An in-situ regeneration method of a supported imidazole salt catalyst for preparing dimethyl carbonate by decarboxylation of dimethyl oxalate

Abstract

The application is directed to the deactivated supported imidazole salt catalyst for the preparation of dimethyl carbonate by the directional decarboxylation of dimethyl oxalate, and provides an in-situ regeneration method of the supported imidazole salt catalyst for the preparation of dimethyl carbonate by the decarboxylation of dimethyl oxalate. The method of catalyst regeneration is that the deactivated catalyst is impregnated with the alcohol solution of imidazole salt for several times, and then dried. The supported imidazole salt catalyst applied to the fixed bed regeneration method is refluxed and circulated for impregnation with the alcohol solution of imidazole salt in-situ on line, and then dried with nitrogen. The regeneration method applied to the liquid phase slurry bed is that the deactivated catalyst is washed with dimethyl carbonate until no dimethyl oxalate is left, and then dried after impregnation for several times. The technical means of the application can greatly restore the activity of the catalyst, recycle, prolong the service life of the catalyst, and greatly reduce the cost of the catalyst. Especially for the gas-solid phase reactor, the catalyst can be regenerated on line directly without disassembling the catalyst. The catalyst regeneration method is green, simple and easy to operate, and has economic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of chemical industrial catalysis, and particularly relates to an in-situ regeneration method for a supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate. Background Technology

[0002] Dimethyl carbonate has a wide range of uses. In addition to being used as an additive for gasoline and diesel fuels and as a green and environmentally friendly solvent for paints and coatings, it is also used as an alkylating agent, carbonylating agent, and solvent in the synthesis of polycarbonate, polyurethane, and resins in the pharmaceutical and pesticide fields. It also has good application prospects in lithium-ion battery electrolytes in the new energy field, making it a very useful compound.

[0003] Due to severe overcapacity in the coal-to-ethylene glycol industry, the development of targeted decarbonylation of dimethyl oxalate, an intermediate product of coal-to-ethylene glycol, into dimethyl carbonate has become increasingly popular. In recent years, various supported or unsupported solid catalysts for the targeted decarbonylation of alkali metal salts have been disclosed in CN98125031.9 by Harada Katsumasa et al. of Ube Industries, Ltd. of Japan, CN202010792572.3 by Tao Lingyun et al. of Wuhan Juchuan Technology Co., Ltd. of Shandong Province, CN202110388271.9 by Zhang Wei et al., and CN202110781605.9 by Yu Xiaolong et al. of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences.

[0004] Related catalyst processes include both liquid-phase high-pressure reactor systems (CN 202211384255.3, CN202211469440.2, CN202211543857.9) and gas-solid phase fixed-bed reactor systems. However, catalyst regeneration technology is scarce in both published articles and patents. CN202211543857.9 mentions using methanol as the solvent medium in the reaction system. After filtering, washing, and discharging the deactivated catalyst, the methanol wash liquid is mixed again with an alkali metal-alkaline earth metal composite organic salt in a catalyst tank, and then fed into the reactor. First, the catalyst mentioned in this patent does not fall under the category of catalyst regeneration; it is merely the replacement of fresh catalyst. Second, it is well known that methanol and dimethyl carbonate form an azeotrope. This method increases the difficulty of separating the product dimethyl carbonate and methanol, thus increasing the production cost of dimethyl carbonate. Furthermore, existing catalysts all suffer from short lifespans and deactivation issues to varying degrees. Once a catalyst is deactivated, its lifespan and the economic viability of producing dimethyl carbonate are affected. Therefore, catalyst regeneration is of paramount importance. Summary of the Invention

[0005] This invention addresses the problems of short lifespan, easy loss, and carbon deposition deactivation of supported imidazole salt catalysts used in the directional synthesis of dimethyl carbonate from dimethyl oxalate. It provides a regeneration method that restores the activity of catalysts used in the production of dimethyl carbonate without complex processes such as calcination, thereby enabling the reuse of the catalysts.

[0006] The in-situ regeneration method for a supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized in that the supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate is impregnated several times with an alcoholic solution of imidazole salt, followed by a drying process.

[0007] The in-situ regeneration method for a supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized in that the impregnation and drying processes of the supported imidazole salt catalyst in a gas-solid phase fixed-bed reactor for the decarbonylation of dimethyl oxalate to dimethyl carbonate include:

[0008] Prepare an alcoholic solution of an imidazole salt with a specific molar concentration;

[0009] An alcoholic solution of imidazole salt was added to a fixed bed containing a deactivated catalyst and refluxed at a certain temperature until the pH of the solution remained constant. The reflux residue was then discharged.

[0010] The imidazole salt catalyst in the fixed bed is purged with nitrogen gas at a certain flow rate and temperature until the ethanol content of nitrogen in the tail gas is less than 0.02%, thus obtaining the regenerated catalyst.

[0011] The in-situ regeneration method for a supported imidazole salt catalyst used in the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized by the following steps: impregnation and drying of the supported imidazole salt catalyst in a liquid-phase slurry bed.

[0012] The deactivated catalyst was repeatedly washed with dimethyl carbonate until no dimethyl oxalate residue remained, and then vacuum dried.

[0013] Prepare an alcoholic solution of an imidazole salt with a specific molar concentration;

[0014] The catalyst dried in step a is placed in step b for further impregnation and aging;

[0015] After removing the filtrate, the filtered catalyst is dried under certain conditions to obtain the regenerated catalyst.

[0016] The in-situ regeneration method for a supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized in that the molar concentration of the alcohol solution of the imidazole salt is 0.1-10 mol / L, and the alcohol is one or more combinations of C1-C4 alcohols.

[0017] The in-situ regeneration method of the supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized in that the b-process in the gas-solid phase fixed bed reactor is cyclically repeated several times, and the temperature of the b-process is 20-70℃.

[0018] The in-situ regeneration method of the supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate, as described above, is characterized by the repeated impregnation of the liquid-phase slurry bed c treatment step at a temperature of 50-150°C.

[0019] Whether in a fixed-bed reactor or a liquid-phase slurry bed, the regeneration method of the supported imidazole salt catalyst of this invention produces a regenerated catalyst with good regeneration effect and good activity recovery effect, which can greatly extend the catalyst life and reduce the catalyst cost. Especially for fixed-bed reactors, the catalyst can be directly regenerated in situ online without disassembling it, reducing catalyst loading and unloading operations, simplifying the catalyst process, greatly reducing the catalyst cost, and improving the yield of dimethyl carbonate. It is a simple and easy catalyst regeneration method. Implementation

[0020] To better understand the technical solution of the present invention, the following embodiments are used to further illustrate the present invention in detail. However, this content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence of the technical solution of the present invention and the scope of protection of the claims.

[0021] Example 1: 20g of fresh supported potassium imidazolium / activated carbon catalyst was weighed and loaded into a gas-solid fixed-bed reactor. Under reaction conditions of 190℃, the liquid hourly space velocity (LHSV) of DMO was 2 kg / (kg h). After being vaporized in a preheater, the catalyst entered the fixed bed for decarbonylation reaction. The gaseous product was condensed into DMC via a cold trap. The non-condensable gas CO was metered by a flow meter and then catalytically combusted. When the catalyst conversion rate was below 55%, it was considered that the catalyst had been essentially deactivated, and the experiment was stopped by cooling down. During the experiment, the catalyst conversion rate and selectivity were recorded after half an hour of reaction. At the end of the experiment, the mass of DMC produced per gram of catalyst was calculated.

[0022] Catalyst regeneration: Prepare 40 mL of a 1.86 mol / L potassium imidazolium methanol solution and add it to the fixed-bed reactor. Circulate the solution continuously using a pump at a temperature of 50°C. Check the pH of the solution every half hour until the pH remains constant for two consecutive cycles. Discharge the residual liquid, raise the reactor temperature to 130°C, and purge with nitrogen until the methanol content in the tail gas is ≤0.01%. Then, use fresh catalyst evaluation conditions to observe the mass of total DMC collected in the cold trap.

[0023] Example 2: 20g of fresh supported potassium imidazolium / activated carbon catalyst was weighed and loaded into a gas-solid fixed-bed reactor. Under reaction conditions of 190℃, the liquid hourly space velocity (LHSV) of DMO was 2 kg / (kg h). After being vaporized in a preheater, the DMO entered the fixed bed for decarbonylation reaction. The gaseous product was condensed into DMC via a cold trap. The non-condensable gas CO was metered by a flow meter and then catalytically combusted. When the catalyst conversion rate was below 55%, it was considered that the catalyst had been essentially deactivated, and the experiment was stopped by cooling down. During the experiment, the catalyst conversion rate and selectivity were recorded after half an hour of reaction. At the end of the experiment, the mass of DMC produced per gram of catalyst was calculated.

[0024] Catalyst regeneration: Prepare 40 mL of 1.16 mol / L potassium imidazolium ethanol solution and add it to the fixed-bed reactor. Circulate the solution continuously using a pump at a temperature of 30°C. Check the pH of the solution every half hour until the pH remains constant for two consecutive cycles. Discard the residual solution. Prepare the same potassium imidazolium solution again and repeat the same circulation process. Heat the reactor to 80°C and purge with nitrogen until the ethanol content in the tail gas is ≤0.01%. Then, using fresh catalyst evaluation conditions, observe the mass of total DMC collected in the cold trap.

[0025] Example 3: 20g of fresh supported sodium imidazolium / activated carbon catalyst was weighed and loaded into a gas-solid fixed-bed reactor. Under reaction conditions of 190℃, the liquid hourly space velocity (LHSV) of DMO was 2 kg / (kg h). After being vaporized in a preheater, the DMO entered the fixed bed for decarbonylation reaction. The gaseous product was condensed into DMC via a cold trap. The non-condensable gas CO was metered by a flow meter and then catalytically combusted. When the catalyst conversion rate was below 55%, it was considered that the catalyst had been essentially deactivated, and the experiment was stopped by cooling down. During the experiment, the catalyst conversion rate and selectivity were recorded after half an hour of reaction. At the end of the experiment, the mass of DMC produced per gram of catalyst was calculated.

[0026] Catalyst regeneration: Prepare 40 mL of 2.75 mol / L sodium imidazolium in methanol, add potassium imidazolium solution to the fixed-bed reactor, and continuously circulate it using a pump. Set the circulation temperature to 60 °C, and check the pH value of the solution every half hour until the pH value of the solution remains constant for two consecutive times. Discharge the residual liquid, heat the reactor to 100 °C, and purge with nitrogen until the methanol content in the tail gas is ≤0.01%. Then, use fresh catalyst evaluation conditions to observe the mass of total DMC collected in the cold trap.

[0027] Example 4: 20g of fresh supported sodium imidazolium / activated carbon catalyst was weighed and loaded into a gas-solid fixed-bed reactor. Under reaction conditions of 190℃, the liquid hourly space velocity (LHSV) of DMO was 2 kg / (kg h). After being vaporized in a preheater, the DMO entered the fixed bed for decarbonylation reaction. The gaseous product was condensed into DMC via a cold trap. The non-condensable gas CO was metered by a flow meter and then catalytically combusted. When the catalyst conversion rate was below 55%, it was considered that the catalyst was essentially deactivated, and the experiment was stopped by cooling down. During the experiment, the catalyst conversion rate and selectivity were recorded after half an hour of reaction. At the end of the experiment, the mass of DMC produced per gram of catalyst was calculated.

[0028] Catalyst regeneration: Prepare 40 mL of 4.12 mol / L potassium imidazole ethanol solution, add the potassium imidazole solution to the fixed-bed reactor, and continuously circulate it using a pump. Set the circulation temperature to 30℃, and check the pH value of the solution every half hour until the pH value of the solution remains unchanged for two consecutive times. Discharge the residual liquid, raise the reactor temperature to 120℃, and purge with nitrogen until the ethanol content in the tail gas is ≤0.01%. Then, use fresh catalyst evaluation conditions to observe the mass of total DMC collected in the cold trap.

[0029] Example 5: Weigh 20g of fresh supported potassium imidazolium / activated carbon catalyst and load it into a liquid-phase stirred tank reactor. Initially, add 200g of DMO, close the reactor, and after nitrogen purging, feed DMO continuously at 165℃ and 0.3MPa using a diaphragm pump with adjusted flow rate. The liquid hourly space velocity (LHSV) of DMO is 0.5-10 kg / (kg h). The tail gas and product DMC are continuously collected until the catalyst conversion rate is below 55%, at which point the catalyst is considered deactivated, and the experiment is stopped by cooling. Record the catalyst conversion rate and selectivity after half an hour of reaction. Calculate the mass of DMC produced per gram of catalyst at the end of the experiment.

[0030] Catalyst regeneration: The deactivated catalyst was repeatedly filtered and washed with DMC until no DMO residue remained, and then vacuum dried at 105℃. A 30 mL solution of 3.09 mol / mL potassium imidazolium in methanol was prepared. The deactivated catalyst was then impregnated again and aged for 3 h. The filtrate was then removed by filtration, and the filtered catalyst was dried at 120℃ for 12 h to obtain the regenerated catalyst. The evaluation conditions for the regenerated catalyst were the same as for the fresh catalyst, and the mass of the total DMC collected in the cold trap was calculated.

[0031] Example 6: Weigh 20g of fresh supported potassium imidazolium / activated carbon catalyst and load it into a liquid-phase stirred tank reactor. Initially, add 200g of DMO, close the reactor, and after nitrogen purging, continuously feed DMO to the raw material at 165℃ and 0.3MPa using a diaphragm pump with adjusted flow rate. The liquid hourly space velocity (LHSV) of DMO is 0.5-10 kg / (kg h). The tail gas and product DMC are continuously collected until the catalyst conversion rate is below 55%, at which point the catalyst is considered deactivated, and the experiment is stopped by cooling. Record the catalyst conversion rate and selectivity after half an hour of reaction. Calculate the mass of DMC produced per gram of catalyst at the end of the experiment.

[0032] Catalyst regeneration: The deactivated catalyst was repeatedly filtered and washed with DMC until no DMO residue remained, and then vacuum dried at 105℃. A 30 mL solution of 2.78 mol / mL potassium imidazolium in ethanol was prepared. The deactivated catalyst was then impregnated again and aged for 3 h. The filtrate was then removed by filtration, and the filtered catalyst was dried at 80℃ for 12 h to obtain the regenerated catalyst. The evaluation conditions for the regenerated catalyst were the same as for the fresh catalyst, and the mass of the total DMC collected in the cold trap was calculated.

[0033] Example 7: Weigh 20g of fresh supported sodium imidazolium / activated carbon catalyst and load it into a liquid-phase stirred tank reactor. Initially, add 200g of DMO, close the reactor, and after nitrogen purging, continuously feed DMO to the raw material at 165℃ and 0.3MPa using a diaphragm pump with adjusted flow rate. The liquid hourly space velocity (LHSV) of DMO is 0.5-10 kg / (kg h). The tail gas and product DMC are continuously collected until the catalyst conversion rate is below 55%, at which point the catalyst is considered deactivated, and the experiment is stopped by cooling. Record the catalyst conversion rate and selectivity after half an hour of reaction. Calculate the mass of DMC produced per gram of catalyst at the end of the experiment.

[0034] Catalyst regeneration: The deactivated catalyst was repeatedly filtered and washed with DMC until no DMO residue remained, and then vacuum dried at 105℃. A 30 mL solution of 2.93 mol / mL imidazoline sodium in methanol was prepared. The deactivated catalyst was then re-impregnated and aged for 3 h. The filtrate was then removed by filtration, and the same imidazoline sodium in methanol solution was prepared again for repeated impregnation. The filtrate was then removed, and the filtered catalyst was dried at 105℃ for 12 h to obtain the regenerated catalyst. The evaluation conditions for the regenerated catalyst were the same as for the fresh catalyst, and the mass of the total DMC collected in the cold trap was calculated.

[0035] Example 8: Weigh 20g of fresh supported sodium imidazolium / activated carbon catalyst and load it into a liquid-phase stirred tank reactor. Initially, add 200g of DMO, close the reactor, and after nitrogen purging, continuously feed DMO to the raw material at 165℃ and 0.3MPa using a diaphragm pump with adjusted flow rate. The liquid hourly space velocity (LHSV) of DMO is 0.5-10 kg / (kg h). The tail gas and product DMC are continuously collected until the catalyst conversion rate is below 55%, at which point the catalyst is considered deactivated, and the experiment is stopped by cooling. Record the catalyst conversion rate and selectivity after half an hour of reaction during the experiment. Calculate the mass of DMC produced per gram of catalyst at the end of the experiment.

[0036] Catalyst regeneration: The deactivated catalyst was repeatedly filtered and washed with DMC until no DMO residue remained, and then vacuum dried at 105℃. A 30 mL solution of 3.29 mol / mL imidazole sodium in ethanol was prepared. The deactivated catalyst was then impregnated again and aged for 3 h. The filtrate was then removed by filtration, and the filtered catalyst was dried at 110℃ for 12 h to obtain the regenerated catalyst. The evaluation conditions for the regenerated catalyst were the same as for the fresh catalyst, and the mass of the total DMC collected in the cold trap was calculated.

[0037] In the table above, X represents conversion rate, S represents selectivity, and P represents the mass of DMC produced per gram of catalyst; DMO is dimethyl oxalate, and DMC is dimethyl carbonate.

[0038] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. Those skilled in the art should understand that modifications can still be made to the specific embodiments of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solution of the present invention. All such modifications and substitutions should be covered within the scope of protection of the technical solution claimed by the present invention. It should be noted that the symbol "-" in the text means "from...to...", such as a reaction temperature of 50-150℃, which means that the reaction temperature can be any temperature between 50℃ and 150℃.

Claims

1. An in-situ regeneration method for a supported imidazole salt catalyst used in the decarbonylation of dimethyl oxalate to dimethyl carbonate, characterized in that... The supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate is impregnated several times with an alcoholic solution of imidazole salt, followed by a drying process. The impregnation and drying processes of this supported imidazole salt catalyst in a gas-solid phase fixed-bed reactor for the decarbonylation of dimethyl oxalate to dimethyl carbonate include: Step a: Prepare an alcoholic solution of imidazole salt with a certain molar concentration, wherein the alcohol is ethanol; Step b: Add the alcoholic solution of imidazole salt to a fixed bed containing the deactivated catalyst, reflux at a certain temperature until the pH of the solution remains unchanged, and then release the reflux residue; Step c: Purge the imidazole salt catalyst in the fixed bed with nitrogen gas at a certain flow rate and a certain temperature until the ethanol content of nitrogen in the tail gas is less than 0.02%, and the regenerated catalyst is obtained.

2. An in-situ regeneration method for a supported imidazole salt catalyst used in the decarbonylation of dimethyl oxalate to dimethyl carbonate, characterized in that... The supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate is subjected to several impregnation steps with an alcoholic solution of imidazole salt, followed by a drying process. The impregnation and drying steps of this supported imidazole salt catalyst in a liquid-phase slurry bed include: Step a: The deactivated catalyst is repeatedly washed with dimethyl carbonate until no dimethyl oxalate residue remains, and then vacuum dried; Step b: Prepare an alcoholic solution of imidazole salt with a certain molar concentration, wherein the alcohol is one or more combinations of C1-C4 alcohols; The catalyst dried in step a is placed in step b for further impregnation and aging; Step c: Remove the filtrate and dry the filtered catalyst under certain conditions to obtain the regenerated catalyst.

3. The in-situ regeneration method for a supported imidazole salt catalyst for the decarbonylation of dimethyl oxalate to dimethyl carbonate according to claim 1 or 2, characterized in that... The molar concentration of the alcoholic solution of the imidazole salt is 0.1-10 mol / L.