A long-life catalyst and its application in the synthesis of propylene carbonate

Abstract

The invention discloses a long-life catalyst and its application in the synthesis of propylene carbonate. The catalyst for synthesizing propylene carbonate of the invention has the following chemical composition by mass: nitrogen content of 1.7-2.3%, oxygen content of 4.1-5.6%, bromine content of 9.2-13.8%, lanthanum content of 16.1-24.1%, and the remainder of carbon and hydrogen. The catalyst of the invention has the characteristics of high activity and long life, and at the same time, the catalyst has significant stability, and the active component is not easy to be lost during the reaction.

Description

Technical Field

[0001] The present invention relates to a method for preparing a solid catalyst for propylene carbonate, in particular to a method for preparing a catalyst for preparing propylene carbonate from CO2 and propylene oxide in a fixed bed reactor. Background Art

[0002] The cycloaddition reaction of propylene oxide and carbon dioxide to form propylene carbonate is an exothermic reaction with a reduced volume. The product propylene carbonate is an organic solvent with excellent performance and an organic synthesis intermediate. This reaction is an important way to achieve CO2 emission reduction.

[0003] Heterogeneous catalysts have the characteristics of being easy to separate from the product and regenerated. Bimetallic oxide catalysts with Lewis acid-base properties, such as MgO-Al2O3, have relatively good conversion and selectivity. However, these heterogeneous catalysts require the solvent DMF. If DMF is not used as a solvent, or other non-polar solvents are used, the conversion rate of the reaction will be lower. When SmOCl is used as a catalyst and DMF is used as a solvent, the yield of propylene carbonate can reach 99%. Under the same reaction conditions, if no solvent is used, the yield of propylene carbonate is only 57%. The addition of solvents obviously has an adverse effect on the entire process, requiring product separation, etc., which reduces the quality of the product and increases the cost. ZnAl hydrotalcite prepared by coprecipitation and hydrothermal treatment has both abundant basic sites and relatively strong acidic sites. Moreover, the interlayer anions have relatively strong nucleophilicity, so they have relatively good catalytic activity and heterogeneous catalytic effect.

[0004] Alkaline resins with quaternary ammonium salt groups have catalytic activity, but the activity is low. The reaction can only be fully carried out under high temperature and pressure. Ionic liquids grafted on mesoporous SiO2, chitosan and cellulose have high catalytic activity. Various functional groups are grafted on ionic liquids to further improve their catalytic performance. The most important progress is the grafting of alcohol hydroxyl or carboxyl groups on ionic liquids. And the grafting of ionic liquids on other carriers containing alcohol hydroxyl or carboxyl groups, such as chitosan, carboxymethyl cellulose, etc. An imidazole catalyst grafted with diol hydroxyl groups was prepared. The grafting of diol groups improves the catalytic activity of ionic liquids.

[0005] Patent CN200910237124.0 proposes a solid catalyst, which uses SiO2 prepared by hydrolysis of ethyl orthosilicate as a carrier, zinc salt, halogen and organic amine as active components. The reactants have a high conversion rate.

[0006] Patent CN201210215810.X discloses a catalyst for synthesizing propylene carbonate, which uses a mesoporous silica foam material as a carrier and an ionic liquid as an active component.

[0007] Patent CN201110275209.5 discloses a catalyst for synthesizing propylene carbonate, which uses a polydivinylbenzene polymer as a carrier and an imidazole ionic liquid as an active component. The catalyst was evaluated by the reaction of epoxide and CO2 in a kettle reactor, and the activity of the catalyst was very high.

[0008] Patent CN201210184990.X discloses a catalyst for synthesizing propylene carbonate, which uses a polystyrene polymer as a carrier and a quaternary ammonium salt as an active component.

[0009] Patent CN201310429816.1 discloses a catalyst for synthesizing propylene carbonate, which uses a phenolic resin mesoporous material as a carrier and imidazole as an active component. Imidazole is immobilized on a chloromethylated FDU mesoporous phenolic resin to obtain a chloromethylated FDU mesoporous phenolic resin-loaded imidazole ion liquid precursor, and then the loaded imidazole ion liquid precursor is reacted with a halide containing different functional groups to prepare a catalyst. The catalyst is used for the reaction of various epoxides with CO2 and has a high catalytic activity.

[0010] However, there are many problems with the catalysts currently used. Catalysts grafted with quaternary ammonium salts or ionic liquids usually have the problem of decreased catalytic activity, serious swelling of the polymer carrier, which is not conducive to the loading of the catalyst in the fixed bed reactor, and the problem of reactor blockage during the reaction. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a long-life high-efficiency catalyst to facilitate the reaction of synthesizing propylene carbonate from CO2 and propylene oxide on a fixed bed.

[0012] According to a first aspect of the present invention, the present invention provides a catalyst for synthesizing propylene carbonate.

[0013] The catalyst for synthesizing propylene carbonate of the present invention has the following chemical composition by mass: nitrogen content of 1.7-2.3%, oxygen content of 4.1-5.6%, bromine content of 9.2-13.8%, lanthanum content of 16.1-24.1%, and the remainder of carbon and hydrogen.

[0014] Furthermore, the catalyst is cylindrical, generally has a thickness of 0.4-0.8 cm, and a diameter of 0.3-0.5 cm.

[0015] According to a second aspect of the present invention, the present invention provides a method for preparing the above catalyst.

[0016] The catalyst preparation method provided by the present invention comprises the following steps:

[0017] Lanthanum oxybromide, 3-hydroxy-N,N-dimethylaniline, phenolic resin and urotropine are crushed and mixed together to prepare powder; then the powder is pressed into tablets at 100-150° C.; the molding pressure is 1-3 MPa, and the molding time is 2-5 minutes; then the powder is heated at 150-180° C. for 1-3 hours to prepare the catalyst.

[0018] Furthermore, the weight ratio of lanthanum oxybromide to 3-hydroxy-N,N-dimethylaniline, phenolic resin and urotropine is 1:(1-3.5):(1-3.5):(0.1-0.35), preferably 1:(1.5-2.5):(1.5-2.5):(0.15-0.25).

[0019] Furthermore, the phenolic resin is a thermoplastic phenolic resin with a softening point of 150-160° C. and a free phenol content of 0.5-1%.

[0020] According to the third aspect of the present invention, the present invention also provides a method for synthesizing propylene carbonate, wherein the catalyst described above is used.

[0021] Specifically, the propylene carbonate synthesis method of the present invention comprises the following contents: CO2 and propylene oxide are subjected to a catalytic reaction in the presence of a propylene carbonate catalyst, and the reaction product is separated to obtain propylene carbonate.

[0022] Furthermore, the reaction is a batch reaction or a continuous reaction, preferably a continuous reaction. In the case of a continuous reaction, the conditions for the catalytic reaction of CO2 and propylene oxide are as follows: the molar ratio of CO2 to propylene oxide is 2:1 to 1.5:1, and the volume space velocity (LHSV) is 1 to 3 h -1 , the reaction pressure is 2~4MPa, and the reaction temperature is 90~160℃.

[0023] Compared with the existing catalysts, the catalyst of the present invention has the following characteristics:

[0024] 1. The catalyst of the present invention has the characteristics of high activity and long life. The main active component of the catalyst of the present invention is lanthanum oxybromide, which has high stability and is not easy to coke during the reaction. At the same time, the phenolic resin effectively adjusts the surface electronic properties of lanthanum oxybromide and can effectively inhibit the generation of coking precursors. 3-Hydroxy-N,N-dimethylaniline is a co-catalyst. The strong Lewis acidity and hydrogen bonds of the three components activate CO2 and propylene oxide respectively in the reaction. The components of the catalyst have a high synergistic catalytic effect and the catalyst activity is high.

[0025] 2. The catalyst of the present invention has remarkable stability, and the active components are not easy to be lost during the reaction. The main active component of the catalyst, lanthanum oxybromide, is an inorganic solid and is not easy to be lost during the reaction. The loss of active components in the prior art is mainly caused by the breaking of the chemical bonds of the co-catalyst. In the present invention, 3-hydroxy-N,N-dimethylaniline is used as a co-catalyst, and multiple chemical bonds are bonded with the phenolic resin during the preparation process. The multiple chemical bonds effectively stabilize the co-catalyst. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0027] The phenolic resin used in the examples is a commercially available resin, with a free phenol content of 1%, a volatile content of 0.5%, and a softening point of 99-109° C. Lanthanum oxybromide, 3-hydroxy-N,N-dimethylaniline, and urotropine were purchased from J&K and were chemically pure. The element detection of the catalyst was performed using a ZSX100e X-ray fluorescence spectrometer produced by Rigaku Corporation of Japan.

[0028] The calculation formulas for conversion rate and selectivity in the embodiments and comparative examples are:

[0029]

[0030]

[0031] .

[0032] Example 1

[0033] 60g of lanthanum oxybromide, 60g of 3-hydroxy-N,N-dimethylaniline, 60g of phenolic resin and 6g of urotropine were crushed and mixed to make powder; then the powder was pressed into tablets at 150°C, with a pressure of 3MPa for 5 minutes; then the powder was heated at 180°C for 3 hours to obtain catalyst C1. The composition of catalyst C1 is listed in Table 1.

[0034] Example 2

[0035] 60g of lanthanum oxybromide, 210g of 3-hydroxy-N,N-dimethylaniline, 210g of phenolic resin and 21g of urotropine were pulverized and mixed to prepare powder; then tableted at 100°C, with a pressure of 1MPa for 2 minutes; then heated at 150°C for 1 hour to prepare catalyst C2. The composition of catalyst C2 is listed in Table 1.

[0036] Example 3

[0037] 60g of lanthanum oxybromide, 90g of 3-hydroxy-N,N-dimethylaniline, 90g of phenolic resin and 9g of urotropine were crushed and mixed to make powder; then tabletted at 120°C, with a pressure of 2MPa for 3 minutes; then heated at 160°C for 2 hours to obtain catalyst C3. The composition of catalyst C3 is listed in Table 1.

[0038] Example 4

[0039] 60g of lanthanum oxybromide, 150g of 3-hydroxy-N,N-dimethylaniline, 150g of phenolic resin and 15g of urotropine were crushed and mixed to prepare powder; then tableted at 120°C, with a pressure of 2MPa for 3 minutes; then heated at 160°C for 2 hours to prepare catalyst C1. Catalyst C4 was prepared. The composition of catalyst C4 is listed in Table 1.

[0040] Example 5

[0041] 60g of lanthanum oxybromide, 120g of 3-hydroxy-N,N-dimethylaniline, 120g of phenolic resin and 12g of urotropine were pulverized and mixed to prepare powder; then tableted at 130°C, with a pressure of 2MPa for 4 minutes; then heated at 150°C for 1 hour to prepare catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0042] Comparative Example 1

[0043] 20 g of chlorine balls, 8 g of 1-methylimidazole and 80 g of toluene were added to a three-necked flask and refluxed at 110° C. for 24 hours. After filtering, it was washed three times with toluene and ethanol, and then vacuum dried at 80° C. for 24 hours to obtain the active component Ap.

[0044] 20 grams of active component Ap, 20 grams of lanthanum chloride, 20 grams of phenolic resin, and 2 grams of urotropine were crushed and mixed to prepare powder; the powder was pressed into tablets, and then heated at 180° C. for 2 hours under nitrogen protection to obtain catalyst Cp.

[0045] Table 1 Catalyst properties (unit: wt%)

[0046]

[0047] Example 6

[0048] 200 mL of the catalyst C1 prepared in Example 1 was placed in a reaction tube with a diameter of 5 cm and a length of 60 cm. The air tightness was checked, and then the temperature was quickly raised to 90°C, and then slowly raised to the reaction temperature to avoid a violent reaction and a temperature runaway. After the reaction temperature was kept constant for 1 hour, sampling began. The reaction conditions were as follows: the molar ratio of CO2 to propylene oxide was 2:1, and the volume space velocity was 1 h -1, the reaction temperature was 120°C, and the reaction pressure was 2MPa. The reaction results are listed in Table 2.

[0049] Example 7

[0050] The catalyst C2 prepared in Example 2 was loaded into the reactor. The reaction conditions were the same as in Example 6. The reaction results are listed in Table 2.

[0051] Example 8

[0052] The catalyst C3 prepared in Example 3 was loaded into the reactor. The reaction conditions were the same as in Example 6. The reaction results are listed in Table 2.

[0053] Example 9

[0054] The catalyst C4 prepared in Example 4 was loaded into the reactor. The reaction conditions were the same as in Example 6. The reaction results are listed in Table 2.

[0055] Example 10

[0056] The catalyst C5 prepared in Example 5 was loaded into the reactor. The reaction conditions were the same as in Example 6. The reaction results are listed in Table 2.

[0057] Comparative Example 2

[0058] The catalyst Cp prepared in Comparative Example 1 was loaded into a reactor. The reaction conditions were the same as in Example 6. The reaction results are listed in Table 2.

[0059] Table 2 Catalyst evaluation results (unit: mol%)

[0060]

[0061] The reaction results show that the catalyst prepared by the method of the present invention has high activity, good catalyst stability and long operation time. Under the reaction conditions, the conversion rate of the reactants is very high and the selectivity of the product reaches more than 99 mol%.

Claims

1. A catalyst for synthesizing propylene carbonate, characterized in that: The chemical composition by mass is as follows: nitrogen content is 1.7-2.3%, oxygen content is 4.1-5.6%, bromine content is 9.2-13.8%, lanthanum content is 16.1-24.1%, and the balance is carbon and hydrogen; The preparation method of the catalyst comprises the following steps: lanthanum oxybromide, 3-hydroxy-N,N-dimethylaniline, phenolic resin and urotropine are pulverized and mixed together to prepare powder; then the powder is pressed into tablets at 100-150°C; the molding pressure is 1-3MPa and the molding time is 2-5 minutes; then the catalyst is heated at 150-180°C for 1-3 hours to prepare the catalyst.

2. The catalyst according to claim 1, characterized in that The catalyst is cylindrical, with a thickness of 0.4-0.8 cm and a diameter of 0.3-0.5 cm.

3. The catalyst according to claim 1, characterized in that The weight ratio of lanthanum oxybromide to 3-hydroxy-N,N-dimethylaniline, phenolic resin and hexamethylenetetramine is 1:(1-3.5):(1-3.5):(0.1-0.35).

4. The catalyst according to claim 3, characterized in that The weight ratio of lanthanum oxybromide to 3-hydroxy-N,N-dimethylaniline, phenolic resin and hexamethylenetetramine is 1:(1.5-2.5):(1.5-2.5):(0.15-0.25).

5. The catalyst according to claim 1, characterized in that The phenolic resin is a thermoplastic phenolic resin with a softening point of 150-160° C. and a free phenol content of 0.5-1%.

6. A method for synthesizing propylene carbonate from CO2 and propylene oxide, wherein the catalyst described in any one of claims 1 to 5 is used.

7. The method according to claim 6, characterized in that The method comprises the following contents: CO2 and propylene oxide are subjected to catalytic reaction in the presence of a propylene carbonate catalyst, and the reaction product is separated to obtain propylene carbonate.

8. The method according to claim 7, characterized in that The reaction is a continuous reaction. The conditions for the catalytic reaction of CO2 and propylene oxide are as follows: the molar ratio of CO2 to propylene oxide is 2:1-1.5:1, and the volume space velocity is 1-3h -1 , the reaction pressure is 2~4MPa, and the reaction temperature is 90~160℃.

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