Ionic liquid catalyst and preparation method thereof, methyl methyl carbamate and preparation method, preparation system and application thereof

Abstract

The invention provides an ionic liquid catalyst and a preparation method thereof, methyl methyl carbamate and a preparation method, a preparation system and application thereof. The structural formula of the ionic liquid catalyst is [Zn (CH3NHC (O) OCH3) 2] < 2 + >. 2 (CH2COO)-. According to the invention, urea, methanol and dimethyl carbonate are used as raw materials, and methyl carbamate is prepared under the catalytic action of the ionic liquid catalyst. Methanol, dimethyl carbonate and urea are subjected to multi-step alcoholysis reaction and ammonolysis reaction, the target product selectivity is high, the raw material conversion rate is high, the methyl methyl carbamate product purity is high, no organic tin residues exist, and the catalyst cost is low.

Description

Technical Field

[0001] The invention relates to an ionic liquid catalyst and a preparation method thereof, methyl methyl carbamate and a preparation method, a preparation system and application thereof, and belongs to the field of methyl methyl carbamate. Background Art

[0002] Methyl methyl carbamate is an important fine chemical product, which can be used in the fields of medicine, pesticides and organic solvents. In the field of medicine, for example, trichloroethyl carbamate, physostigmine, phenyl carbamate compounds, etc. In the field of pesticides, for example, high-efficiency and low-toxic pesticides such as mefenamic acid, chlorfenapyr, chlorpropham, propamocarb, and ethofluthrin.

[0003] At present, the product is still in the early stage of research and development. There are three main synthesis methods recorded in the published literature:

[0004] Method 1: CN103524381A discloses a method for preparing methyl N-methylcarbamate, which uses dimethyl carbonate and 1,3-dimethylurea as raw materials, mixed in a molar ratio of 15 to 1:1, and reacts under the action of a catalyst dibutyltin oxide (DBTO) at a reaction temperature of 80-200°C and a pressure of 0.1Mpa-5.0Mpa to obtain methyl N-methylcarbamate.

[0005] Method 2: "Synthesis of Methyl N-Methylcarbamate" (Fine Chemicals, Vol. 31, No. 5, 2014) discloses a method for preparing methyl N-methylcarbamate, and its raw material route and process conditions are basically the same as the method disclosed in CN103524381A.

[0006] Method 3: CN112409214A discloses a method for preparing methyl N-methylcarbamate, which uses urea and methanol as raw materials, mixed in a molar ratio of 1:10-20, and obtains methyl N-methylcarbamate through alcoholysis reaction at a reaction temperature of 220-240°C and a pressure of 5.92Mpa-7.69Mpa.

[0007] However, in both method one and method two, the reaction requires the use of organotin catalysts, which are expensive and not conducive to environmental protection, and the downstream application areas are limited. Since the catalyst dibutyltin oxide is involved in the preparation of methyl methyl carbamate, which is a homogeneous reaction, the subsequent separation is extremely troublesome, and poor separation will affect the purity of the product. Especially when used in the field of polyurethane material production, the organotin residues in the product can catalyze and accelerate the cross-linking reaction speed of groups such as isocyanate and hydroxyl, resulting in adverse effects such as a significant shortening of the activation period of the cross-linking system. In method three, the reaction temperature is high, the energy consumption is high, the raw material turnover is large, and the reaction pressure is high, resulting in high technical requirements for industrial production equipment and large investment. In particular, this scheme only undergoes alcoholysis reaction, and the raw material conversion rate is low.

[0008] Therefore, it is necessary to provide a new method for preparing methyl N-methylcarbamate to improve the above problems. Summary of the invention

[0009] In order to solve the above technical problems, the purpose of the present invention is to provide an ionic liquid catalyst and a preparation method thereof, methyl methyl carbamate and a preparation method thereof, a preparation system and application thereof. The present invention uses urea, methanol and dimethyl carbonate as raw materials to prepare methyl methyl carbamate under the catalytic action of an ionic liquid catalyst. Methanol, dimethyl carbonate and urea undergo multi-step alcoholysis and aminolysis reactions, and the target product has high selectivity and high raw material conversion rate. The methyl methyl carbamate product has high purity, no organic tin residue, and low catalyst cost.

[0010] To achieve the above object, the present invention provides an ionic liquid catalyst having the structural formula [Zn(CH3NHC(O)OCH3)2] 2 +·2(CH2COO)-.

[0011] Compared with the commonly used organotin catalysts, the catalyst of the present invention has excellent catalytic effect when subsequently used in a chemical reaction for preparing methyl methyl carbamate using methanol, dimethyl carbonate and urea as raw materials. More importantly, on the one hand, no additional impurities are introduced into the system, so that a methyl methyl carbamate product with high purity can be obtained through subsequent simple separation treatment; on the other hand, the cost is low and there is no organotin residue, so the environmental protection and downstream applicability of the product are better.

[0012] The present invention also provides a method for preparing the aforementioned ionic liquid catalyst, which comprises: mixing methyl methyl carbamate and zinc acetate to carry out a first chemical reaction to obtain the ionic liquid catalyst.

[0013] The ionic liquid catalyst obtained based on the preparation method does not introduce other impurity cations, and the reaction product system has a simple composition, and the aforementioned ionic liquid catalyst product can be obtained by simple separation means later. Moreover, the preparation process of the preparation method is simple and easy to implement, and the reaction raw materials are simple, cheap and easy to obtain. At the same time, there is no three wastes discharged in the preparation process, which is economical and environmentally friendly, and easy to achieve large-scale industrial production.

[0014] Furthermore, the temperature of the first chemical reaction is 100-150°C.

[0015] Furthermore, the first chemical reaction time is 60 to 150 minutes.

[0016] Furthermore, the molar ratio of methyl methyl carbamate to zinc acetate is 6 to 10:1.

[0017] Furthermore, the first chemical reaction is carried out under an inert gas atmosphere, and the inert gas may be, for example, nitrogen.

[0018] The present invention also provides a method for preparing methyl methyl carbamate, which comprises: mixing methanol, dimethyl carbonate, urea and the aforementioned ionic liquid catalyst to carry out a second chemical reaction to obtain methyl methyl carbamate.

[0019] The present invention uses urea, methanol and dimethyl carbonate as raw materials to prepare methyl methyl carbamate under the catalytic action of the above-mentioned ionic liquid catalyst. The main reaction process involved in the preparation process and the reaction process expression are as follows:

[0020] Methanol and urea undergo catalytic alcoholysis, and the products are methyl carbamate and ammonia:

[0021]

[0022] Methyl carbamate and methanol continue to undergo catalytic alcoholysis reaction, and the products are dimethyl carbonate and ammonia:

[0023]

[0024] Urea and dimethyl carbonate undergo catalytic alcoholysis and aminolysis reactions simultaneously to produce methyl methyl carbamate, ammonia and carbon dioxide:

[0025]

[0026] The preparation method improves the target product selectivity and raw material conversion rate of multi-step alcoholysis reaction and aminolysis reaction of methanol, dimethyl carbonate and urea, and the preparation process is simple and the reaction conditions are relatively mild. In addition, the by-products obtained in the preparation process, such as ammonia and carbon dioxide, can be subsequently recycled for the synthesis of urea, the raw material used in the present invention, thereby reducing production costs and avoiding environmental pollution, thereby achieving green and environmentally friendly production. Moreover, there is no discharge of three wastes in the preparation process, which is economical and environmentally friendly, and is easy to achieve large-scale industrial production.

[0027] Furthermore, the temperature of the second chemical reaction is 200-220° C.; the pressure of the second chemical reaction is 6.0-8.0 MPa; and the time of the second chemical reaction is 2-3 h.

[0028] Furthermore, the molar ratio of methanol, dimethyl carbonate and urea is 3-8:3-8:1.

[0029] Furthermore, the dosage of the ionic liquid catalyst is 3-10% of the weight of urea.

[0030] Furthermore, the second chemical reaction is carried out under an inert gas atmosphere, and the inert gas may be, for example, nitrogen.

[0031] Further, in the second chemical reaction process, the reaction product system is subjected to gas-liquid separation in real time or in batches to discharge the gaseous by-products in the reaction product system. In the reaction process, the gaseous by-products are separated in time, which is conducive to reducing the reverse reaction, and is also conducive to the reaction to be carried out in the direction of synthesizing methyl methyl carbamate. The by-products ammonia, carbon dioxide and other gases are discharged from the reaction system in real time or in batches, the balance of the reaction can be regulated, and the conversion efficiency of urea into methyl methyl carbamate can be further improved. Moreover, after the by-products ammonia, carbon dioxide etc. are discharged, they can all be subsequently entered into the urea production line and used as raw materials, and continue to be synthesized into urea, and can continue to be used as the raw material cycle of the present invention, and the beneficial effect of the recycling of by-product gas is realized, which is environmentally friendly and green energy-saving.

[0032] Preferably, the reaction product system is subjected to gas-liquid separation in batches, for example, ammonia and carbon dioxide are extracted 2 to 4 times. It should be understood that the more times ammonia and carbon dioxide are extracted, the more favorable the forward reaction and the generation of the product methyl methyl carbamate are, and the higher the total yield of methyl methyl carbamate is. However, frequently extracting the by-product gas of the synthesis reaction process will cause the fluctuation of the pressure and temperature in the methyl methyl carbamate preparation kettle, which is not conducive to the stability of the reaction. The present invention does not specifically limit the number of times the by-product gas is extracted, and those skilled in the art can make corresponding adjustments according to their own technical requirements, which can also be achieved by those skilled in the art, and will not be elaborated here.

[0033] The present invention also provides a system for preparing methyl methyl carbamate, which comprises an ionic liquid catalyst preparation kettle and a methyl methyl carbamate preparation kettle which are connected in sequence; the ionic liquid catalyst preparation kettle is used to mix methyl methyl carbamate and zinc acetate to carry out a first chemical reaction to obtain an ionic liquid catalyst; the methyl methyl carbamate preparation kettle is used to mix methanol, dimethyl carbonate, the aforementioned ionic liquid catalyst and urea to carry out a second chemical reaction to obtain methyl methyl carbamate.

[0034] Furthermore, the ionic liquid catalyst preparation kettle has a feed hand hole, and methyl methyl carbamate and zinc acetate can be added into the ionic liquid catalyst preparation kettle through the feed hand hole.

[0035] Furthermore, the ionic liquid catalyst preparation kettle is controllably connected with the nitrogen generator, the thermal oil furnace, and the coolant through valves and pipelines.

[0036] Furthermore, the top of the methyl methyl carbamate preparation kettle and the bottom of the ionic liquid catalyst preparation kettle are connected through pipelines and valves, so that the ionic liquid catalyst prepared in the ionic liquid catalyst preparation kettle can be quantitatively added to the methyl methyl carbamate preparation kettle in a controlled manner during the feeding stage.

[0037] Furthermore, the methyl methyl carbamate preparation kettle has a feed hand hole, and reaction raw materials (such as methanol, dimethyl carbonate and urea) can be added into the methyl methyl carbamate preparation kettle through the feed hand hole.

[0038] Furthermore, the methyl methyl carbamate preparation kettle is controllably connected with the nitrogen generator, the thermal oil furnace and the coolant through valves and pipelines.

[0039] Furthermore, the methyl methyl carbamate preparation kettle is a pressure-resistant kettle reactor, which has the functions of heating, cooling, sealing, and pressure-bearing of the materials in the kettle, and is controllably connected to the feed hand hole, the methanol and dimethyl carbonate recovery device, the condensation circulation reflux unit, and the discharge port through the opening and closing of the valve. The reaction pressure of the methyl methyl carbamate preparation kettle is an autogenous pressure, which is the result of the combined effects of nitrogen in the kettle, heated and gasified methanol and dimethyl carbonate, ammonia generated by the reaction, carbon dioxide gas, and the heated volume expansion of the reaction materials in the kettle.

[0040] In a preferred embodiment, the system for preparing methyl methyl carbamate further includes a condensation circulation reflux unit; the condensation circulation reflux unit includes a first-stage packing demister, a first-stage vertical condenser, a second-stage packing demister, a second-stage vertical condenser, a horizontal shell-and-tube condenser and a gas-liquid separator which are connected in sequence; the discharge port at the top of the methyl methyl carbamate preparation kettle is connected to the feed port of the first-stage packing demister; the liquid phase outlet of the gas-liquid separator is connected to the methyl methyl carbamate preparation kettle through a reflux pipe, and a reflux circulation pump is provided on the reflux pipe.

[0041] The invention forms a vertical tower section by first arranging a first-stage packing demister, a first-stage vertical condenser, a second-stage packing demister and a second-stage vertical condenser before the horizontal shell-and-tube condenser. The foam of part of the reaction materials in the methyl methyl carbamate preparation kettle due to the heat reaction and stirring action is blocked, and part of the liquid in the foam directly flows back into the above-mentioned synthesis reaction kettle due to the gravity action to continue to participate in the reaction. Part of the methanol and dimethyl carbonate gas that are not separated evaporates upward together with the by-products ammonia and carbon dioxide gas to perform preliminary gas-liquid separation. Part of the material foam and material gas are cooled into a liquid phase in the vertical tower section, and directly flow back to the methyl methyl carbamate preparation kettle under the action of gravity to continue to participate in the reaction, so as to maintain the balance of the reaction materials in the methyl methyl carbamate preparation kettle and improve the conversion rate of the reaction.

[0042] The phase separation of methanol, dimethyl carbonate and reaction byproduct gases ammonia and carbon dioxide is carried out in a gas-liquid separator. The liquid phase outlet of the gas-liquid separator is connected to the methyl methyl carbamate preparation kettle through a reflux pipeline. The condensed liquid phase collected in the gas-liquid separator can be refluxed (for example, using a reflux circulation pump) to the methyl methyl carbamate preparation kettle to maintain the reaction mass balance and temperature balance in the methyl methyl carbamate preparation kettle.

[0043] In the condensation circulation reflux unit, ammonia, carbon dioxide and unreacted methanol, dimethyl carbonate, etc. enter the methyl methyl carbamate preparation kettle in gaseous state for gas-liquid separation, and then ammonia and carbon dioxide enter the reaction by-product gas recovery unit in gaseous state; unreacted methanol, dimethyl carbonate, etc. flow downward from the overflow port on the side of the gas-liquid separator in liquid state, enter the inlet of the circulation reflux pump through a pipeline connection, and are transported to the methyl methyl carbamate preparation kettle through the circulation reflux pump. The balance of reaction materials in the methyl methyl carbamate preparation kettle is maintained through reflux circulation, thereby improving the conversion rate of the reaction.

[0044] Furthermore, the packing in the packing demister is one or a combination of Raschig rings, ball rings or structured packing. The vertical condenser and the horizontal tube-in-tube condenser are both provided with materials running inside the tube and cooling liquid running between the tubes.

[0045] In a preferred embodiment, the system for preparing methyl methyl carbamate further comprises a reaction by-product gas recovery unit; the reaction by-product gas recovery unit is connected to the gas phase outlet of the gas-liquid separator (for example, the reaction by-product gas recovery unit and the condensation circulation reflux unit can be controllably connected by opening and closing a valve). The reaction by-product gas recovery unit is used to recover the reaction by-products such as ammonia and carbon dioxide. After the methanol, dimethyl carbonate and other reaction material gases in the methyl methyl carbamate preparation kettle and the generated ammonia and carbon dioxide gases pass through the condensation circulation reflux unit together, the gas-liquid two phases are separated, and the methanol and dimethyl carbonate are all condensed into liquid phases and refluxed into the methyl methyl carbamate preparation kettle for use, and the ammonia and carbon dioxide gases are released as gas phases by decompression and enter the reaction by-product gas recovery unit.

[0046] Furthermore, the reaction by-product gas recovery unit is connected to the urea production line, and the urea production line can be controllably connected to the reaction by-product gas recovery unit through a valve to achieve the beneficial effect that the recovered ammonia and carbon dioxide can be reused for urea synthesis. The generated urea can continue to be used as a raw material for this method, further reducing production costs. The above-mentioned urea production line of the present invention is a common urea production line and is not particularly limited.

[0047] Furthermore, the reaction by-product gas recovery unit includes two gas buffer tanks connected in sequence, and a pressure regulator is provided on each of the connecting passages between the gas-liquid separator and the gas buffer tank, between the gas buffer tank and the gas buffer tank, and between the gas buffer tank and the urea production line.

[0048] In a preferred embodiment, the system further comprises a synthetic mixed liquid storage tank, which is arranged between the methyl methyl carbamate preparation kettle and the subsequent distillation kettle. After the reaction is terminated, the reaction materials in the methyl methyl carbamate preparation kettle are cooled to room temperature and depressurized to normal pressure; then, they are transported to the synthetic mixed liquid storage tank through pipelines, valves, and finally through a synthetic mixture delivery pump for standby use, wherein the main components are methanol, dimethyl carbonate, methyl methyl carbamate, ionic liquid catalyst, and trace urea (mainly dissolved in methanol, dimethyl carbonate, and methyl methyl carbamate).

[0049] In a preferred embodiment, the system for preparing methyl methyl carbamate further comprises a refining unit; the refining unit comprises a distillation kettle and a distillation tower which are connected in sequence; the feed port of the distillation kettle is connected to the product system discharge port of the methyl methyl carbamate preparation kettle (when the system comprises a synthetic mixed liquid storage tank, the feed port of the distillation kettle is connected to the discharge port of the synthetic mixed liquid storage tank); the distillation tower has a discharge port for refined methyl methyl carbamate.

[0050] The refining unit of the present invention adopts a combined method of distillation and rectification to obtain a methyl methyl carbamate product with higher purity, and can effectively separate components such as methanol, dimethyl carbonate, and ionic liquid catalyst in the synthetic mixed solution, thereby achieving more efficient recycling.

[0051] First, since the boiling point difference between methanol, dimethyl carbonate and methyl methyl carbamate and ionic liquid catalyst is greater than 70°C, the low-boiling methanol (distillation range is about 65°C) and dimethyl carbonate (distillation range is about 90-91°C) in the synthetic mixed solution are heated and gasified by steam heating in the still, and then rise to the still vertical condenser and the still horizontal condenser connected to the top of the still, where they are condensed into liquid and separated. The methanol and dimethyl carbonate mixed solution separated by distillation is used as raw materials for the synthesis reaction of the present invention again after component analysis. The high-boiling methyl methyl carbamate, ionic liquid catalyst and a small amount of urea do not undergo phase change, and remain at the bottom of the still to become the residual mixed solution of distillation, which is pumped into the still heavy component storage tank of the still through the still heavy component delivery pump. Subsequently, the residual mixed solution of distillation is allowed to enter the rectifying tower, and the methyl methyl carbamate, ionic liquid catalyst and a small amount of urea in the residual mixed solution of distillation are subjected to atmospheric pressure continuous rectification and separation. Methyl methyl carbamate (distillation range is about 167-168°C) is separated from the upper part of the distillation section (purity can be as high as 99.5% or higher), the ionic liquid catalyst is separated from the lower part of the stripping section (can be reused 6-7 times), and a small amount of urea is finally discharged from the bottom of the stripping section.

[0052] The process of preparing methyl methyl carbamate in the distillation tower is carried out continuously. The mixed liquid of the heavy component of the still kettle in the heavy component material storage tank is transported by the feed pump of the distillation tower, and is first pumped into the feed preheating heat exchanger for preliminary heat exchange with the hot material out of the distillation tower. The temperature of the mixed liquid of the heavy component of the still kettle rises, and then enters the first heat exchanger of the distillation tower to continue heat exchange with the hot heat transfer oil. After the mixed liquid of the heavy component of the still kettle reaches a higher temperature, it is continuously added to the distillation tower from the upper part of the stripping section. The liquid methyl methyl carbamate at the bottom of some distillation sections enters the top of the stripping section, where it is mixed with the residual mixed liquid of the distillation entering the distillation tower, and then flows down from the top of the stripping section. At the same time, the downstream liquid and the ascending air flow interact with each other to transfer mass and heat, so that the volatile methyl methyl carbamate in the liquid is partially vaporized and rises, and the gas phase methyl methyl carbamate is stripped to the distillation section, and the liquid phase methyl methyl carbamate, the non-volatile ionic liquid catalyst, a small amount of urea and other liquid phase substances continue to descend to the bottom of the distillation section, enter the stripping section heater for heating, and are re-transported to the middle of the distillation section. The methyl methyl carbamate that is partially heated and converted from the liquid phase to the gas phase rises to the distillation section and is continuously distilled and separated; the ionic liquid catalyst, a small amount of urea and other liquid phase substances are finally discharged from the bottom of the stripping section after the methyl methyl carbamate content therein is qualified, and enter the ionic liquid catalyst recovery and storage unit to be used again as raw materials for the synthesis reaction of the present invention. The gaseous methyl methyl carbamate rising to the top of the rectifying section passes through the first condenser of the rectifying section to obtain part of the gaseous methyl methyl carbamate and liquid methyl methyl carbamate, and then enters the gas-liquid separation tank of the rectifying section to separate the gaseous methyl methyl carbamate, and at the same time, the liquid methyl methyl carbamate is re-transported to the middle of the rectifying section through the rectifying section reflux pump. When the purity of the methyl methyl carbamate reaches the requirement, it is cooled again by the second heat exchanger of the rectifying section, and then transported to the methyl methyl carbamate storage unit through a pipeline.

[0053] The present invention also provides a methyl methyl carbamate, which is prepared by the above-mentioned preparation method of methyl methyl carbamate. The structural formula of the methyl methyl carbamate is

[0054] The present invention also provides an application of the aforementioned methyl methyl carbamate in electronic cleaning solvents, synthetic leather slurries, water-based coatings, water-based inks, water-based adhesives, leather finishing agents, organic solvents, and new energy battery electrolytes.

[0055] Based on the above reasons, the methyl methyl carbamate of the present invention is used as an electronic cleaning solvent, and has excellent physical and chemical properties, that is, it has excellent solubility, suitable volatilization speed, excellent non-toxic, safe and environmentally friendly performance. In addition, the methyl methyl carbamate of the present invention can be miscible with water in any proportion, and can be widely used in industrial fields that require water solubility, such as synthetic leather slurry, water-based coatings, water-based inks, water-based adhesives, leather finishing agents, etc.; In addition, the methyl methyl carbamate of the present invention is non-irritating, has very low toxicity, is even non-toxic, is safe and environmentally friendly, and can replace a large number of ethylene glycol ethers and propylene glycol ether solvents, and can also replace a large number of organic solvents such as xylene, butyl acetate, trimethylbenzene (S100 solvent oil), tetramethylbenzene (150 solvent oil), ethylene glycol ethyl ether acetate (CAC), propylene glycol methyl ether acetate (PMA), and ethylene glycol diacetate (EGDA). More importantly, the methyl methyl carbamate of the present invention can be used in new energy battery electrolytes, replacing methyl carbamate (MC), dimethyl carbonate (DMC), N-methylpyrrolidone (NMP), etc., which are currently used in large amounts in new energy battery electrolytes. The methyl methyl carbamate has more stable performance, is safer, more efficient, non-toxic, non-irritating, and has broad application prospects.

[0056] In summary, the above technical solution of the present invention has the following advantages:

[0057] The ionic liquid catalyst of the present invention has a simple preparation process and is easy to implement, and the reaction raw materials are simple in composition, cheap and easy to obtain, and the cost is low. The obtained ionic liquid catalyst has good stability and can be reused many times.

[0058] The ionic liquid catalyst of the invention has high reaction activity, short reaction time, high urea conversion rate, good selectivity for generating methyl methyl carbamate, and easy control of the reaction process.

[0059] The cation component of the ionic liquid catalyst of the present invention is the reaction product methyl methyl carbamate, and no other cations are introduced. The composition of the reaction liquid and the subsequent separation are simple.

[0060] The synthetic reaction equipment of the invention has simple connection, high efficiency in gas-liquid separation of byproducts in the preparation process, and simple and easy control of reaction temperature, foam in the kettle and method for maintaining balance of reaction materials in the kettle.

[0061] In the preparation process, the present invention discharges byproducts such as ammonia and carbon dioxide from the reaction system in batches in a controlled manner, regulates the balance of the reaction, and improves the urea conversion rate. The byproducts such as ammonia and carbon dioxide can all enter the urea production device as raw materials, continue to be synthesized into urea, and can continue to be recycled as raw materials of the present invention, realizing the recycling of byproduct gases, and is an environmentally friendly green chemical technology.

[0062] The synthesis of methyl methyl carbamate by the present invention is a medium-pressure reaction with a short reaction time, a large difference in boiling points between the raw materials and the finished product, and simple separation.

[0063] The invention does not discharge three kinds of wastes during the entire preparation process, is economical and environmentally friendly, and is easy to realize large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The present invention is a process flow chart for synthesizing methyl methyl carbamate according to an embodiment of the present invention.

[0065] Among them, 1-methyl methyl carbamate preparation kettle, 2-ionic liquid catalyst preparation kettle, 3-gas-liquid separator, 4-reflux circulation pump, 5-1st level packing demister, 6-1st level vertical condenser, 7-2nd level packing demister, 8-2nd level vertical condenser, 9-horizontal shell and tube condenser, 10-synthetic mixture delivery pump, 11-first gas buffer tank, 12-first pressure regulating valve 1, 13-second gas buffer tank, 14-second pressure regulating valve 2, 15-third pressure regulating valve 3, 16-synthetic mixed liquid storage tank, 17-methanol and dimethyl carbonate mixed liquid storage unit, 18-high-pressure steam supply unit, 19-still kettle feed pump, 20-still kettle, 21-still kettle vertical condenser, 22-still kettle Horizontal condenser, 23-still kettle gas-liquid separator, 24-condensed water outlet, 25-distillation tower feed pump, 26-still kettle heavy component storage tank, 27-distillation section, 28-distillation tower, 29-distillation tower first heat exchanger, 30-feed pre-heat exchanger, 31-distillation section first condenser, 32-distillation section gas-liquid separation tank, 33-distillation section reflux pump, 34-distillation section second heat exchanger, 35-stripping section, 36-stripping section heater, 37-methyl methyl carbamate storage unit, 38-ionic liquid catalyst recovery storage unit, 39-first drain pipe, 40-urea production line, 41-thermal oil furnace, 42-nitrogen generator, 43-second drain pipe, 44-cooling liquid pipeline, 45-still kettle heavy component delivery pump. DETAILED DESCRIPTION

[0066] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0067] Example 1

[0068] The present invention provides a system for preparing methyl methyl carbamate, such as Figure 1 As shown ( Figure 1 All the connections between the devices are pipeline connections, and all arrow directions indicate the movement direction of liquid or gas phase substances). The system includes:

[0069] (1) Methyl methyl carbamate preparation kettle 1, wherein:

[0070] The methyl methyl carbamate preparation reactor 1 is used to mix methanol, dimethyl carbonate, an ionic liquid catalyst and urea to carry out a second chemical reaction to obtain methyl methyl carbamate.

[0071] The volume of the methyl methyl carbamate preparation kettle 1 is 5 L, and it is controllably connected with the nitrogen generator 42, the thermal oil furnace 41, and the coolant pipeline 44 through valves and pipelines.

[0072] The methyl methyl carbamate preparation kettle 1 includes a feed hand hole to add methanol, dimethyl carbonate and urea into the methyl methyl carbamate preparation kettle 1.

[0073] (2) Ionic liquid catalyst preparation kettle 2; wherein,

[0074] The ionic liquid catalyst preparation kettle 2 is used to mix methyl methyl carbamate and zinc acetate to carry out a first chemical reaction to obtain an ionic liquid catalyst.

[0075] The capacity of the ionic liquid catalyst preparation kettle 2 is 1 L, and it is controllably connected to the nitrogen generator 42, the thermal oil furnace 41, and the coolant pipeline 44 through valves and pipelines.

[0076] The ionic liquid catalyst preparation kettle 2 comprises a feed hand hole, from which methyl methyl carbamate and zinc acetate are added into the ionic liquid catalyst preparation kettle 2.

[0077] The feed port at the top of the methyl methyl carbamate preparation kettle 1 and the discharge port at the bottom of the ionic liquid catalyst preparation kettle 2 are connected through pipelines and valves to controllably add the ionic liquid catalyst prepared in the ionic liquid catalyst preparation kettle 2 to the methyl methyl carbamate preparation kettle 1 in a quantitative manner during the feeding stage.

[0078] (3) A condensation circulation reflux unit, wherein:

[0079] The condensation circulation reflux unit comprises a first-stage packing demister 5, a first-stage vertical condenser 6, a second-stage packing demister 7, a second-stage vertical condenser 8, a horizontal shell-and-tube condenser 9 and a gas-liquid separator 3 which are sequentially connected.

[0080] The discharge port at the top of the methyl methyl carbamate preparation kettle 1 is communicated with the feed port of the first-stage filler demister 5 .

[0081] The liquid phase outlet of the gas-liquid separator 3 is connected to the methyl methyl carbamate preparation kettle 1 through a reflux pipeline. The condensation circulation reflux unit also includes a circulation reflux pump 4, which is arranged on the reflux pipeline between the liquid phase outlet of the gas-liquid separator 3 and the methyl methyl carbamate preparation kettle 1.

[0082] The first-stage packed demister 5, the first-stage vertical condenser 6, the second-stage packed demister 7, and the second-stage vertical condenser 8 are assembled into a vertical tower section, which can first perform preliminary gas-liquid separation on the materials in the foam state and the gaseous materials volatilizing upward in the methyl methyl carbamate preparation kettle 1, and part of the material foam and material gas are cooled into liquid phase in the vertical tower section, and directly flow back to the methyl methyl carbamate preparation kettle 1 under the action of gravity to continue to participate in the reaction, thereby maintaining the balance of the reaction materials in the methyl methyl carbamate preparation kettle 1 and improving the conversion rate of the reaction.

[0083] Phase separation of methanol, dimethyl carbonate and reaction by-product gases ammonia and carbon dioxide is carried out in the gas-liquid separator 3. Ammonia, carbon dioxide and unreacted methanol, dimethyl carbonate, etc. enter the gas-liquid separator 3 from the methyl methyl carbamate preparation kettle 1 in a gaseous state for gas-liquid separation, and then ammonia and carbon dioxide enter the subsequent reaction by-product gas recovery unit in a gaseous state; unreacted methanol, dimethyl carbonate, etc. flow downward from the side overflow port of the gas-liquid separator 3 in a liquid state, enter the inlet of the circulating reflux pump 4 through a pipeline connection, and are transported to the methyl methyl carbamate preparation kettle 1 through the circulating reflux pump 4. The reaction material balance in the methyl methyl carbamate preparation kettle 1 is maintained through reflux circulation to improve the conversion rate of the reaction.

[0084] (4) a reaction by-product gas recovery unit, wherein:

[0085] The gas phase outlet of the gas-liquid separator 3 can be controllably connected to a reaction by-product gas recovery unit to recover ammonia and carbon dioxide produced as reaction by-products.

[0086] The reaction byproduct gas recovery unit is connected to the urea production line 40 so that the recovered ammonia and carbon dioxide can be used for urea synthesis.

[0087] The reaction by-product gas recovery unit includes a first gas buffer tank 11 and a second gas buffer tank 13 which are connected in sequence. A first pressure regulating valve 12 is arranged on the connecting passage between the gas-liquid separator 3 and the first gas buffer tank 11, a second pressure regulating valve 14 is arranged on the connecting passage between the first gas buffer tank 11 and the second gas buffer tank 13, and a third pressure regulating valve 15 is arranged on the connecting passage between the second gas buffer tank 13 and the urea production line 40.

[0088] (5) Synthetic mixed liquid storage tank 16, wherein:

[0089] The synthetic mixed liquid storage tank 16 is arranged between the methyl methyl carbamate preparation kettle 1 and the subsequent distillation kettle 20 .

[0090] After the reaction is terminated, the reaction materials in the methyl methyl carbamate preparation kettle 1 are cooled and depressurized, and then transported to the synthetic mixed liquid storage tank 16 for standby use through pipelines, valves, and a synthetic mixture delivery pump 10. The main components of the synthetic mixed liquid storage tank 16 are methanol, dimethyl carbonate, methyl methyl carbamate, an ionic liquid catalyst, and a trace amount of urea (mainly dissolved in methanol, dimethyl carbonate, and methyl methyl carbamate).

[0091] (6) A refining unit, wherein:

[0092] The refining unit includes: a methanol and dimethyl carbonate mixed liquid storage unit 17, a high-pressure steam supply unit 18, a distillation kettle feed pump 19, a condensed water outlet 24, a distillation kettle 20, a distillation kettle vertical condenser 21, a distillation kettle horizontal condenser 22, a distillation kettle gas-liquid separator 23, a distillation kettle heavy component storage tank 26, a distillation kettle heavy component delivery pump 45, a distillation tower 28 (having a distillation section 27 and a stripping section 35), a distillation tower feed pump 25, a distillation tower first heat exchanger 29, a feed pre-heat exchanger 30, a distillation section first condenser 31, a distillation section gas-liquid separation tank 32, a distillation section reflux pump 33, a distillation section second heat exchanger 34, a stripping section heater 36, a coolant pipeline 44, a thermal oil furnace 41, an ionic liquid catalyst recovery storage unit 38, and a methyl methyl carbamate storage unit 37.

[0093] The feed port of the still 20 is connected to the discharge port of the synthetic mixed liquid storage tank 16. Since the boiling point difference between methanol, dimethyl carbonate and methyl methyl carbamate and ionic liquid catalyst is greater than 70°C, the low-boiling methanol and dimethyl carbonate in the synthetic mixed liquid are heated and gasified by steam heating in the still 20, and then rise to the horizontal condenser 22 connected to the top of the still, where they are condensed into liquid and separated. The methanol and dimethyl carbonate mixed liquid separated by distillation will be used as raw materials for the synthesis reaction of the present invention again after component analysis. The high-boiling methyl methyl carbamate, ionic liquid catalyst and a small amount of urea do not undergo phase change, and remain at the bottom of the still 20 to become the residual mixed liquid of distillation, which is pumped into the still heavy component storage tank 26 by the still heavy component delivery pump 45. Subsequently, the residual mixed liquid of distillation in the still heavy component storage tank 26 continues to enter the rectification tower 28, and the methyl methyl carbamate, ionic liquid catalyst and a small amount of urea in the residual mixed liquid of distillation are subjected to atmospheric pressure continuous rectification and separation. Methyl methyl carbamate is separated from the upper part of the rectifying section 27 , the ionic liquid catalyst is separated from the lower part of the stripping section 35 , and a small amount of urea is finally discharged from the bottom of the stripping section 35 .

[0094] The process of preparing methyl methyl carbamate in the distillation tower 27 is carried out continuously. The mixed liquid of the heavy component of the still kettle in the heavy component material storage tank 26 is transported by the distillation tower feed pump 25, and is first pumped into the feed preheat exchanger 30 for preliminary heat exchange with the hot material out of the distillation tower. The temperature of the mixed liquid of the heavy component of the still kettle increases, and then enters the first heat exchanger 29 of the distillation tower to continue heat exchange with the hot heat transfer oil. After the mixed liquid of the heavy component of the still kettle reaches a higher temperature, it is continuously added to the distillation tower 28 from the upper part of the stripping section 35. The liquid methyl methyl carbamate at the bottom of the partial distillation section 27 enters the top of the stripping section 35, where it is mixed with the residual mixed liquid of the distillation entering the distillation tower 28, and then flows down from the top of the stripping section 35. At the same time, the downstream liquid and the ascending air flow interact with each other to transfer mass and heat, so that the volatile methyl methyl carbamate in the liquid is partially vaporized and rises, and the gas phase methyl methyl carbamate is stripped to the distillation section 27, and the liquid phase methyl methyl carbamate, the non-volatile ionic liquid catalyst, a small amount of urea and other liquid phase substances continue to descend to the bottom of the stripping section 35, enter the stripping section heater 36 for heating, and are re-transported to the middle part of the stripping section 35. Part of the methyl methyl carbamate that is converted from the liquid phase to the gas phase by heat rises to the distillation section 27 and is continuously distilled and separated; the ionic liquid catalyst, a small amount of urea and other liquid phase substances are finally discharged from the bottom of the stripping section 35 after the methyl methyl carbamate content therein is qualified, and enter the ionic liquid catalyst recovery storage unit 38, and will be used as raw materials again for the synthesis reaction of the present invention. The gaseous methyl methyl carbamate rising to the top of the rectifying section 27 passes through the first condenser 31 of the rectifying section to obtain part of the gaseous methyl methyl carbamate and liquid methyl methyl carbamate, and then enters the rectifying section gas-liquid separation tank 32 to separate the gaseous methyl methyl carbamate, and at the same time, the liquid methyl methyl carbamate is re-transported to the middle of the rectifying section through the rectifying section reflux pump 33. When the purity of the methyl methyl carbamate reaches the requirement, it is cooled again by the second heat exchanger 34 of the rectifying section, and then transported to the methyl methyl carbamate storage unit 37 through a pipeline.

[0095] (7) The first drain pipe 39 and the second drain pipe 43 are used for system draining operation.

[0096] This embodiment also provides a method for preparing methyl methyl carbamate, which comprises:

[0097] Using the above Figure 1 The system is prepared in Figure 1In the system shown, 372.1 g (4.181 mol) of methyl methyl carbamate and 127.9 g (0.697 mol) of zinc acetate (molar ratio of 6:1) are added to the ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring is started, and the thermal oil furnace is turned on for heating. After reacting at 150°C for 60 minutes, the temperature is cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0098] Add 374.8g (11.7mol) methanol, 1053.9g (11.7mol) dimethyl carbonate, 234.2g (3.9mol) urea (molar ratio of 3:3:1), and 7.03g (3% of the urea feed amount) of the above-prepared ionic liquid catalyst to the methyl methyl carbamate preparation kettle 1, seal the methyl methyl carbamate preparation kettle 1, and start stirring to dissolve the materials. Open the vacuum to extract the air in the kettle, and then fill the kettle with nitrogen to make up the pressure to 0.7MPa. Turn on the thermal oil furnace to heat and increase the temperature. Raise the temperature to 200℃, and the pressure in the kettle is 6.0MPa at this temperature. Under this condition, the reactants in the kettle are partially vaporized and rise to the condensation circulation reflux unit to form normal reflux, and the condensed methanol and dimethyl carbonate liquids are normally refluxed into the kettle. The reaction was carried out at the temperature and pressure for 40 minutes, and the control valve 15 of the reaction by-product gas recovery unit was opened to slowly release ammonia and carbon dioxide gas once to the reaction by-product gas recovery unit. The pressure in the methyl methyl carbamate preparation kettle will drop, and after the ammonia and carbon dioxide gas are discharged, the valve 15 is closed. When the reaction time reaches 60 minutes, the pressure in the kettle is 7.2MPa, and the ammonia and carbon dioxide gas are released and discharged once again. When the reaction materials in the kettle continue to react at 220°C for 2h, the pressure in the kettle is controlled at 8.0MPa, and the reaction is completed. Stop heating, pass coolant to cool down, and stop cooling when it is below 50°C. Then remove all the reaction materials to the distillation kettle 20, and perform distillation operation by steam heating to completely separate methanol and dimethyl carbonate. Then move the distillation residue to the distillation tower 28 for distillation. 241.7g of methyl methyl carbamate is obtained. It is calculated that the urea conversion rate is 99.8% and the methyl methyl carbamate selectivity is 69.6%.

[0099] Example 2

[0100] This embodiment provides a method for preparing methyl methyl carbamate, which comprises:

[0101] Using the methyl methyl carbamate preparation system in Example 1, Figure 1In the equipment shown, 397.5 g (4.466 mol) of methyl methyl carbamate and 102.5 g (0.559 mol) of zinc acetate (molar ratio of 8:1) are added to the ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring and heating are started, and the reaction is carried out at 100°C for 105 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0102] 374.8g (11.7mol) methanol, 1053.9g (11.7mol) dimethyl carbonate, 234.2g (3.9mol) urea (molar ratio of 3:3:1), and 15.22g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as those in Example 1. 243.2g of methyl methyl carbamate was obtained.

[0103] Example 3

[0104] Using the methyl methyl carbamate preparation system in Example 1, Figure 1 In the equipment shown, 414.5 g (4.657 mol) of methyl methyl carbamate and 85.5 g (0.466 mol) of zinc acetate (molar ratio of 10:1) are added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring and heating are started, and the reaction is carried out at 125°C for 150 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0105] 374.8g (11.7mol) methanol, 1053.9g (11.7mol) dimethyl carbonate, 234.2g (3.9mol) urea (molar ratio of 3:3:1), and 23.42g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to 220°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 241.3g of methyl methyl carbamate was obtained.

[0106] Example 4

[0107] Using the methyl methyl carbamate preparation system in Example 1, Figure 1In the equipment shown, 372.1 g (4.181 mol) of methyl methyl carbamate and 127.9 g (0.697 mol) of zinc acetate (molar ratio of 6:1) were added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 150°C for 105 min, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0108] 246.1g (7.68mol) methanol, 1268.3g (14.08mol) dimethyl carbonate, 153.8g (2.56mol) urea (molar ratio of 3:5.5:1), and 15.38g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 169.3g of methyl methyl carbamate was obtained.

[0109] Example 5

[0110] Using the methyl methyl carbamate preparation system in Example 1, Figure 1 In the equipment shown, 397.5 g (4.466 mol) of methyl methyl carbamate and 102.5 g (0.559 mol) of zinc acetate (molar ratio of 8:1) are added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring and heating are started, and the reaction is carried out at 100°C for 150 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0111] 246.1g (7.68mol) methanol, 1268.3g (14.08mol) dimethyl carbonate, 153.8g (2.56mol) urea (molar ratio of 3:5.5:1), and 10g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to 200°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 170.7g of methyl methyl carbamate was obtained.

[0112] Example 6

[0113] Using the methyl methyl carbamate preparation system in Example 1, Figure 1In the equipment shown, 414.5 g (4.657 mol) of methyl methyl carbamate and 85.5 g (0.466 mol) of zinc acetate (molar ratio of 10:1) are added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring and heating are started, and the reaction is carried out at 125°C for 60 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0114] 246.1g (7.68mol) methanol, 1268.3g (14.08mol) dimethyl carbonate, 153.8g (2.56mol) urea (molar ratio of 3:5.5:1), and 4.61g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 167.7g of methyl methyl carbamate was obtained.

[0115] Example 7

[0116] Using the methyl methyl carbamate preparation system in Example 1, Figure 1 In the equipment shown, 372.1 g (4.181 mol) of methyl methyl carbamate and 127.9 g (0.697 mol) of zinc acetate (molar ratio of 6:1) were added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 150°C for 150 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0117] 182.7g (5.7mol) methanol, 1369.3g (15.2mol) dimethyl carbonate, 114.2g (1.9mol) urea (molar ratio of 3:8:1), and 7.42g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 122g of methyl methyl carbamate was obtained.

[0118] Example 8

[0119] Using the methyl methyl carbamate preparation system in Example 1, Figure 1In the equipment shown, 397.5 g (4.466 mol) of methyl methyl carbamate and 102.5 g (0.559 mol) of zinc acetate (molar ratio of 8:1) are added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen is introduced into the kettle, stirring and heating are started, and the reaction is carried out at 100°C for 60 minutes, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0120] 182.7g (5.7mol) methanol, 1369.3g (15.2mol) dimethyl carbonate, 114.2g (1.9mol) urea (molar ratio of 3:8:1), and 3.426g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 124.3g of methyl methyl carbamate was obtained.

[0121] Example 9

[0122] Using the methyl methyl carbamate preparation system in Example 1, Figure 1 In the equipment shown, 414.5 g (4.657 mol) of methyl methyl carbamate and 85.5 g (0.466 mol) of zinc acetate (molar ratio of 10:1) were added to a 1L ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 125°C for 105 min, and then cooled to room temperature to obtain a colorless transparent liquid, which is an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0123] 182.7g (5.7mol) methanol, 1369.3g (15.2mol) dimethyl carbonate, 114.2g (1.9mol) urea (molar ratio of 3:8:1), and 11.42g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 123g of methyl methyl carbamate was obtained.

[0124] Example 10

[0125] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as in Example 1.

[0126] 581.6 g (18.15 mol) methanol, 891.8 g (9.9 mol) dimethyl carbonate, 198.2 g (3.3 mol) urea (molar ratio of 5.5:3:1), and 12.88 g (6.5% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 218.6 g of methyl methyl carbamate was obtained.

[0127] Embodiment 11

[0128] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 2.

[0129] 581.6 g (18.15 mol) methanol, 891.8 g (9.9 mol) dimethyl carbonate, 198.2 g (3.3 mol) urea (molar ratio of 5.5:3:1), and 5.95 g (3% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 220.9 g of methyl methyl carbamate was obtained.

[0130] Example 12

[0131] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 3.

[0132] 581.6 g (18.15 mol) methanol, 891.8 g (9.9 mol) dimethyl carbonate, 198.2 g (3.3 mol) urea (molar ratio of 5.5:3:1), and 19.82 g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 221.8 g of methyl methyl carbamate was obtained.

[0133] Example 13

[0134] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 4.

[0135] 401.8 g (12.54 mol) methanol, 1129.6 g (12.54 mol) dimethyl carbonate, 137 g (2.28 mol) urea (molar ratio of 5.5:5.5:1), and 4.11 g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as those in Example 1. 151.6 g of methyl methyl carbamate was obtained.

[0136] Embodiment 14

[0137] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 5.

[0138] 401.8 g (12.54 mol) methanol, 1129.6 g (12.54 mol) dimethyl carbonate, 137 g (2.28 mol) urea (molar ratio of 5.5:5.5:1), and 8.91 g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 155.5 g of methyl methyl carbamate was obtained.

[0139] Embodiment 15

[0140] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 6.

[0141] 401.8 g (12.54 mol) methanol, 1129.6 g (12.54 mol) dimethyl carbonate, 137 g (2.28 mol) urea (molar ratio of 5.5:5.5:1), and 13.7 g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 156.9 g of methyl methyl carbamate was obtained.

[0142] Example 16

[0143] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 7.

[0144] 307.6g (9.6mol) methanol, 1257.5g (13.96mol) dimethyl carbonate, 104.8g (1.745mol) urea (molar ratio of 5.5:8:1), and 3.14g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 120.3g of methyl methyl carbamate was obtained.

[0145] Embodiment 17

[0146] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 8.

[0147] 307.6g (9.6mol) methanol, 1257.5g (13.96mol) dimethyl carbonate, 104.8g (1.745mol) urea (molar ratio of 5.5:8:1), and 6.81g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 119.3g of methyl methyl carbamate was obtained.

[0148] Embodiment 18

[0149] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 9.

[0150] 307.6g (9.6mol) methanol, 1257.5g (13.96mol) dimethyl carbonate, 104.8g (1.745mol) urea (molar ratio of 5.5:8:1), and 10.48g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 120.7g of methyl methyl carbamate was obtained.

[0151] Embodiment 19

[0152] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as in Example 1.

[0153] 730.5 g (22.8 mol) methanol, 770.2 g (8.55 mol) dimethyl carbonate, 171.2 (2.85 mol) urea (molar ratio of 8:3:1), and 11.128 g (6.5% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 191.6 g of methyl methyl carbamate was obtained.

[0154] Embodiment 20

[0155] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 2.

[0156] 730.5g (22.8mol) methanol, 770.2g (8.55mol) dimethyl carbonate, 171.2 (2.85mol) urea (molar ratio of 8:3:1), and 17.12g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 193.3g of methyl methyl carbamate was obtained.

[0157] Embodiment 21

[0158] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 3.

[0159] 730.5g (22.8mol) methanol, 770.2g (8.55mol) dimethyl carbonate, 171.2 (2.85mol) urea (molar ratio of 8:3:1), and 5.136g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 192.6g of methyl methyl carbamate was obtained.

[0160] Embodiment 22

[0161] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 4.

[0162] 525.5g (16.4mol) methanol, 1015.6g (11.275mol) dimethyl carbonate, 123.1g (2.05mol) urea (molar ratio of 8:5.5:1), and 1.23g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 139.4g of methyl methyl carbamate was obtained.

[0163] Embodiment 23

[0164] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 5.

[0165] 525.5g (16.4mol) methanol, 1015.6g (11.275mol) dimethyl carbonate, 123.1g (2.05mol) urea (molar ratio of 8:5.5:1), and 3.69g (3% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 138.5g of methyl methyl carbamate was obtained.

[0166] Embodiment 24

[0167] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 6.

[0168] 525.5g (16.4mol) methanol, 1015.6g (11.275mol) dimethyl carbonate, 123.1g (2.05mol) urea (molar ratio of 8:5.5:1), and 8g (3% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 138.9g of methyl methyl carbamate was obtained.

[0169] Embodiment 25

[0170] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 7.

[0171] 412.7 g (12.88 mol) methanol, 1160.2 g (12.88 mol) dimethyl carbonate, 96.7 g (1.61 mol) urea (molar ratio of 8:8:1), and 2.901 g (3% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 200°C, and the by-product ammonia and carbon dioxide were released twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 111.9 g of methyl methyl carbamate was obtained.

[0172] Embodiment 26

[0173] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 8.

[0174] 412.7 g (12.88 mol) methanol, 1160.2 g (12.88 mol) dimethyl carbonate, 96.7 g (1.61 mol) urea (molar ratio of 8:8:1), and 6.286 g (6.5% of urea feed) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 210°C, and by-product ammonia and carbon dioxide were released 3 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 112.4 g of methyl methyl carbamate was obtained.

[0175] Embodiment 27

[0176] The methyl methyl carbamate preparation system in Example 1 was used, and the ionic liquid catalyst preparation method was the same as that in Example 9.

[0177] 412.7 g (12.88 mol) methanol, 1160.2 g (12.88 mol) dimethyl carbonate, 96.7 g (1.61 mol) urea (molar ratio of 8:8:1), and 9.67 g (10% of the urea feed amount) of the above-prepared ionic liquid catalyst were added to the methyl methyl carbamate preparation kettle 1. The reaction temperature was controlled to be 220°C, and the by-product ammonia and carbon dioxide were released 4 times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 112.5 g of methyl methyl carbamate was obtained.

[0178] Comparative Example

[0179] Referring to the Chinese invention patent application publication number CN103524381A, the catalyst is dibutyltin oxide (DBTO). The comparative examples all use dibutyltin oxide to replace the ionic liquid catalyst of the present invention, and the addition amount is 1 to 12 mol% of the raw material substituted urea in the Chinese invention patent application publication number CN103524381A. The other process conditions and methods are consistent with the implementation method of the present invention, and methyl methyl carbamate is prepared by reaction.

[0180] Comparative Example 1

[0181] use Figure 1 In the system shown, 374.8g (11.7mol) methanol, 1053.9g (11.7mol) dimethyl carbonate, 234.2g (3.9mol) urea (molar ratio of 3:3:1), and 9.71g (1% of the molar amount of urea) dibutyltin oxide are added to a 5L methyl methyl carbamate preparation kettle, and the methyl methyl carbamate preparation kettle is sealed and stirred to dissolve the materials. The air in the kettle is pumped out by vacuum, and then nitrogen is filled into the kettle to make up the pressure to 0.7MPa. The heat transfer oil is turned on to heat and the temperature is raised. The temperature is raised to 200℃, and the pressure in the kettle is 6.0MPa at this temperature. Under this condition, the reactants in the kettle are partially vaporized and rise to the condensation circulation reflux device to form normal reflux, and the condensed methanol and dimethyl carbonate liquids are normally refluxed into the kettle. React at this temperature and pressure for 40 minutes, open the control valve of the by-product gas recovery device, and slowly release ammonia and carbon dioxide gas once to the reaction by-product gas recovery unit. The pressure in the methyl methyl carbamate preparation kettle will drop. After the ammonia and carbon dioxide are discharged, valve 15 is closed. When the reaction time reaches 60 minutes, the pressure in the kettle is 6.7MPa, and the ammonia and carbon dioxide gas are released and discharged once again. When the reaction materials in the kettle continue to react at 220°C for 2h, the pressure in the kettle is controlled at 7.3MPa, and the reaction is completed. Stop heating, pass coolant to cool down, and stop cooling when it is below 50°C. Then remove all the reaction materials to the distillation kettle, perform distillation operation by steam heating, and first separate methanol and dimethyl carbonate completely. Then move the distillation residue to the distillation tower, and obtain 106.5g of methyl methyl carbamate by distillation. It is calculated that the urea conversion rate is 44.0% and the methyl methyl carbamate selectivity is 30.7%.

[0182] Comparative Example 2

[0183] Except that the catalyst is replaced by dibutyltin oxide with the ionic liquid catalyst of the present invention, the other process conditions and methods are the same as those of Example 14, and the raw material composition and control conditions are as follows:

[0184] Add 401.8g (12.54mol) methanol, 1129.6g (12.54mol) dimethyl carbonate, 137g (2.28mol) urea (molar ratio of 5.5:5.5:1), and 36.9g (6.5% of the molar amount of urea) dibutyltin oxide. Control the reaction temperature to 210℃, and release by-product ammonia and carbon dioxide twice during the synthesis reaction. Obtain 70.8g of methyl methyl carbamate. Calculated, the urea conversion rate is 45.4%, and the methyl methyl carbamate selectivity is 34.9%.

[0185] Comparative Example 3

[0186] Except that the catalyst is replaced by dibutyltin oxide with the ionic liquid catalyst of the present invention, the other process conditions and methods are the same as those of Example 26, and the raw material composition and control conditions are as follows:

[0187] Add 412.7g (12.88mol) methanol, 1160.2g (12.88mol) dimethyl carbonate, 96.7g (1.61mol) urea (molar ratio of 8:8:1), and 48.1g (12% of the molar amount of urea) dibutyltin oxide. Control the reaction temperature to 210℃, and release by-product ammonia and carbon dioxide gas 3 times during the synthesis reaction. Obtain 52.7g of methyl methyl carbamate. Calculated, the urea conversion rate is 46.8%, and the methyl methyl carbamate selectivity is 36.8%.

[0188] The reaction conditions and comparative data for the preparation of the ionic liquid catalysts in the above examples are shown in Table 1 below.

[0189] Table 1

[0190]

[0191] The reaction conditions for preparing methyl methyl carbamate in the above examples and comparative examples are shown in Table 2 below.

[0192] Table 2

[0193]

[0194]

[0195] In Table 2, the molar ratio of methanol: dimethyl carbonate: urea is used; the amount of catalyst added is based on the weight of urea feed as 100%; the unit of reaction temperature is °C; the unit of reaction pressure is MPa; the unit of reaction time is h; and the by-product gases are ammonia and carbon dioxide.

[0196] The above examples and comparative examples are shown in Table 3 below.

[0197] Table 3

[0198]

[0199]

[0200] As shown in Table 3, when the molar ratio of methanol, dimethyl carbonate and urea raw materials is within the range of 3-8:3-8:1, and the amount of the ionic liquid catalyst added (based on the amount of urea) is 3-10%, the reaction temperature is 200-220°C, and the reaction pressure range is 6.0-8.0MPa, the urea conversion rate is close to 100%, and the methyl methyl carbamate selectivity is 69.5-78.5%. In the comparative example, when the amount of the catalyst dibutyl tin oxide added (based on the molar number of urea), the reaction temperature is 200-220°C, and the reaction pressure range is 6.0-8.0MPa, the urea conversion rate is 44.0-46.8%, and the methyl methyl carbamate selectivity is 30.7-36.8%. Using dibutyl tin oxide as a catalyst has no obvious effect on the preparation method of preparing methyl methyl carbamate using methanol, dimethyl carbonate and urea as raw materials.

Claims

1. An ionic liquid catalyst, wherein: The structural formula of the ionic liquid catalyst is [Zn(CH3NHC(O)OCH3)2] 2 +·2(CH2COO)-.

2. A method for preparing the ionic liquid catalyst according to claim 1, wherein: Methyl methyl carbamate and zinc acetate are mixed to perform a first chemical reaction to obtain an ionic liquid catalyst.

3. The method for preparing the ionic liquid catalyst according to claim 2, wherein: The temperature of the first chemical reaction is 100-150° C. and the time is 60-150 min.

4. The method for preparing an ionic liquid catalyst according to claim 2, wherein: The molar ratio of the methyl methyl carbamate to the zinc acetate is 6 to 10:

1.

5. A method for preparing methyl methyl carbamate, wherein: include: Methanol, dimethyl carbonate and urea are mixed and subjected to a second chemical reaction under the catalytic action of the ionic liquid catalyst of claim 1 to obtain methyl methyl carbamate.

6. The method for preparing methyl methyl carbamate according to claim 5, wherein The temperature of the second chemical reaction is 200-220° C., the pressure is 6.0-8.0 MPa, and the time is 2-3 hours.

7. The method for preparing methyl methyl carbamate according to claim 5, wherein The molar ratio of the methanol, the dimethyl carbonate and the urea is 3 to 8:3 to 8:1; The dosage of the ionic liquid catalyst is 3-10% of the weight of the urea.

8. The method for preparing methyl methyl carbamate according to claim 5, wherein During the second chemical reaction, gaseous by-products in the reaction product system are discharged.

9. A system for preparing methyl methyl carbamate, wherein: It comprises an ionic liquid catalyst preparation kettle and a methyl methyl carbamate preparation kettle which are connected in sequence; The ionic liquid catalyst preparation kettle is used to mix methyl methyl carbamate and zinc acetate to perform a first chemical reaction to obtain an ionic liquid catalyst; The methyl methyl carbamate preparation kettle is used to mix methanol, dimethyl carbonate, the ionic liquid catalyst and urea to perform a second chemical reaction to obtain methyl methyl carbamate.

10. The system for preparing methyl methyl carbamate according to claim 9, wherein: It also includes a condensation circulation reflux unit; The condensation circulation reflux unit comprises a first-stage packing demister, a first-stage vertical condenser, a second-stage packing demister, a second-stage vertical condenser, a horizontal shell-and-tube condenser and a gas-liquid separator which are connected in sequence; The discharge port at the top of the methyl methyl carbamate preparation kettle is connected to the feed port of the first-stage filler demister; The liquid phase outlet of the gas-liquid separator is connected to the methyl methyl carbamate preparation kettle through a reflux pipeline.

11. The system for preparing methyl methyl carbamate according to claim 10, wherein: Also included is a reaction by-product gas recovery unit; The gas phase outlet of the gas-liquid separator is communicated with the reaction by-product gas recovery unit.

12. The system for preparing methyl methyl carbamate according to claim 10, wherein: Also includes a refining unit; The refining unit comprises a distillation kettle and a rectification tower which are connected in sequence; The feed inlet of the distillation kettle is connected to the discharge port at the bottom of the methyl methyl carbamate preparation kettle; The distillation tower is provided with a discharge port for refined methyl methyl carbamate.

13. A methyl methyl carbamate, wherein The methyl methyl carbamate is prepared by the preparation method of any one of claims 5 to 8.

14. Use of the methyl methyl carbamate according to claim 13 in electronic cleaning solvents, synthetic leather slurries, water-based coatings, water-based inks, water-based adhesives, leather finishing agents, organic solvents, and new energy battery electrolytes.

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