mg / g, and the selectivity is 3.66.

[0035] Example 2 is the same as Example 1, except that 14.89 g of ferric chloride is used as the metal salt when preparing the metal oxide / β molecular sieve material, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol by dodecyltrimethylammonium bromide / Fe2O3 / β molecular sieve adsorbent is 1056.14 mg / g, the saturated adsorption capacity of dimethyl carbonate is 476.63 mg / g, and the selectivity is 2.21.

[0036] Example 3 is the same as Example 1, except that 12.04 g of ferrous chloride is used as the metal salt when preparing the metal oxide / β molecular sieve material, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of dodecyltrimethylammonium bromide / Fe3O4 / β molecular sieve adsorbent for methanol is 1161.74 mg / g, the saturated adsorption capacity for dimethyl carbonate is 502.79 mg / g, and the selectivity is 2.31.

[0037] Example 4 is the same as Example 1, except that 10.61 g of manganese chloride is used as the metal salt when preparing the metal oxide / β molecular sieve material, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol by dodecyltrimethylammonium bromide / MnO2 / β molecular sieve adsorbent is 969.49 mg / g, the saturated adsorption capacity of dimethyl carbonate is 439.42 mg / g, and the selectivity is 2.20.

[0038] Example 5 is the same as Example 1, except that when preparing the metal oxide / β molecular sieve material, 7.84 g of ammonium metatungstate is used as the metal salt, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol of dodecyltrimethylammonium bromide / WO3 / β molecular sieve adsorbent is 738.68 mg / g, the saturated adsorption capacity of dimethyl carbonate is 412.35 mg / g, and the selectivity is 1.79.

[0039] Example 6 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 1.68 g of tetradecyl trimethyl ammonium bromide is used as the modifier, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of tetradecyl trimethyl ammonium bromide / Al2O3 / β molecular sieve composite adsorbent for methanol is 1881.04 mg / g, the saturated adsorption capacity for dimethyl carbonate is 542.18 mg / g, and the selectivity is 3.47.

[0040] Example 7 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 1.60g of hexadecyltrimethylammonium chloride is used as the modifier, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of hexadecyltrimethylammonium chloride / Al2O3 / β molecular sieve composite adsorbent for methanol is 956.23mg / g, the saturated adsorption capacity for dimethyl carbonate is 301.72mg / g, and the selectivity is 3.16.

[0041] Example 8 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 1.96 g of octadecyl trimethyl ammonium bromide is used as the modifier, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol by the octadecyl trimethyl ammonium bromide / Al2O3 / β molecular sieve composite adsorbent is 915.85 mg / g, the saturated adsorption capacity of dimethyl carbonate is 296.15 mg / g, and the selectivity is 3.09.

[0042] Example 9 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 0.5g of polycarboxylic acid ammonium salt dispersant (industrial grade, purchased from Beijing Qifei Technology Development Co., Ltd.) is used as the modifier, and the remaining operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of the polycarboxylic acid ammonium salt dispersant / Al2O3 / β molecular sieve composite adsorbent for methanol is 1235.66mg / g, the saturated adsorption capacity for dimethyl carbonate is 405.96mg / g, and the selectivity is 3.04.

[0043] Example 10 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 3.08 g of dodecyl trimethyl ammonium bromide is used as a modifier to prepare a hydrophobic modifier aqueous solution with a concentration of 0.2 mol / L, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1657.59 mg / g, the saturated adsorption capacity of dimethyl carbonate was 476.91 mg / g, and the selectivity was 3.47.

[0044] Example 11 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 4.62 g of dodecyltrimethylammonium bromide is used as a modifier to prepare a hydrophobic modifier aqueous solution with a concentration of 0.3 mol / L, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was measured to be 989.73 mg / g, the saturated adsorption capacity of dimethyl carbonate was 291.69 mg / g, and the selectivity was 3.39.

[0045] Example 12 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 6.16 g of dodecyltrimethylammonium bromide is used as a modifier to prepare a hydrophobic modifier aqueous solution with a concentration of 0.4 mol / L, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1026.16 mg / g, the saturated adsorption capacity of dimethyl carbonate was 331.75 mg / g, and the selectivity was 3.09.

[0046] Example 13 is the same as Example 1, except that when preparing the hydrophobic modifier / metal oxide / β molecular sieve composite material, 7.70 g of dodecyl trimethyl ammonium bromide is used as a modifier to prepare a hydrophobic modifier aqueous solution with a concentration of 0.5 mol / L, and the rest of the operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1091.38 mg / g, the saturated adsorption capacity of dimethyl carbonate was 347.17 mg / g, and the selectivity was 3.14.

[0047] Example 14 is the same as Example 1, except that the concentration of the azeotropic simulated solution added in the static experiment is 56:24:20 in the mass ratio of methanol: dimethyl carbonate: DMF, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was 2058.49 mg / g, the saturated adsorption capacity of dimethyl carbonate was 577.93 mg / g, and the selectivity was 3.56.

[0048] Example 15 is the same as Example 1, except that the concentration of the azeotropic simulated solution added in the static experiment is 42:18:40 in the mass ratio of methanol: dimethyl carbonate: DMF, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was 1951.04 mg / g, the saturated adsorption capacity of dimethyl carbonate was 552.18 mg / g, and the selectivity was 3.53.

[0049] Example 16 is the same as Example 1, except that the concentration of the azeotropic simulated solution added in the static experiment is 28:12:60 in the mass ratio of methanol: dimethyl carbonate: DMF, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was 1832.21 mg / g, the saturated adsorption capacity of dimethyl carbonate was 532.84 mg / g, and the selectivity was 3.43.

[0050] Example 17 is the same as Example 1, except that the concentration of the azeotropic simulated solution added in the static experiment is 14:6:80 in the mass ratio of methanol: dimethyl carbonate: DMF, and the rest of the operation is the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was 1766.42 mg / g, the saturated adsorption capacity of dimethyl carbonate was 516.63 mg / g, and the selectivity was 3.41.

[0051] Comparative Example 1 is the same as Example 1, except that the metal oxide / β molecular sieve material is prepared by a single impregnation method, and there is no back-mixing impregnation operation. The remaining operations are the same as Example 1. Take 69.46g of aluminum chloride, add 50mL of deionized water, and stir at room temperature for 10min to dissolve it evenly. Then add 5g of β molecular sieve carrier powder, stir at room temperature for 2h, and filter out the solid. Then put it in a 105℃ oven and dry it for 6h, grind and sieve 100 mesh. Finally, calcine at 350℃ in a muffle furnace for 4h to obtain Al2O3 / β molecular sieve. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1543.33mg / g, the saturated adsorption capacity of dimethyl carbonate was 459.33mg / g, and the selectivity was 3.35.

[0052] Comparative Example 2 is the same as Example 1, except that after the metal oxide / β molecular sieve material is prepared by the back-mixing impregnation method, there is no subsequent modification process, and the remaining operations are the same as Example 1. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1813.39 mg / g, the saturated adsorption capacity of dimethyl carbonate was 569.46 mg / g, and the selectivity was 3.18.

[0053] Comparative Example 3 is the same as Example 1, except that only a single impregnation method is used to prepare the metal oxide / β molecular sieve material, there is no back-mixing impregnation operation, and there is no subsequent modification process. The remaining operations are the same as Example 1. Take 69.46gAlCl3·6H2O, add 50mL deionized water, and stir for 10min at room temperature to dissolve it evenly. Then add 5gβ molecular sieve carrier powder, stir for 2h at room temperature, and filter out the solid. Then put it in a 105℃ oven to dry for 6h, grind and sieve 100 mesh. Finally, calcine at 350℃ in a muffle furnace for 4h to obtain Al2O3 / β molecular sieve. After the static experiment, the saturated adsorption capacity of methanol was measured to be 1509.74mg / g, the saturated adsorption capacity of dimethyl carbonate was 485.59mg / g, and the selectivity was 3.10.

[0054] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope, characterized in that: The hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent is prepared by sequentially subjecting the β molecular sieve to acid treatment, metal loading, calcination, and hydrophobic modifier treatment.

2. The method for preparing a hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 1, characterized in that: The metal loading adopts the back-mixing impregnation method, and the specific steps are as follows: The metal salt solution is placed in a stirring kettle, and then the acid-treated β molecular sieve is immersed in the metal salt solution and stirred at room temperature for 1 to 2 hours, filtered to obtain a solid filter cake, dried, and sieved. The obtained solid particles are then returned to the stirring kettle, remixed with the residual metal salt solution in the kettle, and continued to stir at room temperature for 1 to 2 hours, filtered, dried the filter cake, and sieved.

3. The method for preparing the hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 2, characterized in that: The metal salt is one of aluminum chloride, ferric chloride, ferrous chloride, manganese chloride, and ammonium metatungstate; and / or, the concentration of the metal salt solution is 0.05 to 3 mol / L; And / or, the metal salt is one of aluminum chloride, ferric chloride, ferrous chloride, manganese chloride, and ammonium metatungstate; And / or, the mass ratio of the acid-treated β molecular sieve to the metal salt is 1:1 to 1:

10.

4. The method for preparing the hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 1, characterized in that: The acid treatment comprises the following steps: dispersing the beta molecular sieve in a hydrochloric acid solution with a concentration of 1 to 3 mol / L, stirring at room temperature for 1 to 2 hours to remove impurities inside the molecular sieve and dredge the pores; filtering, washing the filter cake with deionized water until the filtrate is neutral, drying, and sieving; The dosage ratio of the beta molecular sieve to hydrochloric acid is 0.8-1.5 g: 10-15 mL.

5. The method for preparing a hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 1, characterized in that: The hydrophobic modifier treatment comprises the following steps: The calcined β molecular sieve is immersed in an aqueous solution of a hydrophobic modifier, stirred at 50-60° C. for 1-2 hours, filtered, washed, dried, and sieved.

6. The method for preparing the hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 5, characterized in that: The hydrophobic modifier includes one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and polycarboxylate ammonium salt dispersant; The concentration of the hydrophobic modifier aqueous solution is 0.1 to 0.5 mol / L; The mass ratio of the calcined beta molecular sieve to the hydrophobic modifier is 1:0.1 to 1:2.

5.

7. The method for preparing a hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent for separation of methanol-dimethyl carbonate azeotrope according to claim 1, characterized in that: The calcination temperature is 300-350° C. and the calcination time is 2-4 hours.

8. A hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent prepared by the method according to any one of claims 1 to 7.

9. Use of the hydrophobic modifier / metal oxide / β molecular sieve composite adsorbent according to claim 8 in separation of methanol-dimethyl carbonate azeotrope.

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