Catalyst for preparing propylene carbonate as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for preparing propylene carbonate as well as a preparation method and application of the catalyst. The catalyst comprises a component I and quaternary ammonium salt; the component I is a reaction product of alkyl glycol, halide salt and glycerol triglycidyl ether; the quaternary ammonium salt comprises at least one of tetramethyl ammonium halide, tetraethyl ammonium halide, tetrapropyl ammonium halide and tetrabutyl ammonium halide; the weight ratio of the component I to the quaternary ammonium salt is 1: (0.5-10). The catalyst has the advantages of low cost, high activity, high selectivity and good stability when being applied to a reaction for preparing propylene carbonate.

Description

Technical Field

[0001] The invention belongs to the field of propylene carbonate synthesis, and particularly relates to a catalyst for preparing propylene carbonate, a preparation method and an application thereof. Background Art

[0002] The cycloaddition reaction of propylene oxide with carbon dioxide to produce propylene carbonate is an exothermic, volume-reducing reaction. The product, propylene carbonate, is an excellent organic solvent and organic intermediate. This reaction is an important approach to reducing CO2 emissions. Currently, the industrial production technology for propylene carbonate relies on a homogeneous catalytic tubular reactor and distillation separation process. The most commonly used catalyst in industry is a combination of KI and tetraethylammonium bromide (TEABr). The reaction temperature exceeds 170°C, and the reaction pressure exceeds 4 MPa. Catalyst stability is a crucial evaluation metric. Catalyst instability requires continuous replenishment during the production process, and the high-temperature and high-pressure processes produce byproducts, creating hazardous waste.

[0003] CN102302952A discloses a ZnX1X2-Ph4PX3 (X1, X2, X3 = Cl, Br, I) homogeneous catalyst composition. The catalyst remains unchanged in conversion and selectivity after three reuses. However, the catalyst's limited reuse capacity makes it unsuitable for long-term recycling.

[0004] CN106040296A discloses a chlorinated 1-aminopolypropyl ether-3-methylimidazolium ionic liquid. After one cycle, the catalyst achieved a conversion rate of 100% and a selectivity of 95.6%. After 10 cycles, the catalyst achieved a conversion rate of 99.5% and a selectivity of 94.5%. After 10 cycles, the reaction conversion rate and selectivity decreased. Furthermore, the catalyst failed to achieve both good stability and good performance, particularly selectivity.

[0005] Existing catalysts suffer from varying degrees of poor stability, low selectivity, and low conversion rates. In particular, the catalysts can be reused only a few times, typically no more than 10 times. This necessitates constant replenishment during the production process. Summary of the Invention

[0006] To address the problems of the prior art, the present invention provides a catalyst for preparing propylene carbonate, a preparation method thereof, and its use. The catalyst is suitable for the reaction of synthesizing propylene carbonate from CO2 and propylene oxide. The catalyst has the advantages of low cost, high activity, high selectivity, and good stability when used in this reaction.

[0007] In a first aspect, the present invention provides a catalyst for preparing propylene carbonate. The catalyst comprises component I and a quaternary ammonium salt; the component I is the reaction product of an alkyl glycol, a halide salt, and glycerol triglycidyl ether.

[0008] According to the present invention, in the catalyst, the weight ratio of component I to the quaternary ammonium salt is 1:(0.5-10), preferably 1:(0.5-6), and more preferably 1:(0.5-4).

[0009] According to the present invention, the alkyl glycol comprises at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol, preferably ethylene glycol. The halide salt comprises at least one of aluminum halide, iron halide, and zinc halide, preferably zinc bromide. The molar ratio of the alkyl glycol, halide salt, and glycerol triglycidyl ether is 1:(1-2):(1-2), preferably 1:(1-2):(1.1-1.5). Component I is prepared by reacting the alkyl glycol, halide salt, and glycerol triglycidyl ether.

[0010] According to the present invention, the quaternary ammonium salt comprises at least one of tetramethylammonium halide, tetraethylammonium halide, tetrapropylammonium halide and tetrabutylammonium halide. The halogen in the quaternary ammonium salt comprises at least one of chlorine, bromine and iodine. The quaternary ammonium salt is preferably tetraethylammonium bromide.

[0011] A second aspect of the present invention provides a method for preparing a catalyst for preparing propylene carbonate. The method comprises:

[0012] (1) mixing an alkyl glycol, a halide salt, and glycerol triglycidyl ether to react to obtain component I;

[0013] (2) uniformly mixing component I and the quaternary ammonium salt to obtain the catalyst.

[0014] According to the present invention, in step (1), the alkyl glycol comprises at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol, preferably ethylene glycol. The halide salt is at least one of aluminum halide, iron halide, and zinc halide, preferably zinc bromide. The molar ratio of the alkyl glycol, halide salt, and glycerol triglycidyl ether is 1:(1-2):(1-2), preferably 1:(1-2):(1.1-1.5).

[0015] According to the present invention, the reaction apparatus in step (1) can be an autoclave. The reaction conditions are: reaction at 90-120°C for 1-12 hours. The reaction is carried out under stirring. The reaction product is yellow. The reaction product is a polyether mixture.

[0016] According to the present invention, in step (1), the timing of adding the halide salt is not particularly limited; the halide salt can be added simultaneously with the alkyl glycol and glycerol triglycidyl ether. Alternatively, the alkyl glycol and glycerol triglycidyl ether can be mixed and reacted before adding the halide salt.

[0017] According to the present invention, in step (2), the weight ratio of component I to the quaternary ammonium salt is 1:(0.5-10), preferably 1:(0.5-6), more preferably 1:(0.5-4). The reaction apparatus can be a glass kettle.

[0018] The third aspect of the present invention provides use of the catalyst in the synthesis of propylene carbonate.

[0019] According to the present invention, the application is that CO2 is contacted with propylene oxide to react in the presence of a catalyst.

[0020] According to the present invention, the reaction conditions are: the volume ratio of the catalyst to propylene oxide is 1:(1000-5000), the molar ratio of CO2 to propylene oxide is (1.1-1.5):1. The reaction residence time is 30-100 minutes, the reaction pressure is 1-3 MPa, and the reaction temperature is 90-160°C.

[0021] Compared with existing catalysts, the catalyst of the present invention has the following characteristics:

[0022] (1) Component I in the catalyst of the present invention is the reaction product of an alkyl glycol, a halide salt, and glycerol triglycidyl ether. Component I has strong metal complexing properties, which promotes the dissolution of the metal salt in the reactants and the release of halide ions, thereby improving the activity of the catalyst.

[0023] (2) The quaternary ammonium salt in the catalyst of the present invention works synergistically with component I to further stabilize the metal salt, and the catalyst has significant stability, and the catalytic activity and selectivity do not decrease after multiple cycles of reaction.

[0024] (3) The preparation process of the catalyst of the present invention does not generate any waste and is environmentally friendly.

[0025] (4) The catalyst of the present invention has low preparation cost. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] (1) 62 g of ethylene glycol, 270 g of zinc bromide and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain component I.

[0029] (2) 100 g of component I from step (1) and 150 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C1.

[0030] Example 2

[0031] (1) 62 g of ethylene glycol, 360 g of zinc bromide and 416 g of glycerol triglycidyl ether were added to an autoclave, heated to 110° C., and stirred for reaction for 8 hours to obtain component I.

[0032] (2) 100 g of component I from step (1) and 80 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C2.

[0033] Example 3

[0034] (1) 62 g of ethylene glycol, 270 g of zinc bromide and 468 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 12 hours to obtain component I.

[0035] (2) 100 g of component I from step (1) and 1000 g of tetraethylammonium chloride were added to a glass kettle and mixed uniformly to obtain catalyst C3.

[0036] Example 4

[0037] (1) 62 g of ethylene glycol, 225 g of zinc bromide and 260 g of glycerol triglycidyl ether were added to an autoclave, heated to 120° C., and stirred for reaction for 4 hours to obtain component I.

[0038] (2) 100 g of component I from step (1) and 50 g of tetrapropylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C4.

[0039] Example 5

[0040] (1) 62 g of ethylene glycol, 319 g of aluminum bromide and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 120° C., and stirred for reaction for 4 hours to obtain component I.

[0041] (2) 100 g of component I from step (1) and 180 g of tetrapropylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C5.

[0042] Example 6

[0043] (1) 62 g of ethylene glycol, 194 g of ferric chloride and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain component I.

[0044] (2) 100 g of component I from step (1) and 150 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C6.

[0045] Example 7

[0046] (1) 76 g of 1,3-propylene glycol, 270 g of zinc bromide and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain component I.

[0047] (2) 100 g of component I from step (1) and 150 g of tetramethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C7.

[0048] Example 8

[0049] (1) 90 g of 1,4-butanediol, 270 g of zinc bromide and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain component I.

[0050] (2) 100 g of component I from step (1) and 150 g of tetrabutylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst C8.

[0051] Comparative Example 1

[0052] The difference from Example 1 is that no ethylene glycol is added to the catalyst raw material.

[0053] (1) 270 g of zinc bromide and 312 g of glycerol triglycidyl ether were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain reaction product I.

[0054] (2) 100 g of the reaction product I of step (1) and 150 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst DC1.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that glycerol triglycidyl ether is not added to the catalyst raw material.

[0057] (1) 62 g of ethylene glycol and 270 g of zinc bromide were added to an autoclave, heated to 100° C., and stirred for reaction for 6 hours to obtain reaction product I.

[0058] (2) 100 g of the reaction product I of step (1) and 150 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst DC2.

[0059] Comparative Example 3

[0060] (1) 264 g of 18-crown ether-6 and 270 g of zinc bromide were added to an autoclave, heated to 60° C., and stirred for reaction for 2 hours to obtain reaction product I.

[0061] (2) 100 g of the reaction product I of step (1) and 150 g of tetraethylammonium bromide were added to a glass kettle and mixed uniformly to obtain catalyst DC3.

[0062] Application Examples

[0063] The catalytic performance of the catalysts of Examples 1-8 and Comparative Examples 1-3 in the synthesis of propylene carbonate was tested. The reaction conditions were as follows: a volume ratio of catalyst to propylene oxide of 1:3000, a molar ratio of CO2 to propylene oxide of 1.2:1, a reaction residence time of 60 minutes, a reaction pressure of 1.4 MPa, and a reaction temperature of 150°C. The apparatus used was a tubular microreactor. The reactor had a diameter of 50 mm and a length of 1200 mm. After checking for airtightness, the catalyst and reactants were injected into the reaction tube, then the temperature was rapidly raised to 90°C and then slowly raised to the reaction temperature to avoid a vigorous reaction and a runaway temperature. After the reaction temperature was maintained constant for 1 hour, sampling began. The evaluation results are shown in Table 2. The reaction results show that the catalyst of the present invention is a highly active catalyst, with a high conversion rate of the reactants under the reaction conditions, and the product selectivity can reach over 99%.

[0064] Table 2 Catalyst evaluation results

[0065] catalyst Conversion rate mol% Selectivity mol% Example 1 C1 97.1 99.7 Example 2 C2 93.3 99.8 Example 3 C3 86.6 99.9 Example 4 C4 88.7 99.7 Example 5 C5 90.1 99.8 Example 6 C6 87.8 99.7 Example 7 C7 81.6 99.9 Example 8 C8 84.4 99.8 Comparative Example 1 DC1 45.2 99.2 Comparative Example 2 DC2 48.6 97.8 Comparative Example 3 DC3 51.5 99.2

[0066] The reaction products of Examples 1-8 and Comparative Example 3 were distilled to separate the catalysts, which were then reintroduced into the reaction for a cyclic reaction under the same reaction conditions. After 12 cycles, the activity of the catalysts in the Examples remained essentially unchanged, while the activity of the catalyst in Comparative Example 3 was significantly reduced. The results of the 12 cycles are shown in Table 3.

[0067] Table 3 Catalyst cycle evaluation results

[0068]

Claims

1. A catalyst for preparing propylene carbonate, comprising component I and a quaternary ammonium salt; wherein component I is the reaction product of an alkyl glycol, a halide salt, and glycerol triglycidyl ether; The quaternary ammonium salt includes at least one of tetramethylammonium halide, tetraethylammonium halide, tetrapropylammonium halide and tetrabutylammonium halide; The weight ratio of component I to the quaternary ammonium salt is 1:(0.5-10).

2. The catalyst according to claim 1, characterized in that The alkyl glycol includes at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, and 1,4-butylene glycol, preferably ethylene glycol.

3. The catalyst according to claim 1, characterized in that The halide salt is at least one of aluminum halide, iron halide and zinc halide, preferably zinc bromide.

4. The catalyst according to claim 1, characterized in that The halogen in the quaternary ammonium salt includes at least one of chlorine, bromine and iodine; further, the quaternary ammonium salt is preferably tetraethylammonium bromide.

5. The catalyst according to claim 1, characterized in that The molar ratio of the alkyl glycol, the halide salt and the glycerol triglycidyl ether is 1:(1-2):(1-2), preferably 1:(1-2):(1.1-1.5).

6. A method for preparing a catalyst for preparing propylene carbonate, comprising: (1) mixing an alkyl glycol, a halide salt, and glycerol triglycidyl ether to react to obtain component I; (2) uniformly mixing component I and the quaternary ammonium salt to obtain the catalyst.

7. The preparation method according to claim 6, characterized in that: The quaternary ammonium salt includes at least one of tetramethylammonium halide, tetraethylammonium halide, tetrapropylammonium halide, and tetrabutylammonium halide; the halogen in the quaternary ammonium salt includes at least one of chlorine, bromine, and iodine; further, the quaternary ammonium salt is preferably tetraethylammonium bromide.

8. The preparation method according to claim 6, characterized in that: The alkyl glycol includes at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, and 1,4-butylene glycol, preferably ethylene glycol; and / or, the halide salt is at least one of aluminum halide, iron halide, and zinc halide, preferably zinc bromide; And / or, the molar ratio of the alkyl glycol, the halide salt and glycerol triglycidyl ether is 1:(1-2):(1-2), preferably 1:(1-2):(1.1-1.5).

9. The preparation method according to claim 6, characterized in that: The weight ratio of component I to the quaternary ammonium salt is 1:(0.5-10).

10. The method according to claim 6, characterized in that: The reaction conditions of step (1) are: reaction at 90-120° C. for 1-12 hours.

11. Use of the catalyst according to any one of claims 1 to 5 or the catalyst prepared by the preparation method according to any one of claims 6 to 10 in the synthesis of propylene carbonate.

12. The application according to claim 11, characterized in that: The application is that CO2 contacts propylene oxide in the presence of a catalyst to react.

13. The application according to claim 12, characterized in that: The reaction conditions are: the volume ratio of the catalyst to propylene oxide is 1:(1000-5000); and / or the molar ratio of CO2 to propylene oxide is (1.1-1.5):1; and / or the reaction residence time is 30-100 min, the reaction pressure is 1-3 MPa, and the reaction temperature is 90-160°C.

Images