阅读说明：本技术 一种无氯催化合成碳酸二甲酯产物的预分离工艺 (Pre-separation process for synthesizing dimethyl carbonate product by chlorine-free catalysis ) 是由 郑华艳 李忠 王玉春 周龙 张国强 于 2020-04-16 设计创作，主要内容包括：本发明公开了一种涉及原料为无氯催化甲醇氧化羰基化合成DMC的混合产物的产品预分离工艺,所述产品预分离工艺设置至少两个温度水平的产物混合气冷凝换热工序及相应数量的气液分离设备；针对不同的液相冷凝液,所述产品预分离工艺配套不同的精制工艺。与现有技术相比,本发明所述的产品预分离工艺操作灵活。工艺针对性强,且与全凝工艺相比节能效果显著。(The invention discloses a product pre-separation process for synthesizing DMC (dimethyl formamide) by oxidizing and carbonylating methanol under the catalysis of chlorine-free catalyst, which comprises at least two product mixed gas condensation heat exchange processes with temperature levels and corresponding gas-liquid separation equipment; aiming at different liquid phase condensate liquids, the product pre-separation process is matched with different refining processes. Compared with the prior art, the product pre-separation process is flexible to operate. The process has strong pertinence and obvious energy-saving effect compared with the full condensation process.)

1. A product pre-separation process, the raw material is the mixed product of methanol oxidation carbonylation synthesis DMC without chlorine catalysis, characterized by that, the said product pre-separation process sets up the product gas mixture condensation heat exchange process of at least two temperature levels and corresponding amount of gas-liquid separation equipment, wherein the temperature range of the condensation heat exchange process of the first temperature level is 60 duC-80 duC, the temperature range of the condensation heat exchange process of the second temperature level is 30 duC-40 duC; and setting a corresponding refining process according to the composition of the liquid phase condensate product.

2. The product preseparation process according to claim 1, characterized in that it comprises the following processes:

mixing fresh methanol with distilled and recovered methanol to obtain a methanol mixed solution;

after the methanol mixed solution and the raw material mixed gas react, the reaction product is subjected to heat exchange and temperature reduction through a primary gas-gas heat exchanger;

the reaction product after the heat exchange and temperature reduction of the primary gas-gas heat exchanger is subjected to temperature reduction treatment and gas-liquid separation by the primary gas-liquid heat exchanger to obtain a first gas-phase mixture and a first liquid-phase mixture;

the first gas-phase mixture exchanges heat with the raw material gas and is cooled in a secondary gas-gas heat exchanger, then the first gas-phase mixture is further cooled through the secondary gas-liquid heat exchanger, and then the first gas-phase mixture is separated through a secondary gas-liquid separator to obtain a second gas-phase mixture and a second liquid-phase mixture;

a process of discharging a portion of the second gas phase mixture as purge gas;

the first liquid phase mixture is subjected to a stripping process to recover organic matters;

the second liquid phase mixture is further separated and purified by a rectification process;

and fresh O₂And mixing the CO with the rest of the second gas-phase mixture, compressing and pressurizing, and then exchanging heat with the product gas mixture.

3. The product pre-separation process of claim 2, wherein the product pre-separation process is provided with two temperature levels of product gas mixture condensation heat exchange procedures, and the product pre-separation process comprises 2 gas-gas heat exchangers, 2 gas-liquid separators, 1 raw gas mixing tank and 1 circulating gas compressor.

4. The product preseparation process of claim 3, characterized in that it comprises the following processes:

a. the mixed solution of fresh methanol from a raw material storage tank and distilled and recovered methanol enters from the upper part of the reactor (1), the raw material mixed gas from a circulating gas compressor (9) enters from the lower part of the reactor (1), and the fresh methanol and the distilled and recovered methanol are in countercurrent contact in the reactor (1) to react; the reaction product is discharged from the top of the reactor (1) in the form of gas phase mixture, enters a first-stage gas-gas heat exchanger (2) for heat exchange and temperature reduction, and the reaction residue is discharged from the bottom of the reactor (1) intermittently;

b. the reaction product after heat exchange and temperature reduction by the primary gas-gas heat exchanger (2) is sequentially cooled to a first temperature level of 60-80 ℃ by the primary gas-gas heat exchanger (3), then enters a primary gas-liquid separator (4), and is subjected to gas-liquid separation to obtain a first gas-phase mixture and a first liquid-phase mixture; wherein the first gas-phase mixture is sent to a secondary gas-gas heat exchanger (5), and the first liquid-phase mixture is sent to a stripping process to recover organic matters;

c. the first gas-phase mixture exchanges heat with the raw material gas and is cooled in a secondary gas-gas heat exchanger (5), the mixed gas is cooled to a second temperature level of 30-40 ℃ through a secondary gas-liquid heat exchanger (6), and then the mixed gas enters a secondary gas-liquid separator (7); after gas-liquid separation, one part of the second gas-phase mixture is used as purge gas to be emptied, the other part of the second gas-phase mixture returns to the raw material gas mixing tank (8), and the second liquid-phase mixture is subjected to rectification process for further separation;

d. fresh O₂And the CO enters a raw material gas mixing tank (8) to be mixed with a second gas-phase mixture returned after gas-liquid separation, and then enters a circulating gas compressor (9) for compression and pressurization, and then enters a reactor (1) after heat exchange through a secondary gas-gas heat exchanger (5) and a primary gas-gas heat exchanger (2) in sequence.

5. The product preseparation process according to claim 4, characterized in that the reactor (1) is operated at a temperature of 110 ℃ to 140 ℃ and a reaction pressure of 2.5MPa to 3.5 MPa.

6. The product preseparation process of claim 4, wherein the components of the first liquid-phase mixture are primarily water and small amounts of organics.

7. The product preseparation process according to claim 4, characterized in that the components of the second liquid-phase mixture are mainly methanol, DMC and small amounts of water, DMM and MF.

8. The product preseparation process of claim 4, wherein said fresh O₂And the CO enters a raw material gas mixing tank (8) to be mixed with the rest second gas-phase mixture, and then the mixture is sent to a compressor (9) to be compressed and pressurized to 2.5-3.5 MPa.

Technical Field

The invention belongs to the technical field of separation of water-containing gas phase mixture products, and particularly relates to a product pre-separation process for synthesizing dimethyl carbonate by oxidative carbonylation of methanol under the catalysis of chlorine-free catalyst.

Background

Dimethyl carbonate (DMC) is a green fine chemical. The non-toxic solvent can be widely applied to the coating industry, can be used as a solvent of lithium battery electrolyte, can replace phosgene to be used as a carbonylation reagent, and can also replace methyl tert-butyl ether (MTBE) to be used as an oil additive.

Methods for synthesizing DMC include phosgene method, ester exchange method, methyl nitrite carbonylation method, methanol oxidation carbonylation method, urea alcoholysis method, direct methanol and carbon dioxide synthesis method, etc., wherein the phosgene method, ester exchange method, methyl nitrite carbonylation method, methanol oxidation carbonylation method, etc. have been industrialized. The phosgene method is eliminated at present due to the use of highly toxic raw materials, strong corrosivity of byproducts, serious environmental pollution in the production process and the like. The ester exchange method is the main process of DMC production in China at present, but the raw material propylene oxide is greatly influenced by petroleum price, and meanwhile, the price of the byproduct propylene glycol is not high, so that the process economic benefit is low. Methyl nitrite carbonylation was first developed by UBE corporation, and the starting materials NO and methyl nitrite are hazardous chemicals and the catalysts used have a short life. The synthesis of DMC by liquid-phase oxidative carbonylation, which was originally developed and commercialized by Enichem, Italy, using CuCl or CuCl as the catalyst₂However, loss of chloride ion is likely to cause problems such as catalyst deactivation and serious corrosion of equipment. The methanol oxidation carbonylation method adopting the chlorine-free catalyst has the advantages of cheap and easily obtained raw materials, low toxicity, low cost and the like, and becomes a method with great prospect for DMC production.

The industrial process for producing dimethyl carbonate by methanol oxidation and carbonylation all uses chlorine-containing catalyst, and its raw materials are CO and O₂The methanol and product pre-separation process basically adopts a full condensation process. The production process comprises the steps of enabling a raw material mixed gas from a circulating gas compressor to exchange heat with a product mixed gas through a two-stage heat exchanger, heating the product mixed gas, enabling the product mixed gas to enter a reactor from the lower part, enabling liquid-phase methanol to enter the reactor from the upper part, and reacting DMC, methanol, water, Methyl Formate (MF), methylal (DMM), CO and CO₂Trace amount of O₂The mixture escapes from the top of the reactor in the form of gas phase mixture, and then is sequentially subjected to multiple heat exchanges to be reduced to the lowest temperature, first-stage gas-liquid separation and circulationThe main processes of ring gas compression, rectification and the like are used for finishing the production of the product. When the gas phase mixture is initially cooled, the components allowed by gas-liquid equilibrium are recovered in the form of mixture by adopting a full-component (for DMC, methanol, water, DMM and MF) condensation process (namely, a full-condensation process), and then the product DMC is obtained by rectifying and separating the liquid phase mixture. The adoption of the total condensation process has the defects of unreasonable energy utilization and higher energy consumption; the process control flexibility is low; after all materials are completely condensed, a new separation process needs to be designed to separate and purify the mixture again, so that the separation difficulty is increased.

Disclosure of Invention

The invention aims to provide a DMC mixed product pre-separation process with simple process, high recovery rate and low energy consumption aiming at the property and the extraction mode of a reaction mixture on the basis of researching the process for producing DMC by a chlorine-free catalysis method.

The invention designs a continuous separation process, which takes a mixed product of methanol oxidative carbonylation to synthesize DMC as a raw material, and changes most of water in a gas-phase mixture into a liquid phase after primary partial condensation through a combined process of primary partial condensation (or primary fractional condensation) and secondary total condensation (or secondary total condensation), thereby realizing the removal of water in the gas-phase mixture.

The first-stage partial condensation process is that a product mixed gas is cooled at a first temperature level and then subjected to gas-liquid separation, only most of water and a small amount of organic components are condensed at the temperature level to obtain a first liquid phase mixture and a first gas phase mixture, wherein the first liquid phase mixture is used as a stripping tower raw material to strip and recover low-boiling-point organic matters; the first gas phase mixture is further cooled.

The two-stage total condensation process according to the invention means that the first gas-phase mixture obtained at the first temperature level is further cooled to a second temperature level at which a substantial part of the methanol, DMC, traces of water and other organic constituents are condensed. And carrying out gas-liquid separation to obtain a second liquid phase mixture and a second gas phase mixture. Wherein the second liquid phase mixture is rectified and separated to obtain a product DMC; the second gas phase mixture is sent to other devices.

The invention adopts the following technical scheme for realizing the purpose:

a product pre-separation process, the raw material is the mixed product of methanol oxidation carbonylation synthesis DMC without chlorine catalysis, characterized by that, the said product pre-separation process sets up the product gas mixture condensation heat exchange process of at least two temperature levels and corresponding amount of gas-liquid separation equipment, wherein the temperature range of the condensation heat exchange process of the first temperature level is 60 duC-80 duC, the temperature range of the condensation heat exchange process of the second temperature level is 30 duC-40 duC; and setting a corresponding refining process according to the composition of the liquid phase condensate product.

Further, the product pre-separation process comprises the following steps:

mixing fresh methanol with distilled and recovered methanol to obtain a methanol mixed solution;

after the methanol mixed solution and the raw material mixed gas react, the reaction product is subjected to heat exchange and temperature reduction through a primary gas-gas heat exchanger;

the reaction product after the heat exchange and temperature reduction of the primary gas-gas heat exchanger is subjected to temperature reduction treatment and gas-liquid separation by the primary gas-liquid heat exchanger to obtain a first gas-phase mixture and a first liquid-phase mixture;

the first gas-phase mixture exchanges heat with the raw material gas and is cooled in a secondary gas-gas heat exchanger, then the first gas-phase mixture is further cooled through the secondary gas-liquid heat exchanger, and then the first gas-phase mixture is separated through a secondary gas-liquid separator to obtain a second gas-phase mixture and a second liquid-phase mixture;

a process of partial discharge of the second gas-phase mixture;

the first liquid phase mixture is subjected to a stripping process to recover organic matters;

the second liquid phase mixture is further separated through a rectification process;

and fresh O₂And mixing the CO with the rest of the second gas-phase mixture, compressing and pressurizing, and then exchanging heat with the product gas mixture.

A further preferable technical solution is that the product pre-separation process is provided with two condensation heat exchange procedures of product mixed gas at temperature levels, and the product pre-separation process comprises 2 gas-gas heat exchangers, 2 gas-liquid separators, 1 raw gas mixing tank and 1 circulating gas compressor. The product pre-separation process comprises the following processes:

a. the mixed solution of fresh methanol from a raw material storage tank and methanol recovered by distillation enters from the upper part of the reactor, the mixed gas of raw materials from a circulating gas compressor enters from the lower part of the reactor, and the mixed gas and the raw material gas are in countercurrent contact in the reactor to react; discharging a reaction product in a gas phase mixture form from the top of the reactor, entering a primary gas-gas heat exchanger for heat exchange and temperature reduction, and intermittently discharging reaction residues from the bottom of the reactor;

b. the reaction product after heat exchange and temperature reduction by the primary gas-liquid heat exchanger is sequentially cooled to a first temperature level of 60-80 ℃ by the primary gas-liquid heat exchanger, then enters a primary gas-liquid separator, and is subjected to gas-liquid separation to obtain a first gas-phase mixture and a first liquid-phase mixture; wherein the first gas-phase mixture is sent to a secondary gas-gas heat exchanger, and the first liquid-phase mixture is sent to a stripping process to recover organic matters;

c. the first gas-phase mixture exchanges heat with the raw material gas and is cooled in a secondary gas-liquid heat exchanger, the mixed gas is cooled to a second temperature level of 30-40 ℃ through the secondary gas-liquid heat exchanger, and then the mixed gas enters a secondary gas-liquid separator; after gas-liquid separation, one part of the second gas-phase mixture is used as purge gas to be emptied, the other part of the second gas-phase mixture returns to the raw material gas mixing tank, and the second liquid-phase mixture is subjected to rectification process for further separation;

d. fresh O₂And the CO enters a feed gas mixing tank and is mixed with a second gas-phase mixture returned after gas-liquid separation, then the mixture is sent to a circulating gas compressor for compression and pressurization, and then the mixture enters a reactor after heat exchange through a secondary gas-gas heat exchanger and a primary gas-gas heat exchanger in sequence.

Furthermore, in the technical scheme, the working temperature of the reactor is 110-140 ℃, and the reaction pressure is 2.5-3.5 MPa.

Still further, in the above technical solution, the components of the first liquid-phase mixture are mainly water and a small amount of organic matter.

Still further, in the above technical solution, the components of the second liquid-phase mixture are mainly methanol, DMC and a small amount of water, DMM and MF.

Still further, in the above technical solution, the fresh O₂And the CO enters a feed gas mixing tank to be mixed with part of the second gas-phase mixture, and then the mixture is compressed by a compressor and pressurized to 2.5-3.5 MPa.

The invention discloses a pre-separation process for synthesizing DMC (dimethyl formamide) by oxidizing and carbonylating methanol under the catalysis of chlorine-free catalysis, which adopts a partial condensation process, namely, the load of a subsequent rectification section is reduced by controlling the condensation temperature for fractional condensation and then refining the mixture obtained by fractional condensation, thereby achieving the purpose of saving energy.

Compared with the prior art, the invention has the following advantages:

1) two condensation heat exchange processes with two temperature levels and corresponding gas-liquid separation equipment are arranged, so that the operation is flexible;

2) the gas phase mixture is subjected to a fractional condensation process to obtain two liquid phase products. The components of the first liquid phase mixture are mainly water and a small amount of organic matters, the mixture is used as a raw material of the stripping tower, and after the organic matters in the mixture are recovered, the waste water can reach the direct discharge standard. The components of the second liquid-phase mixture are mainly methanol, DMC and small amounts of water, DMM and MF, which mixture is refined by a rectification process. Different refining processes are matched for different liquid phase condensate liquids, so that the process has more pertinence;

3) when the same amount of rectification equipment is used, the total condensation process produces a liquid mixture whose components are mainly methanol, DMC, more water, DMM and MF. Because of the high water content, the process of rectifying and recovering the methanol needs to provide more heat. And the second liquid-phase mixture obtained by the fractional condensation process needs to provide less heat in the rectification and recovery of the methanol, and the fractional condensation process saves about 15 percent of energy compared with the full condensation process.

Drawings

Fig. 1 is a schematic diagram illustrating a process flow of a product pre-separation process according to the present invention, taking a product pre-separation process comprising 2 gas-gas heat exchangers, 2 gas-liquid separators, 1 raw gas mixing tank, and 1 recycle gas compressor as an example.

In the figure: 1-a reactor, 2-a first-stage gas-gas heat exchanger, 3-a first-stage gas-liquid heat exchanger, 4-a first-stage gas-liquid separator, 5-a second-stage gas-gas heat exchanger, 6-a second-stage gas-liquid heat exchanger, 7-a second-stage gas-liquid separator, 8-a raw gas mixing tank and 9-a circulating gas compressor.

Detailed description of the preferred embodiments