Production process and system for co-production of dimethyl oxalate and dimethyl carbonate

Abstract

The present invention relates to the technical field of novel chemical processes, and disclosed herein are a production process and system for co-production of dimethyl oxalate and dimethyl carbonate. The co-production process ingeniously utilizes the characteristic that the top of a nitric oxide / methanol / nitric acid redox column in a dimethyl oxalate synthesis process is enriched in methyl nitrite, and the requirement of a raw material ratio of a chlorine-free dimethyl carbonate synthesis catalyst can be well met for production of dimethyl carbonate only by simple purification and adjustments. The co-production process involves a simple process and less capital investment, the product structure can be adjusted in a timely manner, and economic benefits can be increased.

Description

A production process and system for the co-production of dimethyl oxalate and dimethyl carbonate. Technical Field

[0001] This invention patent relates to the field of new chemical process technology, specifically to a production process and system for the co-production of dimethyl oxalate and dimethyl carbonate. Background Technology

[0002] Currently, the gas-phase carbonyl production process for synthesizing dimethyl oxalate (DMO) from carbon monoxide (CO) and methyl nitrite (MN) is mature and widely used. Furthermore, a new process for synthesizing dimethyl carbonate (DMC) from CO and MN carbonyl groups also has certain economic advantages in China. This process currently mainly uses chlorine-containing noble metal catalysts, and a certain concentration of hydrogen chloride needs to be maintained in the reaction cycle gas. However, hydrogen chloride cannot be introduced into the dimethyl oxalate synthesis system, making it difficult to achieve the co-production of dimethyl carbonate from existing dimethyl oxalate units.

[0003] The successful development of a chloride-free dimethyl carbonate synthesis catalyst eliminates the need for hydrogen chloride in the reaction system, thus enabling coupling with the existing dimethyl oxalate synthesis process. In dimethyl carbonate synthesis, the catalyst's active center is +2 valence Pd, which is easily reduced by CO in the feed gas, leading to catalyst deactivation. To maintain the +2 valence state of Pd in ​​the catalyst, the feed gas requires a high MN concentration and a low CO concentration, typically with a molar ratio of MN to CO of 3–7:1. In contrast, the active center of the dimethyl oxalate synthesis catalyst is 0 valence Pd, requiring the opposite molar ratio of CO to MN in the feed gas: a high CO concentration and a relatively low MN concentration, typically 1.5–3:1. This makes it difficult to simultaneously adjust the feed gas composition of the two products in the methyl nitrite esterification regeneration system synthesized from dimethyl oxalate.

[0004] The existing gas-phase carbonyl synthesis process for dimethyl oxalate has been detailed in patent CN101544539. In this process, the tail gas separated from the dimethyl oxalate produced in the carbonylation reactor is recycled to generate methyl nitrite and CO via an esterification regeneration tower. Similarly, the gas-phase carbonyl synthesis process for dimethyl carbonate is also similar to that for dimethyl oxalate. The CO and methyl nitrite feedstock gases pass through a carbonylation reactor, the liquid phase product is collected and purified to obtain dimethyl carbonate, and the gas phase product is recycled or vented to complete the entire process.

[0005] The coal chemical market is constantly changing. The ability to quickly build a dimethyl carbonate production process with minimal investment cost is crucial to improving the market competitiveness of existing dimethyl oxalate producers. Therefore, there is an urgent need to develop a process for the co-production of dimethyl carbonate from dimethyl oxalate. Summary of the Invention

[0006] The purpose of this invention is to provide a production process and system for the co-production of dimethyl oxalate and dimethyl carbonate. It enables the sharing of feed gas systems and circulating gas in both the dimethyl carbonate and dimethyl oxalate production processes, thus achieving the combined production of dimethyl carbonate and dimethyl oxalate.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A process for the co-production of dimethyl oxalate and dimethyl carbonate is provided. The dimethyl carbonate production process uses a chlorine-free dimethyl carbonate catalyst, making it a chlorine-free dimethyl carbonate production process. The process includes a methyl nitrite esterification regeneration tower for methyl nitrite regeneration, providing methyl nitrite feedstock; and a nitric oxide / methanol / nitric acid redox tower for methyl nitrite synthesis through nitric acid supplementation. The circulating gas from the dimethyl oxalate production process is returned to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling.

[0009] In the dimethyl oxalate production process, a stream of overhead gas from the nitric oxide / methanol / nitric acid redox tower is used as the feed gas for dimethyl carbonate synthesis. After washing and purification, the molar ratio of CO to MN in the feed gas is adjusted to the target ratio before dimethyl carbonate synthesis. The recycled gas generated from dimethyl carbonate synthesis is returned to the esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower in the dimethyl oxalate production process for recycling.

[0010] According to the above scheme, the molar ratio of CO to MN in the feed gas for dimethyl carbonate production is 1:3 to 1:7.

[0011] According to the above scheme, the volume content of methyl nitrite in the overhead gas rich in methyl nitrite drawn from the top of the nitric oxide / methanol / nitric acid redox tower is 18-30%.

[0012] According to the above scheme, the CO volume content in the overhead gas rich in methyl nitrite drawn from the top of the nitric oxide / methanol / nitric acid redox tower is 7-22%.

[0013] According to the above scheme, the combined production process of dimethyl oxalate and dimethyl carbonate includes a dimethyl oxalate (DMO) production process and a dimethyl carbonate (DMC) production process.

[0014] In the dimethyl oxalate production process, the methanol-washed MN feed gas from the methyl nitrite esterification regeneration tower is preheated / heated and then enters the CO and MN mixer. Additional CO is introduced to adjust the molar ratio of CO to MN in the feed gas to the target ratio required for dimethyl oxalate production. The CO and MN mixture, having reached the target ratio, is then fed into the DMO carbonylation reactor for catalytic carbonylation under the DMO carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMO absorption tower. The gas phase outlet of the DMO absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower. The liquid phase outlet of the DMO absorption tower collects dimethyl oxalate.

[0015] In the dimethyl carbonate production process, a gas rich in methyl nitrite is drawn from the top of the nitric oxide / methanol / nitric acid redox tower. After being washed with methanol and preheated / heated, it is used as the feed gas for dimethyl carbonate production and enters the CO and MN mixer. The molar ratio of CO to MN in the feed gas is adjusted to the target ratio required for dimethyl carbonate production. The CO and MN mixture with the target ratio is sent to the DMC carbonylation reactor, where a catalytic carbonylation reaction is carried out under the catalysis of a chlorine-free dimethyl carbonate carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMC absorption tower. The gas phase outlet gas of the DMC absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower in the dimethyl oxalate production process. The liquid phase outlet of the DMC absorption tower collects dimethyl carbonate (DMC).

[0016] According to the above scheme, the gas phase outlet gas of the DMO absorber and the gas phase outlet gas of the DMC absorber are combined into a single circulating feed gas. This combined circulating feed gas is then divided into two streams. The majority stream, typically accounting for 70-90% of the total gas volume, directly enters the inlet of the methyl nitrite esterification regeneration tower. The minority stream, typically accounting for 10-30% of the total gas volume, can be regulated by valves or pressurized by an additional compressor before entering the inlet of the nitric oxide / methanol / nitric acid redox tower. Specifically, the gas phase outlet gas of the DMO absorber is connected to the inlets of the methyl nitrite esterification regeneration tower and the redox tower via a first circulating compressor. The gas phase outlet gas of the DMC absorber is sent to the inlets of the methyl nitrite esterification regeneration tower and the redox tower via a second circulating compressor. The first and second circulating compressors are shared; that is, the gas phase outlet gas of the DMC absorber is connected to the inlets of the methyl nitrite esterification regeneration tower and the redox tower via the first circulating compressor in the DMO synthesis system, meaning the outlet gas phase of the DMC absorber is directly connected to the inlet of the circulating compressor in the DMO synthesis system.

[0017] According to the above scheme, the liquid phase outlet of the nitric oxide / methanol / nitric acid redox tower is connected to the inlet of the methanol recovery tower for methanol recovery.

[0018] According to the above scheme, the liquid phase in the methyl nitrite esterification regeneration tower directly enters the nitric oxide / methanol / nitric acid oxidation-reduction tower, and the liquid phase in the nitric oxide / methanol / nitric acid oxidation-reduction tower directly enters the methanol absorption tower. That is, the liquid phases in the two towers are finally mixed together and enter the methanol recovery tower to recover methanol.

[0019] According to the above scheme, in the production of dimethyl oxalate, the outlet gas of the methyl nitrite esterification regeneration tower and the outlet gas of the DMO carbonylation reactor are preheated and heated by heat exchange and then sent to the DMO carbonylation reactor for reaction. The outlet gas of the DMO carbonylation reactor enters the DMO absorption tower after heat exchange.

[0020] In the production of dimethyl carbonate, the overhead gas rich in methyl nitrite from the nitric oxide / methanol / nitric acid redox tower and the outlet gas from the DMC carbonylation reactor are preheated and heated by heat exchange before being sent to the DMC carbonylation reactor for reaction. The outlet gas from the DMC carbonylation reactor is then sent to the DMC absorption tower after heat exchange.

[0021] According to the above scheme, the DMC carbonylation reactor is a tubular reactor, with chlorine-free dimethyl carbonate catalyst packed inside the tubes. Hot water circulation is used to transfer heat outside the tubular reactor, and low-pressure steam is produced as a byproduct for preheating / heating. The reaction pressure is 0.3–0.5 MPa, and the gas space velocity is 3000–8000 h⁻¹. -1 .

[0022] According to the above scheme, the overhead gas from the nitric oxide / methanol / nitric acid redox tower is purified by a methanol scrubbing tower to remove water and acid content to <100×10⁻⁶. -6 (V / V).

[0023] According to the above scheme, the reaction temperature of the DMO carbonylation reactor is 100-130℃; the reaction temperature of the DMC carbonylation reactor is 100-130℃.

[0024] According to the above scheme, the chlorine-free dimethyl carbonate catalyst used in the DMC carbonylation reactor can be selected from, but is not limited to, the chlorine-free dimethyl carbonate catalyst disclosed in patent CN116899614A. This chlorine-free dimethyl carbonate catalyst includes an active component Pd and a molecular sieve support, on which structural stabilizing agents Cu, K, and metal M are also supported. In this catalyst, by mass percentage, Pd is 0.25-2%, Cu is 0.05-10%, K is 0.01-5%, and M is 0.01-1%. Other chlorine-free dimethyl carbonate catalysts are also acceptable. Different chlorine-free dimethyl carbonate catalysts have different activities and slightly different requirements for the molar ratio of MN to CO, but all can be used for the co-production of dimethyl oxalate and dimethyl carbonate in this invention.

[0025] According to the above scheme, the particle size of the chlorine-free dimethyl carbonate catalyst is Φ (3-6) × (3-6) mm.

[0026] According to the above scheme, the DMC absorption tower is a methanol absorption tower. The gas from the outlet of the DMC carbonylation reactor is cooled by heat exchange and cooler before entering the methanol absorption tower to absorb the DMC product with methanol.

[0027] According to the above scheme, the DMO absorption tower is a methanol absorption tower. The gas from the outlet of the DMO carbonylation reactor is cooled by heat exchange and cooler before entering the methanol absorption tower to absorb the DMO product with methanol.

[0028] According to the above scheme, the liquid phase outlet of the DMC absorption tower is sent to a liquid phase separation system for dimethyl carbonate purification. The liquid phase separation system can employ devices such as pressure swing distillation and melt crystallization, and generally includes a light and heavy phase removal tower, a pressurization tower, and a purification tower. The outlet of the DMC absorption tower is connected to the inlet of the light and heavy phase removal tower, the outlet of the light and heavy phase removal tower is connected to the inlet of the pressurization tower, the outlet of the pressurization tower is connected to the inlet of the purification tower, the outlet of the purification tower is connected to the inlet of the melt crystallization device, and the outlet of the melt crystallization device outputs the DMC product.

[0029] According to the above scheme, the melt crystallization device includes a first melt crystallizer and a second melt crystallizer with different purities of DMC, arranged in parallel. The outlet of the refining tower is equipped with a flow regulating valve connected to the inlets of both the first and second DMC melt crystallizers. The outlet of the melt crystallizer is connected to a drying device.

[0030] According to the above scheme, the liquid phase outlet of the DMO absorber is sent to a liquid phase separation system for dimethyl oxalate purification. The liquid phase separation system generally includes a light and heavy phase removal tower, a pressurization tower, and a purification tower. The liquid phase outlet of the DMO absorber is connected to the inlet of the first light and heavy phase removal tower, the outlet of the first light and heavy phase removal tower is connected to the inlet of the pressurization tower, and the outlet of the pressurization tower is connected to the inlet of the first purification tower.

[0031] A second aspect of the present invention provides a production system for the above-mentioned production process of dimethyl oxalate co-producing dimethyl carbonate, the production system comprising a DMO synthesis system and a DMC synthesis system.

[0032] The DMO synthesis system includes a methyl nitrite esterification regeneration tower, a nitric oxide / methanol / nitric acid redox tower, a first heater, a first CO and MN mixer, a DMO carbonylation reactor, a circulating compressor, a DMO absorption tower, and a first liquid phase separation system.

[0033] The top outlet of the methyl nitrite esterification regeneration tower is connected to the inlet of the first heater. The outlet of the first heater is connected to the inlet of the first CO and MN mixer. The outlet of the first CO and MN mixer is then connected to the inlet of the DMO carbonylation reactor. The outlet gas of the DMO carbonylation reactor is cooled by heat exchange and then connected to the inlet of the DMO absorption tower. The gas phase outlet of the DMO absorption tower is connected to the inlets of the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower through a circulating compressor. The liquid phase outlet of the DMO absorption tower is connected to the first liquid phase separation system for the purification of dimethyl oxalate.

[0034] The DMC synthesis system includes a methanol washing and purification tower, a second heater, a second CO and MN mixer, a DMC carbonylation reactor, a circulating compressor, a DMC absorption tower, and a second liquid phase separation system.

[0035] The outlet of the nitric oxide / methanol / nitric acid redox tower in the DMO synthesis system is connected to the inlet of the methanol scrubbing and purification tower. The gas phase outlet of the methanol scrubbing and purification tower is connected to the inlet of the second heater. The outlet of the second heater is connected to the inlet of the second CO and MN mixer. The outlet of the second CO and MN mixer is connected to the inlet of the DMC carbonylation reactor. The outlet gas of the DMC carbonylation reactor, after heat exchange cooling, enters the DMC absorption tower. The gas phase outlet of the DMC absorption tower is connected to the inlet of the methyl nitrite regeneration tower and the inlet of the nitric oxide / methanol / nitric acid redox tower via a circulating compressor. This compressor can utilize the circulating gas compressor of the DMO synthesis system; the circulating compressors of the DMO synthesis system and the DMC synthesis system are shared, meaning the outlet gas phase of the DMC absorption tower is directly connected to the inlet of the circulating gas compressor of the DMO synthesis system. The liquid phase outlet of the DMC absorption tower is connected to a second liquid phase separation system for the purification of dimethyl carbonate.

[0036] According to the above scheme, the DMO synthesis system further includes a first heat exchanger. The cold end inlet of the first heat exchanger is connected to the outlet of the methyl nitrite esterification regeneration tower, the cold end outlet is connected to the inlet of the first CO and MN mixer, the hot end inlet of the first heat exchanger is connected to the gas phase outlet of the DMO carbonylation reactor, and the hot end outlet of the first heat exchanger is connected to the DMO absorption tower. By exchanging heat and preheating the outlet gas of the methyl nitrite esterification regeneration tower with the outlet gas of the DMO carbonylation reactor, the gas is sent into the DMO carbonylation reactor for reaction.

[0037] The DMC synthesis system also includes a second heat exchanger. The cold end inlet of the second heat exchanger is connected to the outlet of the methanol washing and purification tower, the cold end outlet is connected to the inlet of the second CO and MN mixer, the hot end inlet of the second heat exchanger is connected to the gas phase outlet of the DMC carbonylation reactor, and the hot end outlet of the second heat exchanger is connected to the DMC absorption tower. The gas from the nitric oxide / methanol / nitric acid oxidation-reduction tower, which is rich in methyl nitrite, is heated by exchanging heat with the outlet gas of the DMC carbonylation reactor and then fed into the DMC carbonylation reactor for reaction.

[0038] According to the above scheme, the production system also includes a methanol recovery tower. The liquid phase outlet of the nitric oxide / methanol / nitric acid redox tower is connected to the inlet of the methanol recovery tower for methanol recovery.

[0039] Furthermore, the liquid phase outlet of the methyl nitrite esterification regeneration tower is connected to the liquid phase inlet of the nitric oxide / methanol / nitric acid redox tower, and directly enters the nitric oxide / methanol / nitric acid redox tower. After merging with the liquid phase in the nitric oxide / methanol / nitric acid redox tower, it enters the methanol absorption tower. That is, the liquid phases in the two towers are finally mixed together and enter the methanol recovery tower to recover methanol.

[0040] According to the above scheme, the first liquid phase separation system generally includes a light and heavy phase removal tower, a first pressurization tower and a first purification tower. The liquid phase outlet of the DMO absorption tower is connected to the inlet of the first light and heavy phase removal tower, the outlet of the first light and heavy phase removal tower is connected to the inlet of the first pressurization tower, and the outlet of the pressurization tower is connected to the inlet of the first purification tower.

[0041] According to the above scheme, the second liquid phase separation system includes a second light and heavy phase removal tower, a second pressurization tower, a second purification tower, and a melting crystallization device. The liquid phase outlet of the DMC absorption tower is connected to the inlet of the second light and heavy phase removal tower, the outlet of the second light and heavy phase removal tower is connected to the inlet of the second purification tower, and the inlet of the second purification tower is connected to the melting crystallization device.

[0042] In the nitric oxide / methanol / nitric acid redox column, nitric acid is added to replenish the nitrogen oxides consumed in the circulating feed gas. Methyl nitrite is prepared through the reaction of nitric oxide, methanol, and nitric acid, and is used to replenish the methyl nitrite. The overhead gas from the nitric oxide / methanol / nitric acid redox column, after being supplemented with nitric acid, has sufficiently converted NO to MN, resulting in the highest MN concentration in the gas phase within the circulating system. Furthermore, as it is a gas produced after the synthesis reaction, its CO concentration is the lowest in the circulating system, effectively meeting the requirements of the chlorine-free dimethyl carbonate synthesis process. This invention utilizes the overhead gas from the nitric oxide / methanol / nitric acid redox tower as feedstock gas for dimethyl carbonate synthesis. It cleverly takes advantage of the fact that the overhead gas from the redox tower in dimethyl oxalate synthesis is rich in methyl nitrite. After simple purification, it can well meet the feedstock ratio requirements of the chlorine-free dimethyl carbonate synthesis catalyst. The process is simple and saves investment. Based on the existing dimethyl oxalate synthesis equipment, it is easy to achieve co-production of dimethyl carbonate, adjust the product structure, increase economic benefits, and the circulating gas generated by dimethyl carbonate synthesis can be shared with the circulating gas of the dimethyl oxalate production process.

[0043] This invention is based on a chlorine-free gas-phase carbonylation process for the synthesis of dimethyl carbonate (DMC). Technically, through a clever and rational design concept, the feed gas from the relatively mature existing dimethyl oxalate process is directly diverted and treated during recycling to meet the conditions required for DMC production. This allows the DMC production process to be directly integrated into the existing mature DMC process, meaning that most of the equipment and devices can be shared with the DMC process. Only a few additional sets of equipment are needed to easily achieve the co-production of DMC and DMC, significantly reducing investment costs and improving plant production efficiency.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] The process of this invention enables the sharing of raw material gas system and circulating gas in the production processes of dimethyl carbonate and dimethyl oxalate, thereby achieving the joint production of dimethyl carbonate and dimethyl oxalate.

[0046] In the dimethyl carbonate production process, the raw material gas system and circulating gas compression device are shared and co-produced with the dimethyl oxalate production process, which greatly saves equipment investment, significantly reduces the floor space, improves the efficiency of material recycling, reduces energy consumption, and allows for adjustment of product structure and increased economic benefits. Attached Figure Description

[0047] Figure 1 is a schematic flow diagram of the production process of dimethyl oxalate and dimethyl carbonate provided in Example 1 of the present invention. Detailed Implementation

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. For those skilled in the art, as long as the various changes are within the scope defined by the appended claims, all inventions or utility models utilizing the concept of this invention are protected.

[0049] A production system for the co-production of dimethyl oxalate and dimethyl carbonate, as shown in Figure 1, includes a DMO synthesis system and a DMC synthesis system.

[0050] The DMO synthesis system includes a methyl nitrite esterification regeneration tower, a nitric oxide / methanol / nitric acid redox tower, a first heater, a first CO and MN mixer, a DMO carbonylation reactor, a circulating compressor, a DMO absorption tower, and a first liquid phase separation system. Further, the first liquid phase separation system includes a light-to-heavy phase removal tower, a first pressurization tower, and a first purification tower. The liquid phase outlet of the DMO absorption tower is connected to the inlet of the first light-to-heavy phase removal tower, the outlet of the first light-to-heavy phase removal tower is connected to the inlet of the first pressurization tower, and the outlet of the pressurization tower is connected to the inlet of the first purification tower.

[0051] The top outlet of the methyl nitrite esterification regeneration tower is connected to the inlet of the first heater. The outlet of the first heater is connected to the inlet of the first CO and MN mixer. The outlet of the first CO and MN mixer is then connected to the inlet of the DMO carbonylation reactor. The outlet gas of the DMO carbonylation reactor is cooled by heat exchange and then connected to the inlet of the DMO absorption tower. The gas phase outlet of the DMO absorption tower is connected to the inlets of the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower via a circulating compressor. The liquid phase outlet of the DMO absorption tower is connected to the first liquid phase separation system for the purification of dimethyl oxalate. Specifically, the liquid phase outlet of the DMO absorption tower is connected to the inlet of the first light and heavy removal tower, and the outlet of the first light and heavy removal tower is connected to the inlet of the first purification tower.

[0052] In the dimethyl oxalate production process, the methanol-washed MN feed gas from the methyl nitrite esterification regeneration tower is preheated / heated and then enters the CO and MN mixer. Additional CO is introduced to adjust the molar ratio of CO to MN in the feed gas to the target ratio required for dimethyl oxalate production. The CO and MN mixture, having reached the target ratio, is then fed into the DMO carbonylation reactor for catalytic carbonylation under the DMO carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMO absorption tower. The gas phase outlet of the DMO absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower. The liquid phase outlet of the DMO absorption tower collects dimethyl oxalate.

[0053] The DMC synthesis system includes a methanol washing and purification tower, a second heater, a second CO and MN mixer, a DMC carbonylation reactor, a circulating compressor, a DMC absorption tower, and a second liquid phase separation system. Further, the second liquid phase separation system includes a light and heavy phase removal tower, a pressurization tower, and a purification tower. The outlet of the DMC absorption tower is connected to the inlet of the light and heavy phase removal tower, the outlet of the light and heavy phase removal tower is connected to the inlet of the pressurization tower, the outlet of the pressurization tower is connected to the inlet of the purification tower, the outlet of the purification tower is connected to the inlet of the melt crystallization unit, and the outlet of the melt crystallization unit outputs DMC product.

[0054] The outlet of the nitric oxide / methanol / nitric acid redox tower in the DMO synthesis system is connected to the inlet of the methanol scrubbing and purification tower. The gas phase outlet of the methanol scrubbing and purification tower is connected to the inlet of the second heater. The outlet of the second heater is connected to the inlet of the second CO and MN mixer. The outlet of the second CO and MN mixer is connected to the inlet of the DMC carbonylation reactor. The outlet gas of the DMC carbonylation reactor, after heat exchange cooling, enters the DMC absorption tower. The gas phase outlet of the DMC absorption tower is connected to the inlet of the methyl nitrite esterification regeneration tower and the inlet of the nitric oxide / methanol / nitric acid redox tower via a circulating compressor. This compressor can utilize the circulating gas compressor of the DMO synthesis system. The circulating compressors of the DMO synthesis system and the DMC synthesis system are shared, meaning the outlet gas phase of the DMC absorption tower is directly connected to the inlet of the circulating gas compressor of the DMO synthesis system. The liquid phase outlet of the DMC absorption tower is connected to the second liquid phase separation system for the purification of dimethyl carbonate. Specifically, the liquid phase outlet of the DMC absorption tower is connected to the inlet of the second light and heavy removal tower. The outlet of the second light and heavy removal tower is connected to the inlet of the second purification tower. The inlet of the second purification tower is connected to the melting crystallization device.

[0055] In the dimethyl carbonate production process, a gas rich in methyl nitrite is drawn from the top of the nitric oxide / methanol / nitric acid redox tower. After being washed with methanol and preheated / heated, it is used as the feed gas for dimethyl carbonate production and enters the CO and MN mixer. The molar ratio of CO to MN in the feed gas is adjusted to the target ratio required for dimethyl carbonate production. The CO and MN mixture with the target ratio is sent to the DMC carbonylation reactor, where a catalytic carbonylation reaction is carried out under the catalysis of a chlorine-free dimethyl carbonate carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMC absorption tower. The gas phase outlet gas of the DMC absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower in the dimethyl oxalate production process. The liquid phase outlet of the DMC absorption tower collects dimethyl carbonate (DMC).

[0056] Furthermore, the DMO synthesis system also includes a first heat exchanger. The cold end inlet of the first heat exchanger is connected to the outlet of the methyl nitrite esterification regeneration tower, the cold end outlet is connected to the inlet of the first CO and MN mixer, the hot end inlet of the first heat exchanger is connected to the gas phase outlet of the DMO carbonylation reactor, and the hot end outlet of the first heat exchanger is connected to the DMO absorption tower. By exchanging heat and preheating the outlet gas of the methyl nitrite esterification regeneration tower with the outlet gas of the DMO carbonylation reactor, the gas is fed into the DMO carbonylation reactor for reaction.

[0057] The DMC synthesis system also includes a second heat exchanger. The cold end inlet of the second heat exchanger is connected to the outlet of the methanol washing and purification tower, the cold end outlet is connected to the inlet of the second CO and MN mixer, the hot end inlet of the second heat exchanger is connected to the gas phase outlet of the DMC carbonylation reactor, and the hot end outlet of the second heat exchanger is connected to the DMC absorption tower. The gas from the nitric oxide / methanol / nitric acid oxidation-reduction tower, which is rich in methyl nitrite, is heated by exchanging heat with the outlet gas of the DMC carbonylation reactor and then fed into the DMC carbonylation reactor for reaction.

[0058] Furthermore, the above-mentioned production system also includes a methanol recovery tower for recovering methanol. The liquid phase outlet of the methyl nitrite esterification regeneration tower is connected to the liquid phase inlet of the nitric oxide / methanol / nitric acid redox tower and directly enters the nitric oxide / methanol / nitric acid redox tower. After merging with the liquid phase in the nitric oxide / methanol / nitric acid redox tower, it enters the methanol absorption tower. That is, the liquid phases in the two towers are finally mixed together and enter the methanol recovery tower to recover methanol.

[0059] Specifically, the inlet gas composition of the dimethyl oxalate synthesis reactor is CO 15-32%, MN 10-16%, NO 2-10%, with the remainder being inert components such as CH3OH, N2O, CO2, CH4, and N2 that do not participate in the reaction. The outlet gas from the reactor exhibits decreased CO and MN concentrations and increased NO concentration. The gas after the reaction is absorbed and compressed by DMO before entering the esterification regeneration tower and redox tower. Gas from the redox tower of the dimethyl oxalate production system is drawn into the DMC synthesis system, with key components of CO 7-22%, MN 18-30%, NO 1-5%, and the remainder being CH3OH, N2O, CO2, CH4, and N2. Using this gas rich in methyl nitrite as feedstock, the gas then passes through a methanol scrubbing tower to remove water and acid content to <100×10⁻⁶. -6 (V / V), and then adjust the molar ratio of CO to MN in the raw material gas to 1:3 to 1:7 by adding a small amount of CO or not, as needed, and mix them thoroughly and evenly in the CO and MN mixer.

[0060] Then, the temperature is preheated / raised to 100–130°C before entering the tubular dimethyl carbonate synthesis reactor. The tubes are filled with Pd-Cu supported on NaY molecular sieves as catalyst, with a catalyst particle size of Φ(3-6)×(3-6) mm. Hot water circulation is used to transfer heat outside the tubes and produce low-pressure steam as a byproduct. The reaction pressure is 0.3–0.5 MPa, and the gas space velocity is 3000–8000 h⁻¹. -1 After a full catalytic reaction, the gas exiting the dimethyl carbonate synthesis reactor is cooled by a heat exchanger and cooler before entering the product absorption tower. The dimethyl carbonate product is absorbed by methanol, and the gas phase is then pressurized by a compressor before returning to the esterification regeneration tower and redox tower of dimethyl oxalate synthesis, thus achieving a closed-loop cycle, reducing material loss and increasing product yield.

[0061] Finally, the absorbent in the DMC absorber enters the liquid-phase separation system, which employs pressure swing distillation. The pressure swing distillation system includes a light and heavy component removal column, a pressurization column, and a purification column. The light and heavy component removal column operates at a top pressure of 0-100 kPaG and a temperature of 20-180℃; the pressurization column operates at a top pressure of 0.2-2 MPaG and a temperature of 20-200℃; and the purification column operates at a top pressure of 0-80 kPaG and a temperature of 15-160℃. The purification column yields 99.1-99.5% dimethyl carbonate.

[0062] To further improve product quality, the outlet of the refining tower is also connected to a melting crystallization unit. The 99.1-99.5% dimethyl carbonate product from the refining tower is fed into the melting crystallization unit, which is equipped with premium-grade and high-purity melting crystallizers to ensure high-quality products of different specifications. After passing through the melting crystallization system, a dimethyl carbonate product with ≥99.99% purity can be obtained, meeting the needs of the high-end market.

[0063] The specific implementation examples are as follows: Example 1

[0064] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 27%; in the CO and MN mixer, the molar ratio of CO to MN is 1:3; the preheating / heater temperature is 110℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 5000h⁻¹. -1 After the feed gas is fully reacted with Pd-Cu-KV as catalyst (0.4% Pd•7.2% Cu•0.8% K•2.4% V•89.2% mixed molecular sieve, ZSM-35 mixed molecular sieve and 0.5g Naβ molecular sieve by mass percentage), the space-time yield of its DMC is 273g / (L•h).

[0065] In the DMC absorber, the absorbent operates at a pressure of 80 kPaG and a temperature of 80°C at the top of the light and heavy component removal tower; at 0.6 MPaG and a temperature of 110°C at the top of the pressurization tower; and at 80 kPaG and a temperature of 130°C at the top of the purification tower. The product obtained from the purification tower is 97.9% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 2

[0066] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 18%; in the CO and MN mixer, the molar ratio of CO to MN is 1:3; the preheating / heater temperature is 100℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 3000h⁻¹. -1 After the feed gas fully reacts with a NaY molecular sieve-supported Pd-Cu-KV catalyst (0.4% Pd•7.2% Cu•0.8% K•2.4% V•89.2% mixed molecular sieve, ZSM-35 mixed molecular sieve, and 0.5g Naβ molecular sieve), the space-time yield of its DMC is 135g / (L•h).

[0067] The absorbent in the DMC absorber operates at a pressure of 70 kPaG and a temperature of 110°C at the top of the light and heavy component removal tower; at 0.5 MPaG and a temperature of 100°C at the top of the pressurization tower; and at 60 kPaG and a temperature of 80°C at the top of the purification tower. The purified product is 97.4% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are then recycled to a methyl nitrite esterification regeneration tower and a nitric oxide / methanol / nitric acid redox tower for co-production of dimethyl oxalate and dimethyl carbonate. Example 3

[0068] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 21%; in the CO and MN mixer, the molar ratio of CO to MN is 1:3; the preheating / heater temperature is 110℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 6000h. -1After the feed gas fully reacts with a catalyst supported on NaY molecular sieve, Pd-Cu-K-Fe-Mn (1.0% Pd, 1.3% Cu, 2.0% K, 0.05% Fe, 0.02% Mn, and 95.63% NaY by mass percentage), the space-time yield of its DMC is 289 g / (L•h).

[0069] In the DMC absorber, the absorbent operates at a pressure of 80 kPaG and a temperature of 110°C at the top of the light and heavy component removal tower; at 0.7 MPaG and a temperature of 100°C at the top of the pressurization tower; and at 60 kPaG and a temperature of 100°C at the top of the purification tower. The product obtained from the purification tower is 98.7% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 4

[0070] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 21%; in the CO and MN mixer, the molar ratio of CO to MN is 1:5; the preheating / heater temperature is 120℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 7000h⁻¹. -1 After the feed gas is fully reacted with the catalyst (1.25% Pd•0.86% Cu•0.05% K•0.83% Mn•97.87% MCM-41 by mass percentage), the space-time yield of DMC is 368 g / (L•h).

[0071] In the DMC absorber, the absorbent operates at a pressure of 60 kPaG and a temperature of 100°C at the top of the light and heavy component removal tower; at 0.9 MPaG and 100°C at the top of the pressurization tower; and at 70 kPaG and 110°C at the top of the purification tower. The product obtained from the purification tower is 97.5% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 5

[0072] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 24%; in the CO and MN mixer, the molar ratio of CO to MN is 1:6; the preheating / heater temperature is 125℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.4MPa, and the gas hourly space velocity is 6000h.-1 After the feed gas is fully reacted with Pd-Cu-K-Ag as catalyst (1.0%Pd•3.0%Cu•0.45%K•0.5%Ag•95.05% mixed molecular sieve, the mixed molecular sieve being NaY and 1.5g of NaX molecular sieve), the space-time yield of its DMC is 375g / (L•h).

[0073] In the DMC absorber, the absorbent operates at a pressure of 80 kPaG and a temperature of 130°C at the top of the light and heavy component removal tower; at 0.5 MPaG and 80°C at the top of the pressurization tower; and at 60 kPaG and 120°C at the top of the purification tower. The purified product is 98.9% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 6

[0074] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 25%; in the CO and MN mixer, the molar ratio of CO to MN is 1:5; the preheating / heater temperature is 120℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.4MPa, and the gas space velocity is 7000h⁻¹. -1 After the feed gas is fully reacted with Pd-Cu-K-Ag as catalyst (1.0%Pd•3.0%Cu•0.45%K•0.5%Ag•95.05% mixed molecular sieve, the mixed molecular sieve being NaY and 1.5g of NaX molecular sieve), the space-time yield of its DMC is 401g / (L•h).

[0075] In the DMC absorber, the absorbent operates at a pressure of 60 kPaG and a temperature of 90°C at the top of the light and heavy component removal tower; at 0.9 MPaG and a temperature of 70°C at the top of the pressurization tower; and at 70 kPaG and a temperature of 110°C at the top of the purification tower. The product obtained from the purification tower is 98.2% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 7

[0076] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6(V / V); MN volume content is 25%; in the CO and MN mixer, the molar ratio of CO to MN is 1:3; the preheating / heater temperature is 110℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 6000h⁻¹. -1 After the feed gas is fully reacted with Pd-Cu-K-Eu as catalyst (0.25%Pd•5.1%Cu•4.3%K•0.57%Eu•89.78% mixed molecular sieve, the mixed molecular sieve is MCM-41 and Naβ molecular sieve), the space-time yield of its DMC is 289 g / (L•h).

[0077] In the DMC absorber, the absorbent operates at a pressure of 80 kPaG and a temperature of 110°C at the top of the light and heavy component removal tower; at 0.7 MPaG and a temperature of 100°C at the top of the pressurization tower; and at 60 kPaG and a temperature of 100°C at the top of the purification tower. The product obtained from the purification tower is 98.7% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 8

[0078] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶. -6 (V / V); MN volume content is 27%; in the CO and MN mixer, the molar ratio of CO to MN is 1:6; the preheating / heater temperature is 110℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.3MPa, and the gas space velocity is 8000h⁻¹. -1 After the feed gas is fully reacted with the catalyst (1.25% Pd, 0.86% Cu, 0.05% K, 0.83% Mn, and 97.87% MCM-41 by mass percentage), the space-time yield of DMC is 257 g / (L•h).

[0079] In the DMC absorber, the absorbent operates at a pressure of 75 kPaG and a temperature of 130°C at the top of the light and heavy component removal tower; at 1.1 MPaG and a temperature of 120°C at the top of the pressurization tower; and at 70 kPaG and a temperature of 100°C at the top of the purification tower. The product obtained from the purification tower is 99.1% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate. Example 9

[0080] The water and acid content in the raw gas MN is less than 100 × 10⁻⁶.-6 (V / V); MN volume content is 28%; in the CO and MN mixer, the molar ratio of CO to MN is 1:4; the preheating / heater temperature is 125℃; the reaction pressure of the tubular dimethyl carbonate synthesis reactor is 0.4MPa, and the gas space velocity is 8000h. -1 After the feed gas is fully reacted with Pd-Cu-K-Eu as catalyst (0.25%Pd•5.1%Cu•4.3%K•0.57%Eu•89.78 mixed molecular sieve by mass percentage, the mixed molecular sieve is MCM-41 and Naβ molecular sieve), the space-time yield of its DMC is 437 g / (L•h).

[0081] In the DMC absorber, the absorbent operates at a pressure of 60 kPaG and a temperature of 90°C at the top of the light and heavy component removal tower; at 1.2 MPaG and a temperature of 110°C at the top of the pressurization tower; and at 70 kPaG and a temperature of 90°C at the top of the purification tower. The product obtained from the purification tower is 98.2% dimethyl carbonate. The gaseous outlet gas from the DMC absorber is compressed by a circulating compressor and split into two streams, which are sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling, respectively, to co-produce dimethyl oxalate and dimethyl carbonate.

[0082] The catalysts in Examples 1-9 can be prepared according to the preparation examples of the chlorine-free dimethyl carbonate catalyst disclosed in CN116899614A.

[0083] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A process for the production of dimethyl oxalate co-produced with dimethyl carbonate, characterized in that: The dimethyl carbonate production process uses a chlorine-free dimethyl carbonate catalyst, making it a chlorine-free dimethyl carbonate production process. The dimethyl oxalate production process uses a methyl nitrite esterification regeneration tower for methyl nitrite regeneration, providing methyl nitrite feedstock. A nitric oxide / methanol / nitric acid redox tower synthesizes methyl nitrite by adding nitric acid, used to replenish methyl nitrite. The circulating gas from the dimethyl oxalate production process is returned to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower for recycling. In the dimethyl oxalate production process, a stream of overhead gas from the nitric oxide / methanol / nitric acid redox tower is used as the feed gas for dimethyl carbonate synthesis. After washing and purification, the molar ratio of CO to MN in the feed gas is adjusted to the target ratio before dimethyl carbonate synthesis. The recycled gas generated from dimethyl carbonate synthesis is returned to the esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower in the dimethyl oxalate production process for recycling.

2. The production process according to claim 1, characterized in that: The molar ratio of CO to MN in the feed gas for dimethyl carbonate production is 1:3 to 1:

7.

3. The production process according to claim 1, characterized in that: The overhead gas rich in methyl nitrite drawn from the top of the nitric oxide / methanol / nitric acid redox tower has a volume content of 18-30% methyl nitrite.

4. The production process according to claim 1, characterized in that: The CO volume content in the overhead gas rich in methyl nitrite drawn from the top of the nitric oxide / methanol / nitric acid redox column is 7-22%.

5. The production process according to claim 1, characterized in that: The combined production process of dimethyl oxalate and dimethyl carbonate includes a dimethyl oxalate (DMO) production process and a dimethyl carbonate (DMC) production process. In the dimethyl oxalate production process, the methanol-washed MN feed gas from the methyl nitrite esterification regeneration tower is preheated / heated and then enters the CO and MN mixer. Additional CO is introduced to adjust the molar ratio of CO to MN in the feed gas to the target ratio required for dimethyl oxalate production. The CO and MN mixture, having reached the target ratio, is then fed into the DMO carbonylation reactor for catalytic carbonylation under the DMO carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMO absorption tower. The gas phase outlet of the DMO absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower. The liquid phase outlet of the DMO absorption tower collects dimethyl oxalate. In the dimethyl carbonate production process, a gas rich in methyl nitrite is drawn from the top of the nitric oxide / methanol / nitric acid redox tower. After being washed with methanol and preheated / heated, it is used as the feed gas for dimethyl carbonate production and enters the CO and MN mixer. The molar ratio of CO to MN in the feed gas is adjusted to the target ratio required for dimethyl carbonate production. The CO and MN mixture with the target ratio is sent to the DMC carbonylation reactor, where a catalytic carbonylation reaction is carried out under the catalysis of a chlorine-free dimethyl carbonate carbonylation catalyst. After the catalytic carbonylation reaction, the gas enters the DMC absorption tower. The gas phase outlet gas of the DMC absorption tower is sent to the methyl nitrite esterification regeneration tower and the nitric oxide / methanol / nitric acid redox tower in the dimethyl oxalate production process. The liquid phase outlet of the DMC absorption tower collects dimethyl carbonate (DMC).

6. The production process according to claim 1 or 5, characterized in that: The gas phase outlet gas of the DMO absorber and the gas phase outlet gas of the DMC absorber are combined into a single circulating feed gas. The combined circulating feed gas is then divided into two feed gas streams. One stream, which accounts for 70-90% of the total gas volume, directly enters the inlet of the methyl nitrite esterification regeneration tower; the other stream enters the inlet of the nitric oxide / methanol / nitric acid oxidation-reduction tower.

7. The production process according to claim 5, characterized in that: In the production of dimethyl oxalate, the outlet gas from the methyl nitrite esterification regeneration tower and the outlet gas from the DMO carbonylation reactor are preheated and heated by heat exchange before being sent to the DMO carbonylation reactor for reaction. The outlet gas from the DMO carbonylation reactor is then sent to the DMO absorption tower after heat exchange. In the production of dimethyl carbonate, the overhead gas rich in methyl nitrite from the nitric oxide / methanol / nitric acid redox tower and the outlet gas from the DMC carbonylation reactor are preheated and heated by heat exchange before being sent to the DMC carbonylation reactor for reaction. The outlet gas from the DMC carbonylation reactor is then sent to the DMC absorption tower after heat exchange.

8. The production process according to claim 5, characterized in that: The DMO absorption tower is a methanol absorption tower. The gas from the outlet of the DMO carbonylation reactor is cooled by heat exchange and cooler before entering the methanol absorption tower to absorb the DMO product with methanol. The DMC absorption tower is a methanol absorption tower. The gas from the outlet of the DMC carbonylation reactor is cooled by heat exchange and a cooler before entering the methanol absorption tower to absorb the DMC product with methanol.

9. The production process according to claim 5, characterized in that: A methanol recovery tower is provided, with the liquid phase outlet of the nitric oxide / methanol / nitric acid redox tower connected to the inlet of the methanol recovery tower for methanol recovery.

10. The production process according to claim 9, characterized in that: The liquid phase in the methyl nitrite esterification regeneration tower directly enters the nitric oxide / methanol / nitric acid redox tower, and the liquid phase in the nitric oxide / methanol / nitric acid redox tower directly enters the methanol absorption tower. That is, the liquid phases in the two towers are finally mixed together and enter the methanol recovery tower to recover methanol.

11. The production process according to claim 5, characterized in that: The DMC carbonylation reactor is a column reactor, the column is filled with chlorine-free dimethyl carbonate catalyst, the column reactor is heated by hot water circulation and low-pressure steam is produced for preheating / heating, the reaction pressure is 0.3-0.5 MPa, the gas space velocity is 3000-8000 h -1 ; The reaction temperature of the DMC carbonylation reactor is 100-130℃; The overhead gas from the nitric oxide / methanol / nitric acid redox column is passed through a methanol wash scrubber column to remove water and acid content of the feed gas to <100 x 10 -6 (V / V).

12. A production system for the production process of dimethyl oxalate co-produced with dimethyl carbonate according to any one of claims 1 to 5, characterized by: The production system includes a DMO synthesis system and a DMC synthesis system. The DMO synthesis system includes a methyl nitrite esterification regeneration tower, a nitric oxide / methanol / nitric acid redox tower, a first heater, a first CO and MN mixer, a DMO carbonylation reactor, a circulating compressor, a DMO absorption tower, and a first liquid phase separation system. The top outlet of the methyl nitrite esterification regeneration tower is connected to the inlet of the first heater. The outlet of the first heater is connected to the inlet of the first CO and MN mixer. The outlet of the first CO and MN mixer is then connected to the inlet of the DMO carbonylation reactor. The outlet gas of the DMO carbonylation reactor is cooled by heat exchange and then connected to the inlet of the DMO absorption tower. The gas phase outlet of the DMO absorption tower is connected to the inlets of the methyl nitrite esterification regeneration tower and the redox tower through a circulating compressor. The liquid phase outlet of the DMO absorption tower is connected to the first liquid phase separation system for the purification of dimethyl oxalate. The DMC synthesis system includes a methanol washing and purification tower, a second heater, a second CO and MN mixer, a DMC carbonylation reactor, a circulating compressor, a DMC absorption tower, and a second liquid phase separation system. The outlet of the nitric oxide / methanol / nitric acid redox tower of the DMO synthesis system is connected to the inlet of the methanol washing and purification tower. The gas phase outlet of the methanol washing and purification tower is connected to the inlet of the second heater. The outlet of the second heater is connected to the inlet of the second CO and MN mixer. The outlet of the second CO and MN mixer is connected to the inlet of the DMC carbonylation reactor. The outlet gas of the DMC carbonylation reactor is cooled by heat exchange and then enters the DMC absorption tower. The gas phase outlet of the DMC absorption tower is connected to the inlet of the methyl nitrite regeneration tower and the inlet of the nitric oxide / methanol / nitric acid redox tower through a circulating compressor. The circulating compressors of the DMO synthesis system and the DMC synthesis system are shared. The liquid phase outlet of the DMC absorption tower is connected to the second liquid phase separation system for the purification of dimethyl carbonate.

13. The production system of claim 12, characterized in that: The DMO synthesis system further includes a first heat exchanger. The cold end inlet of the first heat exchanger is connected to the outlet of the methyl nitrite esterification regeneration tower, the cold end outlet is connected to the inlet of the first CO and MN mixer, the hot end inlet of the first heat exchanger is connected to the gas phase outlet of the DMO carbonylation reactor, and the hot end outlet of the first heat exchanger is connected to the DMO absorption tower. The outlet gas of the methyl nitrite esterification regeneration tower and the outlet gas of the DMO carbonylation reactor are preheated and heated by heat exchange, and then fed into the DMO carbonylation reactor for reaction. The DMC synthesis system also includes a second heat exchanger. The cold end inlet of the second heat exchanger is connected to the outlet of the methanol washing and purification tower, the cold end outlet is connected to the inlet of the second CO and MN mixer, the hot end inlet of the second heat exchanger is connected to the gas phase outlet of the DMC carbonylation reactor, and the hot end outlet of the second heat exchanger is connected to the DMC absorption tower. The gas from the nitric oxide / methanol / nitric acid oxidation-reduction tower, which is rich in methyl nitrite, is heated by exchanging heat with the outlet gas of the DMC carbonylation reactor and then fed into the DMC carbonylation reactor for reaction.

14. The production system of claim 12, characterized in that: It also includes a methanol recovery tower, where the liquid phase outlet of the nitric oxide / methanol / nitric acid redox tower is connected to the inlet of the methanol recovery tower for methanol recovery; The first liquid phase separation system includes a light and heavy phase removal tower, a first pressurization tower, and a first purification tower. The liquid phase outlet of the DMO absorption tower is connected to the inlet of the first light and heavy phase removal tower, the outlet of the first light and heavy phase removal tower is connected to the inlet of the first pressurization tower, and the outlet of the pressurization tower is connected to the inlet of the first purification tower. The second liquid phase separation system includes a second light and heavy phase separation tower, a second pressurization tower, a second purification tower, and a melting crystallization device. The liquid phase outlet of the DMC absorption tower is connected to the inlet of the second light and heavy phase separation tower, the outlet of the second light and heavy phase separation tower is connected to the inlet of the second purification tower, and the inlet of the second purification tower is connected to the melting crystallization device.

15. The production system of claim 14, characterized in that: The liquid phase outlet of the methyl nitrite esterification regeneration tower is connected to the liquid phase inlet of the nitric oxide / methanol / nitric acid redox tower, and directly enters the nitric oxide / methanol / nitric acid redox tower. After merging with the liquid phase in the nitric oxide / methanol / nitric acid redox tower, it enters the methanol absorption tower. That is, the liquid phases in the two towers are finally mixed together and enter the methanol recovery tower to recover methanol.

Images