阅读说明：本技术 含草酸二甲酯的混合物流的处理方法及处理系统与应用 (Treatment method, treatment system and application of mixed material flow containing dimethyl oxalate ) 是由 杨卫胜 施德 贺来宾 于 2019-10-22 设计创作，主要内容包括：本发明提供含草酸二甲酯的混合物流的处理方法和处理系统与应用,主要解决现有技术中存在的采出含重组分草酸二甲酯量大、处理困难的问题,所述处理方法包括将所述混合物流进行草酸二甲酯精馏,侧线液相采出草酸二甲酯产品,塔釜采出含重组分的草酸二甲酯物流送入脱羰反应系统,在所述脱羰反应系统中得到包括碳酸二甲酯、CO和副产CO-2、副产二甲醚的物流；其中,进行草酸二甲酯精馏时,将生成的CO循环回偶联单元进一步回收的技术方案较好地解决了该问题,可用于合成气制乙二醇过程草酸二甲酯处理。(The invention provides a treatment method, a treatment system and application of a mixture flow containing dimethyl oxalate, which mainly solve the problems of large amount of dimethyl oxalate containing heavy components and difficult treatment in the prior artDimethyl carbonate, CO and CO byproduct 2 And a byproduct stream of dimethyl ether; wherein, when rectifying dimethyl oxalate, the technical proposal of recycling the generated CO to the coupling unit for further recovery better solves the problem and can be used for processing dimethyl oxalate in the process of preparing ethylene glycol from synthesis gas.)

1. a method of treating a mixed stream containing dimethyl oxalate comprising: rectifying the mixed material flow by dimethyl oxalate, taking out dimethyl oxalate material flow containing heavy components and sending the dimethyl oxalate material flow into a decarbonylation reaction system to obtain dimethyl carbonate, CO and byproduct CO₂And a byproduct stream of dimethyl ether.

2. The process of claim 1, wherein said rectifying dimethyl oxalate comprises introducing said mixed stream comprising dimethyl oxalate into a dimethyl oxalate rectification column, wherein,

a side-stream liquid phase is adopted to obtain a dimethyl oxalate product, preferably from a side-stream liquid phase of a rectifying section; and/or

Dimethyl oxalate material flow containing heavy components is extracted from the tower bottom and sent to the decarbonylation reaction system; and/or

And (3) collecting dimethyl oxalate containing light components from the tower top, and recycling the dimethyl oxalate, wherein the light components comprise dimethyl carbonate.

3. The processing method according to claim 2,

the tower kettle extraction proportion of the dimethyl oxalate rectifying tower is 0.01-20%, and preferably 0.5-10%; and/or

The operating pressure of the rectifying tower is-0.1-1 MPaG, and the temperature is 70-250 ℃; preferably, the operating pressure of the rectifying tower is-0.05-0.1 MPaG, and the temperature is 138-190 ℃.

4. The treatment method according to claim 1, wherein an alkaline earth metal compound catalyst is arranged in the decarbonylation reaction system, preferably, the reaction temperature in the decarbonylation reaction system is 100-300 ℃,the weight airspeed of the material flow is 0.1-10 h^-1。

5. The treatment method as claimed in claim 2, wherein the dimethyl oxalate stream containing heavy components extracted from the bottom of the dimethyl oxalate rectifying tower is subjected to heating gasification treatment, then the heavy components are removed, and then the stream is sent to the decarbonylation reaction system;

preferably, gas-solid phase reaction or gas-liquid-solid three-phase reaction, preferably gas-solid phase reaction, is carried out in the decarbonylation reaction system.

6. The treatment method according to any one of claims 1 to 5, wherein the stream treated by the decarbonylation reaction system is subjected to dimethyl carbonate recovery; preferably, the stream is sent to a dimethyl carbonate recovery tower, and a crude dimethyl carbonate liquid phase product and a crude CO gas phase product are extracted from the top of the dimethyl carbonate recovery tower, and more preferably, the crude dimethyl carbonate liquid phase product comprises dimethyl carbonate and dissolved CO and CO₂Dimethyl ether, wherein CO and CO₂The total weight content of dimethyl ether is 0.01-0.5%, and the crude CO gas-phase product comprises CO, dimethyl carbonate and CO₂Dimethyl ether, wherein dimethyl carbonate and CO₂The total molar content of dimethyl ether is 0.1 to 20%, preferably 0.1 to 10%.

7. The process of claim 6, wherein the crude CO gas phase product is recycled back to the coupling unit for the production of gaseous ethylene glycol;

preferably, the crude CO gas phase product is stripped of its CO with methanol₂And dimethyl ether to obtain a CO product, and then recycling the CO product to a coupling unit for preparing ethylene glycol from gas.

8. A treatment system of a mixture flow containing dimethyl oxalate, which is used for carrying out the treatment method of any one of claims 1 to 7, wherein the treatment system comprises a dimethyl oxalate rectifying tower, a decarbonylation reaction system and a dimethyl carbonate recovery tower which are connected in sequence.

9. The processing system of claim 8,

a protective bed is arranged between the tower kettle of the dimethyl oxalate rectifying tower and the decarbonylation reaction system and is used for removing heavy components in materials in the tower kettle of the dimethyl oxalate rectifying tower, preferably, more than two protective beds are arranged, one protective bed is in a working state, and the other protective beds are in a standby state; more preferably, inert alumina ceramic balls are filled in the protective bed; and/or

A side line extraction position is arranged at the rectifying section of the dimethyl oxalate rectifying tower and is used for extracting a dimethyl oxalate product from a side line liquid phase; and/or

The decarbonylation reaction system comprises a fixed bed reactor, preferably comprises a fixed bed reactor with a heating device, more preferably comprises a tubular fixed bed reactor, and the shell side is heated by saturated steam.

10. Use of the treatment method according to any one of claims 1 to 7 or the treatment system according to any one of claims 8 to 9 in the treatment of dimethyl oxalate in a process of preparing ethylene glycol from syngas, preferably, the mixture stream containing dimethyl oxalate is a mixture stream separated by a coupling unit in a process of preparing ethylene glycol from syngas.

Technical Field

The invention relates to treatment of dimethyl oxalate, in particular to a treatment method, a treatment system and application of a mixture flow containing dimethyl oxalate, and particularly relates to treatment of dimethyl oxalate separated in a process of preparing ethylene glycol from synthesis gas.

Background

Dimethyl oxalate is an important organic chemical raw material, can be used for producing various dyes, solvents, extracting agents and various intermediates, and is widely applied to fine chemical engineering. In addition, the dimethyl oxalate can be used for preparing the ethylene glycol through hydrogenation reaction, and the method is a new large-scale industrialized ethylene glycol synthesis process route. Ethylene glycol has long been prepared mainly by petroleum routes, and is relatively high in cost.

The traditional dimethyl oxalate synthesis process is prepared by heating and esterifying oxalic acid and alcohols in a toluene solvent, and the method has the advantages of high production cost, large energy consumption, large wastewater discharge and serious pollution. The d.f. fenton research of united states oil company in the last sixties of the century found that carbon monoxide, alcohol and oxygen can be directly synthesized into dialkyl oxalate through oxidative hydroxylation. After several generations of scientific research efforts, the most suitable route for preparing dimethyl oxalate by coupling carbon monoxide is that carbon monoxide and alkyl nitrite are coupled to react to generate dialkyl oxalate and generate nitrogen monoxide, and the nitrogen monoxide is then reacted with methanol and oxygen to regenerate alkyl nitrite, and the reaction equation is as follows:

coupling reaction: 2CO +2RONO → 2NO + (COOR)2 (1)

Esterification reaction: 2ROH +0.5O₂+2NO→2RONO+H₂O (2)

Wherein R represents an alkyl group. The nitric oxide and alkyl nitrite in the route are cyclically regenerated in the system.

After dimethyl oxalate generated by the coupling reaction is absorbed by alcohol, a crude dimethyl oxalate product is usually extracted from a tower kettle after the alcohol and dimethyl carbonate are removed, such as CN203960094U and CN106518675A in the prior art, however, the dimethyl oxalate extracted from the tower kettle usually contains trace metal and catalyst element impurities, mainly comes from slow loss and metal corrosion of a catalyst, and in addition, because a coupling-esterification system is a nitrogen oxide circulating system, a nitrogen-containing compound with high boiling point is inevitably generated, and the dimethyl oxalate finally enters the tower kettle (when R is methyl). Although the content of the impurities is low, the impurities can affect the stability of the hydrogenation system after entering the hydrogenation reaction system. Separation is necessary, but a certain amount of dimethyl oxalate containing heavy components is generally required to be discharged in the separation process, and the treatment is difficult.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention adopts a rectification mode to remove the heavy components, effectively reduces heavy metals, nitrogen-containing compounds and other heavy components in the dimethyl oxalate product, and simultaneously adopts a mode of taking out a liquid phase from the side of a rectification section to effectively separate light components which are possibly generated by decomposition in the process of removing the heavy components from the dimethyl oxalate. The produced high-quality dimethyl oxalate product is used for the process of preparing ethylene glycol by hydrogenation, so that the stability of a hydrogenation reaction system is effectively improved. Simultaneously, decarbonylation treatment is carried out on the discharged dimethyl oxalate material flow containing the heavy components, and the main reaction equation is as follows:

decarbonylation main reaction of dimethyl oxalate: (COOCH)₃)₂→CO+CO(OCH₃)₂ (3)

Decarbonylation side reaction of dimethyl oxalate: (COOCH)₃)₂→CO+CO₂+CH₃OCH₃ (4)

The main reaction generates dimethyl carbonate and carbon monoxide, and the side reaction generates carbon dioxide and dimethyl ether, and the reaction product is sent into a dimethyl carbonate recovery tower and recovered to obtain dimethyl carbonate and CO. The method can be well applied to the treatment of the waste dimethyl oxalate and the co-production of dimethyl carbonate in the process of preparing the ethylene glycol from the synthesis gas.

One of the purposes of the invention is to provide a method for treating a mixed material flow containing dimethyl oxalate, which comprises the steps of rectifying the mixed material flow by dimethyl oxalate, collecting a dimethyl oxalate material flow containing heavy components and sending the dimethyl oxalate material flow into a decarbonylation reaction system to obtain dimethyl carbonate, CO and a byproduct CO₂And a byproduct stream of dimethyl ether.

Wherein the decarbonylation products mainly comprise dimethyl carbonate and CO, and CO is a byproduct₂And the content of by-product dimethyl ether is relatively small.

In a preferred embodiment, the mixed stream comprises dimethyl oxalate, dimethyl carbonate and heavies, preferably the heavies comprise nitrogen-containing compounds and heavy metals.

In a further preferred embodiment, the mixed stream is a stream containing dimethyl oxalate separated from a coupling unit in a process of preparing ethylene glycol from synthesis gas.

In a preferred embodiment, the nitrogen-containing compound is contained in an amount of 0 to 500ppm (in terms of nitrogen element) and the heavy metal is contained in an amount of 0 to 100ppm, based on the total weight of the mixed stream.

In a preferred embodiment, the content of dimethyl oxalate is 99.0-99.99% and the content of dimethyl carbonate is 0-1% based on 100% of the mixture flow.

In a further preferred embodiment, the content of dimethyl oxalate is more than 99.8% and the content of methyl carbonate is less than 0.2% based on 100% of the mixture flow.

In a preferred embodiment, the dimethyl oxalate rectification comprises introducing the mixed material flow containing dimethyl oxalate into a dimethyl oxalate rectification tower, and taking out a dimethyl oxalate material flow containing heavy components from the tower bottom and sending the dimethyl oxalate material flow into the decarbonylation reaction system, wherein preferably, the taking-out proportion from the tower bottom is 0.01-20%, and more preferably 0.5-10%.

Wherein, because the dimethyl oxalate in the tower bottom contains heavy metal and other heavy components and is easy to decompose under the high-temperature condition, the quality of the dimethyl oxalate product extracted from the tower bottom is improved. The large amount of the extracted tower bottom material flow can be further treated (decarbonylation reaction is carried out to co-produce dimethyl carbonate) without increasing material consumption, so the invention can increase the discharge ratio of the tower bottom to 20 percent to improve the quality of dimethyl oxalate.

In a further preferred embodiment, dimethyl oxalate containing light components is extracted from the top of the dimethyl oxalate rectifying tower and recycled, wherein the light components comprise dimethyl carbonate.

Wherein, the mixed material flow contains a very small amount of dimethyl carbonate, and meanwhile, dimethyl oxalate is easy to decompose to generate dimethyl carbonate, CO and the like in the rectification process under the high-temperature condition, and the mixed material flow is led out from the top of the tower to form a circulating material flow in the rectification process. Wherein, the non-condensable gas at the tower top is absorbed by methanol and then is discharged to a torch or is recycled to the system.

In a further preferred embodiment, the dimethyl oxalate product is withdrawn in a side stream from a dimethyl oxalate rectification column, preferably from a rectification section (above the feed inlet) side stream.

The invention adopts a rectification mode to remove the weight, effectively reduces the metal and nitrogen-containing compounds in the dimethyl oxalate product, adopts a mode of taking a liquid phase from the side line of a rectification section to effectively separate light components which are possibly decomposed and generated in the process of removing the weight of the dimethyl oxalate, increases the external discharge capacity of a tower kettle, and can further improve the purity of the dimethyl oxalate product, thereby effectively improving the stability of a hydrogenation reaction system of the dimethyl oxalate product in the process of preparing ethylene glycol by hydrogenation.

In the invention, the purity of the dimethyl oxalate product is 99.8-99.99%, preferably 99.9-99.99%.

In a preferred embodiment, the number of theoretical plates of the rectifying tower is 2-20, the feeding position is 0-18 theoretical plates, wherein 0 represents a tower kettle.

In the invention, the rectifying tower can be a plate tower or a packed tower.

In a further preferred embodiment, the number of theoretical plates of the rectifying tower is 5-15, and the feeding position is 1-8.

The method can treat trace heavy components in raw materials (high-purity dimethyl oxalate), simultaneously solves light components generated by decomposition of dimethyl oxalate in the treatment process, has large difference between the boiling points of the trace heavy components and the dimethyl oxalate, needs a small number of theoretical plates, theoretically can realize separation by directly feeding and evaporating from a tower kettle, can feed materials at a position close to the tower kettle, and preferably adopts the theoretical plates above the tower kettle for further reducing entrainment.

In a preferred embodiment, the rectification column is operated at a pressure of-0.1 to 1MPaG and a temperature of 70 to 250 ℃.

In a further preferred embodiment, the rectification column is operated at a pressure of-0.05 to 0.1MPaG and a temperature of 138 to 190 ℃.

The rectifying tower has higher pressure, can back pressure the non-condensable gas at the top of the tower to a main device, has simple flow, and can cause the temperature of the tower kettle to be overhigh. Pure dimethyl oxalate has a stable structure, but impurities such as heavy metals in the tower bottom material of the invention can promote the decomposition of dimethyl oxalate after being concentrated, and the decomposition can be accelerated after the temperature is increased, so the tower bottom temperature is not too high, the tower top temperature is not too low, the tower top operating temperature is too low, the crystallization of dimethyl oxalate can be caused, a lower vacuum degree is also required, the preferred operating temperature is more than 138 ℃, and the tower top gas phase can be utilized to generate low-pressure steam to recover heat.

In a preferred embodiment, the mixed stream containing dimethyl oxalate is a mixed stream separated from a coupling unit in a process of preparing ethylene glycol from synthesis gas.

Wherein, preferably, the mixed stream obtained by the separation of the coupling unit is the material from the tower bottom, such as CN203960094U stream 12 or CN106518675A stream 31.

In a preferred embodiment, an alkaline earth metal compound catalyst is provided in the decarbonylation reaction system.

Wherein alkaline earth metal compound catalysts which have been disclosed in the prior art are used. Preferably, the alkaline earth metal compound catalyst is supported on activated carbon, alumina, silica, and preferably, the alkaline earth metal compound comprises a carbonate, nitrate or halide of potassium, sodium, rubidium, cesium.

In a further preferred embodiment, in the decarbonylation reaction system, the reaction temperature is 100-300 ℃, and the weight space velocity of the material flow is 0.1-10 h^-1(ii) a Preferably, the reaction temperature is 180-300 ℃, and the weight space velocity of material flow is 2-10 h^-1。

The heavy component-containing dimethyl oxalate stream can also undergo decarbonylation reaction under high-temperature and non-catalytic conditions, but in order to improve the selectivity of the decarbonylation reaction and reduce the side reaction of generating carbon dioxide and dimethyl ether, an alkaline earth metal compound catalyst is filled in a decarbonylation reaction system.

In a preferred embodiment, the dimethyl oxalate stream containing heavy components extracted from the bottom of the dimethyl oxalate rectifying tower is subjected to heating gasification treatment, then the heavy components are removed, and then the stream is sent to the decarbonylation reaction system, and is preferably introduced into a protective bed to remove the heavy components.

Wherein, gas-solid phase reaction or gas-liquid-solid three-phase reaction is carried out in the decarbonylation reaction system, preferably gas-solid phase reaction is carried out, and before the gas-phase raw material enters the reactor, heavy components (such as heavy metals, carbon deposition and other impurities) in the gas-phase raw material are removed (preferably, a protection bed is arranged). Specifically, the dimethyl oxalate material flow containing heavy metals and other impurities are easy to coke and deposit carbon after gasification, so a protective bed is required to be arranged before the gas-phase material enters the reactor, and preferably more than two protective beds are arranged, wherein one protective bed is in a working state, and the other protective bed is in a standby state, so that the continuous operation period of the decarbonylation reaction is prolonged, and specifically, the protective bed can reduce the deposition of impurities on the catalyst and reduce the possibility of pressure difference rising.

In a further preferred embodiment, the guard bed is filled with inert alumina ceramic balls.

The impurities such as heavy metal, carbon deposit and the like in the protective bed are not easy to gasify and can be deposited on the protective bed, so that the pressure difference of a catalyst bed layer is prevented from rising due to the deposition of the impurities such as heavy metal, carbon deposit and the like on the decarburization catalyst, and the service cycle of the catalyst is prolonged.

In a further preferred embodiment, the operating conditions of the guard bed are: 100 to 300 ℃ and 0 to 5 MPaG.

In a preferred embodiment, the stream after the decarbonylation reaction system is treated is subjected to dimethyl carbonate recovery; preferably, said stream is sent to a dimethyl carbonate recovery column.

Wherein the decarbonylation reaction system mainly comprises dimethyl carbonate, CO and CO₂A stream of dimethyl ether.

In a further preferred embodiment, a crude dimethyl carbonate liquid phase product and a crude CO gas phase product are withdrawn at the top of the dimethyl carbonate recovery column, more preferably, the crude dimethyl carbonate liquid phase product comprises dimethyl carbonate and dissolved CO, CO₂Dimethyl ether, wherein CO and CO₂The total weight content of dimethyl ether is 0.01-0.5%, and the crude CO gas-phase product comprises CO, dimethyl carbonate and CO₂Dimethyl ether, wherein dimethyl carbonate and CO₂The total molar content of dimethyl ether is 0.1 to 20%, preferably 0.1 to 10%.

Wherein the crude CO gas phase product is recycled to a coupling unit for making ethylene glycol from the gas; preferably, the crude CO gas phase product is stripped of CO using methanol₂And dimethyl ether to obtain a CO product, and then recycling the CO product to a coupling unit for preparing ethylene glycol from gas.

Wherein the gas-phase product of the crude CO mainly contains CO, but also contains a small amount of dimethyl carbonate and CO₂And dimethyl ether, if recycled directly back to the coupling reactor system, will result in CO₂And dimethyl ether are accumulated in a coupling reaction circulating gas system, particularly dimethyl ether is difficult to separate after entering a coupling reactor system due to the fact that the boiling point of dimethyl ether is close to that of methyl nitrite, and therefore the dimethyl ether needs to be removed firstly and can be removed in a methanol absorption mode. Therefore, the crude CO gas phase product is preferably recycled to the reaction system as the coupling reaction raw material after being absorbed by methanol.

Preferably, the methanol absorption liquid can be used for removing dimethyl ether in a methanol light component removal tower (a tower for removing light components such as methyl formate) of the coupling unit.

The other purpose of the invention is to provide a treatment system of a mixed material flow containing dimethyl oxalate, which is used for carrying out the treatment method of the first purpose of the invention, wherein the treatment system comprises a dimethyl oxalate rectifying tower, a decarbonylation reaction system and a dimethyl carbonate recovery tower which are connected in sequence.

In a preferred embodiment, a protective bed is further arranged between the tower bottom of the dimethyl oxalate rectifying tower and the decarbonylation reaction system and used for removing heavy components in tower bottom materials of the dimethyl oxalate rectifying tower, and preferably, the number of the protective beds is more than two, one of the protective beds is in a working state, and the other protective beds are in a standby state.

In a further preferred embodiment, inert alumina ceramic balls are filled on the protective bed,

impurities such as heavy metal, carbon deposition and the like are not easy to gasify and can deposit on the protective bed, thereby avoiding the pressure difference of a catalyst bed layer from rising caused by the deposition of the impurities such as heavy metal, carbon deposition and the like on the decarburization catalyst and prolonging the service cycle of the catalyst.

In a preferred embodiment, a side-draw position is arranged at the rectifying section of the dimethyl oxalate rectifying tower, and is used for side-drawing liquid phase to draw out a dimethyl oxalate product.

In a preferred embodiment, the decarbonylation reaction system comprises a fixed bed reactor, preferably a fixed bed reactor with a heating device, more preferably a multi-stage fixed bed reactor with an intermediate heating type.

Wherein, when the dimethyl oxalate is decarbonylated, the reaction is an endothermic reaction, and the temperature of the reaction product is greatly lower than that of the reaction raw materials under adiabatic conditions, for example, under gas phase conditions, at 100% conversion rate of dimethyl oxalate, the adiabatic temperature drop of the reaction is about 100 ℃, and in order to avoid overhigh inlet temperature and reduce the selectivity of the reaction under the condition of ensuring the reaction efficiency, a plurality of reactors can be adopted to heat materials among the reactors.

In a further preferred embodiment, the decarbonylation reaction system comprises a tubular fixed bed reactor, and the shell side is heated with saturated steam.

The third purpose of the invention is to provide the application of the treatment method of the first purpose or the treatment system of the second purpose in the treatment of dimethyl oxalate in the process of preparing ethylene glycol from synthesis gas.

In a preferred embodiment, the mixed stream containing dimethyl oxalate is a mixed stream separated from a coupling unit in a process of preparing ethylene glycol from synthesis gas.

In a further preferred embodiment, the CO generated by the treatment method or the treatment system according to the present invention is recycled to the coupling unit, and the generated dimethyl carbonate can be sold as a product after light removal, wherein the light removal is to remove dissolved CO and avoid the release of CO during transportation, which causes safety risk.

The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual values, and between the individual values may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein. In the above, the various technical solutions can in principle be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in the present invention.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention adopts a rectification mode to remove the heavy components, effectively reduces the heavy components such as heavy component metals, nitrogen-containing compounds and the like in the dimethyl oxalate product, and simultaneously adopts a mode of extracting a liquid phase from the lateral line of a rectification section to effectively separate light components which are possibly generated by decomposition in the process of removing the heavy components from the dimethyl oxalate;

(2) in order to further improve the quality of the dimethyl oxalate product, the discharge proportion of a dimethyl oxalate rectifying tower is increased;

(3) the produced high-quality dimethyl oxalate product is used in the process of preparing ethylene glycol by hydrogenation, so that the stability of a hydrogenation reaction system is effectively improved, and the high-quality dimethyl oxalate product can be well applied to the process of preparing ethylene glycol by synthesis gas;

(4) decarbonylation treatment is carried out on the large-discharge material flow extracted from the tower bottom of the dimethyl oxalate rectifying tower, so that co-production of dimethyl carbonate is realized, and material waste is effectively avoided.

Drawings

FIG. 1 shows a schematic diagram of the method and system of the present invention.

In fig. 1, 1 is a dimethyl oxalate rectifying tower, 2 is a decarburization reaction system, 3 is a dimethyl carbonate recovery tower, 4 is a mixed material stream containing dimethyl oxalate, 5 is dimethyl oxalate containing light components, 6 is dimethyl oxalate containing heavy components, 7 is a material stream treated by the decarbonylation reaction system, 8 is a material stream containing dimethyl oxalate, 9 is a crude CO gas-phase product, 10 is a dimethyl oxalate product, and 11 is a crude dimethyl carbonate liquid-phase product.

In the figure 1, a mixed material flow 4 containing dimethyl oxalate is introduced into a dimethyl oxalate rectifying tower 1, a dimethyl oxalate material flow 6 containing heavy components is extracted from the tower bottom, dimethyl oxalate 5 containing light components is extracted from the tower top, and dimethyl oxalate is extracted from a side line liquid phase to produce a dimethyl oxalate 10; after the weight of the dimethyl oxalate is removed by the protective bed, dimethyl oxalate material flow 6 containing heavy components is sent to the decarbonylation reaction system 2 for decarbonylation reaction, the material flow after the reaction is sent to the dimethyl carbonate recovery tower 3, a crude dimethyl carbonate liquid phase product 11 and a crude CO gas phase product 9 are extracted from the tower top, and a material flow 8 containing dimethyl oxalate is discharged from the tower bottom.

Detailed Description

While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.

It is to be further understood that the various features described in the following detailed description may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In the examples, conventional components such as dimethyl oxalate and dimethyl carbonate were analyzed by gas chromatography, the content of nitrogen was analyzed by ultraviolet spectrophotometry, and the content of heavy metals was analyzed by inductively coupled plasma mass spectrometry (ICP-MS).

Example 1

The system of this example is a scale unit for 20 ten thousand tons of ethylene glycol annually.

The stream to be treated containing dimethyl oxalate had a weight composition of (composition excluding trace amounts of nitrides and heavy metals) of 52 t/h: 99.9 percent of dimethyl oxalate and 0.1 percent of dimethyl carbonate. The content of N-containing compound was 100ppm (in terms of nitrogen element) and the content of heavy metal was 2 ppm.

The dimethyl oxalate rectifying tower adopts a float valve tower, the number of theoretical plates is 10, the feeding position is the 4 th theoretical plate, the dimethyl oxalate product is extracted at the 5 th theoretical plate, and liquid phase is extracted.

The operating pressure of the dimethyl oxalate rectifying tower is 0.05MPaG, and the operating temperature of the top of the tower is 173 ℃.

The flow rate of a dimethyl oxalate product collected from the side line is 51t/h, and the weight composition is (the composition does not contain trace nitride and heavy metal): 0.04% of dimethyl carbonate and 99.96% of dimethyl oxalate. The content of N-containing compound (calculated as nitrogen element) was 10ppm, and the content of heavy metal was 0.5 ppm.

The waste dimethyl oxalate is extracted from the tower bottom of a dimethyl oxalate rectifying tower for 0.5t/h, the waste dimethyl oxalate is heated and gasified, passes through a protective bed (the temperature of the protective bed is 200 ℃, and the pressure is 0.15MPaG), then enters a decarbonylation reactor from top to bottom, and the weight space velocity of material flow is 1h^-1The decarbonylation reactor is a tubular fixed bed, an alumina catalyst loaded with potassium nitrate is filled in the decarbonylation reactor, the temperature of the outlet of the reactor is controlled at 230 ℃, and the shell pass is heated by adopting 4.0MPaG steam. The conversion rate of dimethyl oxalate is 99 percent, and the selectivity of generating dimethyl carbonate is 98 percent.

The decarbonylation reaction product enters a dimethyl carbonate recovery tower, the gas phase flow of crude CO at the top of the tower is 144kg/h, wherein dimethyl carbonate and CO₂The total molar content of dimethyl ether is 3 percent; 326kg/h crude dimethyl carbonate is extracted from the liquid phase, the purity of the dimethyl carbonate is 99.6 percent (weight), and the rest is trace CO,CO₂And dimethyl ether. 30kg/h of dimethyl oxalate-containing material flow is extracted from the tower bottom. Wherein 144kg/h of gas phase is firstly sent to a methanol absorption tower to absorb CO generated by side reaction in the methanol absorption tower₂And dimethyl ether, are recycled back to the coupling reactor system.

The discharged waste liquid is reduced by more than 90 percent, and the main components are changed from dimethyl oxalate which is easy to crystallize into dimethyl carbonate, so that the treatment is easier.

Example 2

The system of this example is a scale unit for 20 ten thousand tons of ethylene glycol annually.

The stream to be treated containing dimethyl oxalate had a weight composition of (composition excluding trace amounts of nitrides and heavy metals) of 52 t/h: 99.9 percent of dimethyl oxalate and 0.1 percent of dimethyl carbonate. The content of N-containing compound was 100ppm (in terms of nitrogen element) and the content of heavy metal was 2 ppm.

The dimethyl oxalate rectifying tower adopts a float valve tower, the number of theoretical plates is 10, the feeding position is the 4 th theoretical plate, the dimethyl oxalate product is extracted at the 5 th theoretical plate, and liquid phase is extracted.

The operating pressure of the dimethyl oxalate rectifying tower is 0.05MPaG, and the operating temperature of the top of the tower is 173 ℃.

The flow rate of dimethyl oxalate product collected from the side line is 47.5t/h, and the weight composition is (the composition does not include trace nitride and heavy metal): 0.02% of dimethyl carbonate and 99.98% of dimethyl oxalate. The content of N-containing compound (calculated as nitrogen element) was 5ppm, and the content of heavy metal was 0.3 ppm.

Collecting dimethyl oxalate product in the side liquid phase of a dimethyl oxalate rectifying tower, wherein the discharge proportion of the tower bottom is 4%, collecting waste dimethyl oxalate for 2t/h, heating and gasifying the waste dimethyl oxalate, passing through a protective bed (the temperature of the protective bed is 230 ℃, and the pressure is 0.4MPaG), then entering a decarbonylation reactor from top to bottom, and the weight space velocity of material flow is 1h^-1The decarbonylation reactor is a tubular fixed bed, an alumina catalyst loaded with potassium nitrate is filled in the decarbonylation reactor, the temperature of the outlet of the reactor is controlled at 230 ℃, and the shell pass is heated by adopting 4.0MPaG steam. The conversion rate of dimethyl oxalate is 99 percent, and the selectivity of generating dimethyl carbonate is 98 percent.

The decarbonylation reaction product enters a dimethyl carbonate recovery towerThe gas phase flow of the crude CO at the tower top is 576kg/h, wherein the dimethyl carbonate and the CO are₂The total molar content of dimethyl ether is 3 percent; 1394kg/h dimethyl carbonate is extracted from the liquid phase, the purity of the dimethyl carbonate is 99.6 percent (weight), and the rest is trace CO and CO₂And dimethyl ether. 30kg/h of dimethyl oxalate-containing material flow is extracted from the tower bottom. Wherein 576kg/h of gas phase is firstly sent to a methanol absorption tower to absorb CO generated by side reaction in the methanol absorption tower₂And dimethyl ether, are recycled back to the coupling reactor system.

The production of the dimethyl carbonate with high added value is increased by 1394kg/h, the economic benefit of the device is greatly improved, the output of the waste dimethyl oxalate is increased to 2t/h, the product quality of the dimethyl oxalate subjected to hydrogenation reaction is obviously improved, and the contents of impurities such as dimethyl carbonate, heavy metal, nitrogen and the like in the dimethyl oxalate product are reduced.

Examples 3 to 7

The dimethyl oxalate stream of example 1 was processed using a dimethyl oxalate rectification column with different parameters, different bottoms draw ratios, different decarbonylation reaction parameters, etc., as shown in table 1 below.

Comparative example 1

The procedure of example 2 was repeated except that: the crude CO gas phase at the top of the tower is directly circulated back to the coupling reactor system without being absorbed by methanol, so that the dimethyl ether is accumulated in the coupling reactor system and is difficult to discharge, the flow of the purge tail gas of the coupling reactor system is greatly increased, the stability of the coupling reactor system is influenced, and the material consumption of the coupling reactor system is increased.

Comparative example 2

The procedure of example 1 was repeated except that: in a dimethyl oxalate rectifying tower, the extraction position of a dimethyl oxalate product is changed into the tower top, the content of dimethyl oxalate in the obtained dimethyl oxalate product is reduced to 99.75 percent, and the content of dimethyl carbonate is 0.25 percent.

Comparative example 3

The procedure of example 1 was repeated except that: the phase state of the produced dimethyl oxalate product is changed into gas phase production, and the content of dimethyl oxalate in the obtained gas phase dimethyl oxalate product is also reduced to 99.75 percent, the content of dimethyl carbonate is 0.21 percent, and the content of CO is 0.04 percent.

Table 1: