A high-activity propylene carbonate catalyst and preparation method thereof

Abstract

The present invention discloses a propylene carbonate catalyst and a preparation method and application thereof. The preparation method of the catalyst of the present invention comprises: (1) refluxing a mixture of halogenated alkane and melamine formaldehyde resin in a toluene solvent for 12 to 36 hours, rotary evaporating to obtain a white powder, and preparing an active component A; (2) pulverizing and mixing the active component A, zirconium oxychloride, phenolic resin, and urotropine, and hot pressing to obtain a catalyst C. The catalyst of the present invention has the characteristics of high activity and low cost. The catalyst prepared by the method of the present invention 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 high-activity propylene carbonate catalyst and a preparation method thereof, and in particular to a catalyst for preparing propylene carbonate by reacting CO2 with propylene oxide in a fixed bed reactor and a preparation method thereof. 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] KI and TEABr are the most commonly used homogeneous catalysts. Their conversion rate and selectivity are very high under high pressure. Quaternary ammonium salts and quaternary phosphonium salts such as octadecyltrimethylammonium bromide and tricyclohexylphosphine are good catalysts. However, homogeneous reactions have a series of separation problems and high energy consumption problems. Heterogeneous catalysts and heterogeneous reactions can effectively alleviate these problems.

[0004] Heterogeneous catalysts have the characteristics of being easy to separate from the product and regenerated. Bimetallic oxide catalysts with Lewis acid-base properties have good catalytic activity. 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. Using SmOCl as a catalyst and DMF 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 costs.

[0005] In the research of heterogeneous catalysts, 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 high pressure. A better catalyst is a homogeneous catalyst grafted on mesoporous SiO2. Chitosan and cellulose are a class of more important catalysts. They have high catalytic activity when used as catalysts together with quaternary ammonium salts or ionic liquids. Chitosan is used as a catalyst and ionic liquids are used as solvents to catalyze the synthesis of propylene carbonate, achieving efficient synthesis at low temperature and low pressure.

[0006] Ionic liquids have extremely high catalytic activity. Various functional groups are grafted onto ionic liquids to further improve their catalytic performance. The most important progress is the grafting of alcoholic hydroxyl groups or carboxyl groups onto ionic liquids. As well as grafting ionic liquids onto other carriers containing alcoholic hydroxyl groups or carboxyl groups, such as chitosan and carboxymethyl cellulose. Imidazole catalysts grafted with diol hydroxyl groups were prepared, and the grafting of diol groups improved the catalytic activity of ionic liquids.

[0007] Patent CN02158701.9 discloses a solid catalyst with activated carbon, metal oxide or molecular sieve as carrier and potassium salt as active component. The reaction is carried out in an autoclave and the reaction requires the addition of methyl iodide as an iodination agent.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] There are many problems with the catalysts currently used. Catalysts grafted with quaternary ammonium salts or ionic liquids usually have low catalytic activity, poor catalytic stability, and rapid decline in catalytic activity. Summary of the invention

[0014] The technical problem to be solved by the present invention is to provide a high-activity propylene carbonate catalyst to facilitate the efficient synthesis of propylene carbonate from CO2 and propylene oxide on a fixed bed.

[0015] According to a first aspect of the present invention, the present invention provides a method for preparing a propylene carbonate catalyst.

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

[0017] (1) reflux a mixture of halogenated alkane and melamine formaldehyde resin in a toluene solvent for 12 to 36 hours, evaporate the solvent to obtain a white powder, and prepare an active component A;

[0018] (2) The active component A, zirconium oxychloride, phenolic resin and urotropine are pulverized and mixed together, and then hot-pressed to obtain catalyst C.

[0019] Furthermore, the halogenated alkane in step (1) is at least one of bromopropane, bromobutylene, chlorobutylene, iodopropane and iodobutylene, preferably bromopropane. The mass ratio of halogenated alkane, melamine formaldehyde resin and toluene is 1: (0.5-1): (4-7), preferably 1: (0.2-0.3): (4-5).

[0020] Furthermore, the solvent evaporation in step (1) adopts conventional operating techniques, such as rotary evaporation, distillation or reduced pressure distillation.

[0021] Furthermore, the phenolic resin in step (2) is a thermoplastic phenolic resin having a softening point of 70-110° C. and a free phenol content of 1-4%.

[0022] Furthermore, in step (2), the weight ratio of active component A, zirconium oxychloride, phenolic resin and urotropine is 1: (0.5-1.5): (2-4): (0.2-0.4), preferably 1: (0.6-0.8): (2-3): (0.2-0.3).

[0023] Furthermore, in step (2), the temperature of the hot pressing molding is 100-160° C., the pressure is 1-3 MPa, and the time of holding under pressure is 1-3 minutes.

[0024] According to the second aspect of the present invention, the present invention also provides a propylene carbonate catalyst, which is obtained by the above-mentioned preparation method.

[0025] The characteristics of the propylene carbonate catalyst are as follows: based on the mass of the catalyst, its elemental composition is: nitrogen content is 1.4-2.8%, oxygen content is 6.3-8.6%, bromine content is 0-13.3%, chlorine content is 2.2-4.4%, iodine content is 0-12.1%, zirconium content is 5.1-9.2%, and the remainder is carbon and hydrogen.

[0026] Furthermore, the propylene carbonate catalyst is cylindrical, and its height is generally 0.4-0.8 cm, and its diameter is generally 0.3-0.5 cm.

[0027] According to the third aspect of the present invention, the present invention also provides a catalytic reaction of CO2 and propylene oxide, wherein the propylene carbonate catalyst described above is used.

[0028] Furthermore, 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 (LHSV) is 1~3h -1 , the reaction pressure is 2~4MPa, the reaction temperature is 90~160℃; preferably, the molar ratio of CO2 to propylene oxide is 2:1, and the volume space velocity (LHSV) is 1~1.5h -1 , the reaction pressure is 2~3MPa, and the reaction temperature is 110~130℃.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The catalyst of the present invention has the characteristics of high activity and low cost. The main catalyst of the catalyst of the present invention is a quaternary ammonium salt generated by halogenated alkane and melamine formaldehyde resin, which has extremely strong nucleophilicity and electrophilicity, can effectively activate CO2 and propylene oxide, and has a high unit active center density. The catalyst has high activity.

[0031] 2. The catalyst of the present invention has remarkable stability, and the active components are not easy to be lost during the reaction. In the prior art, the loss of active components is mainly caused by the breaking of chemical bonds of the main catalyst. In the present invention, the quaternary ammonium salt generated by the melamine formaldehyde resin is bonded by multiple chemical bonds, which can effectively stabilize the main catalyst and improve the firmness of the active components.

[0032] 3. In the catalyst of the present invention, melamine formaldehyde resin and phenolic resin have good similarity, the catalyst has good molding effect and high mechanical strength. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with specific embodiments, and the percentages are by mass unless otherwise specified.

[0034] The melamine formaldehyde resin used in the examples is commercially available, white particles, with a molecular weight of 2500, a water absorption of 0.1%, and a melting point of 156° C. The phenolic resin used is a commercially available resin with a free phenol content of 1% and a softening point of 70-110° C. The element detection of the catalyst was performed using a ZSX100e X-ray fluorescence spectrometer produced by Rigaku Corporation of Japan.

[0035] The calculation formulas for conversion rate and selectivity in the embodiments and comparative examples are:

[0036]

[0037]

[0038] .

[0039] Example 1

[0040] (1) A mixture of 80 g of bromopropane and 80 g of melamine formaldehyde resin was refluxed in 560 g of toluene solvent for 12 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0041] (2) 100 g of active component A1, 150 g of zirconium oxychloride, 400 g of phenolic resin, and 40 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C1. The composition of catalyst C1 is listed in Table 1.

[0042] Example 2

[0043] (1) A mixture of 80 g of bromopropane and 40 g of melamine formaldehyde resin was refluxed in 320 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0044] (2) 100 g of active component A2, 50 g of zirconium oxychloride, 200 g of phenolic resin, and 20 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 100°C, a pressure of 3 MPa, and a time of 3 minutes to obtain catalyst C2. The composition of catalyst C2 is listed in Table 1.

[0045] Example 3

[0046] (1) A mixture of 80 g of bromopropane and 48 g of melamine formaldehyde resin was refluxed in 320 g of toluene solvent for 24 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0047] (2) 100 g of active component A3, 60 g of zirconium oxychloride, 200 g of phenolic resin, and 20 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 140°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C3. The composition of catalyst C3 is listed in Table 1.

[0048] Example 4

[0049] (1) A mixture of 80 g of bromopropane and 64 g of melamine formaldehyde resin was refluxed in 400 g of toluene solvent for 30 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0050] (2) 100 g of active component A, 80 g of zirconium oxychloride, 300 g of phenolic resin, and 30 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 150°C, a pressure of 2 MPa, and a time of 2 minutes to obtain catalyst C. The composition of catalyst C6 is listed in Table 1.

[0051] Example 5

[0052] (1) A mixture of 80 g of bromopropane and 56 g of melamine formaldehyde resin was refluxed in 360 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0053] (2) 100 g of active component A, 70 g of zirconium oxychloride, 250 g of phenolic resin, and 25 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0054] Example 6

[0055] (1) A mixture of 80 g of butyl bromide and 56 g of melamine formaldehyde resin was refluxed in 360 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0056] (2) 100 g of active component A, 70 g of zirconium oxychloride, 250 g of phenolic resin, and 25 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0057] Example 7

[0058] (1) A mixture of 80 g of butyl chloride and 56 g of melamine formaldehyde resin was refluxed in 360 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0059] (2) 100 g of active component A, 70 g of zirconium oxychloride, 250 g of phenolic resin, and 25 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0060] Example 8

[0061] (1) A mixture of 80 g of iodopropane and 56 g of melamine formaldehyde resin was refluxed in 360 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0062] (2) 100 g of active component A, 70 g of zirconium oxychloride, 250 g of phenolic resin, and 25 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0063] Example 9

[0064] (1) A mixture of 80 g of iodobutane and 56 g of melamine formaldehyde resin was refluxed in 360 g of toluene solvent for 36 hours, and then rotary evaporated to obtain a white powder to obtain an active component A;

[0065] (2) 100 g of active component A, 70 g of zirconium oxychloride, 250 g of phenolic resin, and 25 g of urotropine were pulverized and mixed, and then hot-pressed at a temperature of 160°C, a pressure of 3 MPa, and a time of 1 minute to obtain catalyst C5. The composition of catalyst C5 is listed in Table 1.

[0066] Comparative Example 1

[0067] 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.

[0068] 20 grams of active component Ap, 20 grams of zirconium bromide, 20 grams of phenolic resin, and 2 grams of urotropine were crushed and mixed to make powder. The powder was pressed into tablets and then heated at 180°C for 2 hours under nitrogen protection to obtain catalyst Cp.

[0069] The elemental compositions and properties of the catalysts prepared in Examples 1-9 and Comparative Example 1 are shown in Table 1.

[0070] Table 1 Catalyst properties (unit, wt%)

[0071]

[0072] Example 10

[0073] The catalyst prepared in Example 1 was loaded into a fixed bed microreactor for activity evaluation. 100 mL of the catalyst was loaded into a reaction tube with a diameter of 60 mm and a length of 1200 mm, 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 causing 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.

[0074] Embodiment 11

[0075] The catalyst prepared in Example 2 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0076] Example 12

[0077] The catalyst prepared in Example 3 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0078] Example 13

[0079] The catalyst prepared in Example 4 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0080] Embodiment 14

[0081] The catalyst prepared in Example 5 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0082] Implementation 15

[0083] The catalyst prepared in Example 6 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0084] Implementation 16

[0085] The catalyst prepared in Example 7 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0086] Implementation 17

[0087] The catalyst prepared in Example 8 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0088] Implementation 18

[0089] The catalyst prepared in Example 9 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0090] Comparative Example 2

[0091] The catalyst prepared in Comparative Example 1 was loaded into a reactor. The reaction conditions were the same as in Example 10. The reaction results are listed in Table 2.

[0092] Table 2 Catalyst evaluation results (unit, mol%)

[0093]

[0094] The reaction results show that the catalyst prepared by the method of the present invention has high activity and good catalyst stability. 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 method for preparing a propylene carbonate catalyst, comprising the following steps: (1) Reflux a mixture of halogenated alkane and melamine formaldehyde resin in a toluene solvent for 12 to 36 hours, and then perform rotary evaporation to obtain a white powder to obtain an active component A; (2) The active component A, zirconium oxychloride, phenolic resin and urotropine are pulverized and mixed together, and then hot-pressed to obtain catalyst C.

2. The preparation method according to claim 1, characterized in that: The halogenated alkane is at least one of bromopropane, bromobutylene, chlorobutylene, iodopropane and iodobutylene.

3. The preparation method according to claim 1, characterized in that: The mass ratio of halogenated alkane, melamine formaldehyde resin and toluene is 1:(0.5~1):(4~7).

4. The preparation method according to claim 1, characterized in that: The phenolic resin is a thermoplastic phenolic resin with a softening point of 70-110° C. and a free phenol content of 1-4%.

5. The preparation method according to claim 1, characterized in that: In step (2), the weight ratio of active component A, zirconium oxychloride, phenolic resin and hexamethylenetetramine is 1:(0.5-1.5):(2-4):(0.2-0.4).

6. The preparation method according to claim 1, characterized in that: The temperature of the hot pressing molding in step (2) is 100-160° C., the pressure is 1-3 MPa, and the time of holding under pressure is 1-3 minutes.

7. The preparation method according to claim 2, characterized in that: The halogenated alkane is bromopropane.

8. The preparation method according to claim 3, characterized in that: The mass ratio of halogenated alkane, melamine formaldehyde resin and toluene is 1:(0.2~0.3):(4~5).

9. The preparation method according to claim 1, characterized in that: In step (2), the weight ratio of active component A, zirconium oxychloride, phenolic resin and hexamethylenetetramine is 1:(0.6-0.8):(2-3):(0.2-0.3).

10. The propylene carbonate catalyst obtained by the preparation method according to any one of claims 1 to 9.

11. The catalyst according to claim 10, characterized in that The elemental composition based on the mass of the catalyst is as follows: nitrogen content is 1.4~2.8%, oxygen content is 6.3~8.6%, bromine content is 0~13.3%, chlorine content is 2.2~4.4%, iodine content is 0~12.1%, zirconium content is 5.1~9.2%, and the remainder is carbon and hydrogen.

12. The catalyst according to claim 10 or 11, characterized in that The propylene carbonate catalyst is cylindrical, with a height of 0.4-0.8 cm and a diameter of 0.3-0.5 cm.

13. A method for the catalytic reaction of CO2 and propylene oxide, wherein the propylene carbonate catalyst according to any one of claims 10 to 12 is used.

14. The catalytic reaction method according to claim 13, characterized in that: 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℃.

15. The catalytic reaction method according to claim 14, characterized in that: 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, and the volume space velocity is 1~1.5h -1 , the reaction pressure is 2~3MPa, and the reaction temperature is 110~130℃.

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