Online regeneration method of propylene carbonate catalyst

Abstract

The invention discloses an on-line regeneration method of a propylene carbonate catalyst, which comprises the following steps: (1) introducing a regeneration liquid A into a fixed bed reactor filled with an inactivated propylene carbonate catalyst for first regeneration treatment, and after the regeneration treatment is finished, discharging the redundant regeneration liquid A; (2) introducing the regenerated liquid B into a fixed bed reactor filled with an inactivated propylene carbonate catalyst, carrying out second regeneration treatment, and after the regeneration treatment is finished, discharging the redundant regenerated liquid B; and (3) introducing the regenerated liquid C into a fixed bed reactor filled with an inactivated propylene carbonate catalyst, carrying out third regeneration treatment, and discharging the redundant regenerated liquid C after the regeneration treatment is finished. The regenerated catalyst is good in performance, the regeneration liquid can be recycled, the regeneration process is simple and convenient to operate, the loss of the catalyst in the regeneration process can be effectively reduced, and resources and energy consumption are greatly saved.

Description

Technical Field

[0001] The present invention belongs to the field of carbon dioxide conversion and utilization for preparing carbonates, and particularly relates to an online regeneration method for a propylene carbonate catalyst. Background Art

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

[0003] Heterogeneous catalysts have the characteristics of being easy to separate from products and can be regenerated. The important progress in the synthesis of propylene carbonate in the last decade is the research on ionic liquid catalysts. Ionic liquids have extremely high catalytic activity. By grafting various functional groups onto ionic liquids, their catalytic performance can be further improved. The most important progress is the grafting of alcohol hydroxyl groups or carboxyl groups onto ionic liquids. And grafting ionic liquids onto other carriers containing alcohol hydroxyl groups or carboxyl groups, such as chitosan, carboxymethyl cellulose, etc. A variety of supported ionic liquid catalysts have been prepared.

[0004] CN201210215810.X discloses a catalyst for synthesizing propylene carbonate, with mesoporous silica foam material as the carrier and ionic liquid as the active component.

[0005] CN201110275209.5 discloses a catalyst for synthesizing propylene carbonate, with polydivinylbenzene polymer as the carrier and imidazole-based ionic liquid as the active component. The evaluation of the catalyst is carried out by the reaction of epoxide and CO2 in a kettle reactor, and the activity of the catalyst is very high.

[0006] CN201210184990.X discloses a catalyst for synthesizing propylene carbonate, with polystyrene polymer as the carrier and quaternary ammonium salt as the active component.

[0007] CN201310429816.1 discloses a catalyst for synthesizing propylene carbonate, with phenolic resin mesoporous material as the carrier and imidazole as the active component. Imidazole is immobilized on chloromethylated FDU mesoporous phenolic resin to obtain chloromethylated FDU mesoporous phenolic resin supported imidazole ionic liquid precursor, and then the supported imidazole ionic liquid precursor is reacted with halides containing different functional groups to prepare the catalyst. The catalyst is used for the reaction of various epoxides and CO2, and has relatively high catalytic activity.

[0008] The currently used heterogeneous propylene carbonate synthesis catalysts are mainly polydivinylbenzene polymers loaded with imidazole-based ionic liquids, and their lifespan is from half a year to one year. A large amount of waste catalysts are generated every year. If they are directly incinerated without recycling, it will not only cause huge waste but also seriously pollute the environment.

[0009] There has been little research on the recycling of propylene carbonate catalysts. However, the currently used organic resin catalysts will swell when used in a fixed-bed reactor, making their structure loose. When exposed to air, they are very easy to oxidize, their mechanical strength deteriorates, and they are very easy to powderize during the regeneration process.

[0010] Therefore, it is necessary to develop an in-situ regeneration method and regeneration liquid, which can not only reuse waste catalysts but also prevent waste and pollution caused by powderization when the catalyst is replaced and exposed to air. Summary of the Invention

[0011] Aiming at the deficiencies of the prior art, the present invention provides an on-line regeneration method for propylene carbonate catalysts. The catalyst regenerated by the method of the present invention has good performance, the regeneration liquid can be reused, and the regeneration process is simple and convenient to operate, which can effectively reduce the loss of catalysts during the regeneration process and greatly save resources and energy consumption.

[0012] The on-line regeneration method for propylene carbonate catalysts of the present invention includes the following steps: (1) Pass the regeneration liquid A into a fixed-bed reactor containing deactivated propylene carbonate catalyst for the first regeneration treatment. After the regeneration treatment is completed, discharge the excess regeneration liquid A; Then pass the regeneration liquid B into the fixed-bed reactor containing deactivated propylene carbonate catalyst for the second regeneration treatment. After the regeneration treatment is completed, discharge the excess regeneration liquid B; (3) Pass the regeneration liquid C into the fixed-bed reactor containing deactivated propylene carbonate catalyst for the third regeneration treatment. After the regeneration treatment is completed, discharge the excess regeneration liquid C; In the method of the present invention, the regeneration liquid A in step (1) includes: 5wt%-15wt% imidazole, 1wt%-5% bromide salt, and 80wt% - 94wt% solvent A; the bromide salt is one or more of lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, and zinc bromide; the solvent A is one or more of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methanol, and tetrahydrofuran.

[0013] In the method of the present invention, the propylene carbonate catalyst in step (1) is a supported imidazolium ionic liquid catalyst, and the catalyst carrier is generally various resins containing chloromethyl. The deactivated propylene carbonate catalyst generally refers to polystyrene-butadiene resin microspheres loaded with [mim][Cl] ionic liquid, basic resins with quaternary ammonium salt groups, mesoporous SiO2 grafted with ionic liquid, chitosan grafted with ionic liquid, cellulose grafted with ionic liquid catalysts, and mesoporous phenolic resin catalysts loaded with imidazole groups.

[0014] In the method of the present invention, the liquid-solid mass ratio of the regeneration liquid A to the catalyst in step (1) is 3-5:1.

[0015] In the method of the present invention, the first regeneration treatment conditions in step (1) are: the circulation residence time is 0.5-2 hours, the temperature is 30-50 °C, and the regeneration liquid is circulated 10-40 times.

[0016] In the method of the present invention, the regeneration liquid B in step (2) includes: 2wt%-5wt% zinc salt, 25wt%-50wt% dibromoalkane, and 45wt%-73wt% solvent B; wherein the zinc salt is one or more of zinc fluoride, zinc chloride, zinc bromide, and zinc iodide; the dibromoalkane is one or more of 1,2-dibromoethane, 1,3-dibromopropane, and 1,4-dibromobutane; the solvent B is one or more of toluene, cyclohexane, carbon disulfide, ethyl acetate, and dimethyl carbonate.

[0017] In the method of the present invention, the second regeneration treatment conditions in step (2) are: the circulation residence time is 0.5-2 hours, the temperature is 60-80 °C, and the regeneration liquid is circulated 10-40 times.

[0018] In the method of the present invention, the regeneration liquid C in step (3) includes: 6wt%-16wt% alkylimidazole and 84wt%-94wt% recycled regeneration liquid B; wherein the alkylimidazole is one or more of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, or 1-butylimidazole, preferably 1-methylimidazole.

[0019] In the method of the present invention, the second regeneration treatment conditions in step (3) are: the time is 0.5-2 hours, the temperature is 50-80 °C, and the regeneration liquid is circulated 10-40 times.

[0020] In the method of the present invention, the preparation method of the regeneration liquids A, B, and C generally is to mix the components of each regeneration liquid for a period of time to obtain the regeneration liquid, and the mixing time is generally 0.5-2 hours.

[0021] Compared with the prior art, the present invention has the following advantages: When the regeneration liquid A circulates, it can elute the macromolecules on the surface of the catalyst, and at the same time, ion exchange occurs to exchange the anions in the catalytic system with Br - , and graft fresh imidazole groups. When the regeneration liquid B circulates, the introduced Zn 2+ ions and Br - in the catalytic system form ZnBr3 under the attraction of the positively charged imidazole groups -Large groups can effectively enhance the attraction strength between positive and negative charges of ionic liquids, improving the stability of the catalyst. The regenerant C is the recycled regenerant B and alkyl imidazole. The recycled regenerant B forms ZnBr3 under the attraction of positively charged imidazole groups. - Large groups, large anion groups can effectively promote the polarization of alkyl imidazole and react with the catalyst.

[0022] The regenerant of the present invention has good regeneration performance, and can basically completely restore the activity of the regenerated propylene carbonate catalyst to the level of fresh catalyst or even exceed the level of fresh catalyst. The raw materials of the regenerant of the present invention have low prices and can be recycled, greatly saving the production cost. The present invention can directly regenerate the propylene carbonate catalyst in a fixed bed reactor, avoiding oxidation caused by the contact of deactivated catalyst with air, thus avoiding pulverization caused by the decrease of mechanical strength during the regeneration process. Brief Description of the Drawings

[0023] Figure 1 For the evaluation results of the regenerated catalysts D2 and D7. Specific Embodiments

[0024] The technical solutions of the present invention will be further described below in conjunction with specific embodiments. Example 1

[0025] Dissolve 33 g of imidazole and 11 g of zinc bromide in 480 g of acetonitrile, and stir at room temperature for 1 h to obtain the regenerant A1; Dissolve 11.4 g of zinc bromide and 112 g of 1,2-dibromoethane in 270 g of toluene, and stir at room temperature for 1 h to obtain the regenerant B1; Dissolve 48 g of 1-methylimidazole in 400 g of the regenerant B1, and stir at room temperature for 1 h to obtain the regenerant C1. Example 2

[0026] Dissolve 40 g of imidazole and 8 g of sodium bromide in 450 g of acetonitrile, and stir at room temperature for 1 h to obtain the regenerant A2; Dissolve 9.6 g of zinc chloride and 132 g of 1,2-dibromopropane in 250 g of toluene, and stir at room temperature for 1 h to obtain the regenerant B2; Dissolve 60 g of 1-methylimidazole in 390 g of the regenerant B2, and stir at room temperature for 1 h to obtain the regenerant C2. Example 3

[0027] Dissolve 27 g of imidazole and 9 g of zinc bromide in 512 g of acetonitrile, and stir at room temperature for 1 h to obtain the regenerant A3; Dissolve 11.0 g of zinc iodide and 103 g of 1,2-dibromoethane in 300 g of toluene, and stir for 1 h at room temperature to obtain the regeneration liquid B3; Dissolve 53 g of 1-ethylimidazole in 415 g of the regeneration liquid B3, and stir for 1 h at room temperature to obtain the regeneration liquid C3. Example 4

[0028] Dissolve 50 g of imidazole and 13 g of potassium bromide in 580 g of acetonitrile, and stir for 1 h at room temperature to obtain the regeneration liquid A4; Dissolve 8.5 g of zinc bromide and 96 g of 1,2-dibromobutane in 330 g of toluene, and stir for 1 h at room temperature to obtain the regeneration liquid B4; Dissolve 65 g of 1-butylimidazole in 430 g of the regeneration liquid B4, and stir for 1 h at room temperature to obtain the regeneration liquid C4.

[0029] Comparative Example 1 Prepare according to Preparation Example 1 to obtain the regeneration liquids A5, B5, and C5. The only difference is that the regeneration liquid B5 used in preparing the regeneration liquid C5 is fresh regeneration liquid B5.

[0030] Catalyst regeneration: Use the regeneration liquids A, B, and C to regenerate the deactivated propylene carbonate synthesis catalyst. The deactivated catalyst is a polydivinylbenzene polymer loaded with imidazole groups (original reaction conditions: 100 °C, 2 MPa, space velocity 0.4 h -1 , gas-liquid ratio 2:1, reaction for 350 hours, conversion rate 45%) with a loading of 100 g. Example 5

[0031] Introduce 400 g of the regeneration liquid A1 into the reaction tube containing 100 g of the deactivated catalyst, and circulate it 24 times, with each cycle maintained for 1 h. The reactor temperature is maintained at 40 °C. After the circulation is completed, drain the excess regeneration liquid A1; continue to introduce 400 g of the regeneration liquid B1 into the reactor, and circulate the regeneration liquid B1 24 times, with each cycle maintained for 1 h. The reactor temperature is maintained at 80 °C. After the circulation is completed, drain the excess regeneration liquid B1; pump 400 g of the regeneration liquid C1 into the fixed-bed reactor containing the catalyst, and circulate the regeneration liquid C1 24 times. The reactor temperature is maintained at 70 °C. After the circulation is completed, drain the excess regeneration liquid C1 to obtain the in-situ regenerated catalyst D1. Example 6

[0032] According to the method of Example 5, use the regeneration liquids A2, B2, and C2 to regenerate the deactivated catalyst to obtain the in-situ regenerated catalyst D2. Example 7

[0033] According to the method of Example 5, the deactivated catalyst was regenerated with regeneration liquids A3, B3, and C3 to obtain an in-situ regenerated catalyst D3. Example 8

[0034] According to the method of Example 5, the deactivated catalyst was regenerated with regeneration liquids A4, B4, and C4 to obtain an in-situ regenerated catalyst D4.

[0035] Comparative Example 2 According to the method of Example 5, the deactivated catalyst was regenerated with regeneration liquids A5, B5, and C5 to obtain an in-situ regenerated catalyst D5.

[0036] Comparative Example 3 400 g of regeneration liquid A1 was introduced into the reaction tube containing 100 g of the deactivated catalyst and circulated 24 times. Each circulation was maintained for 1 hour, and the reactor temperature was maintained at 40°C. After the circulation ended, the excess regeneration liquid A1 was discharged; then 400 g of regeneration liquid B1 was introduced into the reactor and circulated 24 times. Each circulation was maintained for 1 hour, and the reactor temperature was maintained at 80°C. After the circulation ended, the excess regeneration liquid B1 was discharged to obtain an in-situ regenerated catalyst D6.

[0037] Comparative Example 4 The deactivated catalyst was taken out of the original reaction tube and placed in a beaker. 400 g of regeneration liquid A1 was added, and it was stirred at 40°C for 24 hours. After completion, the regeneration liquid A1 was filtered off; then 400 g of regeneration liquid B1 was added to the beaker and stirred at 80°C for 24 hours. After completion, the regeneration liquid B1 was filtered off; then 400 g of regeneration liquid C1 was added to the beaker and stirred at 70°C for 24 hours. After completion, the regeneration liquid C1 was filtered off to obtain a regenerated catalyst D7, which was placed in the reaction tube for standby. Example 9

[0038] Evaluation of the regenerated catalyst: Propylene oxide was introduced into the reactor to rinse the regenerated catalyst to wash out the residual regeneration liquid, and then it was evaluated under the reaction conditions (100°C, 2 MPa, space velocity 0.4 h -1 , gas-liquid ratio 2:1,) for 100 h. The reaction products were analyzed by gas chromatography, and the results are shown in Table 2.

[0039] Table 2 Catalyst evaluation results.

[0040] catalyst conversion rate selectivity D1 93% 99% D2 96% 99% D3 87% 98% D4 89% 98% D5 83% 98% D6 77% 93% D7 94% 99% fresh catalyst 90% 98% The reaction conversion rate and selectivity of catalyst D7 were very high, comparable to those of catalysts D1 and D2. However, during the catalyst regeneration process, it was exposed to air and there was mechanical friction, resulting in catalyst pulverization and blockage in the reaction tube. The survival time after regeneration was only about 100 hours. For the comparison of the survival time, see Figure 1 .

Claims

1. An online regeneration method for propylene carbonate catalyst, characterized in that The method comprises the following contents: (1) passing regeneration liquid A into a fixed bed reactor containing a deactivated propylene carbonate catalyst for a first regeneration treatment, and discharging excess regeneration liquid A after the regeneration treatment is completed; (2) passing regeneration liquid B into a fixed bed reactor containing a deactivated propylene carbonate catalyst for a second regeneration treatment, and discharging excess regeneration liquid B after the regeneration treatment is completed; (3) passing regeneration liquid C into a fixed bed reactor containing a deactivated propylene carbonate catalyst for a third regeneration treatment, and discharging excess regeneration liquid C after the regeneration treatment is completed; the regeneration liquid A in step (1) comprises: 5wt%-15wt% imidazole, 1wt%-5% bromine salt and 80wt%-94wt% solvent A; the regeneration liquid B in step (2) comprises: 2wt%-5wt% zinc salt, 25wt%-50wt% dibromoalkane and 45wt%-73wt% solvent B; the regeneration liquid C in step (3) comprises: 6wt%-16wt% alkylimidazole and 84wt%-94wt% recycled regeneration liquid B.

2. The method according to claim 1, wherein: The bromide salt in step (1) is one or more of lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide and zinc bromide; and the solvent A is one or more of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methanol and tetrahydrofuran.

3. The method according to claim 1, wherein: The propylene carbonate catalyst described in step (1) is an imidazole-based ionic liquid catalyst, and the catalyst carrier is various resins containing chloromethyl groups; preferably one or more of polystyrene butadiene resin microspheres, alkaline resins with quaternary ammonium salt groups, mesoporous SiO2 grafted with ionic liquids, chitosan grafted with ionic liquids, cellulose grafted with ionic liquids, and mesoporous phenolic resin catalysts loaded with imidazole groups.

4. The method according to claim 1, wherein: The liquid-to-solid mass ratio of the regeneration liquid A to the catalyst in step (1) is 3-5:

1.

5. The method according to claim 1, wherein: The first regeneration treatment conditions described in step (1) are: a circulation residence time of 0.5 to 2 hours, a temperature of 30-50°C, and a regeneration liquid circulation of 10 to 40 times.

6. The method according to claim 1, wherein: The zinc salt in step (2) is one or more of zinc fluoride, zinc chloride, zinc bromide and zinc iodide; the dibromoalkane is one or more of 1,2-dibromoethane, 1,3-dibromopropane and 1,4-dibromobutane; and the solvent B is one or more of toluene, cyclohexane, carbon disulfide, ethyl acetate and dimethyl carbonate.

7. The method according to claim 1, wherein: The second regeneration treatment conditions described in step (2) are: a circulation residence time of 0.5 to 2 hours, a temperature of 60-80°C, and a regeneration liquid circulation of 10 to 40 times.

8. The method according to claim 1, wherein: The alkylimidazole in step (3) is one or more of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole or 1-butylimidazole, preferably 1-methylimidazole.

9. The method according to claim 1, wherein: The second regeneration treatment conditions described in step (3) are: time 0.5 to 2 hours, temperature 50-80°C, and regeneration liquid circulation 10 to 40 times.

10. The method according to claim 1, wherein: The preparation method of the regeneration liquids A, B and C described in the step is to mix the components of each regeneration liquid for a period of time to obtain the regeneration liquid, and the mixing time is 0.5 to 2 hours.

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