Method for producing dimethyl carbonate from dimethyl oxalate

Abstract

The present application provides a method for generating dimethyl carbonate from dimethyl oxalate, wherein dimethyl oxalate, a composite organic salt of an alkali metal-alkaline earth metal, and methanol are sent into a reactor for decarbonylation reaction to generate dimethyl carbonate, and the dimethyl carbonate in the gas phase is washed in a scrubber and then enters a product tower for separation to obtain industrial-grade dimethyl carbonate. The present application also provides a dimethyl carbonate preparation system, using a composite organic salt of an alkali metal-alkaline earth metal as a catalyst, without the need to use a precious metal catalyst; fresh catalysts can be continuously added to maintain reaction activity, without the need to stop and replace catalysts, etc. The reaction gas after decarbonylation all enters the scrubber in the form of a gas phase, avoiding multiple condensation and gasification phenomena, reducing the steam consumption required for separation, and making the process flow more concise.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a method for generating dimethyl carbonate from dimethyl oxalate. Background Art

[0002] At present, the methods for synthesizing dimethyl carbonate include: phosgene method, transesterification method, methanol oxidative carbonylation method, urea alcoholysis method, CO 2 The phosgene method and the transesterification method are mainly used in industrial production. The phosgene method is a traditional synthesis method that uses highly toxic phosgene as a raw material. It has poor safety and pollutes the environment. The byproduct HCl generated is highly corrosive to equipment. The transesterification method uses ethylene carbonate or propylene carbonate and methanol for an ester exchange reaction to generate dimethyl carbonate. The raw material supply depends on petroleum and the production cost is relatively high.

[0003] The synthesis of dimethyl carbonate by methanol vapor phase oxidative carbonylation was first proposed and industrialized by UBE Corporation of Japan. The reaction conditions of this method are mild, part of the reaction products can be recycled in the reaction, the reaction is carried out in the gas phase, no water is generated in the reaction, and the damage of water to the catalyst in the liquid phase method is avoided. In this process, PdCl with a Pd content of more than 1% is used. 2 / Al 2 O 3 Catalysts will be deactivated due to the loss of Cl elements. In order to improve the stability of the catalyst, the most common measure is to add a certain amount of chlorine-containing compounds, such as HCl or methyl chloroformate, to the raw gas. Therefore, in addition to the use of a large amount of precious metal Pd, the production process also requires the use of a large amount of special anti-corrosion equipment, and the dimethyl carbonate product contains trace amounts of Cl, so this technology has not been widely used.

[0004] There are currently a large number of ethylene glycol production companies in China, and the intermediate product dimethyl oxalate has few downstream applications, resulting in serious overcapacity in the entire industry. Therefore, developing an environmentally friendly and energy-saving production process for producing dimethyl carbonate through decarbonylation of dimethyl oxalate is conducive to the healthy development of the entire industry.

[0005] Chinese patent publication No. 1221732A discloses a method for preparing dialkyl carbonate, wherein dialkyl oxalate is gasified under the action of an alkali metal compound, and the reaction temperature is 170-450° C. to perform a gas phase decarbonylation reaction to prepare dialkyl carbonate. At this reaction temperature, dialkyl oxalate is prone to coking and causes catalyst deactivation, and the device needs to be frequently stopped to replace the catalyst.

[0006] The Chinese patent with publication number 112028771A discloses a method and manufacturing system for preparing alkyl carbonate from alkyl oxalate under the action of carbonyl rhodium catalyst. In the preparation method, the reaction gas phase is first condensed to obtain a liquid product, which is then sent to the distillation section for separation. Dimethyl carbonate undergoes multiple condensation and gasification processes, and energy is not reasonably utilized. In addition, there is no description of how to separate products from the existing azeotropic systems of methanol-dimethyl carbonate, ethanol-dimethyl carbonate, and ethanol-methyl ethyl carbonate, and a single tower cannot separate qualified products. In the process, the precious metal rhodium catalyst is precipitated as a solid, and the catalyst use cost is high. The effective components in the inactivated catalyst solid impurities are not treated, and there will be problems of environmental pollution during the precious metal recovery process. Summary of the invention

[0007] The present application provides a method for producing dimethyl carbonate from dimethyl oxalate, in order to solve the problems that the existing solid catalyst is easily coked and deactivated, frequent shutdown and catalyst replacement are required, and the device cannot be continuously produced; and the use of liquid phase precious metal catalysts is easy to precipitate, the catalyst cost is high, the product separation energy consumption is high, and the catalyst waste residue pollutes the environment.

[0008] In order to solve the above technical problems, the present application provides a method for producing dimethyl carbonate from dimethyl oxalate, comprising:

[0009] Step 1: sending dimethyl oxalate, a composite organic salt of an alkali metal-alkaline earth metal, and methanol into a reactor for decarbonylation reaction, wherein the dimethyl oxalate reacts to generate dimethyl carbonate and carbon monoxide, wherein the methanol, the carbon monoxide, and the dimethyl carbonate all enter a washing tower from the reactor in a gas phase for separation, wherein the temperature of the decarbonylation reaction is 70-160° C., and the reaction pressure is 90-500 KPa(A);

[0010] Step 2: adding dimethyl oxalate to the scrubbing tower, scrubbing dimethyl carbonate in the gas phase with the dimethyl oxalate, and then scrubbing the gas phase with methanol, condensing the gas phase at the top of the scrubbing tower to obtain non-condensable gas containing carbon monoxide and crude methanol liquid; extracting crude dimethyl carbonate from the bottom of the scrubbing tower, wherein the crude dimethyl carbonate includes dimethyl oxalate, dimethyl carbonate and methanol with a content of ≤1.0%;

[0011] Step 3: The crude methanol liquid enters a light fraction removal tower for separation, and light components including methyl formate and dimethyl ether are extracted from the top of the tower; liquid methanol is extracted from the bottom of the tower and recycled;

[0012] Step 4: the crude dimethyl carbonate enters the product tower for separation, a methanol-dimethyl carbonate mixture is produced from the top of the product tower, and the methanol-dimethyl carbonate mixture is returned to the lower middle section of the washing tower; industrial-grade dimethyl carbonate is produced from the side line of the upper middle section of the product tower.

[0013] Furthermore, the reaction turbid liquid containing the catalyst alkali metal-alkaline earth metal composite organic salt at the bottom of the reactor is sent to the deactivated catalyst treatment device, the separated clear liquid is returned to the reactor, the separated wet solid is washed with methanol, and the filter residue containing carbonate and oxalate after washing is discharged from the system, the washed methanol solution is mixed with the alkali metal-alkaline earth metal composite organic salt in the catalyst tank, and is sent to the reactor after configuration.

[0014] Furthermore, the mass ratio of the detergent methanol to the filter residue is 1:1 to 10:1.

[0015] Furthermore, in step 2, the operating pressure of the washing tower is 90-400 KPa (A), the tower top temperature is 55-90°C, and the tower bottom temperature is 95-150°C.

[0016] Furthermore, in step 2, the gas phase at the top of the washing tower is subjected to multi-stage condensation, the first-stage condensation temperature is 35-45°C, the second-stage condensation temperature is 0-10°C, and the liquids after the first-stage condensation and the second-stage condensation are combined into the top tank of the washing tower.

[0017] Furthermore, in step 2, the mass ratio of the washing agent dimethyl oxalate to the dimethyl carbonate in the gas phase entering the washing tower is 1.5:1 to 9:1.

[0018] Furthermore, the temperature of the dimethyl oxalate added to the washing tower in step 2 is 55-100°C.

[0019] Furthermore, in step 2, the reflux rate of crude methanol in the washing tower is 30%-150% relative to the mass fraction of dimethyl carbonate in the gas phase entering the washing tower.

[0020] The present invention also provides a dimethyl carbonate preparation system, comprising:

[0021] Reactor, dimethyl oxalate, alkali metal-alkaline earth metal composite organic salt, and methanol are fed into the reactor for decarbonylation reaction, wherein the temperature of the decarbonylation reaction is 70-160° C. and the reaction pressure is 90-500 KPa(A);

[0022] A washing tower, wherein the dimethyl carbonate and carbon monoxide generated by the reaction of dimethyl oxalate and the methanol all enter the washing tower from the reactor in a gas phase state, dimethyl oxalate is added to the washing tower, the dimethyl carbonate in the gas phase is washed by the dimethyl oxalate, the gas phase is then washed by methanol, and the gas phase at the top of the washing tower is condensed to obtain non-condensable gas containing carbon monoxide and crude methanol liquid; the washing tower kettle extracts crude dimethyl carbonate, and the crude dimethyl carbonate includes dimethyl oxalate, dimethyl carbonate and methanol with a content of ≤1.0%;

[0023] A light-removal tower, wherein the crude methanol liquid enters the light-removal tower for separation, light components including methyl formate and dimethyl ether are extracted from the top of the tower, and liquid methanol is extracted from the bottom of the tower;

[0024] The crude dimethyl carbonate enters the product tower for separation, a methanol-dimethyl carbonate mixture is produced from the top of the product tower, the methanol-dimethyl carbonate mixture is returned to the lower middle section of the washing tower, and industrial-grade dimethyl carbonate is produced from the side line of the upper middle section of the product tower.

[0025] Furthermore, the dimethyl carbonate preparation system also includes a deactivated catalyst treatment device, the reaction turbid liquid containing the catalyst alkali metal-alkaline earth metal composite organic salt at the bottom of the reactor is sent to the deactivated catalyst treatment device, the separated clear liquid is returned to the reactor, the separated wet solid is washed with methanol, and the filter residue containing carbonate and oxalate after washing is discharged from the system, the washed methanol solution is mixed with the alkali metal-alkaline earth metal composite organic salt in the catalyst tank, and is sent to the reactor after configuration.

[0026] Furthermore, the deactivated catalyst treatment device includes one of a sedimentation separation washing device and a falling film scraper evaporation complete set.

[0027] The technical solution of this application has at least the following advantages:

[0028] (1) The method of continuously preparing dimethyl carbonate from dimethyl oxalate in the present application includes steps such as decarbonylation catalyst configuration, decarbonylation reaction, reaction gas washing, methanol light recovery, dimethyl carbonate product separation, and deactivated catalyst treatment, which can be carried out in a continuous cycle, which is superior to the production method with some intermittent steps;

[0029] (2) Using alkali metal-alkaline earth metal composite organic salt as catalyst, no need to use precious metal catalyst; fresh catalyst can be continuously added to maintain reaction activity, no need to stop the car to replace the catalyst, etc.;

[0030] (3) Rationally utilizing the reaction raw material dimethyl oxalate as an extractant for separating methanol from dimethyl carbonate, and simply separating dimethyl carbonate from the azeotropic system without introducing other substances, thereby obtaining an industrial-grade dimethyl carbonate product; and, in the process of washing the reaction gas phase, dimethyl oxalate remains in a liquid state, consuming only a small amount of kinetic energy;

[0031] (4) Rationally recycling methanol to achieve the purpose of simultaneously preparing a decarbonylation catalyst, washing dimethyl oxalate entrained in the gas phase, and washing the salts precipitated by the reaction to recover effective catalysts and ester substances;

[0032] (5) All the reaction gases after decarbonylation enter the scrubbing tower in the gas phase, avoiding multiple condensation and gasification phenomena, reducing the steam consumption required for separation, and making the process flow simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A schematic diagram of a process flow for producing dimethyl carbonate from dimethyl oxalate provided in an embodiment of the present invention.

[0035] Wherein, decarbonylation catalyst 1, fresh dimethyl oxalate 2, fresh methanol 3, dimethyl carbonate product 4, CO non-condensable gas 5, light component 6, mixed salt after washing 7, gas phase out of decarbonylation reactor 8, gas phase at the top of washing tower 9, condensate at the top of washing tower 10, crude methanol after gas-liquid separation 11, methanol refluxed from washing tower 12, crude methanol fed to light tower 13, dimethyl oxalate as detergent 14, crude dimethyl carbonate 15, gas phase at the top of product tower 16, condensate at the top of product tower 17, reflux of product tower 18; extraction from the top of product tower 19; extraction from the bottom of product tower 20; dimethyl oxalate entering the reactor 21, dimethyl oxalate after condensation 22; gas phase at the top of light tower 23, condensate at the top of light tower 24, reflux of light tower 25; recovered methanol 26, methanol solution after washing 27, methanol solution of decarbonylation catalyst 28, reaction turbid liquid 29; reaction clear liquid 30;

[0036] Reactor R1, washing tower C1, light-removing tower C2, product tower C3, deactivated catalyst treatment device F1; washing tower top tank V1, light-removing tower top tank V2, product tower top tank V3, catalyst tank V4; washing tower top condenser E1; washing tower kettle reboiler E2; light-removing tower top condenser E3, light-removing tower kettle reboiler E4; product tower top condenser E5, product tower kettle reboiler E6; dimethyl oxalate condenser E7. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] The present application provides a method for producing dimethyl carbonate from dimethyl oxalate, comprising:

[0040] Step 1: sending dimethyl oxalate, a composite organic salt of an alkali metal-alkaline earth metal, and methanol into a reactor for decarbonylation reaction, wherein the dimethyl oxalate reacts to generate dimethyl carbonate and carbon monoxide, wherein the methanol, the carbon monoxide, and the dimethyl carbonate all enter a washing tower from the reactor in a gas phase for separation, wherein the temperature of the decarbonylation reaction is 70-160° C., and the reaction pressure is 90-500 KPa(A);

[0041] Step 2: adding dimethyl oxalate to the washing tower, wherein the temperature of the dimethyl oxalate added to the washing tower is 55-100°C, washing dimethyl carbonate in the gas phase with the dimethyl oxalate, and then washing the gas phase with methanol, and condensing the gas phase at the top of the tower to obtain non-condensable gas containing carbon monoxide and crude methanol liquid; extracting crude dimethyl carbonate from the bottom of the washing tower, wherein the crude dimethyl carbonate includes dimethyl oxalate, dimethyl carbonate and methanol with a content of ≤1.0%; the operating pressure of the washing tower is 90-400KPa(A), the top temperature is 55-90°C, the bottom temperature is 95-150°C, the gas phase at the top of the washing tower uses multi-stage condensation, the first-stage condensation temperature is 35-45°C, the second-stage condensation temperature is 0-10°C, and the liquid after the first-stage condensation and the second-stage condensation is incorporated into the top tank of the washing tower; the mass ratio of the detergent dimethyl oxalate to the dimethyl carbonate in the gas phase entering the washing tower is 1.5:1 to 9:1. The crude methanol reflux rate of the scrubbing tower is 30%-150% relative to the mass fraction of dimethyl carbonate in the gas phase entering the scrubbing tower.

[0042] Step 3: The crude methanol liquid enters a light fraction removal tower for separation, and light components including methyl formate and dimethyl ether are extracted from the top of the tower; liquid methanol is extracted from the bottom of the tower and recycled;

[0043] Step 4: the crude dimethyl carbonate enters the product tower for separation, a methanol-dimethyl carbonate mixture is produced from the top of the product tower, and the methanol-dimethyl carbonate mixture is returned to the lower middle section of the washing tower; and the product tower is produced from the side line of the upper middle section.

[0044] In the embodiment of the present invention, the reaction turbid liquid containing the composite organic salt of the alkali metal-alkaline earth metal catalyst at the bottom of the reactor is sent to the deactivated catalyst treatment device, the separated clear liquid is returned to the reactor, the separated wet solid is washed with methanol, the filter residue containing carbonate and oxalate after washing is discharged from the system, the washed methanol solution is mixed with the composite organic salt of the alkali metal-alkaline earth metal in the catalyst tank, and is sent to the reactor after preparation. The mass ratio of the detergent methanol to the filter residue is 1:1 to 10:1.

[0045] The present invention also provides a dimethyl carbonate preparation system, comprising:

[0046] Reactor, dimethyl oxalate, alkali metal-alkaline earth metal composite organic salt, and methanol are fed into the reactor for decarbonylation reaction, wherein the temperature of the decarbonylation reaction is 70-160° C. and the reaction pressure is 90-500 KPa(A);

[0047] A washing tower, wherein the dimethyl carbonate and carbon monoxide generated by the reaction of dimethyl oxalate and the methanol all enter the washing tower from the reactor in a gas phase state, dimethyl oxalate is added to the washing tower, the dimethyl carbonate in the gas phase is washed by the dimethyl oxalate, the gas phase is then washed by methanol, and the gas phase at the top of the tower is condensed to obtain non-condensable gas containing carbon monoxide and crude methanol liquid; the washing tower bottom produces crude dimethyl carbonate, which includes dimethyl oxalate, dimethyl carbonate and methanol with a content of ≤1.0%;

[0048] A light-removal tower, wherein the crude methanol liquid enters the light-removal tower for separation, light components including methyl formate and dimethyl ether are extracted from the top of the tower, and liquid methanol is extracted from the bottom of the tower;

[0049] The crude dimethyl carbonate enters the product tower for separation, a methanol-dimethyl carbonate mixture is produced from the top of the product tower, the methanol-dimethyl carbonate mixture is returned to the lower middle section of the washing tower, and industrial-grade dimethyl carbonate is produced from the side line of the upper middle section of the product tower.

[0050] The dimethyl carbonate preparation system also includes a deactivated catalyst treatment device, wherein the reaction turbid liquid containing the composite organic salt of the catalyst alkali metal-alkaline earth metal at the bottom of the reactor is sent to the deactivated catalyst treatment device, the separated clear liquid is returned to the reactor, the separated wet solid is washed with methanol, and the filter residue containing carbonate and oxalate after washing is discharged from the system, and the washed methanol solution is mixed with the composite organic salt of the alkali metal-alkaline earth metal in the catalyst tank, and is sent to the reactor after configuration.

[0051] The deactivated catalyst treatment device includes one of a sedimentation separation washing device and a falling film scraper evaporation complete set. In the embodiment of the present invention, the deactivated catalyst treatment device is a sedimentation separation washing device.

[0052] Figure 1 The process flow diagram of producing dimethyl carbonate from dimethyl oxalate provided in the embodiment of the present invention is shown in FIG. Figure 1The washed methanol solution 27 obtained from the deactivated catalyst treatment device F1 and the decarbonylation catalyst 1 are mixed in the catalyst tank V4, and the decarbonylation catalyst methanol solution 28 is configured to be sent to the reactor R1 together with the dimethyl oxalate 21 entering the reactor for decarbonylation reaction; the gas phase 8 exiting the decarbonylation reactor containing methanol and the reaction products CO and dimethyl carbonate enters the lower part of the washing tower C1, and the fresh dimethyl oxalate 2 is mixed with the dimethyl oxalate 22 obtained after condensation through the dimethyl oxalate condenser E7 as the washing agent dimethyl oxalate 14 and added to the washing tower C1, and the dimethyl carbonate in the gas phase is washed down by the dimethyl oxalate, and the gas phase in the tower is washed by the washing tower reflux methanol 12 to obtain the washing tower top gas phase 9, and the washing tower top gas phase 9 is condensed by the washing tower top condenser E1 to obtain the washing tower top condensate 10, and the washing tower top condensate 10 is separated by gas and liquid through the washing tower top tank V1 to obtain CO non-condensable gas 5 and crude methanol 11 after gas-liquid separation.

[0053] After gas-liquid separation, part of the crude methanol 11 enters the lightness removal tower C2 as the feed crude methanol 13 for lightness removal tower for separation, the top gas phase 23 of the lightness removal tower passes through the top condenser E3 to obtain the lightness removal tower top condensate 24, the top condensate 24 of the lightness removal tower passes through the top tank V2 to obtain the lightness removal tower reflux 25 and the light components 6, the liquid phase methanol 26 is extracted from the bottom of the lightness removal tower C2, and the methanol returns to the deactivated catalyst treatment device F1 for recycling.

[0054] The crude dimethyl carbonate 15 is taken out from the bottom of the washing tower C1 and enters the product tower C3 for separation. The dimethyl carbonate product 4 is taken out from the side line of the middle and upper section of the product tower C3. The top gas phase 16 of the product tower passes through the top condenser E5 of the product tower to obtain the top condensate 17 of the product tower. After the top condensate 17 of the product tower passes through the top tank V3 of the product tower, part of it is used as the top reflux 18 of the product tower, and the other part is returned to the middle and lower section of the washing tower C1 as the top extraction 19 of the product tower.

[0055] Part of the liquid phase extracted from the bottom of the product tower 20 enters the reactor R1 as the dimethyl oxalate reaction raw material 21, and the other part of the dimethyl oxalate returns to the washing tower C1 through the condenser E7.

[0056] The reaction turbid liquid 29 containing the catalyst at the bottom of the reactor R1 is sent to the deactivated catalyst treatment device F1, and the separated reaction clear liquid 30 is returned to the reactor R1. The separated wet solid is washed with methanol (including fresh methanol 3 and recovered methanol 26). After washing, the mixed salt 7 is discharged from the system, and the washed methanol solution 27 is sent to the reactor R1.

[0057] Example 1

[0058] like Figure 1As shown, 124.6 kg / h of dimethyl oxalate (DMO), 0.4 kg / h of recovered dimethyl oxalate, 9.0 kg / h of methanol (ME) and 1.0 kg / h of lithium-lanthanum composite organic salt catalyst are added to the reactor, and decarbonylation reaction is carried out to generate CO and dimethyl carbonate (DMC) under the conditions of reaction temperature 110° C. and reaction pressure 0.26 MPa (G).

[0059] The reaction gaseous product is sent to the lower middle section of the washing tower, and the detergent DMO with a temperature of 80°C and a mass flow rate of 200.0 kg / h is added to the upper middle section of the washing tower. The gas phase at the top of the washing tower is subjected to primary condensation at 40°C and secondary condensation at 10°C to obtain 1.08 kmol / h of non-condensable gas (molar content: 92.07% CO, 6.56% ME, 0.47% DME, 0.40% MF, 0.50% other impurities) and 57.0 kg / h of crude methanol (mass content: 98.50% ME, 0.95% DMC, 0.28% MF, 0.04% DME, 0.23% other impurities); 50.4 kg / h of the crude methanol is refluxed to the washing tower, and the other 6.6 kg / h of the crude methanol is produced from the top of the washing tower. The washing tower kettle obtains 292.7 kg / h of crude DMC (mass content: 68.93% DMO, 30.91% DMC, 0.15% ME, 0.01% other impurities).

[0060] The operating pressure at the top of the washing tower is 0.01MPa(G), the top temperature of the washing tower is 55.8℃, and the kettle temperature of the washing tower is 120.1℃.

[0061] The crude methanol extracted from the top of the washing tower enters the atmospheric pressure light removal tower for further separation to obtain 1.2 mol / h of top non-condensable gas, 0.06 kg / h of light components, and 6.5 kg / h of recovered methanol.

[0062] The crude DMC enters the product tower for separation, and 1.27 kg / h of methanol-dimethyl carbonate mixture is taken out from the top of the tower, and the mixture is returned to the middle and lower section of the washing tower; 89.9 kg / h of DMC product (DMC purity is 99.91%) is taken out from the side line of the middle and upper section of the product tower, and 201.6 kg / h of DMO is taken out from the kettle of the product tower. 124.6 kg / h of DMO taken out from the kettle of the product tower is sent to the reactor, and the other 77.0 kg / h of DMO is condensed and combined with 123.0 kg / h of fresh DMO and sent to the washing tower.

[0063] The operating pressure at the top of the product tower is 0.01MPa(G), the top temperature is 73.68℃, the bottom temperature is 167.4℃, and the top reflux temperature is 66.0℃.

[0064] The reaction turbid liquid containing the catalyst at the bottom of the reactor is sent to the sedimentation separation and washing integrated machine, and the separated clear liquid is returned to the reactor, and the separated wet solid is 4.4kg / h; 2.5kg / h of fresh methanol is added to the 6.5kg / h of recovered methanol to wash the wet solid, and finally 4.0kg / h of filter residue containing insolubles such as lithium carbonate, lithium oxalate, lanthanum carbonate, and lanthanum oxalate are discharged, and 9.4kg / h of washed methanol solution is obtained. The washed methanol solution is configured with a lithium-lanthanum composite organic salt catalyst (methanol content 86.54%, catalyst content 9.61%, and other 3.85%) and sent to the reactor.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A method for producing dimethyl carbonate from dimethyl oxalate, characterized in that: include: Step 1: sending dimethyl oxalate, a composite organic salt of an alkali metal-alkaline earth metal, and methanol into a reactor for decarbonylation reaction, wherein the dimethyl oxalate reacts to generate dimethyl carbonate and carbon monoxide, wherein the methanol, the carbon monoxide, and the dimethyl carbonate all enter a washing tower from the reactor in a gas phase for separation, wherein the temperature of the decarbonylation reaction is 70-160° C., and the reaction pressure is 90-500 KPa(A); Step 2: adding dimethyl oxalate to the scrubbing tower, scrubbing dimethyl carbonate in the gas phase with the dimethyl oxalate, and then scrubbing the gas phase with methanol, condensing the gas phase at the top of the scrubbing tower to obtain non-condensable gas containing carbon monoxide and crude methanol liquid; extracting crude dimethyl carbonate from the bottom of the scrubbing tower, wherein the crude dimethyl carbonate includes dimethyl oxalate, dimethyl carbonate and methanol with a content of ≤1.0%; Step 3: The crude methanol liquid enters a light fraction removal tower for separation, and light components including methyl formate and dimethyl ether are extracted from the top of the tower; liquid methanol is extracted from the bottom of the tower and recycled; Step 4: the crude dimethyl carbonate enters the product tower for separation, a methanol-dimethyl carbonate mixture is produced from the top of the product tower, and the methanol-dimethyl carbonate mixture is returned to the lower middle section of the washing tower; industrial-grade dimethyl carbonate is produced from the side line of the upper middle section of the product tower.

2. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: The reaction turbid liquid containing the composite organic salt of alkali metal-alkaline earth metal as the catalyst at the bottom of the reactor is sent to the deactivated catalyst treatment device, the separated clear liquid is returned to the reactor, the separated wet solid is washed with methanol, and the filter residue containing carbonate and oxalate after washing is discharged from the system, the washed methanol solution is mixed with the composite organic salt of alkali metal-alkaline earth metal in the catalyst tank, and is sent to the reactor after configuration.

3. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 2, characterized in that: The mass ratio of detergent methanol to filter residue is 1:1 to 10:

1.

4. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: The operating pressure of the washing tower in step 2 is 90-400 KPa (A), the tower top temperature is 55-90°C, and the tower bottom temperature is 95-150°C.

5. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: In step 2, the gas phase at the top of the washing tower is condensed in multiple stages, with the primary condensation temperature being 35-45°C and the secondary condensation temperature being 0-10°C. The liquids after the primary condensation and the secondary condensation are merged into the top tank of the washing tower.

6. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: In step 2, the mass ratio of the washing agent dimethyl oxalate to the dimethyl carbonate in the gas phase entering the washing tower is 1.5:1 to 9:

1.

7. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: The temperature of the dimethyl oxalate added to the washing tower in step 2 is 55-100°C.

8. The method for producing dimethyl carbonate from dimethyl oxalate according to claim 1, characterized in that: In step 2, the reflux rate of crude methanol in the washing tower is 30%-150% relative to the mass fraction of dimethyl carbonate in the gas phase entering the washing tower.

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