Process and device for producing oxamide

Abstract

The invention discloses a process and a device for producing oxamide, and relates to the field of chemical production. The invention provides a process for producing oxamide, which specifically comprises the following steps: mixing a methanol solution of liquid ammonia and a methanol solution of dimethyl oxalate, carrying out ammonolysis reaction, carrying out flash evaporation, filtration and drying on first slurry after the reaction is finished to obtain solid oxamide, and carrying out liquid phase refining to obtain a byproduct methanol, ammonia in the tail gas is washed and absorbed by dimethyl oxalate and then returns to a reaction system. The methanol solution of dimethyl oxalate is used for absorbing excessive ammonia in the reaction process, and the reaction product is continuously used for producing oxamide, so that methanol and ammonia can be thoroughly separated, the conversion rate of ammonia can be greatly improved, and the economical efficiency of the production process is improved; meanwhile, tail gas containing ammonia is not discharged, and the environmental protection property of the production process is improved.

Description

Technical Field

[0001] The invention relates to the field of chemical production, and in particular to a process and a device for producing oxamide. Background Art

[0002] Oxamide is non-toxic, has low solubility, and is easy to store. It is a very stable colorless crystal or powder at room temperature. It is mainly used in the fields of agriculture and chemical industry. Its rational use can effectively promote plant growth and improve the yield and quality of crops. The preparation of oxamide by the reaction of dimethyl oxalate and ammonia is currently the most common production method in the industry. In the production process, excess ammonia is used to increase the conversion rate of dimethyl oxalate. In addition to solid oxamide, the liquid components of the reaction product system are basically methanol and liquid ammonia. How to fully utilize the ammonia in methanol determines the conversion rate and economic benefits of ammonia in the entire production system.

[0003] Existing technologies such as patent application CN 111153823A, patent application CN 113045442A and patent application CN103242188A all use physical means such as stripping and distillation to separate methanol and ammonia in the liquid phase, but it is difficult to completely separate ammonia from methanol by physical separation; the physical separation of ammonia and alcohol requires a large reflux ratio, thereby consuming steam and cooling water; how to improve the utilization rate of ammonia, reduce the energy consumption of alcohol-ammonia separation, and reduce ammonia emissions is of great significance for improving the economy and environmental protection of industrial production. Summary of the invention

[0004] In view of this, the present invention provides a process and device for producing oxalamide. The production process and supporting device provided by the present invention can reuse the liquid ammonia in the mixed solution of liquid ammonia and methanol generated in the production process through chemical reaction; at the same time, the ammonia in various gases generated by the reaction system is also utilized in the form of chemical reaction, thereby improving the utilization rate of ammonia and improving the economy and environmental protection of the production process.

[0005] The present invention first provides a process for producing oxalamide, comprising:

[0006] a) mixing dimethyl oxalate, liquid ammonia and methanol to undergo an ammonolysis reaction to obtain a first slurry;

[0007] b) performing gas-liquid separation on the first slurry obtained in step a) to obtain a first alcohol-ammonia gas phase mixture and a second slurry; performing solid-liquid separation on the second slurry to obtain a first alcohol-ammonia liquid phase mixture and a third slurry;

[0008] c) drying the third slurry obtained in step b) to obtain a second alcohol-ammonia gas phase mixture and oxalamide solid; mixing the first alcohol-ammonia liquid phase mixture obtained in step b) with a methanol solution of dimethyl oxalate to obtain a fourth slurry;

[0009] d) separating the fourth slurry obtained in step c) into a fifth slurry by solid-liquid separation, and further using the fifth slurry in the aminolysis reaction in step a);

[0010] e) mixing the first alcohol-ammonia gas phase mixture obtained in step b) and the second alcohol-ammonia gas phase mixture obtained in step c) with a methanol solution of dimethyl oxalate to obtain a first liquid phase mixture; and further using the first liquid phase mixture in the aminolysis reaction in step a).

[0011] In some specific implementations, the specific method of reacting the first alcohol-ammonia gas phase mixture, the second alcohol-ammonia gas phase mixture and the methanol solution of dimethyl oxalate in step e) is: the liquid phase is from top to bottom, and the gas phase is from bottom to top, and the two are in countercurrent contact and react.

[0012] In some specific implementations, in step c), a portion of the first alcohol-ammonia liquid phase mixture is mixed with a methanol solution of dimethyl oxalate to react to obtain a fourth slurry; the other portion is returned to step a) for aminolysis reaction.

[0013] In some specific implementations, the fourth slurry in step d) further includes a second liquid phase mixture after solid-liquid separation; the second liquid phase mixture is refined to obtain methanol and a third liquid phase mixture, and the third liquid phase mixture is further used in the aminolysis reaction in step a).

[0014] In some specific implementations, in step e), the first alcohol-ammonia gas phase mixture and the second alcohol-ammonia gas phase mixture are mixed with the methanol solution of dimethyl oxalate to produce a first gas phase mixture; the first gas phase mixture is purified and then discharged.

[0015] The present invention also provides a device for producing oxalamide corresponding to the above production process, comprising: a feeding unit, a reaction unit and a separation unit;

[0016] The feeding unit comprises: an alcohol-ammonia mixing device for mixing methanol and liquid ammonia and an alcohol-ester mixing device for mixing methanol and dimethyl oxalate;

[0017] The reaction unit comprises:

[0018] A reactor whose material inlet is respectively connected to the material outlet of the alcohol-ammonia mixing device and the material outlet of the alcohol-ester mixing device;

[0019] A purifier whose material inlet is respectively connected to the material outlet of the alcohol-ammonia mixing device and the material outlet of the reactor;

[0020] The separation unit comprises:

[0021] a gas-liquid separation device having a material inlet connected to a material outlet of the purifier;

[0022] A first solid-liquid separation device having a material inlet connected to a liquid phase discharge port of the gas-liquid separation device, wherein the liquid phase discharge port of the first solid-liquid separation device is respectively connected to a feed port of the alcohol-ammonia mixing device and a feed port of the first alcohol-ammonia separation device;

[0023] A drying device having a material inlet connected to a solid discharge port of the first solid-liquid separation device;

[0024] A first alcohol-ammonia separation device whose material inlet is respectively connected to the liquid phase discharge port of the first solid-liquid separation device and the discharge port of the alcohol-ester mixing device;

[0025] A second solid-liquid separation device having a material inlet connected to the material outlet of the first alcohol-ammonia separation device, and a solid phase discharge port of the second solid-liquid separation device connected to the material inlet of the alcohol-ester mixing device;

[0026] A second alcohol-ammonia separation device wherein the first material inlet is connected to the gas phase discharge port of the gas-liquid separation device and the gas phase discharge port of the drying device respectively, and the second material inlet of the second alcohol-ammonia separation device is connected to the material outlet of the alcohol-ester mixing device.

[0027] In some specific implementations, the first alcohol-ammonia separation device is an ester-ammonia reactor; and the purifier is a plug-flow-like reactor.

[0028] In some specific implementations, the second alcohol-ammonia separation device is a washing tower; the first material inlet of the second alcohol-ammonia separation device is located at the bottom of the tower, and the second material inlet is located at the top of the tower.

[0029] In some specific implementations, the separation unit further includes: a liquid phase separation device having a material inlet connected to a liquid phase outlet of the second solid-liquid separation device, and a material outlet of the liquid phase separation device connected to the alcohol-ester mixing device.

[0030] In some specific implementations, the separation unit further includes: a gas phase purification device having a material inlet connected to a gas phase outlet of the second alcohol-ammonia separation device.

[0031] The present invention provides a device and process for producing oxalamide, which specifically comprises: mixing a methanol solution of liquid ammonia and a methanol solution of dimethyl oxalate to undergo an ammonolysis reaction, flashing, filtering, and drying the first slurry after the reaction to obtain solid oxalamide, refining the liquid phase to obtain byproduct methanol, and returning the tail gas to the reaction system after being absorbed by dimethyl oxalate. In the present invention, the methanol solution of liquid ammonia and the liquid ammonia-methanol mixed gas generated in the production process are reacted with the methanol solution of dimethyl oxalate, and the reaction product is continuously used to produce oxalamide, thereby realizing the reuse of the reaction raw materials. The conversion rate of ammonia in the production process can reach 100%, reducing the cost and operation difficulty of alcohol-ammonia separation, and improving the economy and environmental protection of the entire production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of the device for producing oxamide provided by the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the purifier provided by the present invention.

[0034] The markings in the accompanying drawings are as follows: 1 is an alcohol-ammonia mixing device; 2 is an alcohol-ester mixing device; 3 is a reactor; 4 is a purifier; 5 is a gas-liquid separation device; 6 is a first solid-liquid separation device; 7 is a drying device; 8 is a first alcohol-ammonia separation device; 9 is a second solid-liquid separation device; 10 is a liquid phase separation device; 11 is a second alcohol-ammonia separation device; 12 is a gas phase purification device; 4-1 is a material inlet from the reactor 3 of the purifier 4; 4-2 is a material inlet from the alcohol-ammonia mixing device 1 of the purifier 4; 4-3 is a material outlet from the purifier 4. DETAILED DESCRIPTION

[0035] It should be understood that the expression "one or more of..." includes each of the items recited after the expression individually and in various different combinations of two or more of the recited items, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited items should be understood to have the same meaning, unless otherwise understood from the context.

[0036] The use of the terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, for example not excluding other unrecited elements or steps, unless otherwise specifically stated or otherwise understood from the context.

[0037] It should be understood that the order of steps or the order in which certain actions are performed is not important as long as the present invention remains operable. In addition, two or more steps or actions may be performed simultaneously.

[0038] The use of any and all examples or exemplary language, such as "for example" or "including", herein is intended only to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

[0039] In addition, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value inherently inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise expressly stated, it should be understood that all ranges, quantities, values ​​and percentages used in this disclosure are modified by "about". Here, "about" generally means that the actual value is within plus or minus 10%, 5%, 1% or 0.5% of a specific value or range.

[0040] The present invention first provides a production process of oxamide, which specifically comprises:

[0041] a) mixing dimethyl oxalate, liquid ammonia and methanol to undergo an ammonolysis reaction to obtain a first slurry;

[0042] b) performing gas-liquid separation on the first slurry obtained in step a) to obtain a first alcohol-ammonia gas phase mixture and a second slurry; performing solid-liquid separation on the second slurry to obtain a first alcohol-ammonia liquid phase mixture and a third slurry;

[0043] c) drying the third slurry obtained in step b) to obtain a second alcohol-ammonia gas phase mixture and oxalamide solid; mixing the first alcohol-ammonia liquid phase mixture obtained in step b) with a methanol solution of dimethyl oxalate to obtain a fourth slurry;

[0044] d) separating the fourth slurry obtained in step c) into a fifth slurry by solid-liquid separation, and further using the fifth slurry in the aminolysis reaction in step a);

[0045] e) mixing the first alcohol-ammonia gas phase mixture obtained in step b) and the second alcohol-ammonia gas phase mixture obtained in step c) with a methanol solution of dimethyl oxalate to obtain a first liquid phase mixture; and further using the first liquid phase mixture in the aminolysis reaction in step a).

[0046] The present invention first mixes methanol and liquid ammonia in an alcohol-ammonia mixing device 1, wherein the mass fraction of liquid ammonia is 1% to 50%, preferably 5% to 50%, and more preferably 10% to 50%. Methanol and dimethyl oxalate are mixed in an alcohol-ester mixing device 2, wherein the mass fraction of dimethyl oxalate is 1% to 60%, preferably 5% to 60%, and more preferably 10% to 60%. In some specific implementations, the conditions for transporting methanol in the methanol raw material tank area to the alcohol-ammonia mixing device 1 are a flow rate of 3 to 10 t / h, a temperature of 20 to 30°C, and a pressure of 1.5 to 2.5 MPaG; the conditions for transporting methanol in the methanol raw material tank area to the alcohol-ester mixing device 2 are a flow rate of 15 to 25 t / h, a temperature of 20 to 30°C, and a pressure of 1.5 to 2.5 MPaG. In some specific implementations, the conditions for transporting liquid ammonia in the liquid ammonia raw material tank area to the alcohol-ammonia mixing device 1 are a flow rate of 3 to 6 t / h, a temperature of 20 to 30°C, and a pressure of 2 to 3 MPaG. In some specific implementations, the conditions for conveying dimethyl oxalate from the dimethyl oxalate raw material tank area to the alcohol ester mixing device 2 are flow rate 12~16t / h, temperature 100~110℃, and pressure 1.5~2.5MPaG. In order to improve the reaction efficiency, in some specific implementations of the present invention, the operating temperature of the alcohol ammonia mixing device 1 is 20~40℃, preferably 25~30℃. In some specific implementations, the operating temperature of the alcohol ester mixing device 2 is 40~60℃, preferably 45~60℃, and more preferably 45~55℃. In some specific implementations, the heat preservation device of the alcohol ester mixing device 2 is a constant temperature water jacket.

[0047] The methanol solution of liquid ammonia and the methanol solution of dimethyl oxalate are mixed and introduced into the reactor 3, reacted for 0.2 to 1 h at a pressure of 0.05 to 2.0 MPaG and a temperature of 40 to 130 ° C, and then entered into the purifier 4 to continue the reaction for 0.2 to 0.5 h to obtain a first slurry, the main component of which is a mixed solution of oxalamide, liquid ammonia and methanol.

[0048] In some specific implementations, the reactor 3 is in a mechanical stirring form. In some specific implementations, the reactor 3 is any one of a heat exchange reactor or an adiabatic reactor. In some specific implementations, the molar ratio of liquid ammonia to dimethyl oxalate in the reactor 3 is 2 to 3:1, preferably 2.05 to 2.5:1, and more preferably 2.05 to 2.2:1.

[0049] In order to prevent the reaction product oxamide from settling in the purifier and increase the reaction medium, in some specific implementations of the present invention, liquid ammonia, methanol or a methanol solution of liquid ammonia can be added to the purifier 4, preferably a methanol solution of liquid ammonia, and more preferably a methanol solution of liquid ammonia in the alcohol-ammonia mixing device 1. In some specific implementations, the flow rate of the methanol solution of liquid ammonia in the alcohol-ammonia mixing device 1 into the purifier 4 is 1-3 t / h, preferably 1-2 t / h, and more preferably 1-1.5 t / h.

[0050] After the first slurry is obtained, it is sent to the gas-liquid separation device 5 to obtain a first alcohol-ammonia gas phase mixture whose main components are methanol and ammonia, and a second slurry whose main components are oxalamide, methanol and liquid ammonia. In some specific implementations, the operating temperature of the gas-liquid separation is 60-70°C.

[0051] The obtained second slurry is passed through the first solid-liquid separation device 6 for solid-liquid separation to obtain a third slurry and a first alcohol-ammonia liquid phase mixture, wherein the main component of the third slurry is oxalamide, accompanied by a small amount of methanol and liquid ammonia, and the main components of the first alcohol-ammonia liquid phase mixture are methanol and liquid ammonia. The third slurry is passed through a drying device 7 for drying, wherein the drying temperature is 60-280°C, preferably 100-250°C, and the drying time is 0.3-4h, preferably 0.5-2h, and more preferably 0.6-1h. After drying, an oxalamide solid product and a second alcohol-ammonia gas phase mixture whose main components are methanol and ammonia are obtained.

[0052] In order to improve production efficiency and reduce production costs, the present invention preferably uses a portion of the first alcohol-ammonia liquid phase mixture to replace the methanol flowing in from the outside to enter the ammonia-alcohol mixing device 1, and continue to participate in the subsequent ammonolysis reaction; the other portion reacts with the methanol solution of dimethyl oxalate in the first alcohol-ammonia separation device 8 to obtain a fourth slurry. The fourth slurry is passed into the second solid-liquid separation device 9 for solid-liquid separation to obtain a fifth slurry, and the fifth slurry is further used in the ammonolysis reaction. In some specific implementations, the first solid-liquid separation device 6 and the second solid-liquid separation device 9 are filters.

[0053] In some specific implementations, the fourth slurry further includes a second liquid phase mixture after solid-liquid separation, and the main components of the second liquid phase mixture are methanol and dimethyl oxalate. The present invention preferably refines the second liquid phase mixture to improve the quality of by-product methanol. In some specific implementations, the specific method of refining the second liquid phase mixture is to pass it into a liquid phase separation device 10 for refining to obtain methanol and a third liquid phase mixture, and the third liquid phase mixture is further used for the aminolysis reaction. In some specific implementations, the liquid phase separation device 10 is a distillation tower, and the specific operating parameters are: feed pressure 0.6~1.0MpaG, tower bottom pressure 0.02~0.1MpaG, tower top pressure 0.005~0.008MpaG.

[0054] The present invention passes the first alcohol-ammonia gas phase mixture, the second alcohol-ammonia gas phase mixture, the sealing gas in the device and the safety valve exhaust gas generated in the above production process into the second alcohol-ammonia separation device 11 through the first material inlet; the methanol solution of dimethyl oxalate in the alcohol-ester mixing device 2 is passed into the second alcohol-ammonia separation device 11 through the second material inlet to wash and collect ammonia in the gas. In some specific implementations, the specific method of the reaction of the gas phase and the liquid phase in the second alcohol-ammonia separation device 11 is: the liquid phase is from top to bottom, and the gas phase is from bottom to top, and the two are in countercurrent contact to react. In some specific implementations, the operating pressure of the second alcohol-ammonia separation device 11 is 0.05~0.1 MPaG, and the device temperature is 50~60℃.

[0055] The methanol solution of dimethyl oxalate reacts with the gas produced by the reaction system to obtain a first liquid phase mixture and a first gas phase mixture. The main components of the first liquid phase mixture are the methanol solution of dimethyl oxalate and a small amount of the reaction product of dimethyl oxalate and ammonia, and return to the alcohol ester mixing device 2 to continue the subsequent ammonolysis reaction; the main components of the first gas phase mixture are waste gas and a small amount of methanol, which are passed into the gas phase purification device for purification and then discharged.

[0056] The present invention has no special limitation on the purification method of the first gas phase mixture, and those skilled in the art can select it according to their needs. For example, desalted water can be used to absorb methanol in the first gas phase mixture.

[0057] The present invention also provides a device for producing oxalamide corresponding to the above production process, comprising: a feeding unit, a reaction unit and a separation unit;

[0058] The feeding unit comprises: an alcohol-ammonia mixing device 1 for mixing methanol and liquid ammonia and an alcohol-ester mixing device 2 for mixing methanol and dimethyl oxalate;

[0059] The reaction unit comprises:

[0060] A reactor 3 whose material inlet is respectively connected to the material outlet of the alcohol-ammonia mixing device 1 and the material outlet of the alcohol-ester mixing device 2;

[0061] A purifier 4 whose material inlet is respectively connected to the material outlet of the alcohol-ammonia mixing device 1 and the material outlet of the reactor 3;

[0062] The separation unit comprises:

[0063] A gas-liquid separation device 5 whose material inlet is connected to the material outlet of the reaction device;

[0064] A first solid-liquid separation device 6 whose material inlet is connected to the liquid phase discharge port of the gas-liquid separation device 5, and whose liquid phase discharge port is respectively connected to the feed port of the alcohol-ammonia mixing device 1 and the feed port of the first alcohol-ammonia separation device 8;

[0065] A drying device 7 whose material inlet is connected to the solid discharge port of the first solid-liquid separation device 6;

[0066] A first alcohol-ammonia separation device 8 whose material inlet is respectively connected to the liquid phase discharge port of the first solid-liquid separation device 6 and the discharge port of the alcohol-ester mixing device 2;

[0067] A second solid-liquid separation device 9 whose material inlet is connected to the material outlet of the first alcohol-ammonia separation device 8, and whose solid phase outlet is connected to the material inlet of the alcohol-ester mixing device 2;

[0068] A second alcohol-ammonia separation device 11 having a first material inlet connected to a gas phase discharge port of the gas-liquid separation device 5 and a gas phase discharge port of the drying device 7 , and a second material inlet of the second alcohol-ammonia separation device 11 is connected to a material outlet of the alcohol-ester mixing device 2 .

[0069] The inventors of the present invention have found that the ammonia in the mixed solution of liquid ammonia and methanol produced in the existing process of producing oxalamide is difficult to be effectively utilized; at the same time, the production process involves gas-liquid separation, drying and other processes. Since the atmospheric boiling point of ammonia is -33.5°C, the mixed gas containing ammonia is difficult to be completely condensed into liquid for utilization. Therefore, the inventors of the present invention propose to use the methanol solution of dimethyl oxalate to absorb the excess ammonia in the reaction process, which can not only completely separate methanol from ammonia, but also greatly improve the conversion rate of ammonia and improve the economic efficiency of the production process; at the same time, no tail gas containing ammonia is discharged, which improves the environmental protection of the production process.

[0070] See also Figure 1 , Figure 1The present invention is a schematic diagram of the structure of the device for producing oxalamide, wherein 1 is an alcohol-ammonia mixing device; 2 is an alcohol-ester mixing device; 3 is a reactor in the reaction device, 4 is a purifier in the reaction device; 5 is a gas-liquid separation device; 6 is a first solid-liquid separation device; 7 is a drying device; 8 is a first alcohol-ammonia separation device; 9 is a second solid-liquid separation device; 10 is a liquid phase separation device; 11 is a second alcohol-ammonia separation device; and 12 is a gas phase purification device.

[0071] The device for producing oxalamide provided by the present invention comprises an alcohol-ammonia mixing device 1, which is used to mix methanol and liquid ammonia, and comprises a first material inlet for conveying methanol and a second material inlet for conveying liquid ammonia. After being mixed in the alcohol-ammonia mixing device 1, the methanol and liquid ammonia enter a reactor 3 through the first material outlet and enter a purifier 4 through the second material outlet.

[0072] The alcohol-ester mixing device 2 is used to mix methanol and dimethyl oxalate, and includes a first material inlet for conveying methanol and a second material inlet for conveying dimethyl oxalate. After being uniformly mixed in the alcohol-ester mixing device 2, methanol and dimethyl oxalate enter the reactor 3 through the material outlet.

[0073] The preparation of oxalamide by the aminolysis of dimethyl oxalate is a step-by-step reaction. To improve the reaction efficiency and product purity, the present invention preferably uses a two-stage reactor for the aminolysis reaction. Figure 1 As shown, the reaction device of the present invention comprises a reactor 3 and a purifier 4. Dimethyl oxalate and liquid ammonia undergo an ammonolysis reaction in the reactor 3, and the resulting product enters the purifier 4 through the material outlet for further reaction.

[0074] In order to improve the reaction efficiency, the purifier 4 of the present invention is preferably a plug flow reactor. Figure 2 The purifier structure provided by the present invention is shown, including: a shell, staggered partitions, a material inlet 4-1 from the reactor 3, a material inlet 4-2 and a material outlet 4-3 from the alcohol ammonia mixing device 1. This structure can make the residence time of the reactants in the purifier basically consistent, thereby improving the high purity and uniformity of the reaction products.

[0075] The reaction product from the purifier 4 enters the gas-liquid separation device 5 through the material outlet 4-3 for gas-liquid separation. The gas phase product after gas-liquid separation enters the second alcohol-ammonia separation device 11 through the gas phase outlet, and the liquid phase product enters the first solid-liquid separation device 6 through the liquid phase outlet.

[0076] The first solid-liquid separation device 6 performs solid-liquid separation on the liquid phase product obtained by the gas-liquid separation device, and the obtained solid phase product enters the drying device 7 through the solid phase discharge port for drying to obtain a solid phase product oxamide; the gas phase product obtained by drying enters the second alcohol ammonia separation device 11 through the gas phase discharge port. A part of the liquid phase product obtained by the first solid-liquid separation device 6 enters the first alcohol ammonia separation device 8 through the liquid phase discharge port for separation; the other part is circulated to the alcohol ammonia mixing device 1 through the liquid phase discharge port to continue the aminolysis reaction.

[0077] The first alcohol-ammonia separation device 8 is used to separate the liquid phase product obtained by the first solid-liquid separation device 6, wherein the main components of the liquid phase product are liquid ammonia and methanol. The first alcohol-ammonia separation device 8 uses the methanol solution of dimethyl oxalate to fully react the liquid ammonia in the above liquid phase product, and the resulting mixed solution enters the second solid-liquid separation device 9 through the liquid phase outlet after the reaction.

[0078] The second solid-liquid separation device 9 performs solid-liquid separation on the product of the reaction in the first alcohol-ammonia separation device 8, and the obtained solid slurry is circulated to the alcohol-ester mixing device 2 through the solid phase discharge port to continue to be used for the production of oxalamide.

[0079] In order to improve the utilization rate of the reaction materials and enhance the quality of the byproduct methanol, the present invention preferably separates the liquid phase mixture produced by the second solid-liquid separation device 9. Figure 1 As shown, the device for producing oxalamide of the present invention preferably includes a liquid phase separation device 10. The liquid phase mixture produced by the second solid-liquid separation device 9 enters the liquid phase separation device 10 through the liquid phase discharge port, and the byproduct methanol separated by the liquid phase separation device 10 is output through the liquid phase material outlet, and the obtained mixed solution enters the alcohol ester mixing device 2 through the liquid phase material outlet to continue the subsequent reaction.

[0080] In the present invention, the second alcohol ammonia separation device 11 mainly collects the gas phase mixture produced by the gas-liquid separation device 5 and the drying device 7 for reaction, and the gas phase mixture is input through the first material inlet. The methanol solution of dimethyl oxalate is introduced from the material outlet of the alcohol ester mixing device 2 and input into the second alcohol ammonia separation device 11 through the second material inlet. In the present invention, the second alcohol ammonia separation device 11 undergoes a gas-liquid reaction, and the tower equipment has the advantages of high mass transfer efficiency, a wide range of applications, energy saving and environmental protection, simple operation and convenient maintenance, and strong adaptability. Therefore, in some specific implementations, the second alcohol ammonia separation device 11 of the present invention is preferably a washing tower. According to the characteristics of the gas-liquid reaction, in some specific implementations of the present invention, the first material inlet of the second alcohol ammonia separation device 11 is located at the bottom of the tower, and the second material inlet is located at the top of the tower.

[0081] The present invention preferably purifies the gas generated during the production process to reduce the impact of chemical production on the environment. Figure 1As shown, the device described in the present invention preferably includes a gas phase purification device 12 , and the material inlet of the gas phase purification device 12 is connected to the gas phase discharge port of the second alcohol ammonia separation device 11 .

[0082] According to the above technical scheme, the device for producing oxalamide described in the present invention includes: an alcohol ammonia mixing device 1, an alcohol ester mixing device 2, a reactor 3, a purifier 4, a gas-liquid separation device 5, a first solid-liquid separation device 6, a drying device 7, a first alcohol ammonia separation device 8, a second solid-liquid separation device 9, a liquid phase separation device 10, a second alcohol ammonia separation device 11, a gas phase purification device 12 and necessary components such as pipelines, valves, pumps, etc. commonly used in chemical production processes.

[0083] The present invention provides a process and device for producing oxalamide, which specifically includes: mixing a methanol solution of liquid ammonia and a methanol solution of dimethyl oxalate to undergo an ammonolysis reaction, flashing, filtering, and drying the first slurry after the reaction to obtain solid oxalamide, refining the liquid phase to obtain byproduct methanol, and returning the excess ammonia in the reaction device and the ammonia in the tail gas to the reaction system after being absorbed by dimethyl oxalate. The present invention utilizes a methanol solution of dimethyl oxalate to absorb excess ammonia in the reaction process, and the reaction product is continuously used to produce oxalamide, which can not only completely separate methanol from ammonia, but also greatly improve the conversion rate of ammonia and improve the economic efficiency of the production process; at the same time, no tail gas containing ammonia is discharged, which improves the environmental protection of the production process.

[0084] Example 1

[0085] This embodiment provides a device for producing oxalamide, see Figure 1 .

[0086] like Figure 1 As shown, the device for producing oxalamide provided in this embodiment specifically includes:

[0087] An alcohol-ammonia mixing device 1 whose material inlet is respectively connected to the material outlet of the methanol raw material tank area and the material outlet of the liquid ammonia raw material tank area;

[0088] An alcohol-ester mixing device 2 whose material inlet is respectively connected to the material outlet of the methanol raw material tank area and the material outlet of the dimethyl oxalate raw material tank area;

[0089] A reactor 3 whose material inlet is respectively connected to the material outlet of the alcohol-ammonia mixing device 1 and the material outlet of the alcohol-ester mixing device 2;

[0090] A purifier 4 whose material inlet is connected to the material outlet of the reactor 3 and the material outlet of the alcohol-ammonia mixing device 1 respectively;

[0091] A gas-liquid separation device 5 whose material inlet is connected to the material outlet of the purifier 4, wherein the gas-liquid separation device is a flash tank;

[0092] A first solid-liquid separation device 6 whose material inlet is connected to a liquid phase discharge port of a gas-liquid separation device 5, wherein the first solid-liquid separation device is a filter, and the liquid phase discharge port of the filter is respectively connected to a feed port of the alcohol-ammonia mixing device 1 and a feed port of the first alcohol-ammonia separation device 8;

[0093] A drying device 7 whose material inlet is connected to the solid phase discharge port of the first solid-liquid separation device 6, wherein the drying device is a dryer;

[0094] A first alcohol-ammonia separation device 8 having a material inlet connected to a liquid phase discharge port of a first solid-liquid separation device 6 and a material outlet of an alcohol-ester mixing device 2, wherein the first alcohol-ammonia separation device is an ester-ammonia reactor;

[0095] A second solid-liquid separation device 9 having a material inlet connected to a material outlet of the first alcohol-ammonia separation device 8, wherein the second solid-liquid separation device is a filter, and a solid phase outlet of the filter is connected to the alcohol-ester mixing device 2;

[0096] A liquid phase separation device 10 whose material inlet is connected to the liquid phase discharge port of the second solid-liquid separation device 9, wherein the liquid phase separation device is a distillation tower, and the material outlet of the distillation tower is respectively connected to the material inlet of the methanol raw material tank area and the material inlet of the alcohol ester mixing device 2;

[0097] A second alcohol ammonia separation device 11 having a first material inlet connected to a gas phase discharge port of a gas-liquid separation device 5 and a gas phase discharge port of a drying device 7, respectively, wherein the second alcohol ammonia separation device is a first washing tower, wherein a second material inlet of the first washing tower is connected to a material outlet of an alcohol ester mixing device 2, and a liquid phase discharge port is connected to a material inlet of the alcohol ester mixing device 2;

[0098] A gas phase purification device 12 whose material inlet is connected to the gas phase discharge port of the second alcohol-ammonia separation device 11, wherein the gas phase purification device is a final washing tower.

[0099] Example 2

[0100] This embodiment provides a method for producing oxamide, which specifically comprises:

[0101] 1) Mix liquid ammonia and methanol at a pressure of 1.8 MPaG and a temperature of 27°C to obtain a methanol solution of liquid ammonia, wherein the mass fraction of liquid ammonia is 45%; mix dimethyl oxalate and methanol at a slightly positive pressure and a temperature of 50°C to obtain a methanol solution of dimethyl oxalate, wherein the mass fraction of dimethyl oxalate is 46%;

[0102] 2) subjecting the above-mentioned methanol solution of liquid ammonia and the methanol solution of dimethyl oxalate to an ammonolysis reaction at a pressure of 1.1 MPaG and a temperature of 120° C., wherein the molar ratio of dimethyl oxalate, liquid ammonia and methanol is 1:2.1:5.2, to obtain a mixed slurry of oxalamide, methanol and liquid ammonia;

[0103] 3) flashing the mixed slurry obtained in step 2), wherein the gas phase obtained is a mixed gas of ammonia and methanol, and the liquid phase obtained is a mixed slurry containing oxamide; filtering the mixed slurry containing oxamide to obtain a mixed solution of liquid ammonia and methanol and a solid slurry whose main component is oxamide; drying the solid slurry at 250° C. for 1 hour to obtain oxamide solid and generate a mixed gas of ammonia and methanol;

[0104] 4) A portion of the mixed solution of liquid ammonia and methanol obtained in step 3) reacts with the methanol solution of dimethyl oxalate to obtain a mixed slurry containing oxalamide, dimethyl oxalate and methanol, and the other portion is recycled to step 2) to continue to participate in the ammonolysis reaction; the mixed slurry is filtered again to obtain oxalamide slurry and methanol solution of dimethyl oxalate, the oxalamide slurry continues to participate in the ammonolysis reaction in step 2), the methanol solution of dimethyl oxalate is separated by a distillation tower, the methanol separated by the distillation tower enters the raw material tank area, and the remaining mixed solution continues to participate in the ammonolysis reaction in step 2);

[0105] 5) reacting the mixed gas of ammonia and methanol obtained by flash evaporation in step 3), the mixed gas of ammonia and methanol obtained by drying, the sealing gas in the device and the exhaust gas of the safety valve with the methanol solution of dimethyl oxalate in step 1), the reaction temperature is 55° C., the pressure is 0.05 MPaG, the main method is that the methanol solution of dimethyl oxalate is sprayed from top to bottom, and the mixed gas of ammonia and methanol moves from bottom to top, and the countercurrent contact is obtained to obtain a gas containing a small amount of methanol and a reaction mixed solution;

[0106] 6) The gas containing a small amount of methanol obtained in step 5) is discharged into the atmosphere after being adsorbed by desalted water and the obtained reaction mixture is mixed with the methanol solution of dimethyl oxalate in step 1) to continue the aminolysis reaction.

[0107] In this example, the conversion rate of ammonia is 100%, and the yield of oxalamide is 99.9% (based on the amount of ammonia).

[0108] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A process for producing oxamide, characterized in that: include: a) mixing dimethyl oxalate, liquid ammonia and methanol to undergo an ammonolysis reaction to obtain a first slurry; b) performing gas-liquid separation on the first slurry obtained in step a) to obtain a first alcohol-ammonia gas phase mixture and a second slurry; performing solid-liquid separation on the second slurry to obtain a first alcohol-ammonia liquid phase mixture and a third slurry; c) drying the third slurry obtained in step b) to obtain a second alcohol-ammonia gas phase mixture and oxalamide solid; mixing the first alcohol-ammonia liquid phase mixture obtained in step b) with a methanol solution of dimethyl oxalate to obtain a fourth slurry; d) separating the fourth slurry obtained in step c) into a fifth slurry by solid-liquid separation, and further using the fifth slurry in the aminolysis reaction in step a); e) mixing the first alcohol-ammonia gas phase mixture obtained in step b) and the second alcohol-ammonia gas phase mixture obtained in step c) with a methanol solution of dimethyl oxalate to obtain a first liquid phase mixture; and further using the first liquid phase mixture in the aminolysis reaction in step a).

2. The process according to claim 1, characterized in that The specific manner of reacting the first alcohol-ammonia gas phase mixture, the second alcohol-ammonia gas phase mixture and the methanol solution of dimethyl oxalate in step e) is that the liquid phase is from top to bottom and the gas phase is from bottom to top, and the two are in countercurrent contact to react.

3. The process according to claim 1, characterized in that In the step c), a portion of the first alcohol-ammonia liquid phase mixture is mixed with a methanol solution of dimethyl oxalate to react to obtain a fourth slurry; the other portion is returned to step a) for aminolysis reaction.

4. The process according to claim 1, characterized in that The fourth slurry in step d) further comprises a second liquid phase mixture after solid-liquid separation; The second liquid phase mixture is purified to obtain methanol and a third liquid phase mixture, and the third liquid phase mixture is further used in the aminolysis reaction in step a).

5. The process according to claim 1, characterized in that In the step e), the first alcohol-ammonia gas phase mixture and the second alcohol-ammonia gas phase mixture are mixed with the methanol solution of dimethyl oxalate to produce a first gas phase mixture; The first gas phase mixture is purified and then discharged.

6. A device for producing oxamide, characterized in that: include: Feed unit, reaction unit and separation unit; The feed unit comprises: an alcohol-ammonia mixing device (1) for mixing methanol and liquid ammonia and an alcohol-ester mixing device (2) for mixing methanol and dimethyl oxalate; The reaction unit comprises: A reactor (3) having a material inlet connected to the material outlet of the alcohol-ammonia mixing device (1) and the material outlet of the alcohol-ester mixing device (2); A purifier (4) having a material inlet connected to the material outlet of the alcohol-ammonia mixing device (1) and the material outlet of the reactor (3); The separation unit comprises: A gas-liquid separation device (5) whose material inlet is connected to the material outlet of the purifier (4); a first solid-liquid separation device (6) whose material inlet is connected to the liquid phase discharge port of the gas-liquid separation device (5), and whose liquid phase discharge port is respectively connected to the feed port of the alcohol-ammonia mixing device (1) and the feed port of the first alcohol-ammonia separation device (8); A drying device (7) having a material inlet connected to a solid material outlet of the first solid-liquid separation device (6); a first alcohol-ammonia separation device (8) whose material inlet is respectively connected to the liquid phase discharge port of the first solid-liquid separation device (6) and the discharge port of the alcohol-ester mixing device (2); a second solid-liquid separation device (9) whose material inlet is connected to the material outlet of the first alcohol-ammonia separation device (8), and whose solid phase outlet is connected to the material inlet of the alcohol-ester mixing device (2); A second alcohol-ammonia separation device (11) having a first material inlet connected to the gas phase discharge port of the gas-liquid separation device (5) and the gas phase discharge port of the drying device (7), respectively; and a second material inlet of the second alcohol-ammonia separation device (11) connected to the material outlet of the alcohol-ester mixing device (2).

7. The device according to claim 6, characterized in that The first alcohol-ammonia separation device (8) is an ester-ammonia reactor; The purifier (4) is a plug flow reactor.

8. The device according to claim 6, characterized in that The second alcohol-ammonia separation device (11) is a washing tower; The first material inlet of the second alcohol-ammonia separation device (11) is located at the bottom of the tower, and the second material inlet is located at the top of the tower.

9. The device according to claim 6, characterized in that The separation unit further comprises: A liquid phase separation device (10) whose material inlet is connected to the liquid phase discharge port of the second solid-liquid separation device (9), and whose material outlet is connected to the alcohol-ester mixing device (2).

10. The device according to claim 6, characterized in that The separation unit further comprises: A gas phase purification device (12) having a material inlet connected to a gas phase discharge port of the second alcohol-ammonia separation device (11).

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