A product separation and purification device and process for carbon dioxide esterification to produce dimethyl carbonate

Abstract

This invention discloses a product separation and purification apparatus and process for the production of dimethyl carbonate (DMC) via CO esterification. It includes a pre-separation tower, a primary DMC separation tower, a wastewater DMC recovery tower, a secondary DMC separation tower, a methanol absorption tower, an MN desorption tower, a DMM removal tower, an MF distillation tower, a DMM distillation tower, a pressurized DMC distillation tower, and an atmospheric pressure DMC distillation tower. The feed pipeline for the DMC synthesis product is connected to the inlet of the pre-separation tower; the bottom outlet of the pre-separation tower is connected to the inlet of the wastewater DMC recovery tower; the side outlet of the pre-separation tower is connected to the inlet of the primary DMC separation tower; the top outlets of the pre-separation tower and the primary DMC separation tower are respectively connected to the inlet of the secondary DMC separation tower; the bottom of the secondary DMC separation tower is connected to the inlet of the pressurized DMC distillation tower; and the top of the secondary DMC separation tower is connected to the inlet of the methanol absorption tower. This invention can be used for the separation and purification of DMC product streams, featuring a rational process and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology. Specifically, it relates to a separation and purification apparatus and process for a reaction product system of CO (carbon monoxide) esterification to produce dimethyl carbonate. Background Technology

[0002] Dimethyl carbonate (DMC) is a globally recognized green chemical, primarily used in the production of polycarbonate (PC), isocyanate, pharmaceuticals, and pesticides. It is also used as a solvent in lithium-ion battery electrolytes and coatings, and has potential applications as a substitute for methyl tert-butyl ether (MTBE) as a gasoline additive.

[0003] Currently, there are three industrialized dimethyl carbonate synthesis technologies, and one more technology with promising industrialization prospects:

[0004] (1) Phosgene-methanol method: the raw material phosgene is a highly toxic chemical and the by-product HCl is highly corrosive. Therefore, this route has been eliminated.

[0005] (2) Transesterification. Based on the reactants, industrialized process routes include:

[0006] ①Propylene oxide + CO2 + methanol → DMC + propylene glycol

[0007] This method offers mild reaction conditions and high yields. However, the raw materials (propylene oxide / ethylene oxide) are expensive, and the separation of the byproduct propylene glycol is difficult. Furthermore, the production process of propylene oxide (chlorohydrin method) is highly polluting, and the market for the byproduct propylene glycol is already in large surplus, making sales difficult.

[0008] ②Urea + 1,2-propanediol → propylene carbonate + liquid ammonia

[0009] Propylene carbonate + methanol → DMC + 1,2-propanediol

[0010] This method has low yield and requires large equipment investment.

[0011] ③ Ethylene oxide + CO2 + methanol → DMC + ethylene glycol

[0012] The Institute of Process Engineering, Chinese Academy of Sciences, has invented a supported ionic liquid catalyst with advantages such as high single-pass conversion rate of ethylene oxide, strong adaptability to raw materials, and no need for catalyst separation. It has also achieved mass production and industrial demonstration applications.

[0013] (3) Liquid-phase methanol oxidative carbonylation method

[0014] 2CH3OH + CO + 0.5O2 → DMC + H2O

[0015] This technical route has several drawbacks: the catalyst CuCl is unstable, has a short lifespan, is highly corrosive, and is difficult to regenerate and recycle; the product contains chlorine, which affects product quality; there are many byproducts; and the CO concentration in oxygen is within the explosive limit range (12.5%–74%), making it prone to explosion.

[0016] (4) CO esterification to dimethyl carbonate. This route uses a supported metal nanocatalyst, which has good space-time yield and selectivity. The reaction conditions are mild, with low pressure (0.2-0.5 MPag) and temperature range of 100-150℃, making it a promising technology for industrialization.

[0017] The reaction principle for the production of dimethyl carbonate by CO esterification is as follows:

[0018] CO + 2CH3ONO → (CH3O)2CO + 2NO

[0019] The raw materials are gaseous CO and methyl nitrite (CH3ONO, abbreviated as MN), the main product is dimethyl carbonate, and the byproducts are dimethyl oxalate (DMO), methyl formate (MF), dimethoxymethane (DMM), and methanol, etc. The stoichiometric equations for the side reactions are as follows:

[0020] 2CO + 2MN → DMO + 2NO

[0021] 4MN→MF+2CH3OH+4NO

[0022] 2MN + MeOH → DMM + H2O

[0023] Dimethyl carbonate has a boiling point of 90°C and a melting point of 2–4°C; it is a liquid at room temperature. Dimethyl oxalate has a boiling point of 174°C and a melting point of 54°C; it is a solid at room temperature.

[0024] Chinese patent (CN103901130B) discloses "an online evaluation device, evaluation method, and production method for the production of dimethyl carbonate catalysts." The evaluation device includes a gas control pipeline system, a fixed-bed reaction system, a product separation and purification system, and an online gas chromatography analysis system. The gas control pipeline system comprises three gas control pipelines, each including a sequentially connected gas delivery pipeline, a pressure regulating valve, a pressure gauge, a flow regulating valve, a mass flow controller, and a switching valve. The three gas pipelines are merged into a single gas pipeline via an equal-diameter four-way connector, and a gas mixing chamber is installed on the merged pipeline. This evaluation device can achieve real-time synchronous analysis of all components of raw materials and products using only one online gas chromatograph, resulting in high analytical efficiency, accurate and reliable data, low capital investment, and efficient production and purification of dimethyl carbonate.

[0025] The aforementioned patents provide a reaction route for CO esterification to produce dimethyl carbonate (also known as methanol carbonylation to produce methyl formate), a catalyst evaluation method, and a separation scheme suitable for laboratory scale and equipment, but do not propose a feasible engineering technology route applicable to industrialization. Summary of the Invention

[0026] The purpose of this invention is to propose a complete and industrially suitable product separation and purification method and system for the CO esterification to dimethyl carbonate reaction system, which features a reasonable process and low energy consumption.

[0027] To achieve the above-mentioned objectives, this invention provides a product separation and purification apparatus and process for the production of dimethyl carbonate (DMC) by CO esterification, the specific technical solution of which is as follows.

[0028] This invention provides a product separation and purification apparatus for CO esterification to dimethyl carbonate, characterized in that: the apparatus includes a pre-separation tower, a DMC (dimethyl carbonate) separation tower, a wastewater DMC recovery tower, a secondary DMC separation tower, a methanol absorption tower, an MN desorption tower, a DMM (dimethoxymethane) removal tower, an MF (methyl formate) distillation tower, a DMM distillation tower, a pressurized DMC distillation tower, and an atmospheric pressure DMC distillation tower, wherein the feed pipeline of the dimethyl carbonate synthesis product is connected to the inlet of the pre-separation tower;

[0029] The bottom outlet of the pre-separation tower is connected to the inlet of the wastewater DMC recovery tower, and the bottom outlet of the wastewater DMC recovery tower is connected to the wastewater extraction pipeline. The pre-separation tower has a side outlet, which is connected to the inlet of the primary DMC separation tower. The top outlet of the pre-separation tower and the top outlet of the primary DMC separation tower are respectively connected to the inlet of the secondary DMC separation tower. The top outlet of the wastewater DMC recovery tower and the bottom outlet of the primary DMC separation tower are respectively connected to the DMC product extraction pipeline. The top outlet of the secondary DMC separation tower is connected to the bottom feed inlet of the methanol absorption tower, and the bottom outlet of the secondary DMC separation tower is connected to the inlet of the pressurized DMC distillation tower.

[0030] The methanol absorption tower is equipped with an absorbent inlet at the top. The top outlet of the methanol absorption tower is connected to the circulating gas extraction pipeline. The bottom outlet of the methanol absorption tower is connected to the inlet of the MN desorption tower. The top outlet of the MN desorption tower is connected to the circulating gas extraction pipeline. The bottom outlet of the MN desorption tower is connected to the inlet of the DMM stripping tower. The top outlet of the DMM stripping tower is connected to the feed inlet of the MF distillation tower. The bottom outlet of the DMM stripping tower is connected to the alcohol-containing wastewater extraction pipeline, or it can be connected to both the alcohol-containing wastewater extraction pipeline and the absorbent inlet at the top of the methanol absorption tower. The top outlet of the MF distillation tower is connected to the MF product extraction pipeline. The bottom outlet of the MF distillation tower is connected to the inlet of the DMM distillation tower. The top outlet of the DMM distillation tower is connected to the DMM product extraction pipeline. The bottom outlet of the DMM distillation tower is connected to the methanol recovery A outlet pipeline.

[0031] The pressurized DMC distillation column has a light component outlet at the top, a DMC product extraction pipeline at the bottom outlet, a side outlet at the side line that connects to the inlet of the atmospheric DMC distillation column, an upper outlet at the atmospheric DMC distillation column that connects to the inlet of the pressurized DMC distillation column, and a methanol recovery B outlet at the bottom of the atmospheric DMC distillation column.

[0032] The CO esterification to dimethyl carbonate product separation and purification device of the present invention further includes an electronic-grade DMC heavy component removal tower and an electronic-grade DMC light component removal tower. The DMC product extraction pipeline is directly connected to the primary DMC outlet pipeline, or the DMC product extraction pipeline is divided into two lines, one connected to the primary DMC outlet pipeline and the other connected to the inlet of the electronic-grade DMC heavy component removal tower. The top of the electronic-grade DMC heavy component removal tower is connected to the inlet of the electronic-grade DMC light component removal tower, and the bottom of the electronic-grade DMC heavy component removal tower is connected to the heavy component outlet pipeline. The top of the electronic-grade DMC light component removal tower is connected to the inlet of the pressurized DMC distillation tower, and the bottom of the electronic-grade DMC dehydrogenation tower is connected to the electronic-grade DMC outlet pipeline.

[0033] The CO esterification to dimethyl carbonate product separation and purification device of the present invention, wherein the pre-separation tower, primary DMC separation tower, wastewater DMC recovery tower, methanol absorption tower, MN desorption tower, secondary DMC separation tower, DMM removal tower, MF distillation tower, DMM distillation tower, pressurized DMC distillation tower, atmospheric pressure DMC distillation tower, electronic grade DMC heavy removal tower and electronic grade DMC light removal tower are all packed towers, plate towers or composite towers of packed and plate.

[0034] The pre-separation tower of this invention preferably has 90-150 theoretical plates, and the side sampling position of the pre-separation tower is located 10-30 theoretical plates away from the top of the pre-separation tower, preferably 15-25 theoretical plates; the primary DMC separation tower has 30-50 theoretical plates, preferably 35-45 theoretical plates; the wastewater DMC recovery tower has 90-150 theoretical plates, preferably 110-130 theoretical plates; the secondary DMC separation tower has 20-60 theoretical plates, preferably 25-45 theoretical plates; the methanol absorption tower has 10-40 theoretical plates, preferably 20-30 theoretical plates; the MN desorption tower has 30-75 theoretical plates, preferably 50-60 theoretical plates; and the DMM removal tower has 35-65 theoretical plates, preferably 45-150 theoretical plates. The DMC distillation column has 55 theoretical plates; the MF distillation column has 40-70 theoretical plates, preferably 50-65 theoretical plates; the DMM distillation column has 40-70 theoretical plates, preferably 50-65 theoretical plates; the pressurized DMC distillation column has 60-100 theoretical plates, preferably 75-85 theoretical plates; the atmospheric DMC distillation column has 60-90 theoretical plates, preferably 65-80 theoretical plates; the electronic-grade DMC de-heavy plate column has 70-120 theoretical plates, preferably 85-110 theoretical plates; the electronic-grade DMC de-light plate column has 30-50 theoretical plates, preferably 35-45 theoretical plates; the side feed point of the pressurized DMC distillation column is located 5-20 theoretical plates away from the top of the pressurized DMC distillation column, preferably 8-12 theoretical plates.

[0035] This invention provides a process for separating and purifying dimethyl carbonate produced by CO esterification, characterized by comprising the following steps:

[0036] 1) The product stream from CO esterification to dimethyl carbonate is cooled and condensed before entering a pre-separation tower for pre-separation. The bottom bulk of the pre-separation tower is sent to a wastewater DMC recovery tower to recover DMC product from the wastewater. The liquid side stream after separation in the pre-separation tower is collected and sent to a primary DMC separation tower for further separation. DMC product is obtained at the bottom of the primary DMC separation tower after separation. The top stream of the primary DMC separation tower and the top stream after separation in the pre-separation tower are respectively sent to a secondary DMC separation tower. The pressure at the top of the pre-separation tower is 0.1-0.5 MPa, the temperature at the top is 25-70°C, preferably 40-60°C, and the temperature at the bottom is 120-170°C.

[0037] 2) After the DMC, methanol and other heavy components are removed from the stream entering the secondary DMC separation tower, the top stream of the secondary DMC separation tower is sent to the bottom of the methanol absorption tower, and the bottom heavy components of the secondary DMC separation tower are sent to the pressurized DMC distillation tower.

[0038] 3) In the methanol absorption tower, the stream entering from the bottom of the methanol absorption tower comes into countercurrent contact with the absorbent entering from the top of the methanol absorption tower for absorption. The gas coming out from the top of the methanol absorption tower is used as the circulating gas. The rich absorbent liquid at the bottom of the methanol absorption tower is sent to the MN desorption tower for desorption. Then, the light component comes out from the top of the MN desorption tower as the circulating gas. The heavy component at the bottom of the MN desorption tower is sent to the DMM removal tower for separation. The stream from the top of the DMM removal tower after separation enters the MF distillation tower for distillation to obtain the MF product. The heavy stream from the bottom of the MF distillation tower enters the DMM distillation tower for distillation to obtain the DMM product and recover methanol A. The heavy component at the bottom of the DMM removal tower is extracted, or a portion is extracted and the other portion is returned to the methanol absorption tower.

[0039] 4) The stream entering the pressurized DMC distillation column is further distilled. The light component obtained after distillation in the pressurized DMC distillation column exits from the top of the pressurized DMC distillation column, and the DMC product stream obtained after distillation in the pressurized DMC distillation column exits from the bottom of the pressurized DMC distillation column. The mixed liquid stream obtained after distillation in the pressurized DMC distillation column is collected from the side stream of the pressurized DMC distillation column and then enters the atmospheric DMC distillation column for distillation. The recovered methanol B is obtained from the bottom of the atmospheric DMC distillation column, and the top stream of the atmospheric DMC distillation column is returned to the pressurized DMC distillation column.

[0040] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification. The DMC products obtained from the wastewater DMC recovery tower, the primary DMC separation tower, and the bottom of the pressurized DMC distillation tower are either exported as products, or a portion is exported and the remainder is sent to an electronic-grade DMC de-heavy component tower. Heavy components are extracted from the bottom of the electronic-grade DMC de-heavy component tower, and the top stream from the electronic-grade DMC de-heavy component tower is sent to an electronic-grade DMC de-light component tower. Electronic-grade DMC products are obtained from the bottom of the electronic-grade DMC de-light component tower, and the top stream from the electronic-grade DMC dehydrogenation tower is returned to the pressurized DMC distillation tower.

[0041] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the top temperature of the primary DMC separation column is 100-150℃, preferably 110-140℃, the top pressure is 0.1-0.8MPa, preferably 0.3-0.6MPa, and the bottom temperature is 145-170℃, preferably 150-165℃.

[0042] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the top pressure of the wastewater DMC recovery tower is 0.05-0.12 MPa, preferably 0.75-0.10 MPa, the top temperature is 95-135℃, preferably 100-130℃, and the bottom temperature is 110-150℃, preferably 115-140℃.

[0043] The present invention discloses a product separation and purification process for the production of dimethyl carbonate by CO esterification, wherein the top pressure of the secondary DMC separation column is 0.08-0.4 MPa, preferably 0.1-0.3 MPa, the top temperature is -15-25°C, preferably -10-10°C, and the bottom temperature is 60-120°C, preferably 70-110°C.

[0044] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the methanol absorption tower has a top temperature of -5 to 10°C and a bottom temperature of -15 to 0°C; the MN desorption tower has a top temperature of 0 to 25°C, preferably 10 to 20°C, and a bottom temperature of 100 to 130°C, preferably 105 to 120°C.

[0045] The present invention discloses a product separation and purification process for the production of dimethyl carbonate by CO esterification, wherein the top pressure of the de-DMM tower is 0.07-0.2 MPa, preferably 0.08-0.13 MPa, the top temperature is 35-75°C, preferably 40-65°C, and the bottom temperature is 70-110°C, preferably 80-100°C.

[0046] The present invention discloses a product separation and purification process for the production of dimethyl carbonate by CO esterification, wherein the top pressure of the MF distillation column is 0.07-0.2 MPa, preferably 0.08-0.13 MPa, the top temperature is 35-70°C, preferably 40-60°C, and the bottom temperature is 50-85°C, preferably 55-80°C.

[0047] The present invention discloses a product separation and purification process for the production of dimethyl carbonate by CO esterification, wherein the top pressure of the DMM distillation column is 0.06-0.14 MPa, preferably 0.07-0.13 MPa, the top temperature is 35-70°C, preferably 40-60°C, and the bottom temperature is 50-85°C, preferably 55-80°C.

[0048] The present invention discloses a product separation and purification process for the production of dimethyl carbonate by CO esterification, wherein the pressure of the pressurized DMC distillation column is 1.0-1.5 MPa, preferably 1.1-1.3 MPa, the top temperature is 120-160°C, preferably 130-150°C, and the bottom temperature is 170-210°C, preferably 185-200°C.

[0049] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the pressure at the top of the atmospheric pressure DMC distillation column is 0.06-0.15 MPa, preferably 0.0-0.10 MPa, the temperature at the top of the column is 65-90°C, preferably 70-85°C, and the temperature at the bottom of the column is 70-100°C, preferably 75-95°C.

[0050] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the top pressure of the electronic-grade DMC deweighting tower is 0.06-0.15 MPa, preferably 0.07-0.10 MPa, the top temperature is 95-120°C, preferably 100-115°C, and the bottom temperature is 105-140°C, preferably 110-130°C.

[0051] The present invention discloses a product separation and purification process for the production of dimethyl carbonate from CO esterification, wherein the top pressure of the electronic-grade DMC light component removal tower is 0.06-0.15 MPa, preferably 0.07-0.10 MPa, the top temperature is 80-120°C, preferably 90-115°C, and the bottom temperature is 105-140°C, preferably 110-130°C.

[0052] The present invention describes a product separation and purification process for CO esterification to dimethyl carbonate. The methanol absorption tower typically uses one or more streams as absorbents, preferably three streams. From top to bottom along the methanol absorption tower are fresh methanol, recovered methanol from within the unit, and a mixture containing methanol and DMC from the bottom of the DMM removal tower.

[0053] The product streams from the bottom of the DMM removal column and the top of the pressurized DMC distillation column described in this invention are both DMC-methanol mixtures. They can enter different locations in the pressurized DMC distillation column according to their DMC concentration. The bottom stream of the pressurized DMC distillation column is DMC product, the side stream is a DMC-methanol azeotrope under pressurized conditions, and the top stream discharges trace amounts of light components (non-condensable gases). The DMC-methanol azeotrope extracted from the upper side stream of the pressurized DMC distillation column enters the atmospheric DMC distillation column. The bottom of the atmospheric DMC distillation column is methanol product, which can be recovered and reused within the unit. The top stream of the atmospheric DMC distillation column is a DMC-methanol mixture, which is sent to the feed inlet of the pressurized DMC distillation column.

[0054] This invention can be used for the separation and purification of dimethyl carbonate product logistics, and is mainly used for the separation and purification technology of dimethyl carbonate produced by CO esterification.

[0055] Compared with existing technologies, the product separation and purification apparatus and process for CO esterification to dimethyl carbonate described in this invention have the following advantages:

[0056] (1) This invention proposes a complete product separation and purification method and system suitable for industrial application for the reaction system of CO esterification to dimethyl carbonate, which has the characteristics of reasonable process and low energy consumption.

[0057] (2) This invention incorporates a pre-separation tower and a DMC light component removal tower, which can pre-separate 70-90% of the DMC production, reducing the amount of DMC processed in subsequent processes. This is especially beneficial for the DMC-methanol system (which contains azeotropic components), where separation energy consumption is extremely high, thus significantly saving energy. The bottom product of the pre-separation tower undergoes heavy component removal in the DMC light component removal tower to obtain Grade I DMC. Additionally, the bottom product of the DMC light component removal tower is also Grade I DMC. Together, these two products yield approximately 80-95% Grade I DMC.

[0058] (3) This invention uses a medium-cooling separation method to separate the main products (MF, DMC, methanol, and DMM) in the circulating gas. Compared with conventional methanol absorption technology, this invention uses a medium-cooling distillation method to separate DMC, avoiding the use of methanol absorbent to absorb DMC. The methanol absorption tower is only used to separate MF, so only a small amount of methanol generated in the separation system related to DMC is present. The flow rate entering the DMC-methanol separation section is significantly reduced. Since the DMC-methanol separation has extremely high energy consumption, this invention can significantly save energy.

[0059] (4) This invention uses the main products (MF, DMC, methanol, DMM) in the intermediate-cooled separation circulating gas. Compared with the conventional methanol absorption technology route, the feed DMC concentration entering the DMC-methanol separation section is greatly increased, exceeding the concentration of atmospheric pressure DMC-methanol azeotrope, saving the energy required for DMC concentration in the atmospheric pressure DMC distillation column, thus further reducing the energy consumption of the DMC-methanol separation section.

[0060] (5) This invention combines two methods: a medium-cooling distillation method to separate DMC and a methanol absorbent method to separate MF. Compared with conventional distillation methods, since the boiling point of MF is much lower than that of DMC, the cooling temperature at the top of the distillation column in this patent is higher than that of conventional distillation methods, eliminating the need for very low-temperature cooling and saving investment and energy consumption. Compared with conventional methanol absorption separation methods, this patent avoids methanol entering the DMC-methanol separation system, thus saving energy. Using the methanol absorbent method to separate MF, there is no azeotrope between MF and methanol, resulting in lower separation energy consumption.

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of the invention. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of a product separation and purification apparatus for the CO esterification of methyl formate according to the present invention.

[0063] The reference numerals in the figure are:

[0064] 1-Synthetic product feed line, 2-Pre-separation tower, 3-Primary DMC separation tower, 4-Wastewater DMC recovery tower, 5-Secondary DMC separation tower, 6-Methanol absorption tower, 7-MN desorption tower, 8-DMM removal tower, 9-MF distillation tower, 10-DMM distillation tower, 11-Pressurized DMC distillation tower, 12-Ambient DMC distillation tower, 13-Electronic grade DMC heavy component removal tower, 14-Electronic grade DMC light component removal tower, 15-Wastewater extraction line, 16-DMC product extraction line, 17-Primary grade DMC outlet line, 18-Methanol absorbent line, 19-Circulating gas extraction line, 20-MF product extraction line, 21-DMM product extraction line, 22-Recovered methanol A outlet line, 23-Recovered methanol B outlet line, 24-Heavy component outlet line, 25-Electronic grade DMC outlet line.

[0065] like Figure 1 As shown, the present invention discloses a product separation and purification device for CO esterification to dimethyl carbonate. The device includes a pre-separation tower 2, a DMC (dimethyl carbonate) separation tower 3, a wastewater DMC recovery tower 4, a secondary DMC separation tower 5, a methanol absorption tower 6, an MN desorption tower 7, a DMM (dimethoxymethane) removal tower 8, an MF distillation tower 9, a DMM distillation tower 10, a pressurized DMC distillation tower 11, and an atmospheric pressure DMC distillation tower 12. The dimethyl carbonate synthesis product feed pipeline 1 is connected to the inlet of the pre-separation tower 2.

[0066] The bottom outlet of the pre-separation tower 2 is connected to the inlet of the wastewater DMC recovery tower 4, and the bottom of the wastewater DMC recovery tower is connected to the wastewater extraction pipeline 15. The pre-separation tower 2 has a side outlet, which is connected to the inlet of the primary DMC separation tower 3. The top outlet of the pre-separation tower and the top outlet of the primary DMC separation tower are respectively connected to the inlet of the secondary DMC separation tower 5. The top outlet of the wastewater DMC recovery tower and the bottom outlet of the primary DMC separation tower are respectively connected to the DMC product extraction pipeline 16. The top outlet of the secondary DMC separation tower is connected to the bottom feed inlet of the methanol absorption tower 6, and the bottom outlet of the secondary DMC separation tower is connected to the inlet of the pressurized DMC distillation tower 11.

[0067] The methanol absorption tower 6 is equipped with an absorbent inlet at the top. The top outlet of the methanol absorption tower is connected to the circulating gas extraction pipeline 19. The bottom outlet of the methanol absorption tower is connected to the inlet of the MN desorption tower 7. The top outlet of the MN desorption tower is connected to the circulating gas extraction pipeline 19. The bottom outlet of the MN desorption tower is connected to the inlet of the DMM removal tower 8. The top outlet of the DMM removal tower is connected to the feed inlet of the MF distillation tower 9. The bottom outlet of the DMM removal tower is connected to the alcohol-containing wastewater extraction pipeline, or connected to the alcohol-containing wastewater extraction pipeline and the absorbent inlet at the top of the methanol absorption tower 6 respectively. The top outlet of the MF distillation tower is connected to the MF product extraction pipeline 20. The bottom outlet of the MF distillation tower is connected to the inlet of the DMM distillation tower 10. The top outlet of the DMM distillation tower is connected to the DMM product extraction pipeline 21. The bottom outlet of the DMM distillation tower is connected to the methanol recovery A outlet pipeline 22.

[0068] The pressurized DMC distillation column is provided with a light component outlet at the top and a DMC product extraction pipeline 16 at the bottom. The pressurized DMC distillation column 11 has a side outlet, which is connected to the inlet of the atmospheric DMC distillation column 12. The upper outlet of the atmospheric DMC distillation column 12 is connected to the inlet of the pressurized DMC distillation column 11. The atmospheric DMC distillation column 12 has a methanol recovery B outlet at the bottom, which is connected to the methanol recovery B outlet pipeline 23.

[0069] like Figure 1 As shown, the CO esterification to dimethyl carbonate product separation and purification device of the present invention further includes an electronic-grade DMC heavy component removal tower 13 and an electronic-grade DMC light component removal tower 14. The DMC product extraction pipeline 16 is directly connected to the primary product DMC outlet pipeline 17, or the DMC product extraction pipeline 16 is divided into two paths, one connected to the primary product DMC outlet pipeline 17 and the other connected to the inlet of the electronic-grade DMC heavy component removal tower 13. The top of the electronic-grade DMC heavy component removal tower is connected to the inlet of the electronic-grade DMC light component removal tower 14, and the bottom of the electronic-grade DMC heavy component removal tower is connected to the heavy component outlet pipeline 24. The top of the electronic-grade DMC light component removal tower is connected to the inlet of the pressurized DMC distillation column 11, and the bottom of the electronic-grade DMC light component removal tower is connected to the electronic-grade DMC outlet pipeline 25.

[0070] Unless otherwise specified, the distillation column in the apparatus of this invention refers to the distillation column system, including the distillation column body and auxiliary equipment such as the bottom reboiler, the bottom product transfer pump, the top condenser, the top reflux tank, and the top reflux and product transfer pump.

[0071] CO esterification to synthesize dimethyl carbonate.

[0072] Under conditions of 110–150 °C and 0.1–0.6 MPa, the following reaction occurs in the presence of a catalyst:

[0073] CO+2CH3ONO(MN)→C3H6O3(DMC)+2NO

[0074] 2CO+2CH3ONO(MN)→C4H6O4(DMO)+2NO

[0075] 2CO+H2+2CH3ONO(MN)→2HCOOCH3(MF)+2NO

[0076] 2MN + MeOH → DMM + H2O + 2NO

[0077] 4MN→MF+2CH3OH+4NO

[0078] This invention does not limit the catalyst used in the synthesis of dimethyl carbonate by CO esterification, but preferably uses the catalyst and evaluation method disclosed in Chinese Patent CN103901130B.

[0079] Based on the preferred catalyst and evaluation method, the composition of the reactor outlet gas phase is as follows:

[0080] DMC: 12-20%, MF: 1-3%, DMM: 1-4%, DMO: 0.01-0.1%, MeOH: 1-3%, MN+NO: 20-32%, CO: 1-3%, N2 and other components: 40-60%.

[0081] The operation method of the product separation and purification device for CO esterification to dimethyl carbonate described in this invention is as follows:

[0082] 1) The product stream from CO esterification to dimethyl carbonate is cooled and condensed before entering the pre-separation tower 2 for pre-separation. The bottom weight of the pre-separation tower 2 is sent to the wastewater DMC recovery tower 4 to recover DMC product from the wastewater. The liquid side stream after separation in the pre-separation tower 2 is collected and sent to the primary DMC separation tower 3 for separation. DMC product is obtained at the bottom of the primary DMC separation tower after separation. The top stream of the primary DMC separation tower and the top stream after separation in the pre-separation tower are respectively sent to the secondary DMC separation tower 5. The pressure at the top of the pre-separation tower 2 is 0.1-0.5 MPa, the top temperature is 25-70°C, preferably 40-60°C, and the bottom temperature is 120-170°C.

[0083] 2) After DMC and methanol are separated in the secondary DMC separation tower 5, the top stream of the secondary DMC separation tower is sent to the bottom of the methanol absorption tower 6, and the heavy components at the bottom of the secondary DMC separation tower are sent to the pressurized DMC distillation tower 11.

[0084] 3) In methanol absorption tower 6, the stream entering from the bottom of methanol absorption tower 6 is in countercurrent contact with the absorbent entering from the top of methanol absorption tower 6 to carry out the absorption process. The gas coming out from the top of methanol absorption tower is used as circulating gas. The rich absorbent liquid at the bottom of methanol absorption tower is sent to MN desorption tower 7 for desorption. Then, the light component comes out from the top of MN desorption tower as circulating gas. The heavy component at the bottom of MN desorption tower is sent to DMM removal tower 8 for separation. The stream from the top of DMM removal tower after separation enters MF distillation tower 9 for distillation to obtain MF product. The heavy stream from the bottom of MF distillation tower enters DMM distillation tower 10 for distillation to obtain DMM product and recover methanol A. The heavy component at the bottom of DMM removal tower is extracted, or a portion is extracted and the other portion is returned to methanol absorption tower 6.

[0085] 4) The stream entering the pressurized DMC distillation column 11 is further distilled. The light component obtained after distillation in the pressurized DMC distillation column 11 exits from the top of the pressurized DMC distillation column, and the DMC product stream obtained after distillation in the pressurized DMC distillation column 11 exits from the bottom of the pressurized DMC distillation column. The mixed liquid stream obtained after distillation in the pressurized DMC distillation column 11 is collected from the side stream of the pressurized DMC distillation column 11 and then enters the atmospheric DMC distillation column 12 for distillation. The recovered methanol B is obtained from the bottom of the atmospheric DMC distillation column and exits through the recovered methanol B outlet pipeline 23. The stream from the top of the atmospheric DMC distillation column is returned to the pressurized DMC distillation column 11.

[0086] Figure 1 The DMC products obtained from the wastewater DMC recovery tower 4, the DMC products obtained from the primary DMC separation tower 3, and the DMC products obtained from the bottom of the pressurized DMC distillation tower 11 can be exported via the DMC product extraction pipeline 16, or a portion can be exported and the other portion sent to the electronic-grade DMC de-heavy component tower 13. The heavy components at the bottom of the electronic-grade DMC de-heavy component tower are extracted by the heavy components outlet pipeline 24, and the top stream of the electronic-grade DMC de-heavy component tower is sent to the electronic-grade DMC de-light component tower 14. The electronic-grade DMC product obtained from the bottom of the electronic-grade DMC de-light component tower exits via the electronic-grade DMC product outlet pipeline 25, and the top stream of the electronic-grade DMC dehydrogenation tower is returned to the pressurized DMC distillation tower 11.

[0087] The product stream of CO esterification to produce dimethyl carbonate is cooled and condensed to 55-80°C and then enters the pre-separation tower 2 for pre-separation. The cooling and condensation is preferably carried out by a heat exchanger, which exchanges heat with a suitable stream (e.g., the stream entering the reactor).

[0088] The main function of pre-separation column 2 is to separate heavy components (DMC, H2O, DMO, etc.) from the bulk gaseous reactants, and to collect a high-concentration mixture of DMC and methanol via a side stream. The pre-separation column is a distillation column with a side stream, typically equipped with a bottom reboiler, a liquid side stream collector, a top condenser, and a reflux tank.

[0089] The function of the secondary DMC separation tower 5 is to separate the main products (MF, DMC, methanol, DMM) from the reaction product circulating gas, and the gas phase at the top of the tower can be returned to the esterification unit.

[0090] The function of methanol absorption tower 6 is to absorb reaction products such as DMC, MF, DMM, and DMO in the circulating gas into methanol using methanol absorbent.

[0091] The main function of the DMC-methanol separation section is to separate DMC and methanol. It can employ techniques such as pressure swing distillation, extractive distillation, and azeotropic distillation. This invention preferably uses pressure swing distillation. The DMC-methanol separation section includes a pressurized DMC distillation column 11 and an atmospheric pressure DMC distillation column 12.

[0092] The main function of DMM removal column 8 is to separate the reaction products. The main components at the top of the column are MF and DMM, while the main components at the bottom are DMC and methanol. DMM removal column 8 is a distillation column, equipped with a reboiler at the bottom and a condenser and reflux tank at the top.

[0093] The main function of the primary DMC separation tower 3 is to separate the liquid phase outflow from the pre-separation tower 2 into light components and DMC product. The DMC light phase removal tower 3 is a distillation tower, equipped with a reboiler at the bottom and a condenser and reflux tank at the top. The liquid phase outflow from the pre-separation tower 2 enters the DMC light phase removal tower 3. The top product is DMC, methanol, and other light components, while the bottom product is mainly primary grade DMC (≥99.5%), which can be exported as a product or sent to the electronic-grade DMC refining section for final export as electronic-grade DMC.

[0094] Figure 1 As shown, the gas phase from the top reflux tank of pre-separation tower 2 enters the lower feed inlet of methanol absorption tower 6, with two streams serving as absorbents: fresh methanol and a methanol-DMC mixture from the bottom of DMM removal tower 8, from top to bottom. The gas phase from the top of methanol absorption tower 6 is used as circulating gas and enters the compressor for pressurization, while the rich absorbent liquid from the bottom of the tower is sent to the middle feed inlet of MN desorption tower 7.

[0095] The methanol absorption tower 6 is preferably equipped with 1 to 3 intermediate coolers to ensure absorption efficiency. The temperature range of each absorbent and the intermediate cooler in the absorption tower is 0 to 40°C. The preferred temperature range is 5 to 20°C.

[0096] The main function of MN desorption tower 7 is to separate the rich absorbent from the bottom of methanol absorption tower 6 into light components, which are then returned to the circulating gas system. The bottom of the tower contains heavy components, including DMC, methanol, MF, and DMM. MN desorption tower 7 is a distillation tower, equipped with a reboiler at the bottom and a cooler and condenser at the top.

[0097] The main function of MF distillation column 9 is to separate the feed into MF product at the top and a mixture of DMM and methanol at the bottom. MF distillation column 9 is a distillation column, equipped with a reboiler at the bottom and a condenser and reflux tank at the top.

[0098] The top product from the DMM removal column 8 enters the MF distillation column 9. The top product is MF premium grade (≥96%), which can be used directly as a product or sent to the hydrolysis unit. The bottom product is a mixture of DMM and methanol, which is sent to the feed inlet of the DMM distillation column 10.

[0099] The main function of DMM distillation column 10 is to separate the feed into DMM product at the top and methanol at the bottom. DMM distillation column 10 is a distillation column, with a reboiler at the bottom and a condenser and reflux tank at the top.

[0100] The top product of the DMM distillation column 10 is DMM (divided into three product specifications according to concentrations of 85%, 90%, and 99%), which is directly exported as a product; the bottom product is methanol, which can be recycled.

[0101] The main function of the DMC-methanol separation section is to separate DMC and methanol. It can employ techniques such as pressure swing distillation, extractive distillation, and azeotropic distillation. This invention preferably uses pressure swing distillation. The DMC-methanol separation section includes an atmospheric pressure DMC distillation column 12 and a pressurized DMC distillation column 11.

[0102] Both atmospheric pressure DMC distillation column 12 and pressurized DMC distillation column 11 are distillation columns, each equipped with a reboiler, a top condenser, and a reflux tank.

[0103] The main function of the electronic-grade DMC refining section is to refine DMC (≥99.5%) to obtain electronic-grade DMC (≥99.99%). Common technical routes include crystallization and distillation, and this invention prefers distillation.

[0104] The electronic-grade DMC purification section includes an electronic-grade DMC heavy removal tower 13 and an electronic-grade DMC light removal tower 14, both of which are distillation towers. Each tower is equipped with a reboiler, a top condenser, and a reflux tank.

Claims

1. A product separation and purification apparatus for the CO esterification to dimethyl carbonate production, characterized in that: It includes a pre-separation tower, a primary DMC separation tower, a wastewater DMC recovery tower, a secondary DMC separation tower, a methanol absorption tower, an MN desorption tower, a DMM removal tower, an MF distillation tower, a DMM distillation tower, a pressurized DMC distillation tower, and an atmospheric pressure DMC distillation tower, wherein the dimethyl carbonate synthesis product feed pipeline is connected to the inlet of the pre-separation tower; The bottom outlet of the pre-separation tower is connected to the inlet of the wastewater DMC recovery tower, and the bottom outlet of the wastewater DMC recovery tower is connected to the wastewater extraction pipeline. The pre-separation tower has a side outlet, which is connected to the inlet of the primary DMC separation tower. The top outlet of the pre-separation tower and the top outlet of the primary DMC separation tower are respectively connected to the inlet of the secondary DMC separation tower. The top outlet of the wastewater DMC recovery tower and the bottom outlet of the primary DMC separation tower are respectively connected to the DMC product extraction pipeline. The top outlet of the secondary DMC separation tower is connected to the bottom feed inlet of the methanol absorption tower, and the bottom outlet of the secondary DMC separation tower is connected to the inlet of the pressurized DMC distillation tower. The methanol absorption tower is equipped with an absorbent inlet at the top. The top outlet of the methanol absorption tower is connected to the circulating gas extraction pipeline. The bottom outlet of the methanol absorption tower is connected to the inlet of the MN desorption tower. The top outlet of the MN desorption tower is connected to the circulating gas extraction pipeline. The bottom outlet of the MN desorption tower is connected to the inlet of the DMM stripping tower. The top outlet of the DMM stripping tower is connected to the feed inlet of the MF distillation tower. The bottom outlet of the DMM stripping tower is connected to the alcohol-containing wastewater extraction pipeline, or it can be connected to both the alcohol-containing wastewater extraction pipeline and the absorbent inlet at the top of the methanol absorption tower. The top outlet of the MF distillation tower is connected to the MF product extraction pipeline. The bottom outlet of the MF distillation tower is connected to the inlet of the DMM distillation tower. The top outlet of the DMM distillation tower is connected to the DMM product extraction pipeline. The bottom outlet of the DMM distillation tower is connected to the methanol recovery A outlet pipeline. The pressurized DMC distillation column has a light component outlet at the top, a DMC product extraction pipeline at the bottom outlet, a side outlet at the side line that connects to the inlet of the atmospheric DMC distillation column, an upper outlet at the atmospheric DMC distillation column that connects to the inlet of the pressurized DMC distillation column, and a methanol recovery B outlet at the bottom of the atmospheric DMC distillation column.

2. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 1, characterized in that: The CO esterification to dimethyl carbonate product separation and purification device further includes an electronic-grade DMC heavy component removal tower and an electronic-grade DMC light component removal tower. The DMC product extraction pipeline is divided into two branches: one branch is connected to the primary DMC outlet pipeline, and the other branch is connected to the inlet of the electronic-grade DMC heavy component removal tower. The top outlet of the electronic-grade DMC heavy component removal tower is connected to the inlet of the electronic-grade DMC light component removal tower, and the bottom outlet of the electronic-grade DMC heavy component removal tower is connected to the heavy component outlet pipeline. The top outlet of the electronic-grade DMC light component removal tower is connected to the inlet of the pressurized DMC distillation column, and the bottom outlet of the electronic-grade DMC light component removal tower is connected to the electronic-grade DMC outlet pipeline.

3. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 1, characterized in that: The methanol absorption tower is equipped with one or more absorbent inlets at the top.

4. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 3, characterized in that: The methanol absorption tower has three absorbent inlets arranged sequentially from top to bottom at its upper part.

5. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 1, characterized in that: The bottom outlet of the DMM removal tower is connected to the alcohol-containing wastewater extraction pipeline and the upper absorbent inlet of the methanol absorption tower, respectively.

6. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 2, characterized in that: The pre-separation tower, primary DMC separation tower, wastewater DMC recovery tower, secondary DMC separation tower, methanol absorption tower, MN desorption tower, DMM removal tower, MF distillation tower, DMM distillation tower, pressurized DMC distillation tower, atmospheric pressure DMC distillation tower, electronic grade DMC heavy removal tower, and electronic grade DMC light removal tower are all packed towers, plate towers, or composite towers of packed and plate towers.

7. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 6, characterized in that: The pre-separation tower is equipped with 90-150 theoretical plates. The side sample outlet of the pre-separation tower is located 10-30 theoretical plates away from the top of the pre-separation tower. The primary DMC separation tower is equipped with 30-50 theoretical plates. The wastewater DMC recovery tower is equipped with 90-150 theoretical plates. The secondary DMC separation tower is equipped with 20-60 theoretical plates. The methanol absorption tower is equipped with 10-40 theoretical plates. The MN desorption tower is equipped with 30-75 theoretical plates. The DMM removal tower is equipped with 35-65 theoretical plates. The theoretical plates are set as follows: MF distillation column has 40-70 theoretical plates, DMM distillation column has 40-70 theoretical plates, pressurized DMC distillation column has 60-100 theoretical plates, atmospheric DMC distillation column has 60-90 theoretical plates, electronic grade DMC de-heavy column has 70-120 theoretical plates, electronic grade DMC de-light column has 30-50 theoretical plates, and the side stream of pressurized DMC distillation column is located 5-20 theoretical plates away from the top of the pressurized DMC distillation column.

8. The product separation and purification apparatus for CO esterification to dimethyl carbonate according to claim 7, characterized in that: The side feed point of the pre-separation tower is located 15-25 theoretical plates from the top of the pre-separation tower. The primary DMC separation tower has 35-45 theoretical plates, the wastewater DMC recovery tower has 110-130 theoretical plates, the secondary DMC separation tower has 25-45 theoretical plates, the methanol absorption tower has 20-30 theoretical plates, the MN desorption tower has 50-60 theoretical plates, the DMM removal tower has 45-55 theoretical plates, the MF distillation tower has 50-65 theoretical plates, the DMM distillation tower has 50-65 theoretical plates, the pressurized DMC distillation tower has 75-85 theoretical plates, the atmospheric pressure DMC distillation tower has 65-80 theoretical plates, the electronic-grade DMC heavy removal tower has 85-110 theoretical plates, the electronic-grade DMC light removal tower has 35-45 theoretical plates, and the side feed point of the pressurized DMC distillation tower is located 8-12 theoretical plates from the top of the pressurized DMC distillation tower.

9. A process for separating and purifying the product of CO esterification to dimethyl carbonate as described in claim 1, characterized in that... Includes the following steps: 1) The product stream from CO esterification to dimethyl carbonate is cooled and condensed before entering a pre-separation tower for pre-separation. The bottom heavy phase after separation in the pre-separation tower is sent to a wastewater DMC recovery tower to recover DMC product from the wastewater. The liquid side stream after separation in the pre-separation tower is collected and sent to a primary DMC separation tower for separation. DMC product is obtained at the bottom of the primary DMC separation tower after separation. The top stream of the primary DMC separation tower and the top stream after separation in the pre-separation tower are respectively sent to a secondary DMC separation tower. The pressure at the top of the pre-separation tower is 0.1-0.5 MPa, the temperature at the top is 25-70°C, and the temperature at the bottom is 120-170°C. 2) After DMC and methanol are separated in the secondary DMC separation tower, the top stream of the secondary DMC separation tower is sent to the bottom of the methanol absorption tower, and the heavy components at the bottom of the secondary DMC separation tower are sent to the pressurized DMC distillation tower. 3) In the methanol absorption tower, the stream entering from the bottom of the methanol absorption tower comes into countercurrent contact with the absorbent entering from the top of the methanol absorption tower for absorption. The gas coming out from the top of the methanol absorption tower is used as the circulating gas. The rich absorbent liquid at the bottom of the methanol absorption tower is sent to the MN desorption tower for desorption. Then, the light component comes out from the top of the MN desorption tower as the circulating gas. The heavy component at the bottom of the MN desorption tower is sent to the DMM removal tower for separation. The stream from the top of the DMM removal tower after separation enters the MF distillation tower for distillation to obtain the MF product. The heavy stream from the bottom of the MF distillation tower enters the DMM distillation tower for distillation to obtain the DMM product and recover methanol A. The heavy component at the bottom of the DMM removal tower is extracted, or a portion is extracted and the other portion is returned to the methanol absorption tower. 4) The stream entering the pressurized DMC distillation column is further distilled. The light component obtained after distillation in the pressurized DMC distillation column exits from the top of the pressurized DMC distillation column, and the DMC product stream obtained after distillation in the pressurized DMC distillation column exits from the bottom of the pressurized DMC distillation column. The mixed liquid stream obtained after distillation in the pressurized DMC distillation column is collected from the side stream of the pressurized DMC distillation column and then enters the atmospheric DMC distillation column for distillation. The recovered methanol B is obtained from the bottom of the atmospheric DMC distillation column, and the top stream of the atmospheric DMC distillation column is returned to the pressurized DMC distillation column.

10. The process according to claim 9, characterized in that: The DMC products obtained from the wastewater DMC recovery tower, the DMC products obtained from the primary DMC separation tower, and the DMC products obtained from the bottom of the pressurized DMC distillation tower are exported as products, or partly exported as products and the other part sent to the electronic-grade DMC de-heavy component tower. The heavy components are extracted from the bottom of the electronic-grade DMC de-heavy component tower, and the top stream of the electronic-grade DMC de-heavy component tower is sent to the electronic-grade DMC de-light component tower. Electronic-grade DMC products are obtained from the bottom of the electronic-grade DMC de-light component tower, and the top stream of the electronic-grade DMC de-light component tower is returned to the pressurized DMC distillation tower.

11. The process according to claim 10, characterized in that: The pre-separation column has a top temperature of 40–60°C; the first-stage DMC separation column has a top temperature of 100–150°C, a top pressure of 0.1–0.8 MPa, and a bottom temperature of 145–170°C; the wastewater DMC recovery column has a top pressure of 0.05–0.12 MPa, a top temperature of 95–135°C, and a bottom temperature of 110–150°C; the second-stage DMC separation column has a top pressure of 0.08–0.4 MPa, a top temperature of -15–25°C, and a bottom temperature of 60–120°C; the methanol absorption column has a top temperature of -5–10°C and a bottom temperature of -15–0°C; the MN desorption column has a top temperature of 0–25°C and a bottom temperature of 100–130°C; the DMM removal column has a top pressure of 0.07–0.2 MPa, a top temperature of 35–75°C, and a bottom temperature of 70–110°C; and the MF distillation column has a top pressure of 0.0… 7~0.2MPa, top temperature 35~70℃, bottom temperature 50~85℃; DMM distillation column top pressure 0.06~0.14MPa, top temperature 35~70℃, bottom temperature 50~85℃; pressurized DMC distillation column top pressure 1.0~1.5MPa, top temperature 120~160℃, bottom temperature 170~210℃; atmospheric pressure DMC distillation column top pressure 0.06~0.15MPa, top temperature 65~90℃, bottom temperature 70~100℃; electronic grade DMC deweighting column top pressure 0.06~0.15MPa, top temperature 95~120℃, bottom temperature 105~140℃; electronic grade DMC delighting column top pressure 0.06~0.15MPa, top temperature 80~120℃, bottom temperature 105~140℃.

12. The process according to claim 11, characterized in that: The primary DMC separation column has a top temperature of 110–140℃, a top pressure of 0.3–0.6 MPa, and a bottom temperature of 150–165℃; the wastewater DMC recovery column has a top pressure of 0.75–0.10 MPa, a top temperature of 100–130℃, and a bottom temperature of 115–140℃; the secondary DMC separation column has a top pressure of 0.1–0.3 MPa, a top temperature of -10 to 10℃, and a bottom temperature of 70–110℃; the MN desorption column has a top temperature of 10–20℃ and a bottom temperature of 105–120℃; the DMM removal column has a top pressure of 0.08–0.13 MPa, a top temperature of 40–65℃, and a bottom temperature of 80–100℃; and the MF distillation column has a top pressure of 0.08–0.13 MPa and a top temperature of 40–60℃. The pressure at the top of the DMC distillation column is 0.07–0.13 MPa, the top temperature is 40–60℃, and the bottom temperature is 55–80℃; the pressure at the top of the pressurized DMC distillation column is 1.1–1.3 MPa, the top temperature is 130–150℃, and the bottom temperature is 185–200℃; the pressure at the top of the atmospheric DMC distillation column is 0.0–0.10 MPa, the top temperature is 70–85℃, and the bottom temperature is 75–95℃; the pressure at the top of the electronic grade DMC deweighting column is 0.07–0.10 MPa, the top temperature is 100–115℃, and the bottom temperature is 110–130℃; the pressure at the top of the electronic grade DMC delighting column is 0.07–0.10 MPa, the top temperature is 90–115℃, and the bottom temperature is 110–130℃.

13. The process according to claim 9, characterized in that: The product stream of CO esterification to produce dimethyl carbonate is cooled and condensed to 55-80°C before entering a pre-separation tower for pre-separation.

14. The process according to claim 9, characterized in that: The methanol absorption tower has one or more streams as absorbent.

15. The process according to claim 14, characterized in that: The methanol absorption tower has three streams as absorbents. From top to bottom along the methanol absorption tower, they are fresh methanol, methanol recovered from the product separation and purification unit for CO esterification to dimethyl carbonate, and a mixture containing methanol and DMC from the bottom of the DMM removal tower.

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