Process for the one-pot synthesis of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate

Abstract

The application provides a method for synthesizing dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate by one-pot method, which comprises using dimethyl oxalate and ethanol as raw materials, and simultaneously synthesizing dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate by one-pot method under the action of a silica-supported alkali metal type catalyst; the carrier of the silica-supported alkali metal type catalyst is silica, the alkali metal is one or more of lithium, sodium, potassium, rubidium, cesium and francium, the loading amount of the alkali metal is 0.01-1 wt%, and the space-time yield of the catalyst is 300-800 kg product / (m3.cat.h). The method can generate dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate by one-pot in the same reactor, and can flexibly adjust the proportion according to the market demand of the products, so that the investment is saved, the flexibility is high, and the economic benefit is remarkable.

Description

Technical Field

[0001] This invention relates to the field of carbonate synthesis, and more specifically, to a one-pot method for synthesizing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Background Technology

[0002] Dimethyl carbonate (DMC) is a colorless, transparent, slightly odorous, and slightly sweet liquid at room temperature. It has a melting point of 4°C, a boiling point of 90.1°C, and a density of 1.069 g / cm³. 3 Dimethyl carbonate (DMC) is sparingly soluble in water but miscible with almost all organic solvents, including alcohols, ethers, and ketones. It is an environmentally friendly and widely used chemical raw material. In recent years, downstream demand for DMC has steadily increased, with non-phosgene PC, lithium-ion battery electrolytes, and paints / coatings being the main consumer markets. In non-phosgene PC production, DMC is used to produce DPC, which is then further synthesized into PC. In lithium-ion battery electrolytes, DMC is in high demand as an important solvent. In the paint, coating, and adhesive industries, DMC, due to its non-toxicity, high safety, excellent solubility, wide melting and boiling point range, high surface tension, low viscosity, and low dielectric constant, can replace toxic products such as toluene and xylene. Furthermore, DMC is used as a methylating agent to replace highly toxic dimethyl sulfate in the synthesis of anti-infective drugs, antipyretic analgesics, vitamins, and central nervous system drugs. As a green and environmentally friendly intermediate, DMC also has promising applications in the trend of pesticides becoming less toxic and non-toxic.

[0003] Ethyl methyl carbonate (EMC), also known as ethyl methyl carbonate, is a colorless, transparent liquid with strong hygroscopicity and flammability. It is an ester compound with an asymmetric structure, possessing characteristics of both dimethyl carbonate and diethyl carbonate (DEC). EMC is insoluble in water but soluble in alcohols, ethers, and some other organic solvents. EMC has a wide range of applications, currently primarily used as an excellent solvent for lithium-ion battery electrolytes, and is mainly applied in the lithium battery electrolyte industry.

[0004] Currently, the main production processes for DMC include the phosgene method, methanol oxidative carbonylation method, transesterification method, and urea alcoholysis method. Among them, the phosgene method has been gradually phased out due to the use of highly toxic phosgene, and the domestic technology level of the urea alcoholysis method is not mature. Domestic production capacity is mainly based on the transesterification method, and the main raw material is PO (propylene oxide). Due to the large fluctuations in the seller's market for raw material propylene oxide, the operating rate has remained at a low level of 50% for a long time.

[0005] The synthesis methods for EMC are similar to those for DMC, including the phosgene method, transesterification, and oxidative carbonylation. The phosgene method has high production efficiency, but the raw material phosgene is highly toxic, and the generated HCl is highly corrosive; this method has been gradually phased out. The oxidative carbonylation method uses methanol, ethanol, CO, and O2 as raw materials to synthesize carbonates. This method has a low yield and involves O2, posing certain safety risks, and is still some distance from industrial application. The transesterification method has mild reaction conditions, high catalytic efficiency, and a relatively simple process. Compared to other synthetic routes, it is more environmentally friendly, so the transesterification method is widely used industrially to prepare EMC, and can also simultaneously produce DEC.

[0006] Currently, several domestic institutions are researching catalysts for transesterification in order to provide a method for producing a single product, such as dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate, in a single reactor. To date, no method has been found that can produce all three products, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, in a one-pot reaction in a single reactor.

[0007] In order to improve the production efficiency and overall economic benefits of enterprises, this invention provides a novel method for synthesizing three important products—dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate—in a one-pot process. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a one-pot method for synthesizing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. This method simultaneously yields three products in high market demand through a simple process. The resulting products are of good quality and can be directly used in the electrolyte of new energy batteries, while significantly improving the economic benefits for enterprises.

[0009] This invention provides a one-pot method for synthesizing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, comprising using dimethyl oxalate and ethanol as raw materials, and simultaneously synthesizing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate in one pot under the action of an alkali metal catalyst supported on silica.

[0010] The support for the silica-supported alkali metal catalyst is silica, and the alkali metal is one or more of lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metal loading is 0.01~1wt%, and the catalyst space-time yield is 300~800 kg product / cubic cat.h.

[0011] One method involves synthesis using a fixed-bed tubular reactor with silica-supported alkali metals.

[0012] The catalyst is packed in the tubes, and the mass ratio of dimethyl oxalate to ethanol is (1~10):1, and it is added from the top of the fixed-bed tubular reactor.

[0013] The reaction temperature was 80~180℃, the reaction pressure was 0.1~1.0 MPa·G, and the reaction space velocity was 1000~8000 h⁻¹. -1 .

[0014] As one method, the reaction liquid discharged from the bottom of the fixed-bed tubular reactor enters the methanol absorption chamber.

[0015] The column is washed, and the washed crude product enters the dealcoholization column to remove methanol. The bottom material of the dealcoholization column is pressurized and enters the first product column, where it is distilled at the top to obtain dimethyl carbonate. The bottom material of the first product column is pressurized by a pump and enters the middle of the second product column, where it is distilled at the top to obtain ethyl methyl carbonate. Diethyl carbonate is collected at the bottom of the column.

[0016] As one method, the top temperature of the methanol absorption tower is 30~60℃, and the top pressure is 0.1~1.0 MPa·G.

[0017] The temperature of the reboiler is 80~180℃, and the pressure of the reboiler is 0.1~1.0 MPaG.

[0018] The top temperature of the dealcoholization column is 40~80℃, the top pressure is 0.1~1.0 MPaG, and the bottom temperature is...

[0019] 50~180℃, reboiler pressure 0.1~1.0 MPaG;

[0020] The product column has a top temperature of 40~120℃ and a top pressure of 0.1~1.2 MapG, a bottom temperature of 60~185℃ and a bottom pressure of 0.1~1.2 MapG.

[0021] The product tower has a top temperature of 40~130℃ and a top pressure of -0.1~1.2 MapG, a bottom temperature of 60~200℃ and a bottom pressure of -0.1~1.2 MapG.

[0022] In one embodiment, the methanol addition flow rate of the methanol absorption tower is 0.1 to 1 times the material flow rate entering the absorption tower, and the methanol is added from the upper part of the absorption tower through a pipeline.

[0023] In one manner, the silica-supported alkali metal catalyst is prepared by the following method:

[0024] Step 1: Dissolve the silica precursor in a polar solvent to prepare a silica precursor solution;

[0025] Step 2: Dissolve the carbonate or bicarbonate of the alkali metal in deionized water to prepare a precursor solution of the alkali metal component.

[0026] Step 3: First, treat the carrier silica in 15-20wt% HF acid at 40-50℃ for 3-6h, wash with water, then impregnate it in the silica precursor solution in equal volume, then dry it at 85-180℃ for 9-20h, and then calcine it at 300℃-450℃ for 4-9h to obtain the modified carrier.

[0027] Step 4: The modified support is impregnated in an alkali metal precursor solution with an equal volume, then dried at 75℃~165℃ for 6h~18h, and then calcined at 400℃~650℃ for 4h~10h under an inert atmosphere to obtain the catalyst.

[0028] In one embodiment, the alkali metal carbonate or bicarbonate is selected from sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, or lithium bicarbonate.

[0029] In one embodiment, the silica precursor is sodium silicate, and the polar solvent is deionized water.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. This invention uses dimethyl oxalate and ethanol as raw materials, and under the action of a heterogeneous silica-supported alkali metal catalyst, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate can be produced in one pot in the same reactor.

[0032] The ratio of dimethyl oxalate to ethanol can be flexibly adjusted according to the market demand of various types of products, thereby increasing the output of the corresponding products. It is cost-effective, highly flexible, and has significant economic benefits.

[0033] 2. The raw materials used in the method of the present invention are readily available and low in cost, and the reaction efficiency is high, which helps to improve the economic benefits of enterprises.

[0034] 3. The catalyst in the method of the present invention has a long service life, does not require separation, and has high recyclability.

[0035] 4. The method of this invention produces fewer impurities such as alcohols, esters, aldehydes, and hydrocarbons, making it easier to separate high-purity products and reducing energy consumption. Compared with traditional processes, it can save more than 80% of energy consumption.

[0036] 5. Furthermore, the method of the present invention uses a fixed-bed tubular reactor as the container for one-pot reaction, which reduces the catalyst loss rate by more than 98% compared with traditional stirred tank or slurry bed reactors.

[0037] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0038] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0039] Figure 1 This is a schematic diagram of a process flow diagram for the one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified in the following examples, all raw materials can be obtained through market procurement, and different manufacturers or models will not affect the realization of the basic concept of this invention.

[0042] The method of this invention uses a silica-supported alkali metal catalyst. The alkali metal used is one or more of lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metal loading is 0.01wt%~1wt%. The catalyst space-time yield is 300~800 kg product / cubic cat.h (based on the hourly product yield / catalyst loading). The expected catalyst lifespan is 3~5 years, and the reaction selectivity is ≥99%.

[0043] As an example, the silica-supported alkali metal catalyst used in Examples 1-4 of the present invention was prepared by the following method:

[0044] Step 1: Dissolve the silica precursor in a polar solvent to prepare a silica precursor solution;

[0045] Step 2: Dissolve the carbonate or bicarbonate of the alkali metal in deionized water to prepare a precursor solution of the alkali metal component.

[0046] Step 3: First, treat the carrier silica in 15-20wt% HF acid at 40-50℃ for 3-6h, wash with water, then impregnate it in the silica precursor solution in equal volume, then dry it at 85-180℃ for 9-20h, and then calcine it at 300℃-450℃ for 4-9h to obtain the modified carrier.

[0047] Step 4: The modified support is impregnated in an alkali metal precursor solution with an equal volume, then dried at 75℃~165℃ for 6h~18h, and then calcined at 400℃~650℃ for 4h~10h under an inert atmosphere to obtain the catalyst.

[0048] The silica precursor can be a common material in existing technologies, such as silica sol or solid silica gel. Sodium silicate is used here, and deionized water is used as the polar solvent.

[0049] The total amount of silica precursor and support silica is equal to the total amount of silicon in the catalyst. There is no particular limitation on the amount of each, as long as it is conducive to the operation of equal volume impregnation.

[0050] Alkali metal carbonates or bicarbonates can be selected from sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate. The specific dosage can be calculated and set according to the catalyst formulation in each case.

[0051] Due to space limitations, only the catalyst of Example 1 will be used as an example to provide a specific preparation process:

[0052] Step 1: Dissolve sodium silicate (calculated based on 40% silicon content of the final catalyst product, and add an equal amount) in deionized water to prepare a silica precursor solution.

[0053] Step 2: Dissolve sodium carbonate (calculated based on a sodium loading of 0.8 wt% in the final catalyst product, and add an equal amount) in deionized water to prepare a precursor solution of the alkali metal component;

[0054] Step 3: The carrier silica (calculated based on 60% of the silicon content of the final catalyst product and added in equal amounts) is first treated in 20wt% HF acid at 50℃ for 3h, washed with water, and then impregnated in the silica precursor solution in equal volume. Then it is dried at 120℃ for 13h and calcined at 450℃ for 9h to obtain the modified carrier.

[0055] Step 4: The modified support is impregnated in an alkali metal component precursor solution with an equal volume, then dried at 165°C for 6 hours, and then calcined at 650°C for 4 hours under a nitrogen atmosphere to obtain the catalyst.

[0056] The specific preparation examples above are just one example of the operation process. According to the research results on catalysts, the catalysts obtained by following the basic preparation methods described above all have good effects and can achieve the same or similar results.

[0057] The fixed-bed tubular reactor, absorption tower, dealcoholization tower, product tower one, and product tower two used in the following examples of the present invention can all be mature instruments commonly used in the prior art.

[0058] In the fixed-bed tubular reactor, the catalyst is packed inside the tubes, while the heating or cooling medium is outside the tubes, and the reaction occurs inside the tubes. The absorption tower is a plate tower or a packed tower, where the material achieves gas-liquid phase separation on the tower plates or within the packing. The absorbent is added from the top, and the material enters from the bottom, ultimately achieving the absorption effect. The dealcoholization tower, product tower one, and product tower two are distillation towers, using packed towers or plate towers. A condenser is installed at the top of the tower, and a reboiler is installed at the bottom. The material enters the tower and reaches gas-liquid two-phase equilibrium in the packing or on the tower plates. The lighter components flow upwards, with higher concentrations, while the heavier components flow downwards, with higher concentrations, ultimately achieving the separation of light and heavy components.

[0059] Example 1

[0060] A 20 cubic meter silica-supported alkali metal catalyst was packed into the tubes of a fixed-bed tubular reactor, wherein the supported alkali metal was sodium and the loading amount was 0.8 wt%.

[0061] Dimethyl oxalate was fed into a fixed-bed tubular reactor via pipeline from the top at a feed rate of 10 t / h and ethanol at 3.9 t / h (the mass ratio of dimethyl oxalate to ethanol was 2.564:1). The reaction was endothermic, and steam heating was used to provide the heat of reaction and maintain the required heat for the reaction. Steam was added from the top of the reactor shell side, and the condensate was discharged from the bottom of the reactor shell side. The reaction temperature was controlled at 100℃, the reaction pressure at 0.5 MPa·G, and the reaction space velocity at 3000 h⁻¹. -1 Under the action of a catalyst, the material generates reaction products containing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The space-time yield of the catalyst is 688 kg product / cubic cat.h. The mass ratio of dimethyl carbonate / diethyl carbonate / methyl ethyl carbonate at the outlet of the fixed-bed tubular reactor is 2:1.6:3.

[0062] The reaction products are discharged from the bottom of the fixed-bed tubular reactor at a rate of 13.9 t / h via pipeline and enter the lower middle section of a methanol absorption tower, where they are washed and absorbed by methanol. Methanol is added from the upper middle section of the absorption tower via pipeline, with a flow rate 0.5 times the flow rate of the reaction products entering the absorption tower. The methanol absorption tower has a top temperature of 60℃ and a top pressure of 0.3 MPaG, a bottom temperature of 90℃, and a bottom pressure of 0.32 MPaG.

[0063] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (34 wt%), dimethyl carbonate (20 wt%), diethyl carbonate (16 wt%), and methyl ethyl carbonate (30 wt%).

[0064] The crude product from the bottom of the methanol absorption tower is pumped to 0.6 MapG and then enters the middle of the dealcoholization tower. The dealcoholization tower is a packed distillation tower with a top temperature of 45℃ and a top pressure of 0.15 MapG, a bottom temperature of 120℃ and a bottom pressure of 0.2 MapG.

[0065] The methanol product with a concentration of ≥99.9wt% is collected from the top of the dealcoholization tower. 40wt% of the methanol product is used in the absorption tower, and the remaining methanol can be collected and sold as a commodity.

[0066] The bottom material of the dealcoholization column is pumped to 0.7 MapG and then enters the middle of the product column. The product column is a packed distillation column with a top temperature of 50℃ and a top pressure of 0.15 MapG, a bottom temperature of 140℃ and a bottom pressure of 0.17 MapG, and dimethyl carbonate product with a concentration of ≥99.99wt% is collected from the top of the column.

[0067] The material in the bottom of Product 1 tower is pressurized by a pump and then enters the middle of Product 2 tower. The top temperature of Product 2 tower is 55℃, and the top pressure is 0.13 MPaG. The bottom temperature is 150℃, and the bottom pressure is 0.15 MPaG. Product 2 tower yields methyl ethyl carbonate with a concentration ≥99.99 wt% from the top and diethyl carbonate with a concentration ≥99.99 wt% from the bottom. The products obtained by this method meet the quality requirements for electronic-grade dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and can be directly used in the electrolyte of new energy batteries.

[0068] Example 2

[0069] A 20 cubic meter silica-supported alkali metal catalyst was packed into the tubes of a fixed-bed tubular reactor, wherein the supported alkali metal was potassium and the loading amount was 1 wt%.

[0070] Dimethyl oxalate was fed into a fixed-bed tubular reactor via pipeline from the top at a feed rate of 10 t / h and ethanol at 3.9 t / h (the mass ratio of dimethyl oxalate to ethanol was 2.564:1). The reaction temperature was controlled at 120 °C, the reaction pressure at 1.0 MPa·G, and the reaction space velocity at 6000 h⁻¹. -1 Under the action of a catalyst, the material generates reaction products containing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The space-time yield of the catalyst is 700 products / cubic cat.h. The mass ratio of dimethyl carbonate / diethyl carbonate / methyl ethyl carbonate at the outlet of the fixed-bed tubular reactor is 1.2:2:3.3.

[0071] The reaction products are discharged from the bottom of the fixed-bed tubular reactor at a rate of 13.9 t / h via pipeline and enter the lower middle section of a methanol absorption tower, where they are washed and absorbed by methanol. Methanol is added from the upper middle section of the absorption tower via pipeline, with a flow rate 0.6 times the flow rate of the reaction products entering the absorption tower. The absorption tower has a top temperature of 55℃ and a top pressure of 0.35 MPaG, a bottom temperature of 95℃, and a bottom pressure of 0.37 MPaG.

[0072] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (18.7 wt%), dimethyl carbonate (15 wt%), diethyl carbonate (25 wt%), and methyl ethyl carbonate (41.3 wt%).

[0073] The crude product from the bottom of the absorber is pumped to 0.5 MapG and then enters the middle of the dealcoholization column. The dealcoholization column is a packed distillation column with a top temperature of 40℃ and a top pressure of 0.12 MapG, a bottom temperature of 115℃ and a bottom pressure of 0.17 MapG.

[0074] The methanol product with a concentration of ≥99.9wt% is collected from the top of the dealcoholization tower. 40wt% of the methanol product is used in the absorption tower, and the remaining methanol can be collected and sold as a commodity.

[0075] The bottom material of the dealcoholization column is pumped to 0.65 MapG and then enters the middle of the product column. The product column is a packed distillation column with a top temperature of 55℃ and a top pressure of 0.2 MapG. The bottom temperature is 150℃ and the bottom pressure is 0.22 MapG. The top product is dimethyl carbonate with a concentration of ≥99.99wt%.

[0076] The material in the bottom of Product 1 tower is pressurized by a pump and then enters the middle of Product 2 tower. The top temperature of Product 2 tower is 60℃, and the top pressure is 0.15 MPaG. The bottom temperature is 160℃, and the bottom pressure is 0.18 MPaG. Product 2 tower yields methyl ethyl carbonate with a concentration ≥99.99 wt% from the top and diethyl carbonate with a concentration ≥99.99 wt% from the bottom. The products obtained by this method meet the quality requirements for electronic-grade dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and can be directly used in the electrolyte of new energy batteries.

[0077] Example 3

[0078] A 40 cubic meter silica-supported alkali metal catalyst was packed into the tubes of a fixed-bed tubular reactor, wherein the supported alkali metal was lithium with a loading of 0.01 wt%.

[0079] Dimethyl oxalate was fed into a fixed-bed tubular reactor via pipeline from the top at a feed rate of 10 t / h and ethanol at 3.195 t / h (the mass ratio of dimethyl oxalate to ethanol was 3.13:1). The reaction temperature was controlled at 100℃, the reaction pressure at 1.0 MPa·G, and the reaction space velocity at 5000 h⁻¹. -1 Under the action of a catalyst, the material generates reaction products containing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The space-time yield of the catalyst is 325 kg product / cubic cat.h. The mass ratio of dimethyl carbonate / diethyl carbonate / methyl ethyl carbonate at the outlet of the fixed-bed tubular reactor is 3:2:1.7.

[0080] The reaction products are discharged from the bottom of the fixed-bed tubular reactor at a rate of 13.195 t / h via pipeline and enter the lower part of the methanol absorption tower, where they are washed and absorbed by methanol. Methanol is added from the upper part of the absorption tower via pipeline, with a flow rate 0.3 times the flow rate of the reaction products entering the absorption tower. The top temperature of the absorption tower is 60℃, and the top pressure is 0.4 MPaG; the bottom temperature is 95℃, and the bottom pressure is 0.42 MPaG.

[0081] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (44.1 wt%), dimethyl carbonate (25 wt%), diethyl carbonate (16.7 wt%), and methyl ethyl carbonate (14.2 wt%).

[0082] The crude product from the bottom of the absorber is pumped to a pressure of 0.62 MapG and then enters the middle of the dealcoholization column. The dealcoholization column is a packed distillation column with a top temperature of 53℃ and a top pressure of 0.21 MapG, a bottom temperature of 156℃ and a bottom pressure of 0.22 MapG.

[0083] The methanol product with a concentration of ≥99.9wt% is collected from the top of the dealcoholization tower. 40wt% of the methanol product is used in the absorption tower, and the remaining methanol can be collected and sold as a commodity.

[0084] The bottom material of the dealcoholization column is pumped to 0.72 MapG and then enters the middle of the product column. The product column is a packed distillation column with a top temperature of 55℃ and a top pressure of 0.14 MapG, a bottom temperature of 159℃ and a bottom pressure of 0.16 MapG, and dimethyl carbonate product with a concentration of ≥99.99wt% is collected from the top of the column.

[0085] The material in the bottom of Product 1 column is pumped to 0.66 MapG and then enters the middle of Product 2 column. The top temperature of Product 2 column is 61℃, and the top pressure is 0.16 MapG. The bottom temperature is 161℃, and the bottom pressure is 0.18 MapG. Product 2 column yields methyl ethyl carbonate with a concentration ≥99.99 wt% from the top and diethyl carbonate with a concentration ≥99.99 wt% from the bottom. The products obtained by this method meet the quality requirements for electronic-grade dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and can be directly used in the electrolyte of new energy batteries.

[0086] Example 4

[0087] A 40 cubic meter silica-supported alkali metal catalyst was packed into the tubes of a fixed-bed tubular reactor, wherein the supported alkali metal was sodium with a loading of 0.06 wt%.

[0088] Dimethyl oxalate was fed into a fixed-bed tubular reactor via pipeline from the top at a feed rate of 10 t / h and ethanol at 3.78 t / h (the mass ratio of dimethyl oxalate to ethanol was 2.646:1). The reaction temperature was controlled at 120℃, the reaction pressure at 0.8 MPa·G, and the reaction space velocity at 1000 h⁻¹. -1 Under the action of a catalyst, the material generates reaction products containing dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The space-time yield of the catalyst is 340 kg product / cubic cat.h. The mass ratio of dimethyl carbonate / diethyl carbonate / methyl ethyl carbonate at the outlet of the fixed-bed tubular reactor is 2:1.8:2.4.

[0089] The reaction products are discharged from the bottom of the fixed-bed tubular reactor at a rate of 13.78 t / h via pipeline and enter the lower part of the absorption tower, where they are washed and absorbed with methanol. Methanol is added from the upper part of the absorption tower via pipeline, with a flow rate 0.8 times the flow rate of the reaction products entering the absorption tower. The absorption tower has a top temperature of 55℃ and a top pressure of 0.42 MPaG, a bottom temperature of 94℃, and a bottom pressure of 0.43 MPaG.

[0090] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (38 wt%), dimethyl carbonate (20 wt%), diethyl carbonate (18 wt%), and methyl ethyl carbonate (24 wt%).

[0091] The crude product from the bottom of the absorber is pumped to 0.65 MapG and then enters the middle of the dealcoholization column. The dealcoholization column is a packed distillation column with a top temperature of 40℃ and a top pressure of 0.12 MapG, a bottom temperature of 152℃ and a bottom pressure of 0.13 MapG.

[0092] The methanol product with a concentration of ≥99.9wt% is collected from the top of the dealcoholization tower. 40wt% of the methanol product is used in the absorption tower, and the remaining methanol can be collected and sold as a commodity.

[0093] The bottom material of the dealcoholization column is pumped to 0.85 MapG and then enters the middle of the product column. The product column is a packed distillation column with a top temperature of 50℃ and a top pressure of 0.12 MapG, a bottom temperature of 157℃ and a bottom pressure of 0.13 MapG, and dimethyl carbonate product with a concentration of ≥99.99wt% is collected from the top of the column.

[0094] The material in the bottom of Product 1 tower is pressurized by a pump and then enters the middle of Product 2 tower. The top temperature of Product 2 tower is 46℃, and the top pressure is 0.11 MPaG. The bottom temperature is 158℃, and the bottom pressure is 0.13 MPaG. Product 2 tower yields methyl ethyl carbonate with a concentration ≥99.99 wt% from the top and diethyl carbonate with a concentration ≥99.99 wt% from the bottom. The products obtained by this method meet the quality requirements for electronic-grade dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and can be directly used in the electrolyte of new energy batteries.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the catalyst preparation method is different. Step 1 is not included. Instead, silicon dioxide with an amount equal to the silicon content in the final catalyst is directly used as a carrier for impregnation treatment.

[0097] The other process parameters remain the same as in Example 1.

[0098] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (35wt%), dimethyl carbonate (19wt%), diethyl carbonate (16wt%), methyl ethyl carbonate (29wt%), aldehydes 0.5wt%, and other miscellaneous esters 0.5wt%.

[0099] Comparative Example 2

[0100] The difference from Example 1 is that the catalyst preparation method is different. In step three, the supporting silica was not treated with HF acid, and silica with the same silicon content as the catalyst was directly used as the support for impregnation treatment.

[0101] The other process parameters remain the same as in Example 1.

[0102] Carbon monoxide, after being washed with methanol, is discharged from the top of the tower through a pipeline. The bottom of the tower contains crude product, including: methanol (37wt%), dimethyl carbonate (18wt%), diethyl carbonate (15wt%), methyl ethyl carbonate (28wt%), aldehydes 1wt%, and other miscellaneous esters 1wt%.

[0103] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, characterized in that, This includes the one-pot simultaneous synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate using dimethyl oxalate and ethanol as raw materials and an alkali metal catalyst supported on silica. The support for the silica-supported alkali metal catalyst is silica, and the alkali metal is one or more of lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metal loading is 0.01~1wt%, and the catalyst space-time yield is 300~800 kg product / cubic cat.h. The silica-supported alkali metal catalyst was prepared by the following method: Step 1: Dissolve the silica precursor in a polar solvent to prepare a silica precursor solution; Step 2: Dissolve the carbonate or bicarbonate of the alkali metal in deionized water to prepare a precursor solution of the alkali metal component. Step 3: First, treat the carrier silica in 15-20wt% HF acid at 40-50℃ for 3-6h, wash with water, then impregnate it in the silica precursor solution in equal volume, then dry it at 85-180℃ for 9-20h, and then calcine it at 300℃-450℃ for 4-9h to obtain the modified carrier. Step 4: The modified support is impregnated in an alkali metal component precursor solution with an equal volume, then dried at 75℃~165℃ for 6h~18h, and then calcined at 400℃~650℃ for 4h~10h under an inert atmosphere to obtain the catalyst. The alkali metal carbonate or bicarbonate is selected from sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, or lithium bicarbonate; the silicon dioxide precursor is sodium silicate.

2. The method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to claim 1, characterized in that, The synthesis was performed using a fixed-bed tubular reactor. An alkali metal catalyst supported on silica was packed inside the tubes. The mass ratio of dimethyl oxalate to ethanol was (1~10):1, and the catalyst was added from the top of the fixed-bed tubular reactor. The reaction temperature was 80~180℃, the reaction pressure was 0.1~1.0 MPa·G, and the reaction space velocity was 1000~8000 h⁻¹. -1 .

3. The method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to claim 2, characterized in that, The reaction liquid discharged from the bottom of the fixed-bed tubular reactor enters the methanol absorption tower for washing. The washed crude product enters the dealcoholization tower to remove methanol. The bottom material of the dealcoholization tower is pressurized and enters the first product tower, where it is distilled at the top to obtain dimethyl carbonate. The bottom material of the first product tower is pressurized by a pump and enters the middle of the second product tower, where it is distilled at the top to obtain ethyl methyl carbonate. Diethyl carbonate is collected at the bottom of the second product tower.

4. The method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to claim 3, characterized in that, The methanol absorption tower has a top temperature of 30~60℃ and a top pressure of 0.1~1.0 MPaG, and a bottom temperature of 80~180℃ and a bottom pressure of 0.1~1.0 MPaG. The top temperature of the dealcoholization column is 40~80℃, the top pressure is 0.1~1.0 MapG, the bottom temperature is 50~180℃, and the bottom pressure is 0.1~1.0 MapG. The product column has a top temperature of 40~120℃ and a top pressure of 0.1~1.2 MapG, a bottom temperature of 60~185℃ and a bottom pressure of 0.1~1.2 MapG. The product tower has a top temperature of 40~130℃ and a top pressure of -0.1~1.2 MapG, a bottom temperature of 60~200℃ and a bottom pressure of -0.1~1.2 MapG.

5. The method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to claim 3, characterized in that, The methanol addition flow rate of the methanol absorption tower is 0.1 to 1 times the material flow rate entering the absorption tower, and the methanol is added from the upper part of the absorption tower through a pipeline.

6. The method for one-pot synthesis of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate according to claim 1, characterized in that, The polar solvent is deionized water.

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