Method and system for continuously producing dimethyl carbonate

Abstract

The invention provides a method for continuously producing dimethyl carbonate, which comprises the following steps: 1) washing a carbonylation reaction gas-phase mixture with methanol, and separating to obtain a first gas-phase mixture and a first liquid-phase mixture; 2) carrying out flash evaporation and light component removal on the first liquid-phase mixture to obtain a gas-phase mixture containing methyl nitrite and a second liquid-phase mixture; 3) vaporizing the second liquid-phase mixture to obtain a second gas-phase mixture; and 4) carrying out a decarbonylation catalytic reaction on the second gas-phase mixture to obtain a gas-liquid mixture, carrying out gas-liquid separation on the gas-liquid mixture to obtain a gas-phase product and a liquid-phase product, and rectifying the liquid-phase product to provide a dimethyl carbonate product. The invention further provides a system for continuously producing dimethyl carbonate. According to the method and the system for continuously producing the dimethyl carbonate, provided by the invention, MN can be effectively removed, so that a catalytic reaction for preparing DMC by decarbonylation taking DMO as a raw material is smoothly carried out, and continuous and stable production of the DMC is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of producing dimethyl carbonate, and relates to a method and a system for continuously producing dimethyl carbonate. Background Art

[0002] Dimethyl oxalate (COOCH 3 ) 2 It is an important chemical raw material and can be produced by CO gas phase coupling reaction. Dimethyl oxalate can be further selectively hydrogenated to produce methyl glycolate and ethylene glycol, or it can be decarbonylated to produce dimethyl carbonate.

[0003] Dimethyl carbonate is an emerging green chemical raw material with low toxicity, excellent environmental performance and wide application. It is environmentally friendly. Because its molecular structure contains functional groups such as carbonyl, methyl and methoxy, it has good reactivity, so it can be used to replace traditional oily solvents and toxic phosgene as a raw material for the production of polycarbonate (PC). In view of the wide range of uses and green and environmentally friendly characteristics of dimethyl carbonate, it has broad application prospects in the 21st century, and the synthesis process technology of dimethyl carbonate has received widespread attention at home and abroad.

[0004] At present, the methods for synthesizing dimethyl carbonate include: phosgene method, transesterification method, methanol oxidative carbonylation method, urea alcoholysis method, CO 2 And direct methanol synthesis method, among which the industrial production is mainly based on phosgene method and ester exchange method.

[0005] Dimethyl oxalate is directly decarbonylated to generate dimethyl carbonate and gaseous product carbon monoxide under the action of a catalyst, which has the advantages of simple steps, green environmental protection, high economic efficiency, etc. The generated CO can be circulated to supply the reaction of carbonylation of methyl nitrite to prepare dimethyl oxalate, achieving 100% atomic utilization, meeting the requirements of the development of modern green chemical industry, having a good development prospect, and having a positive significance for the blending of dimethyl oxalate and dimethyl carbonate according to market demand.

[0006] Specifically, dimethyl oxalate reacts under the action of base catalysis to remove the carbonyl group to form dimethyl carbonate. The side reaction is mainly that dimethyl carbonate further removes the carbonyl group and oxygen to form dimethyl ether under the action of base catalysis. Both the main and side reactions are endothermic reactions with increased volume, and the reaction equations are as follows:

[0007] (COOCH 3 ) 2 →(CH 3 O) 2 CO+CO

[0008] Ube of Japan started research on the catalytic synthesis of dimethyl carbonate by decarbonylation of dimethyl oxalate very early, but the Ube process has not yet been industrialized.

[0009] Patent CN 113956161A discloses a method and system for continuously producing dimethyl carbonate, which converts NO, O 2 and methanol are input into a nitrosation reaction device, and a nitrosation reaction is carried out under the conditions of a pressure of 0.1-1MPa and a temperature of room temperature to obtain methyl nitrite; methyl nitrite is subjected to a carbonylation reaction with CO to obtain a crude dimethyl oxalate product; dimethyl oxalate is further subjected to a decarbonylation reaction to obtain dimethyl carbonate. In this method, a crude dimethyl oxalate product is obtained by carbonylation reaction, and dimethyl oxalate is further decarbonylated to produce dimethyl carbonate. The patent does not specify how to deal with the partially unconverted MN in the carbonylation reaction outlet gas. Due to the high temperature of the decarbonylation reaction, if MN enters the decarbonylation reaction stage, not only unnecessary by-products are generated, but also the process of decarbonylating dimethyl oxalate to produce dimethyl carbonate will have a greater risk. Summary of the invention

[0010] In view of the above-mentioned shortcomings of the prior art, in order to overcome the defects of the prior art in that the dimethyl carbonate preparation process cannot be continuously produced and the risk problems existing in the production process, so that the device can operate safely and stably for a long period of time, the purpose of the present invention is to provide a method and system for continuously producing dimethyl carbonate, which can be used to prepare dimethyl oxalate and dimethyl carbonate products according to market demand, thereby extending the product chain in ethylene glycol production.

[0011] To achieve the above object and other related objects, the present invention provides a method for continuously producing dimethyl carbonate in a first aspect, comprising the following steps:

[0012] 1) washing the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture and a first liquid phase mixture;

[0013] 2) flashing and removing light from the first liquid phase mixture obtained in step 1) to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture;

[0014] 3) vaporizing the second liquid phase mixture obtained in step 2) to obtain a second gas phase mixture;

[0015] 4) subjecting the second gas phase mixture obtained in step 3) to a catalytic decarbonylation reaction to obtain a gas-liquid mixture, and then subjecting the mixture to gas-liquid separation to obtain a gas phase product and a liquid phase product, and the liquid phase product is distilled to provide a dimethyl carbonate product.

[0016] A second aspect of the present invention provides a system for continuously producing dimethyl carbonate, comprising:

[0017] A washing tower, used for washing the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture and a first liquid phase mixture;

[0018] A light-removal tower, the light-removal tower is connected to the washing tower, and is used to receive the first liquid phase mixture provided by the washing tower for flash evaporation and light-removal to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture;

[0019] A vaporizer, the vaporizer is connected to the light-removing tower and is used to receive the second liquid phase mixture provided by the light-removing tower and vaporize it to obtain a second gas phase mixture;

[0020] A decarbonylation reactor, the decarbonylation reactor is connected to the vaporizer and is used to receive the second gas phase mixture provided by the vaporizer to perform a decarbonylation catalytic reaction to obtain a gas-liquid mixture;

[0021] A first gas-liquid separator, which is connected to the decarbonylation reactor and is used to receive the gas-liquid mixture provided by the decarbonylation reactor and perform gas-liquid separation to obtain a gas phase product and a liquid phase product;

[0022] The distillation device is connected to the first gas-liquid separator and is used to receive the liquid phase product provided by the first gas-liquid separator for distillation to provide a dimethyl carbonate product.

[0023] As described above, the method and system for continuously producing dimethyl carbonate provided by the present invention have the following beneficial effects:

[0024] (1) The present invention provides a method and system for continuously producing dimethyl carbonate. Through the steps of methanol washing, light removal, vaporization, decarbonylation catalysis, etc., the present invention can solve the problem that the dimethyl oxalate (DMO) mixed material in the outlet logistics of the carbonylation reactor contains methyl nitrite (MN), which is not conducive to the subsequent decarbonylation of DMO to produce dimethyl carbonate (DMC), and can effectively remove methyl nitrite gas.

[0025] (2) The present invention provides a method and system for continuously producing dimethyl carbonate. The removed methyl nitrite can be returned to the carbonylation reactor to provide a stable raw material supply for the catalytic decarbonylation reaction of preparing dimethyl carbonate using dimethyl oxalate as a raw material, so that the catalytic decarbonylation reaction of preparing dimethyl carbonate using dimethyl oxalate as a raw material can proceed smoothly, realizing continuous and stable production of DMC, and can be used for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a system structure diagram for continuously producing dimethyl carbonate.

[0027] Reference numerals

[0028] T-101 Scrubber

[0029] T-102 Lightweight Removal Tower

[0030] R-101 carbonylation reactor

[0031] R-102 Decarbonylation Reactor

[0032] V-101 Second Gas-Liquid Separator

[0033] V-102 Carburetor

[0034] V-103 First Gas-Liquid Separator

[0035] E-101 Heat Exchanger

[0036] E-102 Reboiler

[0037] E-103 Condenser

[0038] E-104 Heater

[0039] E-105 Preheater

[0040] P-101 Reflux Pump

[0041] P-102 First Liquid Pump

[0042] P-103 Second Liquid Pump

[0043] XV-101 regulating valve

[0044] C-101 Circulation Compressor

[0045] 1Methyl nitrite

[0046] 2N 2

[0047] 3CO

[0048] 4 Carbonylation reaction gas mixture

[0049] 5. First gas phase mixture

[0050] 6First gas phase separation

[0051] 7First liquid phase separation

[0052] 8First liquid phase mixture

[0053] 9 Second methanol input port

[0054] 10 Gas mixture containing methyl nitrite

[0055] 11 Second liquid phase mixture

[0056] 12 Degassing logistics

[0057] 13 Hydrogenation Logistics

[0058] 14 Second nitrogen inlet

[0059] 15 Second gas phase mixture

[0060] 16Third nitrogen inlet

[0061] 17 Gas-liquid mixture

[0062] 18 Liquid products

[0063] 19 Gas phase products

[0064] 20First discharge pipeline

[0065] 21First methanol input port

[0066] 22 First packing layer

[0067] 23 First output pipeline

[0068] 24First input pipeline

[0069] 25 Second output pipeline

[0070] 26 Second input pipeline

[0071] 27 Second discharge pipeline

[0072] 28 Second packing layer

[0073] 29First nitrogen inlet

[0074] 30 Third output pipeline

[0075] 31 Third input pipeline

[0076] 32 The third discharge pipeline

[0077] 33 The third packing layer

[0078] 34 Fourth discharge pipeline

[0079] 35 The fifth discharge pipeline

[0080] 36 Sixth discharge pipeline

[0081] 37 Seventh discharge pipeline

[0082] 38Distillation unit DETAILED DESCRIPTION

[0083] The first aspect of the present invention provides a method for continuously producing dimethyl carbonate, comprising the following steps:

[0084] 1) washing the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture and a first liquid phase mixture, wherein the first gas phase mixture includes nitrogen monoxide, carbon monoxide, methyl nitrite, methyl formate and methanol, and the first liquid phase mixture includes dimethyl oxalate (DMO), dimethyl carbonate (DMC), methyl nitrite (MN), methanol and methyl formate;

[0085] 2) flashing and removing the light from the first liquid phase mixture obtained in step 1) to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture, and refluxing the gas phase mixture containing methyl nitrite to prepare a gas phase mixture for carbonylation reaction;

[0086] 3) vaporizing the second liquid phase mixture obtained in step 2) to obtain a second gas phase mixture;

[0087] 4) subjecting the second gas phase mixture obtained in step 3) to a catalytic decarbonylation reaction to obtain a gas-liquid mixture, and then subjecting the mixture to gas-liquid separation to obtain a gas phase product and a liquid phase product, wherein the gas phase product is refluxed to prepare a carbonylation reaction gas phase mixture, and the liquid phase product is distilled to provide a dimethyl carbonate product.

[0088] In step 1) of the above method, the carbonylation reaction gaseous mixture is obtained by carbonylation reaction of methyl nitrite and carbon monoxide (CO).

[0089] In a preferred embodiment, the reaction conditions of the carbonylation reaction are: pressure of 0.1-0.5 MPa, and reaction temperature of 120-150°C.

[0090] The carbonylation reaction is a carbonylation reaction for synthesizing dimethyl oxalate in the ethylene glycol process. The carbonylation reaction is a mixed reaction in which methyl nitrite and CO are used as raw materials to enter a carbonylation reactor to generate dimethyl oxalate.

[0091] In step 1) of the above method, in the carbonylation reaction gas phase mixture, the main product is dimethyl oxalate (DMO), and the by-products are dimethyl carbonate (DMC), methyl nitrite (MN), methanol and methyl formate.

[0092] In the method, the methanol washing is a physical absorption method, which utilizes the solubility of a large amount of methanol in the reaction products and by-products to separate the raw gas from the product in the carbonylation reaction gas phase mixture.

[0093] In step 1) of the above method, the molar ratio of the carbonylation reaction gas phase mixture to methanol is 1:1-10, preferably 1:4-8.

[0094] In step 1) of the above method, the methanol washing is carried out in a washing tower.

[0095] In a preferred embodiment, the top operating temperature of the washing tower is 30-80° C., specifically 30-40° C., 40-60° C., 60-80° C., preferably 40-60° C. The carbonylation reaction gas mixture from the carbonylation reactor enters the methanol washing tower, and dimethyl oxalate in the mixed gas is washed with liquid methanol.

[0096] In a preferred embodiment, the operating temperature of the bottom of the washing tower is 50-130°C, such as 50-70°C, 70-110°C, 110-130°C, preferably 70-110°C.

[0097] In a preferred embodiment, the washing tower is provided with a first packing layer, and the packing in the first packing layer is selected from at least one of polypropylene multifaceted balls, PP Raschig rings, and M250Y packing. The polypropylene multifaceted balls are made of polypropylene plastic and are spherical. The PP Raschig rings are made of PP polypropylene and are made of PP polypropylene. The M250Y packing is a conventionally used M250Y structured packing.

[0098] The methanol washing can achieve the increase of light components such as nitrogen monoxide, carbon monoxide, methyl nitrite, methyl formate and methanol in the carbonylation reaction gas phase mixture by maintaining the bottom operating temperature of the washing tower, and the decrease of heavy components such as dimethyl oxalate and dimethyl carbonate, so as to achieve gas-liquid separation and obtain the first gas phase mixture and the first liquid phase mixture. At the same time, by heating the first liquid phase mixture, the methyl nitrite (MN) dissolved in the first liquid phase mixture can be desorbed as much as possible to avoid affecting the subsequent decarbonylation reaction.

[0099] In step 1) of the above method, the operating pressure of the methanol washing is 0.20-0.40 MPa, specifically 0.20-0.30 MPa, 0.30-0.40 MPa, 0.28-0.38 MPa, preferably 0.28-0.38 MPa.

[0100] In step 1) of the above method, the pressure drop of the methanol washing is 0-30 kPa, specifically 0-10 kPa, 10-20 kPa, 20-30 kPa, preferably 0-10 kPa. The pressure drop is the full tower pressure drop of the washing tower where the methanol washing is located. Controlling the pressure drop within a certain range can avoid a large pressure loss.

[0101] In step 1) of the above method, the first gas phase mixture is condensed to achieve gas-liquid separation to obtain a first gas phase separation product and a first liquid phase separation product. The first gas phase separation product is discharged and the first liquid phase separation product is refluxed as washing methanol.

[0102] In a preferred embodiment, the condensation temperature is 32-45°C.

[0103] In a preferred embodiment, the condensation pressure is 0.26-0.36 MPa.

[0104] Since the saturated vapor pressure of methanol is relatively high, more methanol vapor is carried away from the top of the tower. After condensation, gas-liquid separation is achieved, and the methanol in the first gas phase mixture is separated into the first liquid phase separation product, which is refluxed as the washing methanol of the methanol washing tower. The nitric oxide, methyl nitrite (MN) and methyl formate in the first gas phase mixture are discharged as the non-condensable part of the first gas phase separation product for subsequent treatment.

[0105] In step 2) of the above method, the flash evaporation and light removal are carried out in a light removal tower.

[0106] In a preferred embodiment, a packing is provided at the top of the lightness removal tower, and the packing is selected from one of 500Y plate corrugated packing and 304 stainless steel plate corrugated structured packing. The 500Y plate corrugated packing is a conventionally used 500Y perforated plate corrugated packing. The 304 stainless steel plate corrugated structured packing is a conventionally used plate corrugated structured packing made of 304 stainless steel.

[0107] In a further preferred embodiment, methanol is sprayed into the upper part of the packing, and the amount of methanol is 0.10-0.50m 3 / h, preferably 0.20-0.40m 3 / h. Used to wash dimethyl oxalate (DMO).

[0108] In a further preferred embodiment, nitrogen is introduced into the lower part of the packing during flash evaporation, and the amount of nitrogen is 50-130 Nm 3 / h, preferably 60-120Nm 3 / h. It is used to strip methyl nitrite (MN) in the first liquid phase mixture.

[0109] In a preferred embodiment, the top operating temperature of the light-removal tower is 50-75° C., specifically 50-60° C., 60-75° C., 65-70° C., so as to facilitate the separation of light components MN and the like from the top of the light-removal tower.

[0110] In a preferred embodiment, the bottom operating temperature of the lightness removal tower is 60-80° C., specifically 60-70° C., 70-80° C., 65-75° C., so as to obtain dimethyl oxalate, dimethyl carbonate and a small amount of methanol from the bottom of the tower.

[0111] In step 2) of the above method, the input amount of the first liquid phase mixture is 20-50m 3 / h.

[0112] In step 2) of the above method, the operating pressure of the flash distillation and light removal is 0.03-0.06MPa, specifically 0.03-0.04MPa, 0.04-0.05MPa, 0.05-0.06MPa, so as to facilitate the flash distillation of the light component gas in the mixture by reduced pressure in the light removal tower.

[0113] The above-mentioned flash evaporation and light removal are used to further remove methyl nitrite (MN) in the first liquid phase mixture obtained after methanol washing, and 97% of methyl nitrite in the first liquid phase mixture can be removed.

[0114] In step 2) of the above method, the second liquid phase mixture can also be refined to produce dimethyl oxalate (DMO), and dimethyl oxalate can be further hydrogenated to produce ethylene glycol or methyl glycolate.

[0115] In step 3) of the above method, the input amount of the second liquid phase mixture is 20-50m 3 / h.

[0116] In step 3) of the above method, the vaporization operating temperature is 180-190°C, such as 180-185°C, 185-190°C.

[0117] In step 3) of the above method, the vaporization operating pressure is 0-0.5 MPa, such as 0-0.2 MPa, 0.2-0.4 MPa, 0.4-0.5 MPa.

[0118] In step 3) of the above method, nitrogen is introduced during the vaporization, and the amount of nitrogen used is 50-120 Nm 3 / h, preferably 60-110Nm 3 / h. N 2 It is used to heat and vaporize the second liquid phase mixture after contact with the feed, so as to facilitate the subsequent decarbonylation catalytic reaction of the second gas phase mixture to prepare DMC.

[0119] In a preferred embodiment, the nitrogen is preheated at a temperature of 120-150° C. The nitrogen is preheated by passing through a packing layer.

[0120] In step 3) of the above method, the vaporization is performed in a vaporizer.

[0121] In a preferred embodiment, a packing is arranged in the lower part of the vaporizer, and the packing includes but is not limited to Raschig rings, Pall rings, step rings, arc saddle packing and the like.

[0122] In a further preferred embodiment, the filler is selected from one of Raschig rings, Pall rings, step rings or saddle fillers.

[0123] In step 4) of the above method, the input amount of the second gas phase mixture is 5000-10000 Nm 3 / h.

[0124] In step 4) of the above method, the temperature of the decarbonylation catalytic reaction is 180-300°C, specifically 180-200°C, 200-270°C, 270-300, preferably 200-270°C.

[0125] In step 4) of the above method, the pressure of the decarbonylation catalytic reaction is 0-1.0 MPa, specifically 0-0.1 MPa, 0.1-0.5 MPa, 0.5-1.0 MPa, preferably 0.1-0.5 MPa.

[0126] In step 4) of the above method, the reaction space velocity of the decarbonylation catalytic reaction is 500-9000h -1 , such as 500-3000h -1 , 3000-4000h -1 , 4000-9000h -1 , preferably 3000-4000h -1 .

[0127] In step 4) of the above method, the decarbonylation catalytic reaction uses a decarbonylation catalyst as a supported catalyst.

[0128] In a preferred embodiment, the active component of the supported catalyst is selected from MgCl 2 、ZnCl 2 , K 2 CO 3 、Na 2 CO 3 , KF, Rb 2 CO 3 , Cs 2 CO 3 、Zn(OAC) 2 、Mn(OAC) 2 or Ce(OAC) 2 One or more combinations thereof, wherein the carrier in the supported catalyst is selected from one or more combinations thereof: activated carbon, molecular sieve, diatomaceous earth, alumina, silicon oxide, silica gel or silicon carbide.

[0129] In a further preferred embodiment, the loading amount of the active component in the supported catalyst is 5.0wt%-30.0wt%, specifically 5.0wt%-15.0wt%, 15.0wt%-25.0wt%, 25.0wt%-30.0wt%, preferably 15.0wt%-25.0wt%.

[0130] In step 4) of the above method, the decarbonylation catalytic reaction is carried out in a decarbonylation reactor.

[0131] In step 4) of the above method, the gas-liquid separation is performed at room temperature, which is 20-30°C.

[0132] Since the gas phase product in the gas-liquid mixture is mainly CO, it can be separated from the liquid phase product, mainly dimethyl carbonate, at room temperature to achieve gas-liquid separation. Therefore, the gas phase products such as CO can be recycled and utilized, such as reflux to prepare the gas phase mixture of carbonylation reaction, and the liquid phase product enters the subsequent DMC distillation treatment to obtain the dimethyl carbonate product.

[0133] A second aspect of the present invention provides a system for continuously producing dimethyl carbonate, such as Figure 1 As shown, including:

[0134] A washing tower, used for washing the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture and a first liquid phase mixture;

[0135] A light-removal tower, the light-removal tower is connected to the washing tower, and is used to receive the first liquid phase mixture provided by the washing tower for flash evaporation and light-removal to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture;

[0136] A vaporizer, the vaporizer is connected to the light-removing tower and is used to receive the second liquid phase mixture provided by the light-removing tower and vaporize it to obtain a second gas phase mixture;

[0137] A decarbonylation reactor, the decarbonylation reactor is connected to the vaporizer and is used to receive the second gas phase mixture provided by the vaporizer to perform a decarbonylation catalytic reaction to obtain a gas-liquid mixture;

[0138] A first gas-liquid separator, which is connected to the decarbonylation reactor and is used to receive the gas-liquid mixture provided by the decarbonylation reactor and perform gas-liquid separation to obtain a gas phase product and a liquid phase product;

[0139] The distillation device is connected to the first gas-liquid separator and is used to receive the liquid phase product provided by the first gas-liquid separator for distillation to provide a dimethyl carbonate product.

[0140] In the above system, if Figure 1 As shown, a carbonylation reactor is also included, which is connected to the washing tower, the light-removing tower and the first gas-liquid separator respectively, and is used to prepare a carbonylation reaction gas mixture and provide the carbonylation reaction gas mixture to the washing tower for methanol washing, receive the methyl nitrite-containing gas mixture provided by the light-removing tower for reflux to prepare the carbonylation reaction gas mixture, and receive the gas product provided by the first gas-liquid separator for reflux to prepare the carbonylation reaction gas mixture.

[0141] The carbonylation reactor is a conventional carbonylation reactor, specifically a tube-in-tube fixed bed reactor, in which a catalyst is loaded, methyl nitrite and CO are added as raw materials for reaction, and heat is transferred by saturated water.

[0142] In a preferred embodiment, Figure 1 As shown, a heat exchanger is provided on the feed pipeline of the carbonylation reactor. The heat exchanger is used for preheating. The heat exchanger is a conventional heat exchanger, specifically a horizontal shell-and-tube heat exchanger.

[0143] In a preferred embodiment, Figure 1 As shown, the carbonylation reactor is connected to the feed inlet of the washing tower via a first discharge pipeline.

[0144] In the above system, if Figure 1 As shown, a first methanol inlet is provided at the top of the washing tower.

[0145] In the above system, if Figure 1 As shown, a plurality of first packing layers are arranged in the washing tower, wherein the first packing layer is arranged in the middle of the washing tower, and the feed inlet of the washing tower is arranged in the middle of the washing tower and between the first packing layers.

[0146] The scrubber is a conventional scrubber. The scrubber countercurrently contacts the carbonylation reaction gas mixture from the carbonylation reactor with methanol input from the top of the scrubber, separates the first liquid mixture in the bottom of the scrubber, and separates the first gas mixture at the top of the scrubber. That is, methanol is used to absorb DMO and DMC in the carbonylation reaction gas mixture.

[0147] In the above system, if Figure 1 As shown, the washing tower is provided with a second gas-liquid separator outside, and the second gas-liquid separator is connected to the top of the washing tower through a first output pipeline and a first input pipeline respectively to form a circulation loop. A condenser is also provided on the first output pipeline, which is used to condense the first gas phase mixture from the washing tower through the first output pipeline in the condenser, and the first liquid phase separation obtained after gas-liquid separation in the second gas-liquid separator is refluxed to the washing tower through the first input pipeline as washing methanol.

[0148] The second gas-liquid separator is a conventional gas-liquid separator. The condenser is a conventional condenser.

[0149] In a preferred embodiment, Figure 1 As shown, the first input pipeline is also provided with a reflux pump for providing power for reflux of the first liquid phase separation product. The reflux pump is a conventional centrifugal pump.

[0150] In the above system, if Figure 1 As shown, a reboiler is provided outside the washing tower, and the reboiler is connected to the kettle of the washing tower through a second output pipeline and a second input pipeline respectively to form a circulation loop, which is used to steam heat the kettle of the washing tower to maintain the bottom temperature of the washing tower and realize the separation of the first gas phase mixture and the first liquid phase mixture.

[0151] The reboiler is a conventional reboiler, specifically a vertical tube-in-tube reboiler, that is, steam is transported through the shell side of the reboiler, and DMO, DMC, methanol, etc. are transported through the tube side.

[0152] In the above system, if Figure 1 As shown, the washing tower is connected to the feed port of the light-removing tower via a second discharge pipeline, and a first liquid pump is provided on the second discharge pipeline. The first liquid pump is used to provide power for inputting the first liquid phase mixture into the light-removing tower. The first liquid pump is a conventional centrifugal pump.

[0153] In the above system, if Figure 1 As shown, the top of the light removal tower is provided with a second methanol input port for inputting methanol to wash dimethyl oxalate (DMO). The light removal tower is a conventional light removal tower.

[0154] In the above system, if Figure 1 As shown, the de-lightening tower is provided with a second packing layer, the second packing layer is arranged at the upper part of the de-lightening tower, and the feed port of the de-lightening tower and the first nitrogen input port are respectively arranged below the second packing layer, for inputting the first liquid phase mixture into the N 2 The methyl nitrite in the first liquid phase mixture is stripped.

[0155] In a preferred embodiment, Figure 1 As shown, the feed inlet of the lightness removal tower is arranged in the middle of the lightness removal tower.

[0156] In the above system, if Figure 1 As shown, the lightness removal tower is provided with a heater, which is connected to the bottom of the lightness removal tower through a third output pipeline and a third input pipeline to form a circulation loop, and is used to heat the bottom of the lightness removal tower to maintain the temperature and ensure that DMO does not crystallize and solidify. The heater is a conventional heater.

[0157] In the above system, if Figure 1 As shown, the light removal tower is connected to the feed port of the vaporizer via a third discharge pipeline.

[0158] In a preferred embodiment, Figure 1As shown, the third discharge pipeline is provided with a second liquid pump and a regulating valve in sequence along the direction of inputting into the vaporizer. The second liquid pump is used to provide power for inputting the second liquid phase mixture into the vaporizer. The regulating valve is used to adjust the flow direction and flow rate of the second liquid phase mixture. The second liquid pump can be input not only into the vaporizer but also into the DMO refining section for further hydrogenation to produce ethylene glycol or methyl glycolate. The second liquid pump is a conventional centrifugal pump. The regulating valve is a conventional regulating valve.

[0159] In the above system, if Figure 1 As shown, the vaporizer is provided with a third packing layer, the third packing layer is provided at the lower part of the vaporizer, a feed port of the vaporizer is provided above the third packing layer, and a second nitrogen input port is provided below the third packing layer, which is used to contact and vaporize the nitrogen preheated by the third packing layer with the second liquid phase mixture. The vaporizer is a conventional vaporizer with built-in packing.

[0160] In a preferred embodiment, the feed port of the vaporizer is connected to a liquid distributor for spraying and atomizing the second liquid phase mixture in the vaporizer through the liquid distributor. The liquid distributor is a conventional liquid distributor, such as a trough-type liquid distributor.

[0161] In a preferred embodiment, the second nitrogen inlet is arranged at the bottom of the vaporizer.

[0162] In the above system, if Figure 1 As shown, a heating plate is provided in the vaporizer to ensure the vaporization of the second liquid phase mixture. The heating plate is a conventional heating plate.

[0163] In a preferred embodiment, the heating plate is disposed at the bottom of the vaporizer.

[0164] In the above system, if Figure 1 As shown, the vaporizer is connected to the feed inlet of the decarbonylation reactor via a fourth discharge pipeline.

[0165] In a preferred embodiment, Figure 1 As shown, the fourth discharge pipeline is provided with a circulation compressor and a preheater in sequence along the direction of inputting the decarbonylation reactor, the circulation compressor is used to provide power for inputting the second gas phase mixture into the decarbonylation reactor, and the preheater is used to heat the second gas phase mixture to the required temperature of the decarbonylation reactor. The circulation compressor is a conventional circulation compressor. The preheater is a conventional preheater.

[0166] In a preferred embodiment, Figure 1 As shown, the feed inlet of the decarbonylation reactor is arranged at the top of the decarbonylation reactor.

[0167] In the above system, if Figure 1 As shown, the input end of the decarbonylation reactor is also provided with a third nitrogen inlet for providing nitrogen required for the decarbonylation catalytic reaction.

[0168] The decarbonylation reactor is a conventional decarbonylation reactor, specifically a tube-in-tube fixed bed reactor.

[0169] In a preferred embodiment, Figure 1 As shown, the third nitrogen inlet is arranged at the top of the decarbonylation reactor.

[0170] In the above system, if Figure 1 As shown, a decarbonylation catalyst is arranged in the decarbonylation reactor for carrying out a decarbonylation catalytic reaction.

[0171] In the above system, if Figure 1 As shown, the decarbonylation reactor is connected to the feed port of the first gas-liquid separator via a fifth discharge pipeline, and is used to receive the gas-liquid mixture provided by the decarbonylation reactor for gas-liquid separation to obtain gas phase products and liquid phase products.

[0172] The first gas-liquid separator is a conventionally used gas-liquid separator.

[0173] In the above system, if Figure 1 As shown, the first gas-liquid separator is connected to the distillation device via the sixth discharge pipeline, which is used to receive the liquid phase product provided by the first gas-liquid separator for distillation to provide dimethyl carbonate product. The distillation device is a conventional distillation device. The distillation device refines and purifies the crude product.

[0174] In the above system, if Figure 1 As shown, the first gas-liquid separator is connected to the carbonylation reactor via the seventh discharge pipeline, and receives the gaseous products such as CO provided by the first gas-liquid separator for reflux to prepare a gaseous mixture for carbonylation reaction.

[0175] In the above system, if Figure 1 As shown, the first discharge pipeline, the second discharge pipeline, the third discharge pipeline, the fourth discharge pipeline, and the fifth discharge pipeline are heated by low-pressure steam at a pressure of 0.04-0.05 MpaG to prevent dimethyl oxalate from crystallizing in the equipment and pipelines.

[0176] In the above system, if Figure 1 As shown, the temperature of the first discharge pipeline, the second discharge pipeline, the third discharge pipeline, the fourth discharge pipeline, and the fifth discharge pipeline is kept above 60° C. to prevent dimethyl oxalate from crystallizing in the equipment and pipelines.

[0177] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention.

[0178] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0179] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art; all pressure values ​​and ranges refer to relative pressures.

[0180] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0181] Example 1

[0182] Use Figure 1 The system for continuously producing dimethyl carbonate shown in the figure is used to continuously produce dimethyl carbonate, and the specific steps are as follows:

[0183] (1) Methyl nitrite and carbon monoxide (CO) treated by a heat exchanger are introduced into a carbonylation reactor for carbonylation reaction at a pressure of 0.3 MPa and a reaction temperature of 135° C. to obtain a carbonylation reaction gas phase mixture. In the carbonylation reaction gas phase mixture, the main product is dimethyl oxalate (DMO), and the by-products are dimethyl carbonate (DMC), methyl nitrite (MN), methanol, methyl formate, etc.

[0184] (2) The carbonylation reaction gas phase mixture is fed into the washing tower through the first discharge pipeline from the feed port of the washing tower, and methanol is fed from the first methanol input port at the top of the washing tower, the molar ratio of the carbonylation reaction gas phase mixture to methanol is 1:6, the carbonylation reaction gas phase mixture is washed by methanol, the carbonylation reaction gas phase mixture and methanol are in countercurrent contact on the filler of the first filler layer, and the first gas phase mixture and the first liquid phase mixture are separated by utilizing the large solubility of methanol in absorbing dimethyl oxalate and dimethyl carbonate. The first gas phase mixture includes nitrogen monoxide, carbon monoxide, methyl nitrite, methyl formate and methanol, and the first liquid phase mixture includes dimethyl oxalate (DMO), dimethyl carbonate (DMC), methyl nitrite (MN), methanol and methyl formate.

[0185] The top operating temperature of the washing tower is 50°C, the bottom operating temperature of the washing tower is 90°C, the filler in the first packing layer is a polypropylene multi-faceted ball, the operating pressure of methanol washing is 0.30MPa, and the full tower pressure drop of methanol washing is 10kPa. In the washing tower, methanol can also dissolve methyl nitrite, which will increase the consumption of raw materials for carbonylation reaction. The bottom temperature of the washing tower is maintained by a reboiler to heat the tower kettle, so that light components such as methanol and methyl nitrite in the tower rise, and heavy components such as DMO fall and continuously contact with the rising steam in the tower, and at the same time, the methyl nitrite dissolved in methanol can be desorbed, thereby reducing the methyl nitrite content in the first liquid phase mixture. At the same time, due to the high saturated vapor pressure of methanol, the amount of methanol vapor taken away from the top of the tower is relatively large. The first gas phase mixture is condensed by the condenser at 40°C and 0.31MPa through the first output pipeline, and then separated into gas and liquid by the second gas-liquid separator to obtain the first gas phase separation and the first liquid phase separation. The first gas phase separation includes nitrogen monoxide, carbon monoxide, and methyl nitrite. After being discharged, it can be refluxed into the carbonylation reactor through subsequent treatment to prepare the carbonylation reaction gas phase mixture, thereby reducing the consumption of raw materials. The first liquid phase separation is refluxed into the washing tower through the first output pipeline by the reflux pump as washing methanol.

[0186] (3) The first liquid phase mixture was heated at 35 m 3 The input volume of / h is fed into the de-lightening tower through the second discharge pipeline and the feed port of the de-lightening tower by the first liquid pump, and part of the gas remaining dissolved in the first liquid phase mixture is flashed, and then the light component gas such as methyl nitrite is removed to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture. The upper part of the de-lightening tower is provided with a second packing layer, and the packing in the second packing layer is a 500Y plate corrugated packing. 0.30m methanol is fed into the second methanol input port at the top of the de-lightening tower. 3 / h, dimethyl oxalate is washed, and N is input from the first nitrogen inlet at the bottom of the second packing layer during flash evaporation. 2 90Nm 3 / h stripping methyl nitrite in the first liquid phase mixture. The bottom of the lightness removal tower is heated by a heater connected through a third output pipeline and a third input pipeline to form a circulation loop to maintain the temperature and ensure that DMO does not crystallize and solidify. The top operating temperature of the lightness removal tower is 65°C, the bottom operating temperature of the lightness removal tower is 70°C, and the operating pressure is 0.045MPa. About 97% of DMO is produced in the bottom of the lightness removal tower, and the gas phase mixture containing methyl nitrite is refluxed to the carbonylation reactor to prepare a gas phase mixture for carbonylation reaction.

[0187] (4) The second liquid phase mixture was heated at 35 m 3 The input amount of / h is fed into the vaporizer through the third discharge pipeline and the feed port of the vaporizer by the second liquid pump for vaporization to obtain a second gas phase mixture. The lower part of the vaporizer is provided with a third packing layer, and the packing in the third packing layer is Raschig ring. The vaporization operating temperature is 190°C and the vaporization operating pressure is 0.5MPa. 85Nm nitrogen is fed into the second nitrogen inlet of the vaporizer. 3 / h, nitrogen is preheated at 135°C by passing through the third packing layer, and the second liquid phase mixture is sprayed and atomized through a liquid distributor and vaporized by contacting with the nitrogen preheated by the third packing layer.

[0188] Before the second liquid phase mixture is input into the vaporizer, the flow direction and flow rate of the second liquid phase mixture can be adjusted by a regulating valve. The second liquid phase mixture can be input not only into the vaporizer but also into the DMO refining section for further hydrogenation to produce ethylene glycol or methyl glycolate.

[0189] (5) The second gas phase mixture was heated at 7500 Nm 3 The input volume of / h is output from the top of the vaporizer, pressurized by the circulating compressor through the fourth discharge pipeline, heated to the required reaction temperature of the decarbonylation reactor through the preheater, and input into the decarbonylation reactor from the feed port of the decarbonylation reactor to carry out the decarbonylation catalytic reaction to obtain a gas-liquid mixture. Among them, the temperature of the decarbonylation catalytic reaction is 240°C, the pressure of the decarbonylation catalytic reaction is 0.5MPa, and the reaction space velocity of the decarbonylation catalytic reaction is 3000h -1 The decarbonylation catalytic reaction uses a decarbonylation catalyst as a supported catalyst, and the active component is MgCl 2 The carrier is activated carbon, and the loading amount of the active component is 20.0wt%. If necessary, a small amount of nitrogen can be introduced through the third nitrogen inlet to supplement.

[0190] The gas-liquid mixture is fed into the first gas-liquid separator from the feed port of the first gas-liquid separator through the fifth discharge pipeline, and after gas-liquid separation at room temperature, a gas phase product and a liquid phase product are obtained. The operating temperature of the first gas-liquid separator is room temperature.

[0191] The gas phase product containing CO etc. is subsequently treated and then refluxed into the carbonylation reactor to prepare a carbonylation reaction gas phase mixture. The liquid phase product rich in dimethyl carbonate is fed into the rectification device through the sixth discharge pipeline for rectification to provide a dimethyl carbonate product.

[0192] During operation, the first discharge pipeline, the second discharge pipeline, the third discharge pipeline, the fourth discharge pipeline, and the fifth discharge pipeline are all heated by low-pressure steam and kept above 60°C to prevent dimethyl oxalate from crystallizing in the tower equipment and pipelines.

[0193] Example 2

[0194] Use Figure 1 The system for continuously producing dimethyl carbonate shown in the figure is used to continuously produce dimethyl carbonate, and the specific steps are as follows:

[0195] (1) Methyl nitrite and carbon monoxide (CO) treated by a heat exchanger are introduced into a carbonylation reactor for carbonylation reaction at a pressure of 0.3 MPa and a reaction temperature of 140° C. to obtain a carbonylation reaction gas phase mixture. In the carbonylation reaction gas phase mixture, the main product is dimethyl oxalate (DMO), and the by-products are dimethyl carbonate (DMC), methyl nitrite (MN), methanol, methyl formate, etc.

[0196] (2) The carbonylation reaction gas phase mixture is fed into the washing tower through the first discharge pipeline from the feed port of the washing tower, and methanol is fed from the first methanol input port at the top of the washing tower, the molar ratio of the carbonylation reaction gas phase mixture to methanol is 1:4, the carbonylation reaction gas phase mixture is washed by methanol, the carbonylation reaction gas phase mixture and methanol are in countercurrent contact on the filler of the first filler layer, and the first gas phase mixture and the first liquid phase mixture are separated by utilizing the large solubility of methanol in absorbing dimethyl oxalate and dimethyl carbonate. The first gas phase mixture includes nitrogen monoxide, carbon monoxide, methyl nitrite, methyl formate and methanol, and the first liquid phase mixture includes dimethyl oxalate (DMO), dimethyl carbonate (DMC), methyl nitrite (MN), methanol and methyl formate.

[0197] The top operating temperature of the washing tower is 55°C, the bottom operating temperature of the washing tower is 85°C, the filler in the first packing layer is PP Raschig ring, the operating pressure of methanol washing is 0.28MPa, and the full tower pressure drop of methanol washing is 1kPa. In the washing tower, methanol can also dissolve methyl nitrite, which will increase the consumption of raw materials for carbonylation reaction. The bottom temperature of the washing tower is maintained by the reboiler to heat the tower kettle, so that the light components such as methanol and methyl nitrite in the tower rise, and the heavy components such as DMO fall and continuously contact with the rising steam in the tower, and at the same time, the methyl nitrite dissolved in methanol can be desorbed, reducing the methyl nitrite content in the first liquid phase mixture. At the same time, due to the high saturated vapor pressure of methanol, the amount of methanol vapor taken away from the top of the tower is relatively large. The first gas phase mixture is condensed by the condenser at 32°C and 0.36MPa through the first output pipeline, and then separated into gas and liquid by the second gas-liquid separator to obtain the first gas phase separation and the first liquid phase separation. The first gas phase separation includes nitrogen monoxide, carbon monoxide, and methyl nitrite. After being discharged, it can be refluxed into the carbonylation reactor through subsequent treatment to prepare the carbonylation reaction gas phase mixture, thereby reducing the consumption of raw materials. The first liquid phase separation is refluxed into the washing tower through the first output pipeline by the reflux pump as washing methanol.

[0198] (3) The first liquid phase mixture was heated at 20 m 3 The input volume of / h is fed into the de-lightening tower through the second discharge pipeline and the feed port of the de-lightening tower by the first liquid pump, and part of the gas remaining dissolved in the first liquid phase mixture is flashed, and then the light component gas such as methyl nitrite is removed to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture. Among them, the upper part of the de-lightening tower is provided with a second packing layer, and the packing in the second packing layer is a 304 stainless steel plate corrugated structured packing. Methanol 0.20m is fed from the second methanol input port at the top of the de-lightening tower. 3 / h, dimethyl oxalate is washed, and N is input from the first nitrogen inlet at the bottom of the second packing layer during flash evaporation. 2 60Nm 3 / h stripping methyl nitrite in the first liquid phase mixture. The reactor of the lightness removal tower is heated by a heater connected through the third output pipeline and the third input pipeline to form a circulation loop to maintain the temperature and ensure that DMO does not crystallize and solidify. The top operating temperature of the lightness removal tower is 50°C, the bottom operating temperature of the lightness removal tower is 60°C, and the operating pressure is 0.04MPa. DMO is produced in the reactor of the lightness removal tower, and the gas phase mixture containing methyl nitrite is refluxed to the carbonylation reactor to prepare a gas phase mixture for carbonylation reaction.

[0199] (4) The second liquid phase mixture was heated at 20 m 3The input volume of / h is fed into the vaporizer through the third discharge pipeline and the feed port of the vaporizer by the second liquid pump for vaporization to obtain a second gas phase mixture. The lower part of the vaporizer is provided with a third packing layer, and the packing in the third packing layer is a ball ring. The vaporization operating temperature is 180°C and the vaporization operating pressure is 0.2MPa. 60Nm nitrogen is fed into the second nitrogen inlet of the vaporizer. 3 / h, the nitrogen is preheated at 120°C by passing through the third packing layer, and the second liquid phase mixture is sprayed and atomized through a liquid distributor and vaporized by contacting with the nitrogen preheated by the third packing layer.

[0200] Before the second liquid phase mixture is input into the vaporizer, the flow direction and flow rate of the second liquid phase mixture can be adjusted by a regulating valve. The second liquid phase mixture can be input not only into the vaporizer but also into the DMO refining section for further hydrogenation to produce ethylene glycol or methyl glycolate.

[0201] (5) The second gas phase mixture was heated at 5000 Nm 3 The input volume of / h is output from the top of the vaporizer, pressurized by the circulating compressor through the fourth discharge pipeline, heated to the required reaction temperature of the decarbonylation reactor through the preheater, and input into the decarbonylation reactor from the feed port of the decarbonylation reactor to carry out the decarbonylation catalytic reaction to obtain a gas-liquid mixture. Among them, the temperature of the decarbonylation catalytic reaction is 220°C, the pressure of the decarbonylation catalytic reaction is 0.25MPa, and the reaction space velocity of the decarbonylation catalytic reaction is 3500h -1 The decarbonylation catalytic reaction uses a decarbonylation catalyst as a supported catalyst, and the active component is K 2 CO 3 The carrier is a molecular sieve, and the loading amount of the active component is 15.0wt%. If necessary, a small amount of nitrogen can be introduced through the third nitrogen inlet to supplement.

[0202] The gas-liquid mixture is fed into the first gas-liquid separator from the feed port of the first gas-liquid separator through the fifth discharge pipeline, and after gas-liquid separation at room temperature, a gas phase product and a liquid phase product are obtained. The operating temperature of the first gas-liquid separator is room temperature.

[0203] The gas phase product containing CO etc. is subsequently treated and then refluxed into the carbonylation reactor to prepare a carbonylation reaction gas phase mixture. The liquid phase product rich in dimethyl carbonate is fed into the rectification device through the sixth discharge pipeline for rectification to provide a dimethyl carbonate product.

[0204] During operation, the first discharge pipeline, the second discharge pipeline, the third discharge pipeline, the fourth discharge pipeline, and the fifth discharge pipeline are all heated by low-pressure steam and kept above 60°C to prevent dimethyl oxalate from crystallizing in the tower equipment and pipelines.

[0205] Example 3

[0206] Use Figure 1The system for continuously producing dimethyl carbonate shown in the figure is used to continuously produce dimethyl carbonate, and the specific steps are as follows:

[0207] (1) Methyl nitrite and carbon monoxide (CO) treated by a heat exchanger are introduced into a carbonylation reactor at a pressure of 0.32 MPa and a reaction temperature of 145° C. to carry out a carbonylation reaction to obtain a carbonylation reaction gas phase mixture. In the carbonylation reaction gas phase mixture, the main product is dimethyl oxalate (DMO), and the by-products are dimethyl carbonate (DMC), methyl nitrite (MN), methanol, methyl formate, etc.

[0208] (2) The carbonylation reaction gas phase mixture is fed into the washing tower through the first discharge pipeline from the feed port of the washing tower, and methanol is fed from the first methanol input port at the top of the washing tower, the molar ratio of the carbonylation reaction gas phase mixture to methanol is 1:8, the carbonylation reaction gas phase mixture is washed by methanol, the carbonylation reaction gas phase mixture and methanol are in countercurrent contact on the filler of the first filler layer, and the first gas phase mixture and the first liquid phase mixture are separated by utilizing the large solubility of methanol in absorbing dimethyl oxalate and dimethyl carbonate. The first gas phase mixture includes nitrogen monoxide, carbon monoxide, methyl nitrite, methyl formate and methanol, and the first liquid phase mixture includes dimethyl oxalate (DMO), dimethyl carbonate (DMC), methyl nitrite (MN), methanol and methyl formate.

[0209] The top operating temperature of the washing tower is 60°C, the bottom operating temperature of the washing tower is 100°C, the filler in the first packing layer is M250Y filler, the operating pressure of methanol washing is 0.38MPa, and the full tower pressure drop of methanol washing is 5kPa. In the washing tower, methanol can also dissolve methyl nitrite, which will increase the consumption of carbonylation reaction raw materials. The bottom temperature of the washing tower is maintained by the reboiler to heat the tower kettle, so that the light components such as methanol and methyl nitrite in the tower rise, and the heavy components such as DMO fall and continuously contact with the rising steam in the tower, and at the same time, the methyl nitrite dissolved in methanol can be desorbed, thereby reducing the methyl nitrite content in the first liquid phase mixture. At the same time, due to the high saturated vapor pressure of methanol, the amount of methanol vapor taken away from the top of the tower is relatively large. The first gas phase mixture is condensed by the condenser at 45°C and 0.26MPa through the first output pipeline, and then separated into gas and liquid by the second gas-liquid separator to obtain the first gas phase separation and the first liquid phase separation. The first gas phase separation includes nitrogen monoxide, carbon monoxide, and methyl nitrite. After being discharged, it can be refluxed into the carbonylation reactor through subsequent treatment to prepare the carbonylation reaction gas phase mixture, thereby reducing the consumption of raw materials. The first liquid phase separation is refluxed into the washing tower through the first output pipeline by the reflux pump as washing methanol.

[0210] (3) The first liquid phase mixture was heated at 50 m 3The input volume of / h is fed into the de-lightening tower through the second discharge pipeline and the feed port of the de-lightening tower by the first liquid pump, and part of the gas remaining dissolved in the first liquid phase mixture is flashed, and then the light component gas such as methyl nitrite is removed to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture. The upper part of the de-lightening tower is provided with a second packing layer, and the packing in the second packing layer is a 500Y plate corrugated packing. 0.40m methanol is fed into the second methanol input port at the top of the de-lightening tower. 3 / h, dimethyl oxalate is washed, and N is input from the first nitrogen inlet at the bottom of the second packing layer during flash evaporation. 2 120Nm 3 / h stripping methyl nitrite in the first liquid phase mixture. The kettle of the lightness removal tower is heated by a heater connected through the third output pipeline and the third input pipeline to form a circulation loop to maintain the temperature and ensure that DMO does not crystallize and solidify. The top operating temperature of the lightness removal tower is 60°C, the bottom operating temperature of the lightness removal tower is 75°C, and the operating pressure is 0.05MPa. DMO is produced in the kettle of the lightness removal tower, and the gaseous mixture containing methyl nitrite is refluxed to the carbonylation reactor to prepare a gaseous mixture for carbonylation reaction.

[0211] (4) The second liquid phase mixture was heated at 50 m 3 The input volume of / h is fed into the vaporizer through the third discharge pipeline and the feed port of the vaporizer by the second liquid pump for vaporization to obtain a second gas phase mixture. The lower part of the vaporizer is provided with a third packing layer, and the packing in the third packing layer is an arc saddle packing. The vaporization operating temperature is 190°C and the vaporization operating pressure is 0.3MPa. Nitrogen 110Nm is fed into the second nitrogen inlet of the vaporizer. 3 / h, the nitrogen is preheated at 150°C by passing through the third packing layer, and the second liquid phase mixture is sprayed and atomized through a liquid distributor, and is vaporized by contacting with the nitrogen preheated by the third packing layer.

[0212] Before the second liquid phase mixture is input into the vaporizer, the flow direction and flow rate of the second liquid phase mixture can be adjusted by a regulating valve. The second liquid phase mixture can be input not only into the vaporizer but also into the DMO refining section for further hydrogenation to produce ethylene glycol or methyl glycolate.

[0213] (5) The second gas phase mixture was heated at 10000 Nm 3 The input volume of / h is output from the top of the vaporizer, pressurized by the circulating compressor through the fourth discharge pipeline, heated to the required reaction temperature of the decarbonylation reactor through the preheater, and input into the decarbonylation reactor from the feed port of the decarbonylation reactor to carry out the decarbonylation catalytic reaction to obtain a gas-liquid mixture. Among them, the temperature of the decarbonylation catalytic reaction is 200°C, the pressure of the decarbonylation catalytic reaction is 0.3MPa, and the reaction space velocity of the decarbonylation catalytic reaction is 4000h -1The decarbonylation catalytic reaction uses a decarbonylation catalyst as a supported catalyst, and the active component is Zn(OAC) 2 The carrier is diatomaceous earth, and the loading amount of the active component is 25.0 wt %. If necessary, a small amount of nitrogen can be introduced through the third nitrogen inlet to supplement.

[0214] The gas-liquid mixture is fed into the first gas-liquid separator from the feed port of the first gas-liquid separator through the fifth discharge pipeline, and after gas-liquid separation at room temperature, a gas phase product and a liquid phase product are obtained. The operating temperature of the first gas-liquid separator is room temperature.

[0215] The gas phase product containing CO etc. is subsequently treated and then refluxed into the carbonylation reactor to prepare a carbonylation reaction gas phase mixture. The liquid phase product rich in dimethyl carbonate is fed into the rectification device through the sixth discharge pipeline for rectification to provide a dimethyl carbonate product.

[0216] During operation, the first discharge pipeline, the second discharge pipeline, the third discharge pipeline, the fourth discharge pipeline, and the fifth discharge pipeline are all heated by low-pressure steam and kept above 60°C to prevent dimethyl oxalate from crystallizing in the tower equipment and pipelines.

[0217] Example 4

[0218] The continuous reaction of the system in Example 1 is stably operated. During the continuous reaction, the first liquid phase mixture obtained from the tower kettle of the washing tower, the second liquid phase mixture obtained from the tower kettle of the light removal tower, and the gas-liquid mixture obtained from the decarbonylation reactor are sampled multiple times. By means of weighing, gas chromatography and other means, it can be seen that after treatment by the washing tower, the light removal tower and the decarbonylation reactor, the composition of the decarbonylation reaction raw materials, the conversion rate of the decarbonylation reaction DMO, and the selectivity of the decarbonylation reaction product DMC are as follows. The specific results are shown in Tables 1, 2, and 3.

[0219] In Tables 1, 2 and 3 below, samples 1-6 represent samples sampled at different time points at three sampling points. In Table 3 below, DMO conversion and DMC selectivity are calculated according to the following formulas (1) and (2).

[0220] Formula (1): DMO conversion rate (%) = amount of reactants participating in the reaction / total amount of reactants input × 100%;

[0221] Formula (2): DMC selectivity (%) = amount of reactant converted to target product / amount of reactant participating in the reaction × 100%.

[0222] Table 1 Composition analysis of the first liquid phase mixture obtained from the washing tower kettle

[0223] sample DMO / % Methanol / % DMC / % Methylal / % Methyl formate / % 1 91.32 6.58 1.52 0.01 0.58 2 89.46 8.34 1.75 0.01 0.65 3 90.05 7.36 1.99 0.02 0.59 4 86.24 11.41 1.61 0.03 0.70 5 88.06 9.53 1.72 0.03 0.67 6 86.87 10.47 1.94 0.03 0.69

[0224] Table 2 Composition analysis of the second liquid phase mixture obtained from the bottom of the light removal tower

[0225] sample DMO / % Methanol / % DMC / % Methylal / % Methyl formate / % 1 97.05 1.16 1.41 0.01 0.37 2 96.49 1.26 1.82 0.02 0.41 3 96.59 1.16 1.79 0.01 0.45 4 96.35 1.25 1.94 0.02 0.44 5 96.87 1.12 1.59 0.01 0.42 6 95.40 1.63 2.49 0.03 0.50

[0226] Table 3 Composition analysis of the gas-liquid mixture obtained from the decarbonylation reactor and its conversion rate and selectivity

[0227]

[0228] As shown in Table 1, the first liquid phase mixture composition obtained after washing the carbonylation reaction gas phase mixture with methanol is the feed composition of the light-removing tower. As shown in Table 2, after removing the light components through the light-removing tower, most of the methanol and part of the methyl formate in most of the decarbonylation raw materials can be removed. As shown in Table 3, the gas-liquid mixture composition distribution and decarbonylation performance after the decarbonylation reaction indicate that the process has an excellent decarbonylation effect, so that the vast majority of dimethyl oxalate in the carbonylation reaction gas phase mixture is converted, while maintaining a high selectivity for dimethyl carbonate.

[0229] It can be seen that the present invention provides a system for the continuous production of dimethyl carbonate. Through methanol washing, light removal and other processes, MN and most of the methanol in the DMO decarbonylation raw material can be effectively removed, so that the carbonyl synthesis of DMO and the decarbonylation of DMO to produce DMC are organically combined, and the continuous and stable production of DMC is realized. At the same time, the decarbonylation catalyst provided by the present invention is used in the decarbonylation reaction of dimethyl oxalate, and the selectivity and conversion rate are very good compared with the catalysts in the prior art. It is more economical in industry and suitable for fixed bed continuous reaction, making it more conducive to industrial promotion and use.

[0230] In summary, the present invention further provides a system for continuously producing dimethyl carbonate. The method and system for continuously producing dimethyl carbonate provided by the present invention can effectively remove MN, so that the catalytic reaction of preparing DMC by decarbonylation of DMO as a raw material proceeds smoothly, and the continuous and stable production of DMC is realized. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0231] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for continuously producing dimethyl carbonate, comprising the following steps: 1) washing the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture and a first liquid phase mixture; 2) flashing and removing light from the first liquid phase mixture obtained in step 1) to obtain a gas phase mixture containing methyl nitrite and a second liquid phase mixture; 3) vaporizing the second liquid phase mixture obtained in step 2) to obtain a second gas phase mixture; 4) subjecting the second gas phase mixture obtained in step 3) to a catalytic decarbonylation reaction to obtain a gas-liquid mixture, and then subjecting the mixture to gas-liquid separation to obtain a gas phase product and a liquid phase product, and the liquid phase product is distilled to provide a dimethyl carbonate product.

2. A method for continuously producing dimethyl carbonate according to claim 1, characterized in that, Step 1) includes any one or more of the following conditions: A1) the molar ratio of the carbonylation reaction gas phase mixture to methanol is 1:1-10; A2) the methanol washing is carried out in a washing tower; preferably, the operating temperature of the top of the washing tower is 30-80° C., and the operating temperature of the bottom of the washing tower is 50-130° C.; A3) the operating pressure of the methanol washing is 0.20-0.40MPa; A4) the pressure drop of the methanol washing is 0-30 kPa; A5) The first gas phase mixture is condensed to achieve gas-liquid separation to obtain a first gas phase separation product and a first liquid phase separation product. The first gas phase separation product is discharged and the first liquid phase separation product is refluxed as washing methanol.

3. A method for continuously producing dimethyl carbonate according to claim 1, characterized in that: Step 2) includes any one or more of the following conditions: B1) refluxing the gas phase mixture containing methyl nitrite to prepare a carbonylation reaction gas phase mixture; B2) the flash distillation and light removal are carried out in a light removal tower; B3) The input amount of the first liquid phase mixture is 20-50m 3 / h; B4) The operating pressure of the flash evaporation and light removal is 0.03-0.06MPa.

4. A method for continuously producing dimethyl carbonate according to claim 3, characterized in that: Item B2) also includes any one or more of the following conditions: B21) The upper part of the light removal tower is provided with a packing; preferably, methanol is sprayed into the upper part of the packing, and the amount of methanol is 0.10-0.50m 3 / h, nitrogen is introduced into the lower part of the packing during flash evaporation, and the amount of nitrogen used is 50-130Nm 3 / h; B22) the tower top operating temperature of the light removal tower is 50-75°C; B23) The bottom operating temperature of the lightness removal tower is 60-80°C.

5. A method for continuously producing dimethyl carbonate according to claim 1, characterized in that: Step 3) includes any one or more of the following conditions: C1) The input amount of the second liquid phase mixture is 20-50m 3 / h; C2) the vaporization operating temperature is 180-190°C; C3) the vaporization operating pressure is 0-0.5MPa; C4) Nitrogen is introduced during the vaporization, and the amount of nitrogen is 50-120Nm 3 / h; preferably, the nitrogen is preheated, and the preheating temperature is 120-150°C.

6. A method for continuously producing dimethyl carbonate according to claim 1, characterized in that: Step 4) includes any one or more of the following conditions: D1) Input amount of the second gas phase mixture 5000-10000Nm 3 / h; D2) the temperature of the decarbonylation catalytic reaction is 180-300°C; D3) the pressure of the decarbonylation catalytic reaction is 0-1.0 MPa; D4) The reaction space velocity of the decarbonylation catalytic reaction is 500-9000h -1 ; D5) the decarbonylation catalytic reaction uses a decarbonylation catalyst as a supported catalyst; D6) the gas-liquid separation is carried out at room temperature; D7) refluxing the gaseous product to prepare a gaseous mixture for carbonylation reaction.

7. A method for continuously producing dimethyl carbonate according to claim 6, characterized in that: Item D5) also includes any one or more of the following conditions: D51) the active component in the supported catalyst is selected from one or more combinations of MgCl2, ZnCl2, K2CO3, Na2CO3, KF, Rb2CO3, Cs2CO3, Zn(OAC)2, Mn(OAC)2 or Ce(OAC)2, and the carrier in the supported catalyst is selected from one or more combinations of activated carbon, molecular sieve, diatomaceous earth, alumina, silicon oxide, silica gel or silicon carbide; D52) The loading amount of the active component in the supported catalyst is 5.0 wt%-30.0 wt%.

8. A system for continuously producing dimethyl carbonate, comprising: A washing tower (T-101) is used to wash the carbonylation reaction gas phase mixture with methanol to separate and obtain a first gas phase mixture (5) and a first liquid phase mixture (8); A light-removal tower (T-102), the light-removal tower (T-102) being connected to the washing tower (T-101), and being used for receiving the first liquid phase mixture (8) provided by the washing tower (T-101) for flash evaporation and light-removal to obtain a gas phase mixture (10) containing methyl nitrite and a second liquid phase mixture (11); A vaporizer (V-101), the vaporizer (V-101) is connected to the light-removing tower (T-102), and is used to receive the second liquid phase mixture (11) provided by the light-removing tower (T-102) for vaporization to obtain a second gas phase mixture (15); a decarbonylation reactor (R-102), the decarbonylation reactor (R-102) being connected to the vaporizer (V-101) and being used for receiving the second gas phase mixture (15) provided by the vaporizer (V-101) to carry out a decarbonylation catalytic reaction to obtain a gas-liquid mixture (17); a first gas-liquid separator (V-103), the first gas-liquid separator (V-103) being connected to the decarbonylation reactor (R-102) and being used for receiving the gas-liquid mixture (17) provided by the decarbonylation reactor (R-102) to carry out gas-liquid separation to obtain a gas phase product (19) and a liquid phase product (18); A distillation device (38) is connected to the first gas-liquid separator (V-103) and is used to receive the liquid phase product (18) provided by the first gas-liquid separator (V-103) for distillation to provide a dimethyl carbonate product.

9. A system for continuously producing dimethyl carbonate according to claim 8, characterized in that: The invention also includes a carbonylation reactor (R-101), wherein the carbonylation reactor (R-101) is connected to a washing tower (T-101), a lightness removal tower (T-102), and a first gas-liquid separator (V-103); Preferably, a heat exchanger (E-101) is provided on the feed pipeline of the carbonylation reactor (R-101); the carbonylation reactor (R-101) is connected to the feed port of the washing tower (T-101) via the first discharge pipeline (20).

10. A system for continuously producing dimethyl carbonate according to claim 8, characterized in that: Also includes any one or more of the following conditions: E1) The top of the washing tower (T-101) is provided with a first methanol input port (21); E2) a plurality of first packing layers (22) are provided in the washing tower (T-101), wherein the first packing layer (22) is provided in the middle of the washing tower (T-101), and a feed inlet of the washing tower (T-101) is provided in the middle of the washing tower (T-101) and between the first packing layers (22); E3) The washing tower (T-101) is provided with a second gas-liquid separator (V-101), and the second gas-liquid separator (V-101) is connected to the top of the washing tower (T-101) through a first output pipeline (23) and a first input pipeline (24) to form a circulation loop, and a condenser (E-103) is also provided on the first output pipeline (23); Preferably, the first input pipeline (24) is also provided with a reflux pump (P-101); E4) The washing tower (T-101) is provided with a reboiler (E-102) outside, and the reboiler (E-102) is connected to the bottom of the washing tower (T-101) through a second output pipeline (25) and a second input pipeline (26) to form a circulation loop; E5) the washing tower (T-101) is connected to the feed port of the lightness removal tower (T-102) via the second discharge pipeline (27); E6) The top of the light removal tower (T-102) is provided with a second methanol input port (9); E7) a second packing layer (28) is provided in the lightness removal tower (T-102), the second packing layer (28) is provided at the upper part of the lightness removal tower (T-102), and a feed inlet of the lightness removal tower (T-102) and a first nitrogen inlet (29) are provided below the second packing layer (28); E8) The lightness removal tower (T-102) is provided with a heater (E-104) outside, and the heater (E-104) is connected to the bottom of the lightness removal tower (T-102) through a third output pipeline (30) and a third input pipeline (31) to form a circulation loop; E9) The light removal tower (T-102) is connected to the feed port of the vaporizer (V-102) via the third discharge pipeline (32); preferably, the third discharge pipeline (32) is provided with a second liquid pump (P-103) and a regulating valve (XV-101) in sequence along the direction of inputting the vaporizer (V-102); E10) A third packing layer (33) is provided in the vaporizer (V-102), the third packing layer (33) is provided at the lower part of the vaporizer (V-102), a feed inlet of the vaporizer (V-102) is provided above the third packing layer (33), and a second nitrogen inlet (14) is provided below the third packing layer (33); E11) the vaporizer (V-102) is connected to the feed port of the decarbonylation reactor (R-102) via the fourth discharge pipeline (34); preferably, the fourth discharge pipeline (34) is provided with a circulation compressor (C-101) and a preheater (E-105) in sequence along the direction of inputting the decarbonylation reactor (R-102); E12) The input end of the decarbonylation reactor (R-102) is further provided with a third nitrogen input port (16); E13) a decarbonylation catalyst is provided in the decarbonylation reactor (R-102); E14) the decarbonylation reactor (R-102) is connected to the feed port of the first gas-liquid separator (V-103) via the fifth discharge pipeline (35); E15) the first gas-liquid separator (V-103) is connected to the distillation device (38) via a sixth discharge pipeline (36); E16) The first gas-liquid separator (V-103) is connected to the carbonylation reactor (R-101) via the seventh discharge pipeline (37).

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