Alkali metal supported catalyst, process for its preparation and use thereof

Abstract

The application discloses a catalyst loaded with alkali metal and a preparation method and application thereof. The catalyst comprises P-doped activated carbon and an alkali metal active element loaded on the P-doped activated carbon. The catalyst is applied to a reaction of preparing alkyl carbonate by one-step method of alkyl oxalate, realizes full utilization of alkyl oxalate which is an important intermediate in a coal-to-ethylene glycol process, and prepares high-value-added alkyl carbonate. Compared with a traditional method, the catalyst can efficiently and stably realize decarboxylation of alkyl oxalate to prepare alkyl carbonate, the method has low raw material cost and low equipment requirement, is suitable for large-scale industrial production, and has great practical value and economic value.

Description

Technical Field

[0001] This application relates to a catalyst supported on an alkali metal, its preparation method and application, and belongs to the field of alkali metal catalysts. Background Technology

[0002] Alkyl carbonates, especially dimethyl carbonate (DMC), are important organic chemical intermediates. They resemble common alcohols, esters, and ketones in appearance, are poorly soluble in water, and miscible with alcohols, ketones, esters, and aromatic hydrocarbons. They are low-toxicity, environmentally friendly, and widely used chemical raw materials. They can be used as carbonylating agents or methylating reagents, replacing highly toxic phosgene, methyl chloroformate, and dimethyl sulfate in the production of polycarbonates, isocyanates, polyurethanes, polycarbonate diols, allyl diethylene glycol carbonates, naphthyl methylcarbamate (Sevin), anisole, long-chain alkyl carbonates, carbamates, solid phosgene, malonate, diethyl carbonate, furazolidone, methyl hydrazine, methyl aniline, and many other chemical products. They are hailed as a "new cornerstone of modern organic synthesis" and are also a novel fuel additive with broad application prospects.

[0003] Overseas dimethyl carbonate (DMC) plants are mostly integrated with downstream polycarbonate (PC) or electrolyte production, with PC applications accounting for approximately 65%. In 2017, my country's traditional DMC consumption in sectors such as coatings, adhesives, developers, and pesticide / pharmaceutical intermediates accounted for about 50%. The rapid development of new energy vehicles and the continued advancement of domestic polycarbonate production have significantly boosted the demand for DMC. In 2020, my country's apparent consumption of DMC was approximately 420,000 tons per year, with nearly 70% of that consumption occurring in electrolyte solvents and polycarbonate sectors. With the rapid development of the new energy vehicle and polycarbonate industries, DMC consumption is bound to continue to rise.

[0004] The initial method for producing dimethyl carbonate was the phosgene process, successfully developed in 1918. Phosgene reacts with anhydrous methanol to produce dimethyl carbonate, releasing hydrogen chloride in the process. The toxicity and corrosiveness of phosgene limited the application of this method, which is now obsolete. In the 1980s, the Italian company EniChem commercialized the methanol oxidative carbonylation process for dimethyl carbonate, but the catalyst suffered severe deactivation, resulting in a single-pass conversion rate of only 20%. In the 1990s, the Japanese company Ube improved upon EniChem's methanol oxidative carbonylation process, avoiding catalyst deactivation, increasing the conversion rate, and achieving industrialization. In 1992, the American company Texaco developed a process that reacts ethylene oxide with carbon dioxide to produce ethylene carbonate, which is then transesterified with methanol to produce dimethyl carbonate and co-produce ethylene glycol. This process was industrialized, but the dimethyl carbonate yield is low and the production cost is high. In addition, there are literature reports on the preparation of dimethyl carbonate by the methanol hydrolysis of urea and the preparation of dimethyl carbonate by the direct reaction of CO2 and methanol, but these have not yet been industrialized.

[0005] Ethylene glycol is a major petrochemical product, primarily used in antifreeze and the production of PET polyester. Currently, ethylene glycol is mainly produced using petrochemical technology: ethylene is used as a raw material, epoxidation is used to produce ethylene oxide, and then hydration is used to produce ethylene glycol. This technology consumes a large amount of petroleum resources, and the dehydration separation process is energy-intensive. The development and application of coal chemical technology has provided a new technological route for the non-petroleum production of ethylene glycol. In the coal-to-ethylene glycol process, dimethyl oxalate is an important intermediate, present in large quantities in the ethylene glycol preparation process. It is widely available, inexpensive, and readily available. Therefore, the decarbonylation of dimethyl oxalate to prepare dimethyl carbonate and its derived alkyl esters is a new approach. This has significant practical implications for reducing the preparation cost of alkyl carbonates and improving the comprehensive utilization of intermediate products from coal-to-ethylene glycol production. Summary of the Invention

[0006] In order to improve the comprehensive utilization of products between ethylene glycols and reduce the preparation cost of alkyl carbonates and increase the yield of alkyl carbonates, this application provides an alkali metal-supported catalyst to fully utilize dimethyl oxalate, an important intermediate in the coal-to-ethylene glycol process. By decarbonylating dimethyl oxalate, dimethyl oxalate can be efficiently converted into dimethyl carbonate and its derived alkyl esters under mild conditions.

[0007] According to one aspect of this application, a catalyst supported on an alkali metal is provided, comprising p-doped activated carbon and an alkali metal active element, wherein the alkali metal active element is supported on the p-doped activated carbon.

[0008] Optionally, the alkali metal active element accounts for 2-15% of the mass percentage of the catalyst.

[0009] Optionally, the alkali metal active element accounts for any value or a range between two values ​​from 2%, 6%, 10%, 12%, and 15% by mass of the catalyst.

[0010] Optionally, the alkali metal active element is selected from any one of Li, Na, K, Rh, and Cs.

[0011] According to another aspect of this application, a method for preparing the above-mentioned catalyst is provided, comprising the following steps:

[0012] a) The alkali-treated activated carbon support is placed in an ethanol solution containing P precursor, impregnated for I, and dried for I to obtain P-doped activated carbon support.

[0013] b) Impregnate the P-doped activated carbon support with an equal volume of an aqueous solution containing an alkali metal compound, dry it (II), and calcine it under an inactive atmosphere to obtain the catalyst.

[0014] Optionally, the P-containing precursor is selected from at least one of triphenylphosphine, phenylphosphamide, and phenylphosphoric acid.

[0015] Optionally, the alkali metal compound is selected from at least one of Li2CO3, Na2CO3, K2CO3, Rh2CO3, and Cs2CO3.

[0016] Optionally, the mass ratio of the activated carbon carrier to the P-containing precursor is 20 to 5:1.

[0017] Optionally, the mass ratio of the activated carbon carrier to the P-containing precursor is any value among 20:1, 15:1, 10:1, and 5:1, or a range between two values.

[0018] Optionally, the mass ratio of the P-doped activated carbon support to the alkali metal compound is 50 to 5:1.

[0019] Optionally, the mass ratio of the P-doped activated carbon support to the alkali metal compound is any value or a range between two values ​​from 50:1, 45:1, 35:1, 25:1, 15:1, and 5:1.

[0020] Optionally, the temperature of the impregnation I is 30–80°C, and the impregnation time is 5–10 h.

[0021] Optionally, the temperature of the impregnation I is selected from any value of 30°C, 45°C, 65°C, 75°C, and 80°C, or a range between two values.

[0022] Optionally, the immersion time I is selected from any value of 5h, 6h, 8h, 9h, 10h or a range between two values.

[0023] Optionally, the temperature of the drying process I is 120–180°C, and the drying time is 5–10 hours.

[0024] Optionally, the temperature of the drying I is selected from any value of 120°C, 140°C, 150°C, 160°C, or 180°C, or a range between two values.

[0025] Optionally, the drying time I is selected from any value of 5h, 6h, 8h, 9h, 10h or a range between two values.

[0026] Optionally, the temperature for the equal-volume impregnation is 30–80°C, and the impregnation time is 5–10 hours.

[0027] Optionally, the temperature for the equal-volume impregnation is selected from any value or a range between two of 30°C, 45°C, 65°C, 75°C, and 80°C.

[0028] Optionally, the time for the equal-volume impregnation is selected from any value of 5h, 6h, 8h, 9h, 10h or a range between two values.

[0029] Optionally, the temperature of the second drying step is 120–180°C, and the drying time is 5–10 hours.

[0030] Optionally, the temperature of the drying II is selected from any value or a range between two of 120°C, 140°C, 150°C, 160°C, and 180°C.

[0031] Optionally, the drying time II is selected from any value selected from 5h, 6h, 8h, 9h, 10h or a range between two values.

[0032] Optionally, the calcination conditions are as follows: under an inactive atmosphere, the temperature is increased to 550-580°C at a heating rate of 2-5°C / min, and calcined for 5-10 hours.

[0033] According to another aspect of this application, a method for preparing alkyl carbonate from alkyl oxalate is provided, wherein molten alkyl oxalate is contacted with a catalyst, reacted, and distilled to obtain alkyl carbonate.

[0034] The catalyst is selected from the catalysts described above or the catalysts prepared according to the preparation method described above.

[0035] Optionally, the mass ratio of the alkyl oxalate to the catalyst is 50 to 5:1.

[0036] Optionally, the mass ratio of the homogeneous solution containing alkyl oxalate to the catalyst is any value or a range between two values ​​from 50:1, 45:1, 35:1, 25:1, 15:1, and 5:1.

[0037] Optionally, the molecular formula of the alkyl oxalate is: Wherein R and R' are independently selected from alkyl groups having 1-8 carbon atoms.

[0038] Optionally, the reaction temperature is 80–240°C, the reaction pressure is 0.5–5.0 MPa, and the reaction time is 1.0–5.0 h.

[0039] Optionally, the reaction temperature is any value or a range between two of 80°C, 120°C, 150°C, 180°C, and 240°C.

[0040] Optionally, the pressure of the reaction is any value or a range between two values ​​from 0.5 MPa, 1.5 MPa, 2.5 MPa, 3.5 MPa, 4.5 MPa, and 5.0 MPa.

[0041] Optionally, the reaction time is any value among 1.0h, 2.0h, 3.0h, 4.0h, and 5.0h, or a range between two values.

[0042] Optionally, the reaction is carried out in a high-pressure reactor equipped with a tail gas system, which includes a back pressure valve and a condenser. When the pressure of the reaction system exceeds a set pressure, the gas is automatically vented and the vapor condensate is collected.

[0043] The beneficial effects that this application can produce include:

[0044] 1) The catalyst provided in this application is applied in the preparation of dimethyl carbonate, using dimethyl oxalate as a raw material to prepare dimethyl carbonate via one-step decarbonylation. This method is environmentally friendly, easy to operate, has high dimethyl oxalate conversion efficiency, and dimethyl carbonate is easily separated from the reaction raw materials. The raw material used in this method can be dimethyl oxalate, an intermediate product in the coal-to-ethylene glycol process, which facilitates its use in conjunction with existing coal-to-ethylene glycol production for large-scale industrial production.

[0045] 2) The method for preparing dimethyl carbonate provided in this application employs a batch reaction and a batch reactor, which helps reduce production costs and facilitates industrial production. The entire reaction process is carried out under mild conditions, greatly reducing the equipment requirements and demonstrating broad prospects for industrial application. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0048] In the examples, dimethyl oxalate was derived from a coal-to-ethylene glycol unit;

[0049] Methanol and ethylene glycol were purchased from Tianjin Kemeio Reagent Co., Ltd.

[0050] Dimethyl carbonate was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0051] Li₂CO₃, Na₂CO₃, K₂CO₃, Rh₂CO₃, Cs₂CO₃, triphenylphosphine, and phenylphosphineamide

[0052] Phenylated phosphoric acid was purchased from Shanghai Guoyao Reagent Company.

[0053] In the examples, the decarbonylation catalyst was dried in air at 120°C for 2-12 hours before use.

[0054] In this embodiment, the decarbonylation reaction was carried out in a pressure-resistant batch reactor. The catalyst and dimethyl oxalate were added to the reactor in a specific ratio. The reactor was purged with nitrogen three times, and the reaction system was adjusted to a set pressure via a tail gas back pressure valve. The reaction apparatus was heated to a certain temperature to carry out the decarbonylation reaction. After the reaction, the resulting gas condensate and reaction liquid filtrate were distilled to obtain dimethyl carbonate. The conversion rate of dimethyl oxalate and the yield of dimethyl carbonate were calculated using the internal standard method.

[0055] In the embodiments of this application, the conversion rate and yield are calculated as follows:

[0056] Conversion rate of dimethyl oxalate = (moles of dimethyl oxalate before reaction - moles of dimethyl oxalate after reaction) / moles of dimethyl oxalate before reaction * 100%

[0057] The yield of dimethyl carbonate = (moles of dimethyl carbonate / moles of dimethyl oxalate converted) * 100%.

[0058] Example 1 Preparation of Catalyst A

[0059] An ethanol solution containing 10g of triphenylphosphine was added to an activated carbon support that had been soaked in 50g of 10% NaOH aqueous solution for two hours. The mixture was then fully impregnated at 60℃ for 8 hours, filtered, washed, and dried at 150℃ for 5 hours. The resulting activated carbon containing the triphenylphosphine precursor was then impregnated in an equal volume with an aqueous solution containing 5g of Rh2CO3 at 60℃ for 5 hours and dried at 150℃ for 5 hours to obtain an activated carbon catalyst precursor supported on triphenylphosphine and Rh2CO3. The obtained precursor was then calcined in a muffle furnace under N2 atmosphere at a temperature increased to 550℃ at 2℃ / min for 5 hours to obtain P-doped activated carbon supported on Rh2CO3 catalyst A.

[0060] Example 2 Preparation of Catalyst B

[0061] The preparation method of catalyst B is the same as that of catalyst A in Example 1, except that the alkali metal compound used is Cs2CO3.

[0062] Example 3 Preparation of Catalyst C

[0063] The preparation method of catalyst C is the same as that of catalyst A in Example 1, except that the alkali metal compound used is K2CO3.

[0064] Example 4: Preparation of Catalyst D

[0065] The preparation method of catalyst D is the same as that of catalyst A in Example 1, except that the alkali metal compound used is Na2CO3.

[0066] Example 5 Preparation of Catalyst E

[0067] The preparation method of catalyst E is the same as that of catalyst A in Example 1, except that the alkali metal compound used is Li2CO3.

[0068] Example 6: Preparation of dimethyl carbonate from dimethyl oxalate via decarbonylation catalyzed by a p-doped activated carbon-supported alkali metal catalyst.

[0069] Different P-doped activated carbon-supported alkali metal catalysts were added to a reactor to verify their catalytic activity. The catalyst addition amount was 5g, the reaction temperature was 180℃, the dimethyl oxalate was 50g, the reactor pressure was 2.0MPa, and the reaction time was 2 hours.

[0070] The results obtained by supporting alkali metal catalysts on different P-doped activated carbons are shown in Table 1.

[0071] Table 1. Preparation of dimethyl carbonate from dimethyl oxalate via decarbonylation using alkali metal catalysts supported on alkali metals with different P-doped activated carbon.

[0072]

[0073] As shown in Table 1, among the alkali metal catalysts supported on different P-doped activated carbons, Rh2CO3 and Cs2CO3 supported on P-doped activated carbons exhibited higher decarbonylation conversion of dimethyl oxalate and higher yield of dimethyl carbonate.

[0074] Example 7 Effect of different catalyst feed amounts on the reaction

[0075] Different masses of P-doped activated carbon-supported Rh2CO3 catalyst A were added to a reactor to verify the catalytic activity. The reaction temperature was 180℃, the dimethyl oxalate was 50g, the reactor pressure was 2.0MPa, and the reaction time was 2 hours.

[0076] The results obtained with different catalyst feed amounts are shown in Table 2.

[0077] Table 2 Effect of catalyst feed amount on the decarbonylation of dimethyl oxalate to prepare dimethyl carbonate

[0078]

[0079] As shown in Table 2, increasing the amount of catalyst in reaction A significantly improves the reaction conversion rate. When the mass ratio of dimethyl oxalate to the decarbonylation catalyst is less than 10:1, good results are obtained, with the conversion rate of dimethyl oxalate exceeding 99% and the yield of dimethyl carbonate exceeding 89%.

[0080] Example 8 Effect of reaction temperature

[0081] The catalytic activity was verified by changing the reaction temperature. The catalyst was 5g of catalyst A and 50g of dimethyl oxalate. The pressure of the reactor was 2.0MPa and the reaction time was 2 hours.

[0082] The reaction results at different temperatures are shown in Table 3.

[0083] Table 3. Preparation of dimethyl carbonate from dimethyl oxalate via carbonylation at different reaction temperatures.

[0084]

[0085] As shown in Table 3, the reaction temperature has a significant effect on the conversion rate of dimethyl oxalate. As the reaction temperature increases, the conversion rate of dimethyl oxalate gradually increases and then remains constant, while the yield of dimethyl carbonate decreases with increasing temperature. The optimal reaction temperature is 180℃.

[0086] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A supported alkali metal catalyst for the preparation of alkyl carbonates from alkyl oxalates, characterized in that, It includes P-doped activated carbon and alkali metal active elements, wherein the alkali metal active elements are loaded onto the P-doped activated carbon. The method for preparing the catalyst includes the following steps: a) The alkali-treated activated carbon support is placed in an ethanol solution containing P precursor, impregnated for I, and dried for I to obtain P-doped activated carbon support. b) Impregnate the P-doped activated carbon support with an equal volume of an aqueous solution containing an alkali metal compound, dry it (II), and calcine it under an inactive atmosphere to obtain the catalyst; The phosphorus-containing precursor is selected from at least one of triphenylphosphine, phenylphosphamide, and phenylphosphoric acid; the alkali metal compound is Cs₂CO₃. The calcination conditions are as follows: under an inactive atmosphere, the temperature is increased to 550-580℃ at a heating rate of 2-5℃ / min, and calcined for 5-10 hours. The alkali metal active element accounts for 2-15% of the mass percentage of the catalyst.

2. A process for the preparation of a supported alkali metal catalyst for the preparation of alkyl carbonate esters from alkyl oxalate esters according to claim 1, characterized in that Includes the following steps: a) The alkali-treated activated carbon support is placed in an ethanol solution containing P precursor, impregnated for I, and dried for I to obtain a P-doped activated carbon support. b) Impregnate the P-doped activated carbon support with an equal volume of an aqueous solution containing an alkali metal compound, dry it (II), and calcine it under an inactive atmosphere to obtain the catalyst; The calcination conditions are as follows: under an inactive atmosphere, the temperature is increased to 550-580℃ at a heating rate of 2-5℃ / min, and calcined for 5-10 hours.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the activated carbon carrier to the P-containing precursor is 20~5:

1.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the P-doped activated carbon support to the alkali metal compound is 50 to 5:

1.

5. The preparation method according to claim 2, characterized in that, The temperature of the immersion I is 30~80℃, and the immersion time is 5~10h.

6. The preparation method according to claim 2, characterized in that, The temperature of the drying process I is 120~180℃, and the drying time is 5~10h.

7. The preparation method according to claim 2, characterized in that, The temperature for the equal-volume impregnation is 30~80℃, and the impregnation time is 5~10h.

8. The preparation method according to claim 2, characterized in that, The temperature of the second drying process is 120~180℃, and the drying time is 5~10h.

9. A method for preparing alkyl carbonate from alkyl oxalate, characterized in that, Molten alkyl oxalate is contacted with a catalyst, reacted, and then distilled to obtain alkyl carbonate. The catalyst is selected from the catalyst of claim 1 or the catalyst obtained by the preparation method according to any one of claims 2 to 8.

10. The method according to claim 9, characterized in that, The mass ratio of the alkyl oxalate to the catalyst is 10~5:

1.

11. The method according to claim 9, characterized in that, The molecular formula of the alkyl oxalate is: , where R and R' are independently selected from alkyl groups having 1-8 carbon atoms.

12. The method according to claim 9, characterized in that, The reaction temperature is 150~240℃, the reaction pressure is 0.5~5.0 MPa, and the reaction time is 1.0~5.0 h.

13. The method according to claim 9, characterized in that, The reaction is carried out in a high-pressure reactor equipped with a tail gas system, which includes a back pressure valve and a condenser.

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