阅读说明：本技术 一种连续制备碳酸二甲酯的方法及装置 (Method and device for continuously preparing dimethyl carbonate ) 是由 张旭 龚海燕 王誉蓉 于 2019-10-10 设计创作，主要内容包括：本发明涉及有机化工合成技术领域,公开了一种连续制备碳酸二甲酯的方法及装置,该方法在包括串联设置的一级反应器和二级反应器的装置中进行,所述一级反应器包括并联设置的反应器A和反应器B,所述二级反应器包括反应器C,该装置还包括与二级反应器并联设置的旁路,该方法包括将草酸二甲酯进料至一级反应器中进行一级接触反应,将一级接触反应所得物料可选地送入反应器C中进行二级接触反应,以使得所述装置的草酸二甲酯的总转化率R2≥90重量％。利用本发明提供的方法能够连续且高效地制备碳酸二甲酯。(The invention relates to the technical field of organic chemical synthesis, and discloses a method and a device for continuously preparing dimethyl carbonate, wherein the method is carried out in a device comprising a first-stage reactor and a second-stage reactor which are arranged in series, the first-stage reactor comprises a reactor A and a reactor B which are arranged in parallel, the second-stage reactor comprises a reactor C, the device also comprises a bypass which is arranged in parallel with the second-stage reactor, the method comprises the steps of feeding dimethyl oxalate into the first-stage reactor for first-stage contact reaction, and optionally feeding materials obtained by the first-stage contact reaction into the reactor C for second-stage contact reaction, so that the total conversion rate R2 of the dimethyl oxalate of the device is more than or equal to 90 wt%. The method provided by the invention can be used for continuously and efficiently preparing the dimethyl carbonate.)

1. A process for the continuous preparation of dimethyl carbonate, characterized in that it is carried out in an apparatus comprising a primary reactor and a secondary reactor arranged in series, said primary reactor comprising a reactor A and a reactor B arranged in parallel, said secondary reactor comprising a reactor C, the apparatus further comprising a bypass arranged in parallel with the secondary reactor, the process comprising the steps of:

(1) under the decarbonylation reaction condition, feeding dimethyl oxalate into a reactor A, and carrying out a first-stage contact reaction with a catalyst in the reactor A, wherein when the conversion rate R1 of the dimethyl oxalate in the reactor A is reduced to 60-70 wt%, the feeding of the dimethyl oxalate is switched to a state that the reactor B carries out the first-stage contact reaction with the catalyst in the reactor B, and the catalyst in the reactor A is regenerated or replaced; when the conversion rate R1 of dimethyl oxalate in the reactor B is reduced to 60-70 wt%, switching and feeding dimethyl oxalate into the reactor A to perform a first-stage contact reaction with the catalyst in the reactor A, and regenerating or replacing the catalyst in the reactor B; the reactor A and the reactor B are alternately used in such a way of circulation, so that the conversion rate R1 of the dimethyl oxalate of the first-stage contact reaction is more than or equal to 60 percent by weight;

(2) feeding the material obtained by the first-stage contact reaction into a reactor C, and carrying out second-stage contact reaction with a catalyst in the reactor C under the decarbonylation reaction condition; when the total conversion rate R2 of dimethyl oxalate is reduced to 90-98 wt%, switching a primary reactor to enable a catalyst in the primary reactor to be a fresh or regenerated catalyst, cutting a material obtained by the primary contact reaction out of the secondary reactor, discharging the material from the bypass, regenerating or replacing the catalyst in the secondary reactor, and continuously cutting in, and circulating the steps so that the total conversion rate R2 of the dimethyl oxalate of the device is more than or equal to 90 wt%.

2. The method of claim 1, wherein the dimethyl oxalate is fed as a solution having a concentration of 15-100 wt%.

3. The process of claim 1, wherein the conditions of the primary contact reaction comprise: the reaction temperature is 160-260 ℃, preferably 165-210 ℃; the reaction pressure is 0-0.5 MPa; the mass space velocity of the dimethyl oxalate is 0.1-10h^-1。

4. The method of claim 1, wherein the conditions of the secondary contact reaction comprise: the reaction temperature is 160-260 ℃, preferably 165-210 ℃; the reaction pressure is 0-0.5 MPa.

5. The process of claim 1, wherein the primary reactor comprises one or more reactors a arranged in parallel and one or more reactors B arranged in parallel.

6. The process of any one of claims 1-5, wherein the primary reactor and the secondary reactor are both fixed bed reactors.

7. The process of claim 6, wherein the catalysts in the primary and secondary reactors are each independently selected from at least one supported alkali metal catalyst containing potassium, rubidium, and cesium.

8. The device for continuously preparing the dimethyl carbonate is characterized by comprising a primary reactor and a secondary reactor which are arranged in series, wherein the primary reactor comprises a reactor A and a reactor B which are arranged in parallel, the secondary reactor comprises a reactor C, the primary reactor and the secondary reactor are communicated through a pipeline provided with a valve, the device also comprises a bypass which is arranged in parallel with the secondary reactor, and the bypass is provided with a valve.

9. The apparatus of claim 8, wherein the primary reactor comprises one or more reactors a arranged in parallel and one or more reactors B arranged in parallel.

10. The apparatus of claim 8 or 9, wherein the primary and secondary reactors are fixed bed reactors.

Technical Field

The invention relates to the technical field of organic chemical synthesis, in particular to a method for continuously preparing dimethyl carbonate and a device for continuously preparing dimethyl carbonate.

Background

The molecular structure of the dimethyl carbonate contains carbonyl, methyl, methoxyl and other functional groups, so that the dimethyl carbonate can be widely applied to various organic synthesis reactions and is an important organic chemical intermediate. Meanwhile, the dimethyl carbonate has high volatilization rate and strong degreasing capability, can be well dissolved with various common solvents, can be used as an efficient solvent to be applied to the fields of cleaning, coating and the like, and has good application prospect.

At present, there are several methods for synthesizing dimethyl carbonate in the prior art, such as ester exchange method, which uses ethylene oxide, carbon dioxide and methanol as raw materials to obtain dimethyl carbonate through two-step reaction. The method has high yield and mild conditions, but has harsh operating conditions, complex reaction, low catalyst activity, large raw material danger, dependence on petroleum resources and large influence of market price fluctuation.

Patent publication No. CN1197792A discloses synthesis of dimethyl carbonate by methanol oxidative carbonylation using gases such as methanol, oxygen, and carbon monoxide. Although the method has good stability, the method has the problems of equipment corrosion, short service life of the catalyst and the like.

Patent document CN1103862A discloses that carbon monoxide and methyl nitrite are reacted by a coupling method in the presence of a heterogeneous catalyst to produce dimethyl carbonate. Although the method effectively utilizes rich coal and natural gas resources in China, the service life of the catalyst is short, and continuous production cannot be realized.

Therefore, it is necessary to provide a novel method for producing dimethyl carbonate, which enables dimethyl carbonate to be produced continuously and efficiently.

Disclosure of Invention

The invention aims to overcome the defect that the dimethyl carbonate cannot be continuously produced in the preparation process in the prior art.

In order to achieve the above object, a first aspect of the present invention provides a method for continuously producing dimethyl carbonate, the method being carried out in an apparatus comprising a primary reactor and a secondary reactor arranged in series, the primary reactor comprising a reactor a and a reactor B arranged in parallel, the apparatus further comprising a bypass arranged in parallel with the secondary reactor, the method comprising the steps of:

(1) under the decarbonylation reaction condition, feeding dimethyl oxalate into a reactor A, and carrying out a first-stage contact reaction with a catalyst in the reactor A, wherein when the conversion rate R1 of the dimethyl oxalate in the reactor A is reduced to 60-70 wt%, the feeding of the dimethyl oxalate is switched to a state that the reactor B carries out the first-stage contact reaction with the catalyst in the reactor B, and the catalyst in the reactor A is regenerated or replaced; when the conversion rate R1 of dimethyl oxalate in the reactor B is reduced to 60-70 wt%, switching and feeding dimethyl oxalate into the reactor A to perform a first-stage contact reaction with the catalyst in the reactor A, and regenerating or replacing the catalyst in the reactor B; the reactor A and the reactor B are alternately used in such a way of circulation, so that the conversion rate R1 of the dimethyl oxalate of the first-stage contact reaction is more than or equal to 60 percent by weight;

(2) feeding the material obtained by the first-stage contact reaction into a reactor C, and carrying out second-stage contact reaction with a catalyst in the reactor C under the decarbonylation reaction condition; when the total conversion rate R2 of dimethyl oxalate is reduced to 90-98 wt%, switching a primary reactor to enable a catalyst in the primary reactor to be a fresh or regenerated catalyst, cutting a material obtained by the primary contact reaction out of the secondary reactor, discharging the material from the bypass, regenerating or replacing the catalyst in the secondary reactor, and continuously cutting in, and circulating the steps so that the total conversion rate R2 of the dimethyl oxalate of the device is more than or equal to 90 wt%.

The second aspect of the invention provides a device for continuously preparing dimethyl carbonate, which comprises a first-stage reactor and a second-stage reactor which are arranged in series, wherein the first-stage reactor comprises a reactor A and a reactor B which are arranged in parallel, the second-stage reactor comprises a reactor C, the first-stage reactor and the second-stage reactor are communicated through a pipeline provided with a valve, the device also comprises a bypass which is arranged in parallel with the second-stage reactor, and the bypass is provided with a valve.

The method provided by the invention can be used for preparing the dimethyl carbonate continuously for a long time with high conversion rate, the reaction is simple, and the catalyst does not need to be frequently regenerated in the preparation process, so that the service life of the catalyst is further prolonged.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

FIG. 1 is a schematic view of an apparatus used in the present invention.

Description of the reference numerals

1. First feed valve 2, reactor A3 and first discharge valve

4. A second feed valve 5, a reactor B6 and a second discharge valve

7. Third feed valve 8, reactor C9, third bleeder valve

10. Fourth stop valve

Detailed Description

The endpoints of the ranges and any values disclosed herein 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 points, and between the individual points 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.

As described above, the first aspect of the present invention provides a process for continuously producing dimethyl carbonate, which is carried out in an apparatus comprising a primary reactor and a secondary reactor arranged in series, the primary reactor comprising a reactor a and a reactor B arranged in parallel, the secondary reactor comprising a reactor C, the apparatus further comprising a bypass arranged in parallel with the secondary reactor, the process comprising the steps of:

(1) under the decarbonylation reaction condition, feeding dimethyl oxalate into a reactor A, and carrying out a first-stage contact reaction with a catalyst in the reactor A, wherein when the conversion rate R1 of the dimethyl oxalate in the reactor A is reduced to 60-70 wt%, the feeding of the dimethyl oxalate is switched to a state that the reactor B carries out the first-stage contact reaction with the catalyst in the reactor B, and the catalyst in the reactor A is regenerated or replaced; when the conversion rate R1 of dimethyl oxalate in the reactor B is reduced to 60-70 wt%, switching and feeding dimethyl oxalate into the reactor A to perform a first-stage contact reaction with the catalyst in the reactor A, and regenerating or replacing the catalyst in the reactor B; the reactor A and the reactor B are alternately used in such a way of circulation, so that the conversion rate R1 of the dimethyl oxalate of the first-stage contact reaction is more than or equal to 60 percent by weight;

(2) feeding the material obtained by the first-stage contact reaction into a reactor C, and carrying out second-stage contact reaction with a catalyst in the reactor C under the decarbonylation reaction condition; when the total conversion rate R2 of dimethyl oxalate is reduced to 90-98 wt%, switching a primary reactor to enable a catalyst in the primary reactor to be a fresh or regenerated catalyst, cutting a material obtained by the primary contact reaction out of the secondary reactor, discharging the material from the bypass, regenerating or replacing the catalyst in the secondary reactor, and continuously cutting in, and circulating the steps so that the total conversion rate R2 of the dimethyl oxalate of the device is more than or equal to 90 wt%.

In the present invention, the conversion R1 is (mass of dimethyl oxalate remaining from 1-stage contact reaction/mass of dimethyl oxalate fed to the apparatus) × 100%.

When the secondary reactor is not cut out of reaction:

the total conversion R2 ═ 1- (mass of dimethyl oxalate remaining after the first-stage contact reaction + the second-stage contact reaction)/mass of dimethyl oxalate fed into the apparatus) × 100%.

Because the primary reactor and the secondary reactor are connected in series, and the reaction product finally passes through the secondary reactor discharge device, the mass of dimethyl oxalate remaining after the primary contact reaction plus the secondary contact reaction is the mass of dimethyl oxalate (unreacted dimethyl oxalate) in the product discharged from the secondary reactor.

When the secondary reactor is cut out of reaction:

total conversion R2 ═ conversion R1.

In the invention, when the total conversion rate R2 of dimethyl oxalate in the device is reduced to 90-98 wt%, the first-stage reactor is switched to ensure that the catalyst in the first-stage reactor is a fresh or regenerated catalyst, and the material obtained by the first-stage contact reaction is cut out from the second-stage reactor and discharged from the bypass, thereby utilizing the initial high activity of the catalyst in the first-stage reactor to ensure that the conversion rate of dimethyl oxalate only passes through the first-stage contact reaction can meet the requirement of the total conversion rate.

In the invention, the conversion rate in the first-stage reactor can be lower than that in the prior art by using the serially connected second-stage reactors, and unreacted dimethyl oxalate is converted in the second-stage reactor continuously, so that the service lives of the catalysts in the first-stage reactor and the second-stage reactor can be prolonged. By using multiple primary reactors in parallel, catalyst regeneration/replacement of the primary reactor can be accomplished without plant downtime.

The inventor of the invention skillfully sets the device so that the operation rate of the device is higher and the utilization rate of the catalyst is obviously higher.

Preferably, the catalyst in the secondary reactor is regenerated while the catalyst in the off-line reactor of the primary contact reaction is regenerated to reduce the subsequent regeneration time.

According to the present invention, preferably, the method for regenerating the catalyst is a high temperature heat treatment, and in the present invention, the method for regenerating the catalyst comprises a heat treatment of the catalyst at 400-600 ℃.

Preferably, the dimethyl oxalate is fed in the form of a solution having a concentration of 15 to 100% by weight. The dimethyl oxalate solution is at least one selected from a methanol solution of dimethyl oxalate, an ethanol solution of dimethyl oxalate, dimethyl carbonate of dimethyl oxalate and molten dimethyl oxalate.

Preferably, the conditions of the first-order contact reaction comprise: the reaction temperature is 160-260 ℃, preferably 165-210 ℃; the reaction pressure is 0-0.5 MPa; the mass space velocity of the dimethyl oxalate is 0.1-10h^-1。

In the invention, for convenience, the first-stage contact reaction and the second-stage contact reaction are both measured by the mass space velocity of dimethyl oxalate, and the mass space velocity of dimethyl oxalate refers to the mass space velocity of dimethyl oxalate in a dimethyl oxalate solution introduced into a device.

Preferably, the conditions of the secondary contact reaction include: the reaction temperature is 160-260 ℃, preferably 165-210 ℃; the reaction pressure is 0-0.5MPa, and the mass space velocity of the dimethyl oxalate is 0.1-10h^-1。

In the invention, the material obtained by the first-stage contact reaction is sent into the reactor C for the second-stage contact reaction, so the flow rate of the second-stage contact reaction is the flow rate of the material obtained by the first-stage contact reaction.

In the invention, the inventor finds that the dimethyl oxalate solution and the catalyst are subjected to the first-stage contact reaction and the second-stage contact reaction in a gaseous state by controlling the conditions of the first-stage contact reaction and the second-stage contact reaction, so that the whole process is simpler and more efficient, the operation and the product separation are easy, and the catalyst stability is better.

According to a preferred embodiment of the invention, a non-fixed reaction temperature is adopted, namely the reaction temperature is changed according to the conversion rate of the primary contact reaction and/or the secondary contact reaction, the temperature of the reactor is correspondingly increased by 3-5 ℃ every time the conversion rate in the reactor is reduced by 5-10 wt%, and the temperature is controlled to be 210 ℃ at most, so that the catalytic activity of the catalyst can be improved, and the catalyst is not seriously carbon-deposited, therefore, the conversion rate of the primary contact reaction and/or the secondary contact reaction is increased, the regeneration frequency of the catalyst in the primary reactor and/or the secondary reactor is further reduced, and the service life of the catalyst is prolonged.

Preferably, the primary reactor comprises one or more reactors a arranged in parallel and one or more reactors B arranged in parallel.

Preferably, the primary reactor and the secondary reactor are both fixed bed reactors.

Preferably, the specifications of the first-stage reactor and the second-stage reactor comprise the same diameter, volume, length of the constant temperature section and material.

Preferably, the catalysts in the first-stage reactor and the second-stage reactor are respectively and independently selected from at least one of supported alkali metal catalysts containing potassium, rubidium and cesium. The inventor finds that the conversion efficiency of catalyzing the decarbonylation of dimethyl oxalate to dimethyl carbonate by using the alkali metal catalyst is higher.

In the present invention, the catalyst used is a self-made alkali metal catalyst, and the specific preparation method is disclosed in patent document with publication number CN 1221732A.

As described above, the second aspect of the present invention provides an apparatus for continuously preparing dimethyl carbonate, as shown in fig. 1, the apparatus comprises a first-stage reactor and a second-stage reactor, which are arranged in series, the first-stage reactor comprises a reactor a2 and a reactor B5, which are arranged in parallel, the second-stage reactor comprises a reactor C8, the first-stage reactor and the second-stage reactor are communicated through a pipeline provided with a valve, the apparatus further comprises a bypass, which is arranged in parallel with the second-stage reactor, and the bypass is provided with a valve.

The reactor A2 and the reactor B5 were connected in parallel by a line equipped with a valve.

In the invention, each valve is independently controlled.

According to a specific embodiment of the present invention, the valves and lines in the apparatus are connected in such a way that when the valves on the lines connecting reactor a2 and reactor C8 are opened and the valves on the lines connecting reactor B5 are closed, reactor a2 and reactor C8 are in-line reactors and reactor B5 is an off-line reactor.

According to another specific embodiment of the present invention, the valves and lines in the apparatus are connected in such a way that when the valves on the lines connecting reactor B5 and reactor C8 are opened and the valves on the lines connecting reactor a2 are closed, reactor B5 and reactor C8 are in-line reactors and reactor a2 is an off-line reactor.

According to yet another specific embodiment of the present invention, the valves and lines in the apparatus are connected in such a way that when the valve in the line connecting reactor a2 or reactor B5 is opened, and the valve in the bypass is opened and the valve in the line connecting reactor C8 is closed, reactor a2 or reactor B5 is an on-line reactor and reactor C8 is an off-line reactor.

Preferably, the primary reactor comprises one or more reactors a2 arranged in parallel and one or more reactors B5 arranged in parallel.

Preferably, the primary reactor and the secondary reactor are both fixed bed reactors.

According to one embodiment of the present invention, dimethyl carbonate is produced by the apparatus shown in FIG. 1 using the following process.

(1) Opening a first feeding valve 1, a first discharging valve 3, a third feeding valve 7 and a third discharging valve 8, continuously adding dimethyl oxalate methanol solution with the mass fraction of 20 wt% into a reactor A2 to carry out primary contact reaction to obtain a material I containing dimethyl carbonate, and introducing the material I into a reactor C8 to carry out secondary contact reaction to obtain a material II containing dimethyl carbonate.

(2) When the conversion rate R1 of dimethyl oxalate in the reactor A is lower than a preset value, the first feed valve 1 and the first discharge valve 3 are closed, the second feed valve 4 and the second feed and discharge valve 6 are opened, the first-stage contact reaction is switched from the reactor A2 to the reactor B5 for carrying out, and simultaneously, the catalyst in the reactor A2 is regenerated for later use. So circulating, reactor a2 and reactor B5 were switched.

(3) Monitoring the concentration of dimethyl carbonate in the material discharged from the reactor C8, calculating the total conversion rate R2 of dimethyl oxalate of the device, opening the first feeding valve 1, the first discharging valve 3 and the fourth stop valve 10 when R2 is lower than a preset value, closing the second feeding valve 4, the second discharging valve 6, the third feeding valve 7 and the third discharging valve 9, switching the first-stage contact reaction into the reactor A2 again, and simultaneously regenerating the catalyst in the reactor B5 and the reactor C8.

(4) After the regeneration of the catalyst in the reactor C8 is finished, the third feed valve 7 and the third discharge valve 9 are opened, the fourth stop valve 10 is closed, and the reactor C8 is switched back to the reaction system to continue to participate in the reaction.

The present invention will be described in detail below by way of examples and comparative examples. In the following examples and comparative examples, all the raw materials used were obtained from commercial sources unless otherwise specified.

The catalyst used is a self-made alkali metal catalyst, and the specific preparation method is disclosed in a patent document with the publication number of CN1221732A, and the catalyst containing 20 wt% of potassium carbonate supported on activated carbon is prepared.

Examples 1-3 dimethyl carbonate was produced by using the apparatus shown in FIG. 1, wherein reactor A2, reactor B5 and reactor C8 were fixed bed tubular reactors having the same size and material, the inner diameter was 30mm, the constant temperature section was 300mm, and 20g of an alkali metal catalyst was packed in each reactor.

Example 1

Setting the pressure of a reactor A2, a reactor B5 and a reactor C8 to be 0.3MPa, firstly heating each reactor to 165 ℃, and when the conversion rate R1 of the first-stage contact reaction is reduced to 70 weight percent, increasing the temperature of the first-stage contact reactor to 5 ℃; when the total conversion R2 is reduced to 98 wt%, the temperature of the secondary contact reactor is increased by 3 ℃, the temperature of the reactor is increased to 210 ℃ at most, and the total conversion R2 of the dimethyl oxalate in the device is more than or equal to 98 wt%. Introducing dimethyl oxalate methanol solution with the content of 20 weight percent into the device at the speed of 0.5g/min, wherein the mass space velocity of the first-stage contact reaction is 0.3h^-1。

(1) Opening a first feeding valve 1, a first discharging valve 3, a third feeding valve 7 and a third discharging valve 8, continuously feeding dimethyl oxalate methanol solution with the content of 20 weight percent into a reactor A2 at the speed of 0.5g/min for primary contact reaction to obtain a material I containing dimethyl carbonate, and introducing the material I into a reactor C8 for secondary contact reaction to obtain a material II containing dimethyl carbonate. By the 20 th day of the reaction, the conversion of dimethyl oxalate R1 in reactor A was reduced to 70% by weight, and the total conversion of dimethyl oxalate in the apparatus R2 was 99.8% by weight.

(2) And (3) closing the first feed valve 1 and the first discharge valve 3, opening the second feed valve 4 and the second feed and discharge valve 6, switching the first-stage contact reaction from the reactor A2 to the reactor B5 for carrying out, and simultaneously regenerating the catalyst in the reactor A2 for standby. After a further reaction time of 18 days, the conversion R1 of dimethyl oxalate in reactor B had dropped to 75.7% by weight, and the overall conversion R2 of dimethyl oxalate in the apparatus was 98.0% by weight.

(3) The first feeding valve 1, the first discharging valve 3 and the fourth stop valve 10 are opened, the second feeding valve 4, the second discharging valve 6, the third feeding valve 7 and the third discharging valve 9 are closed, the first-stage contact reaction is switched to be carried out in the reactor A2, and simultaneously, the catalyst in the reactor B5 and the reactor C8 is regenerated.

(4) After the regeneration of the catalyst in the reactor C8 is finished, the third feed valve 7 and the third discharge valve 9 are opened, the fourth stop valve 10 is closed, and the reactor C8 is switched back to the reaction system to continue to participate in the reaction.

(5) This was repeated, and the total conversion R2 of dimethyl oxalate in the apparatus was maintained at 98% by weight or more over 150 days. The interval during which reactor a2 and reactor B5 were used alternately was 20 days, and the catalyst in reactor C8 was regenerated every 38 days.

Example 2

Dimethyl carbonate was prepared in the same manner as in example 1, except that:

introducing dimethyl oxalate methanol solution with dimethyl oxalate content of 20 wt% into the device at a rate of 0.25g/min, wherein the mass space velocity of the first-stage contact reaction is 0.15h^-1Dimethyl carbonate was prepared in the same manner as in example 1 except that the reaction solution was not dissolved in water.

The total conversion R2 of dimethyl oxalate of the apparatus was maintained at 98% by weight and above over 170 days. The interval between reactor A2 and reactor B5 was 40 days, and the catalyst in reactor C was regenerated every 70 days.

Example 3

Dimethyl carbonate was prepared in the same manner as in example 1, except that:

dimethyl carbonate was prepared in the same manner as in example 1 except that the temperatures of the reactor A2, the reactor B5 and the reactor C8 were fixed at 180 ℃.

This was repeated, and the conversion R2 of dimethyl oxalate in the apparatus was maintained at 98% by weight or more over 90 days. The interval during which reactor a2 and reactor B5 were used alternately was 10 days, and the catalyst in reactor C8 was regenerated every 20 days.

Comparative example 1

60g of catalyst is placed in a single reactor, the pressure is set to be 0.3MPa, dimethyl oxalate methanol solution with the content of 20 weight percent is introduced into the reactor at the speed of 0.5g/min, and the mass space velocity is 0.1h^-1The initial temperature of the reactor is set to 165 ℃, when the conversion rate of the dimethyl oxalate in the reactor is reduced to 98 weight percent, the temperature of the reactor is correspondingly increased to 3 ℃, and the temperature is increased to 210 ℃ at most, so that the total conversion rate R2 of the dimethyl oxalate in the reactor is more than or equal to 98 weight percent. The reaction was carried out until day 20, and the temperature reached 210 ℃ but the conversion of dimethyl oxalate decreased to 73.6% by weight, and could not be increased. And regenerating the catalyst in the reactor, and continuing to react after the activity of the catalyst is recovered. The above steps are repeated, the regeneration operation is required to be carried out once every 20 days, the reaction cannot be continuous, and the contents of dimethyl oxalate and dimethyl carbonate in the product are unstable.

Comparative example 2

Evenly distributing 60g of catalyst into two parallel-connected reactors, setting the pressure of the reactors to be 0.3MPa, introducing dimethyl oxalate methanol solution with the content of 20 weight percent into a device at the speed of 0.5g/min, and setting the mass space velocity of a single reactor to be 0.2h^-1The initial temperature of the reactor is set to 165 ℃, when the conversion rate of the dimethyl oxalate in the reactor for reaction is reduced to 98 weight percent, the temperature of the reactor is correspondingly increased to 3 ℃, and the temperature is increased to 210 ℃ at most, so that the total conversion rate R2 of the dimethyl oxalate is more than or equal to 98 weight percent. The reaction proceeded to day 5 to reach a temperature of 210 c, but the conversion of dimethyl oxalate in the apparatus decreased to 90.3 wt%. Switching the reaction to another reactionIn-situ and regenerating the catalyst in the off-line reactor. This was repeated every 5 days, requiring the reactor to be used interchangeably.

Comparative example 3

The reactor A, the reactor B and the reactor C are arranged in parallel through pipelines with valves, 20g of alkali metal catalyst is filled in each reactor, the pressure is set to be 0.3MPa, dimethyl oxalate methanol solution with the content of 20 weight percent is led into the reactors at the speed of 0.5g/min, and the mass space velocity of a single reactor is 0.3h^-1. The initial temperature of the reactor is set to 165 ℃, when the conversion rate of the dimethyl oxalate in the reactor for reaction is reduced to 98 weight percent, the temperature of the reactor is correspondingly increased to 5 ℃, and the temperature is increased to 210 ℃ at most, so that the total conversion rate R2 of the dimethyl oxalate in the device is more than or equal to 98 weight percent.

A20 wt% dimethyl oxalate solution in methanol was continuously fed into the reactor A at a rate of 0.5g/min, and the reaction was carried out for 3 days at a temperature of 210 ℃ with the conversion rate of dimethyl oxalate in the reactor A decreasing to 97.6 wt%. And (3) switching the reaction from the reactor A to the reactor B, and simultaneously regenerating the catalyst in the reactor A for later use. And (3) the reactor B is carried out for 3 days, the temperature reaches 210 ℃, the conversion rate of the dimethyl oxalate in the reactor B is reduced to 96.8 weight percent, then the reaction is switched from the reactor B to the reactor C, and the catalyst in the reactor B is regenerated, so that the reaction is repeated, the conversion rate of the dimethyl oxalate can be basically maintained at 98 weight percent or more after 30 days, and the reactors are switched every 3 days.

The number of days of switching intervals between reactors and the amount of catalyst consumed in each of examples 1 to 3 and comparative example 3 are shown in Table 1.

TABLE 1

Note: the catalyst consumption amount is the weight of the catalyst which needs to be consumed for producing one ton of dimethyl carbonate, and the weight of the consumed catalyst is the weight of the catalyst which is used from the beginning of use, repeated regeneration and use to the time when the catalyst can not be regenerated and must be discarded.

As can be seen from the above examples and comparative examples and table 1, the method provided by the present invention can continuously and efficiently synthesize dimethyl carbonate for a long time, the content of dimethyl carbonate in the obtained product is stable, and the method is simple in operation because frequent reactor switching is not required, and the catalyst does not need to be regenerated frequently, thereby further prolonging the service life of the catalyst and reducing the usage amount of the catalyst in the process of preparing dimethyl carbonate.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.