Ionic liquid catalysts and methods for their preparation, methyl methylcarbamate and methods for its preparation, preparation systems and applications

Abstract

The application provides an ionic liquid catalyst and a preparation method thereof, methyl methylcarbamate and a preparation method thereof, a preparation system and application. The structural formula of the ionic liquid catalyst is [Zn(CH3NHC(O)OCH3)2] 2+ ·2(CH2COO) ‑ The application uses urea, methanol and dimethyl carbonate as raw materials, and methyl methylcarbamate is prepared under the catalysis of the ionic liquid catalyst. The methanol, dimethyl carbonate and urea undergo multi-step alcoholysis and ammonolysis reactions, the selectivity of the target product is high, the raw material conversion rate is high, the purity of the methyl methylcarbamate product is high, there is no organic tin residue, and the catalyst cost is low.

Description

Technical Field

[0001] The present 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 carbamates are an important class of fine chemicals with applications in pharmaceuticals, pesticides, and organic solvents. Examples of pharmaceutical applications include trichloroethyl carbamate, physostigmine, and phenylcarbamate compounds. In pesticides, examples include highly effective, low-toxic pesticides such as metolacarb, chlorpropham, chlorpropham, propamocarb, and ethofluthrin.

[0003] Currently, this product is still in the early stages 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 reacted in the presence of a catalyst dibutyltin oxide (DBTO) at a reaction temperature of 80-200°C and a pressure of 0.1 MPa-5.0 MPa 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, the raw material route and process conditions of which are basically the same as those 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 to 20, and undergoes an alcoholysis reaction at a reaction temperature of 220-240°C and a pressure of 5.92 MPa-7.69 MPa to obtain methyl N-methylcarbamate.

[0007] However, in both methods one and two, the reaction requires the use of organotin catalysts, which are expensive and not conducive to environmental protection, and the downstream application areas are more 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 disadvantages such as high technical requirements and large investment for industrial production equipment. In particular, this solution 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] To address the above-mentioned technical problems, the present invention provides an ionic liquid catalyst and a preparation method thereof, as well as methyl methyl carbamate and its preparation method, preparation system, and application. 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, resulting in high selectivity for the target product and high raw material conversion. The methyl methyl carbamate product is high in purity, free of organotin residues, and has 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 an 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 high-purity methyl methyl carbamate product can be obtained through a simple subsequent 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 using this preparation method does not introduce other impurity cations, and the reaction product system is simple in composition, allowing subsequent separation to yield the aforementioned ionic liquid catalyst product. Furthermore, this preparation method features a simple and easy-to-implement process, using simple, inexpensive, and readily available raw materials. Furthermore, the preparation process eliminates the discharge of three wastes, making it economical and environmentally friendly, and amenable to 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 aforementioned 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 reaction, 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] This preparation method improves the target product selectivity and feedstock conversion rate of the multi-step alcoholysis and ammonolysis reactions of methanol, dimethyl carbonate, and urea, and has a simple preparation process and relatively mild reaction conditions. Furthermore, byproducts obtained during this 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, reducing production costs and avoiding environmental pollution, thereby achieving green and environmentally friendly production. Furthermore, this preparation process does not emit three wastes, is economical and environmentally friendly, and is easy to implement for 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 hours.

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

[0029] Furthermore, the amount of the ionic liquid catalyst used is 3-10% of the weight of the 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 carried out 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 helps to reduce the reverse reaction and also helps the reaction to carry out in the direction of synthesizing methyl methyl carbamate. Gases such as by-products ammonia, carbon dioxide are discharged from the reaction system in real time or in batches, which can regulate the balance of the reaction, further improve the transformation efficiency of urea into methyl methyl carbamate. And, after the by-products ammonia, carbon dioxide etc. are discharged, follow-up can all enter the urea production line and use as raw material, continue to be synthesized into urea, can continue to use as raw material circulation of the present invention again, have realized the beneficial effect of the recycling of by-product gas, environmental friendliness, 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 formation 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 fluctuations in 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 needs. This is also something that those skilled in the art can do on their own and will not be elaborated on 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 sequentially connected; 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 the 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 to 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 by pipes 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 to a nitrogen generator, a thermal oil furnace, and a coolant through valves and pipelines.

[0039] Furthermore, the methyl methyl carbamate production kettle is a pressure-resistant autoclave reactor equipped with functions such as heating, cooling, sealing, and pressure-bearing capabilities. It is controllably connected to the feed manhole, methanol and dimethyl carbonate recovery unit, condensation recirculation unit, and discharge port via valve opening and closing. The reaction pressure in the methyl methyl carbamate production kettle is autogenous, resulting from the combined effects of nitrogen within the kettle, heated and vaporized methanol and dimethyl carbonate, ammonia and carbon dioxide generated by the reaction, and the volume expansion of the reaction materials within the kettle due to heating.

[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 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 droplets of part of the reaction materials in the methyl methyl carbamate preparation kettle due to the thermal reaction and stirring action are blocked, and a part of the liquid in the droplets directly flows back into the above-mentioned synthesis reactor due to the action of gravity to continue to participate in the reaction. Part of the methanol and dimethyl carbonate gas that have not been separated evaporates upward together with the by-products ammonia and carbon dioxide gas to perform preliminary gas-liquid separation. Part of the material droplets and material gas are cooled to 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, thereby maintaining the balance of the reaction materials in the methyl methyl carbamate preparation kettle and improving the conversion rate of the reaction.

[0042] The separation of methanol and dimethyl carbonate from the reaction byproducts, ammonia and carbon dioxide, is performed in a gas-liquid separator. The liquid phase outlet of the gas-liquid separator is connected to the methyl methyl carbamate production kettle via a reflux line. The condensed liquid phase collected in the gas-liquid separator can be refluxed (e.g., using a reflux pump) into the methyl methyl carbamate production kettle to maintain the reaction mass balance and temperature balance within the methyl methyl carbamate production 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 a gaseous state for gas-liquid separation, and then ammonia and carbon dioxide enter the reaction by-product gas recovery unit in a gaseous state; unreacted methanol, dimethyl carbonate, etc. flow downward from the overflow port on the side of the gas-liquid separator in a 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 reflux circulation maintains the balance of reaction materials in the methyl methyl carbamate preparation kettle, thereby improving the conversion rate of the reaction.

[0044] Furthermore, the packing in the packed demister is one or a combination of Raschig rings, Pall rings or structured packing. The vertical condenser and the horizontal shell and tube condenser both have the material pipe inside and the coolant pipe between.

[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-phase separation is carried out, and the methanol and dimethyl carbonate are all condensed into a liquid phase 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 byproduct gas recovery unit is connected to the urea production line. The urea production line can be controllably connected to the reaction byproduct gas recovery unit via a valve, thereby achieving the beneficial effect of reusing the recovered ammonia and carbon dioxide gases for urea synthesis. The generated urea can be further used as a raw material for this method, further reducing production costs. The above-mentioned urea production line of the present invention is a conventional 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 channels between the gas-liquid separator and the gas buffer tank, the gas buffer tank and the gas buffer tank, and the gas buffer tank and the urea production line.

[0048] In a preferred embodiment, the system further includes a synthetic mixed liquid storage tank, which is disposed between the methyl methyl carbamate preparation kettle and the subsequent distillation kettle. After the reaction terminates, the reaction materials in the methyl methyl carbamate preparation kettle are cooled to room temperature and depressurized to normal pressure. The reaction materials are then transported through pipelines, valves, and finally a synthetic mixed liquid delivery pump to the synthetic mixed liquid storage tank for standby use. The synthetic mixed liquid comprises methanol, dimethyl carbonate, methyl methyl carbamate, an ionic liquid catalyst, and a trace amount of urea (primarily dissolved in methanol, dimethyl carbonate, and methyl methyl carbamate).

[0049] In a preferred embodiment, the above-mentioned system for preparing methyl methyl carbamate also includes a refining unit; the refining unit includes a distillation kettle and a distillation tower 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 includes 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 mixture, thereby achieving more efficient recycling.

[0051] First, because the boiling point difference between methanol, dimethyl carbonate, and methyl methyl carbamate and the ionic liquid catalyst is greater than 70°C, the low-boiling methanol (distillation range of approximately 65°C) and dimethyl carbonate (distillation range of approximately 90-91°C) in the synthetic mixture are heated and vaporized in a still. The mixture then rises to the top of the still in a vertical condenser and a horizontal condenser connected to the still, where it is condensed into a liquid and separated. The methanol and dimethyl carbonate mixture separated by distillation is analyzed and reused as raw materials for the synthesis reaction of the present invention. The high-boiling methyl methyl carbamate, ionic liquid catalyst, and a small amount of urea do not undergo a phase change and remain at the bottom of the still as a residual distillation mixture. This residual distillation mixture is then pumped into a still heavy component storage tank via a still heavy component transfer pump. Subsequently, the residual distillation mixture enters a rectifying tower, where the methyl methyl carbamate, ionic liquid catalyst, and a small amount of urea in the residual distillation mixture are subjected to continuous distillation separation at atmospheric pressure. Methyl methyl carbamate (distillation range is around 167-168°C) is separated from the upper part of the rectifying 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 producing methyl methyl carbamate in the distillation tower is continuous. The still kettle heavy component mixed liquid in the still kettle heavy component material storage tank is transported by the distillation tower feed pump and first pumped into the feed preheating heat exchanger for initial heat exchange with the hot material leaving the distillation tower. This raises the temperature of the still kettle heavy component mixed liquid. It then enters the first heat exchanger of the distillation tower for further heat exchange with the hot heat transfer oil. Once the still kettle heavy component mixed liquid reaches a higher temperature, it is continuously fed into the distillation tower from the upper part of the stripping section. Some liquid methyl methyl carbamate at the bottom of the distillation section enters the top of the stripping section, where it mixes with the residual distillation mixed liquid 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, causing the volatile methyl methyl carbamate in the liquid to partially vaporize and rise. The gaseous 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 part of the methyl methyl carbamate that is converted from the liquid phase to the gas phase due to the heat rises to the distillation section and is continuously distilled and separated. The liquid-phase substances such as the ionic liquid catalyst and the small amount of urea are finally discharged from the bottom of the stripping section after the methyl methyl carbamate content therein meets the required standard, enter the ionic liquid catalyst recovery and storage unit, and are reused as raw materials for the synthesis reaction of the present invention. The vaporous methyl methyl carbamate rises to the top of the rectifying section and passes through the first condenser of the rectifying section to produce partially vaporous methyl methyl carbamate and liquid methyl methyl carbamate. The vaporous methyl methyl carbamate then enters the gas-liquid separation tank of the rectifying section to separate the vaporous methyl methyl carbamate. The liquid methyl methyl carbamate is then re-transferred to the middle of the rectifying section via a reflux pump. Once the methyl methyl carbamate reaches the required purity, it is cooled again in the second heat exchanger of the rectifying section before being transferred via pipelines to the methyl methyl carbamate storage unit.

[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 has excellent physical and chemical properties when used as an electronic cleaning solvent, namely, excellent solubility, suitable volatilization speed, excellent non-toxicity, safety and environmental protection. In addition, the methyl methyl carbamate of the present invention is 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, or even non-toxic, is safe and environmentally friendly, and can replace a large number of ethylene glycol ether 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 quantities in new energy battery electrolytes. Methyl methyl carbamate has more stable performance, is safer, more efficient, non-toxic, and 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 and easy preparation process, and the reaction raw materials are simple, cheap and readily available, 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 present 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 cationic 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 solution and subsequent separation are simple.

[0060] The synthetic reaction equipment of the invention has simple connection, efficient gas-liquid separation of by-products 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] During the preparation process, the present invention controls the discharge of byproduct gases such as ammonia and carbon dioxide from the reaction system in batches, thereby regulating the reaction balance and improving the urea conversion rate. The byproducts, such as ammonia and carbon dioxide, can all be fed into a urea production unit as raw materials for further synthesis into urea, which can then be recycled as raw materials for the present invention. This achieves the recycling of byproduct gases and represents 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 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 stage packing demister, 6-1st stage vertical condenser, 7-2nd stage packing demister, 8-2nd stage 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 and 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, objectives 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 understood as limiting the scope of implementation 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 connections between devices are pipe connections, and all arrow directions indicate the direction of movement of liquid or gas phase substances). The system includes:

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

[0070] The methyl methyl carbamate preparation kettle 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 to a nitrogen generator 42 , a thermal oil furnace 41 , and a coolant pipeline 44 through valves and pipelines.

[0072] The methyl methyl carbamate preparation kettle 1 includes a feed hand port 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 perform a first chemical reaction to obtain an ionic liquid catalyst.

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

[0076] The ionic liquid catalyst preparation kettle 2 includes 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 by pipes 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 during the feeding stage.

[0078] (3) 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 connected in sequence.

[0080] The discharge port at the top of the methyl methyl carbamate preparation kettle 1 is connected to 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 pipe. The condensation circulation reflux unit also includes a circulation reflux pump 4, which is arranged on the reflux pipe 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 foamy state and the gaseous materials volatilizing upward in the methyl methyl carbamate preparation kettle 1. Part of the material foam and material gas are cooled to a 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 byproduct 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. Ammonia and carbon dioxide enter the subsequent reaction byproduct gas recovery unit in a gaseous state. Unreacted methanol, dimethyl carbonate, etc., in a liquid state, flow downward from the side overflow port of the gas-liquid separator 3 through a pipeline connection to the inlet of the circulating reflux pump 4, and are transported to the methyl methyl carbamate preparation kettle 1 by the circulating reflux pump 4. The reflux cycle maintains the balance of the reaction materials in the methyl methyl carbamate preparation kettle 1, thereby improving the reaction conversion rate.

[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 the reaction by-products of ammonia and carbon dioxide.

[0086] The reaction by-product 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 connected in sequence. A first pressure regulating valve 12 is provided on the communication channel between the gas-liquid separator 3 and the first gas buffer tank 11, a second pressure regulating valve 14 is provided on the communication channel between the first gas buffer tank 11 and the second gas buffer tank 13, and a third pressure regulating valve 15 is provided on the communication channel 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, passed through pipelines and valves, and transported to the synthetic mixture storage tank 16 for standby use through the synthetic mixture delivery pump 10. The main components of the synthetic mixture storage tank 16 are methanol, dimethyl carbonate, methyl methyl carbamate, ionic liquid catalyst and trace urea (mainly dissolved in methanol, dimethyl carbonate and methyl methyl carbamate).

[0091] (6) 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 and storage unit 38, and a methyl methyl carbamate storage unit 37.

[0093] The feed inlet of the still 20 is connected to the discharge outlet of the synthetic mixture storage tank 16. Because the boiling point difference between methanol, dimethyl carbonate, and methyl methyl carbamate and the ionic liquid catalyst is greater than 70°C, the lower-boiling-point methanol and dimethyl carbonate in the synthetic mixture are vaporized in the still 20 by steam heating. The mixture then rises to the top of the still, where it is condensed into a liquid and separated in a horizontal condenser 22 connected to the still. The methanol and dimethyl carbonate mixture separated by distillation undergoes component analysis and is reused as raw material for the synthesis reaction of the present invention. The higher-boiling-point methyl methyl carbamate, ionic liquid catalyst, and a small amount of urea do not undergo a phase change and remain at the bottom of the still 20 as a residual distillate mixture. This is then pumped into the still heavy component storage tank 26 via the still heavy component transfer pump 45. The residual distillate mixture in the still heavy component storage tank 26 then continues to enter the rectification column 28, where the methyl methyl carbamate, ionic liquid catalyst, and a small amount of urea in the residual distillate mixture are continuously distilled and separated at atmospheric pressure. 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 production of methyl methyl carbamate in distillation tower 27 is carried out continuously. The still kettle heavy component mixed liquid in still kettle heavy component material storage tank 26 is transported by distillation tower feed pump 25 and first pumped into feed preheat exchanger 30 for preliminary heat exchange with the hot material exiting the distillation tower. This raises the temperature of the still kettle heavy component mixed liquid. The still kettle heavy component mixed liquid then enters the first distillation tower heat exchanger 29 for further heat exchange with the hot heat transfer oil. After reaching a higher temperature, the still kettle heavy component mixed liquid is continuously fed into distillation tower 28 from the upper portion of stripping section 35. A portion of the liquid methyl methyl carbamate at the bottom of distillation section 27 enters the top of stripping section 35, where it mixes with the residual distillation mixed liquid entering distillation tower 28 and then flows down from the top of stripping section 35. At the same time, the downstream liquid and the rising air flow interact with each other, transferring mass and heat, causing the volatile methyl methyl carbamate in the liquid to partially vaporize and rise. The gaseous methyl methyl carbamate is stripped to the distillation section 27, and the liquid 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 35, enter the stripping section heater 36 for heating, and are re-transported to the middle of the distillation section 35. The methyl methyl carbamate that is partially converted from the liquid phase to the gas phase due to the 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 and storage unit 38 to be used again as raw materials for the synthesis reaction of the present invention. The vaporous methyl methyl carbamate, which rises to the top of the rectifying section 27, passes through the rectifying section first condenser 31 to produce a portion of vaporous methyl methyl carbamate and liquid methyl methyl carbamate. The vaporous methyl methyl carbamate then enters the rectifying section gas-liquid separation tank 32, where it is separated. The liquid methyl methyl carbamate is then re-delivered to the middle of the rectifying section via the rectifying section reflux pump 33. Once the methyl methyl carbamate reaches the required purity, it is cooled again in the rectifying section second heat exchanger 34 before being transferred via a pipeline to the methyl methyl carbamate storage unit 37.

[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) were added to the ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring was started, and heating was turned on the thermal oil furnace. After reacting at 150°C for 60 minutes, the mixture was cooled to room temperature to obtain a colorless transparent liquid, which was an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0098] To the methyl methyl carbamate preparation reactor 1, 374.8 g (11.7 mol) of methanol, 1053.9 g (11.7 mol) of dimethyl carbonate, 234.2 g (3.9 mol) of urea (molar ratio of 3:3:1), and 7.03 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The methyl methyl carbamate preparation reactor 1 was sealed and stirred to dissolve the materials. A vacuum was applied to evacuate the air from the reactor, and then nitrogen was added to the reactor to maintain the pressure at 0.7 MPa. A thermal oil heater was then used to heat the reactor to 200°C, at which the reactor pressure reached 6.0 MPa. Under these conditions, the reactants in the reactor partially vaporized and rose to the condensation and reflux unit, where they refluxed normally. The condensed methanol and dimethyl carbonate liquids then refluxed normally into the reactor. The reaction is continued at this temperature and pressure for 40 minutes. The control valve 15 of the reaction by-product gas recovery unit is opened, and ammonia and carbon dioxide are slowly released 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 released, valve 15 is closed. At 60 minutes, the pressure in the kettle reaches 7.2 MPa, and ammonia and carbon dioxide are released and released once again. The reaction is complete when the reaction materials in the kettle continue to react at 220°C for 2 hours, with the pressure in the kettle controlled at 8.0 MPa. Heating is discontinued, and coolant is introduced to cool the reaction mixture to below 50°C. Cooling is then stopped. The entire reaction mixture is then removed from the still 20 and steam-heated for distillation to completely separate the methanol and dimethyl carbonate. The distillation residue is then transferred to a distillation column 28 for rectification. 241.7 g of methyl methyl carbamate is obtained. Calculated urea conversion 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) were added to the ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 100°C for 105 minutes. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0102] To a methyl methyl carbamate preparation reactor (1), 374.8 g (11.7 mol) of methanol, 1053.9 g (11.7 mol) of dimethyl carbonate, 234.2 g (3.9 mol) of urea (molar ratio of 3:3:1), and 15.22 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and the byproducts of ammonia and carbon dioxide were released four times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 243.2 g 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) were added to a 1 L 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 150 min. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0105] To a methyl methyl carbamate preparation reactor (1), 374.8 g (11.7 mol) of methanol, 1053.9 g (11.7 mol) of dimethyl carbonate, 234.2 g (3.9 mol) of urea (molar ratio of 3:3:1), and 23.42 g (10% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and ammonia and carbon dioxide were released as byproducts three times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 241.3 g 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 1 L 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. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0108] To a methyl methyl carbamate preparation vessel (1), 246.1 g (7.68 mol) of methanol, 1268.3 g (14.08 mol) of dimethyl carbonate, 153.8 g (2.56 mol) of urea (molar ratio of 3:5.5:1), and 15.38 g (10% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and ammonia and carbon dioxide were released as byproducts three times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 169.3 g 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) were added to a 1 L ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 100 ° C for 150 minutes. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0111] To a methyl methyl carbamate preparation vessel (1), 246.1 g (7.68 mol) of methanol, 1268.3 g (14.08 mol) of dimethyl carbonate, 153.8 g (2.56 mol) of urea (molar ratio of 3:5.5:1), and 10 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C, and ammonia and carbon dioxide were released as byproducts four times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 170.7 g 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) were added to a 1 L 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 60 minutes. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0114] To a methyl methyl carbamate preparation vessel (1), 246.1 g (7.68 mol) of methanol, 1268.3 g (14.08 mol) of dimethyl carbonate, 153.8 g (2.56 mol) of urea (molar ratio of 3:5.5:1), and 4.61 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and ammonia and carbon dioxide were released as byproducts twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 167.7 g 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 1 L 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. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing multi-step alcoholysis and aminolysis reactions of urea with methanol and dimethyl carbonate.

[0117] To a methyl methyl carbamate preparation vessel (1), 182.7 g (5.7 mol) of methanol, 1369.3 g (15.2 mol) of dimethyl carbonate, 114.2 g (1.9 mol) of urea (molar ratio of 3:8:1), and 7.42 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C. Ammonia and carbon dioxide were released as byproducts twice during the synthesis reaction. Other reaction conditions were the same as in Example 1. 122 g 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) were added to a 1 L ionic liquid catalyst preparation kettle 2, nitrogen was introduced into the kettle, stirring and heating were started, and the reaction was carried out at 100 ° C for 60 minutes. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

[0120] To a methyl methyl carbamate preparation reactor (1), 182.7 g (5.7 mol) of methanol, 1369.3 g (15.2 mol) of dimethyl carbonate, 114.2 g (1.9 mol) of urea (molar ratio of 3:8:1), and 3.426 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and ammonia and carbon dioxide were released as byproducts four times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 124.3 g 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 1 L 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 minutes. After cooling to room temperature, a colorless transparent liquid was obtained, which was an ionic liquid catalyst for catalyzing the multi-step alcoholysis reaction and aminolysis reaction of urea with methanol and dimethyl carbonate.

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

[0124] Example 10

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

[0126] To a methyl methyl carbamate preparation reactor (1), 581.6 g (18.15 mol) of methanol, 891.8 g (9.9 mol) of dimethyl carbonate, 198.2 g (3.3 mol) of urea (molar ratio of 5.5:3:1), and 12.88 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and ammonia and carbon dioxide were released as byproducts three 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] Example 11

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

[0129] To a methyl methyl carbamate preparation vessel (1), 581.6 g (18.15 mol) of methanol, 891.8 g (9.9 mol) of dimethyl carbonate, 198.2 g (3.3 mol) of urea (molar ratio of 5.5:3:1), and 5.95 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C, and ammonia and carbon dioxide were released as byproducts 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] To a methyl methyl carbamate preparation reactor (1), 581.6 g (18.15 mol) of methanol, 891.8 g (9.9 mol) of dimethyl carbonate, 198.2 g (3.3 mol) of urea (molar ratio of 5.5:3:1), and 19.82 g (10% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and ammonia and carbon dioxide were released as byproducts four 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 preparation method of the ionic liquid catalyst was the same as that in Example 4.

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

[0136] Example 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] To a methyl methyl carbamate preparation vessel (1), 401.8 g (12.54 mol) of methanol, 1129.6 g (12.54 mol) of dimethyl carbonate, 137 g (2.28 mol) of urea (molar ratio of 5.5:5.5:1), and 8.91 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and ammonia and carbon dioxide were released as byproducts 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] Example 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] To a methyl methyl carbamate preparation reactor (1), 401.8 g (12.54 mol) of methanol, 1129.6 g (12.54 mol) of dimethyl carbonate, 137 g (2.28 mol) of urea (molar ratio of 5.5:5.5:1), and 13.7 g (10% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and ammonia and carbon dioxide were released as byproducts four 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 in Example 7.

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

[0145] Example 17

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

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

[0148] Example 18

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

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

[0151] Example 19

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

[0153] To a methyl methyl carbamate preparation vessel (1), 730.5 g (22.8 mol) of methanol, 770.2 g (8.55 mol) of dimethyl carbonate, 171.2 g (2.85 mol) of urea (molar ratio of 8:3:1), and 11.128 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C. Ammonia and carbon dioxide were released as byproducts 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] Example 20

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

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

[0157] Example 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] To a methyl methyl carbamate preparation vessel (1), 730.5 g (22.8 mol) of methanol, 770.2 g (8.55 mol) of dimethyl carbonate, 171.2 g (2.85 mol) of urea (molar ratio of 8:3:1), and 5.136 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and the byproducts of ammonia and carbon dioxide were released three times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 192.6 g of methyl methyl carbamate was obtained.

[0160] Example 22

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

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

[0163] Example 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] To a methyl methyl carbamate preparation reactor (1), 525.5 g (16.4 mol) of methanol, 1015.6 g (11.275 mol) of dimethyl carbonate, 123.1 g (2.05 mol) of urea (molar ratio of 8:5.5:1), and 3.69 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C, and ammonia and carbon dioxide were released as byproducts three times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 138.5 g of methyl methyl carbamate was obtained.

[0166] Example 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] To a methyl methyl carbamate preparation reactor (1), 525.5 g (16.4 mol) of methanol, 1015.6 g (11.275 mol) of dimethyl carbonate, 123.1 g (2.05 mol) of urea (molar ratio of 8:5.5:1), and 8 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and ammonia and carbon dioxide were released as byproducts four times during the synthesis reaction. Other reaction conditions were the same as in Example 1. 138.9 g of methyl methyl carbamate was obtained.

[0169] Example 25

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

[0171] To a methyl methyl carbamate preparation vessel (1), 412.7 g (12.88 mol) of methanol, 1160.2 g (12.88 mol) of dimethyl carbonate, 96.7 g (1.61 mol) of urea (molar ratio of 8:8:1), and 2.901 g (3% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 200°C, and ammonia and carbon dioxide were released as byproducts 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] Example 26

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

[0174] To a methyl methyl carbamate preparation reactor (1), 412.7 g (12.88 mol) of methanol, 1160.2 g (12.88 mol) of dimethyl carbonate, 96.7 g (1.61 mol) of urea (molar ratio of 8:8:1), and 6.286 g (6.5% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 210°C, and ammonia and carbon dioxide were released as byproducts three 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] Example 27

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

[0177] To a methyl methyl carbamate preparation reactor (1), 412.7 g (12.88 mol) of methanol, 1160.2 g (12.88 mol) of dimethyl carbonate, 96.7 g (1.61 mol) of urea (molar ratio of 8:8:1), and 9.67 g (10% of the urea charge) of the ionic liquid catalyst prepared above were added. The reaction temperature was controlled at 220°C, and the byproducts of ammonia and carbon dioxide were released four 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 are all replaced with dibutyltin oxide instead of 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 the reaction produces methyl methyl carbamate.

[0180] Comparative Example 1

[0181] use Figure 1 In the system shown, 374.8 g (11.7 mol) of methanol, 1053.9 g (11.7 mol) of dimethyl carbonate, 234.2 g (3.9 mol) of urea (molar ratio of 3:3:1), and 9.71 g (1% of the molar amount of urea) of dibutyltin oxide were added to a 5-liter methyl methyl carbamate preparation kettle. The kettle was sealed and stirred to dissolve the materials. A vacuum was applied to evacuate the air from the kettle, and then nitrogen was added to the kettle to pressure it to 0.7 MPa. Thermal oil heating was then activated to increase the temperature to 200°C, at which the kettle pressure reached 6.0 MPa. Under these conditions, the reactants in the kettle partially vaporized and rose to the condensation circulation reflux unit, where they refluxed normally. The condensed methanol and dimethyl carbonate liquids then refluxed back into the kettle. The reaction is continued at this temperature and pressure for 40 minutes. The control valve of the by-product gas recovery unit is opened, and ammonia and carbon dioxide are slowly released 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 released, valve 15 is closed. At 60 minutes of reaction, the pressure in the kettle reaches 6.7 MPa. Ammonia and carbon dioxide are released and released once again. The reaction is complete when the reaction materials in the kettle continue to react at 220°C for 2 hours and the pressure in the kettle is controlled at 7.3 MPa. Heating is stopped, and coolant is introduced to cool the kettle to below 50°C. Cooling is then stopped. All reaction materials are then removed to a distillation kettle, where steam heating is used for distillation to completely separate methanol and dimethyl carbonate. The distillation residue is then transferred to a rectification column for rectification to yield 106.5 g of methyl methyl carbamate. Calculated urea conversion is 44.0%, and methyl methyl carbamate selectivity is 30.7%.

[0182] Comparative Example 2

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

[0184] 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 were added. The reaction temperature was controlled at 210°C. Ammonia and carbon dioxide were released as byproducts twice during the synthesis reaction. 70.8g of methyl methyl carbamate was obtained. Calculated urea conversion was 45.4%, and methyl methyl carbamate selectivity was 34.9%.

[0185] Comparative Example 3

[0186] Except that the catalyst was replaced by dibutyltin oxide, the ionic liquid catalyst of the present invention was used. Other process conditions and methods were the same as those in Example 26. The raw material composition and control conditions were as follows:

[0187] 412.7g (12.88mol) of methanol, 1160.2g (12.88mol) of dimethyl carbonate, 96.7g (1.61mol) of urea (molar ratio of 8:8:1), and 48.1g (12% of the molar amount of urea) of dibutyltin oxide were added. The reaction temperature was controlled at 210°C. Ammonia and carbon dioxide were released as byproducts three times during the synthesis reaction. 52.7g of methyl methyl carbamate was obtained. Calculated urea conversion was 46.8%, and methyl methyl carbamate selectivity was 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 the 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 calculated; 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 data of 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 is within the range of 3-8:3-8:1, the amount of the aforementioned ionic liquid catalyst added (based on the amount of urea used) is 3-10%, the reaction temperature is 200-220°C, and the reaction pressure range is 6.0-8.0 MPa, the urea conversion rate is close to 100%, and the methyl methyl carbamate selectivity is 69.5-78.5%. In contrast, when the amount of the dibutyltin oxide catalyst added (based on the molar amount of urea used) is 1-12%, the reaction temperature is 200-220°C, and the reaction pressure range is 6.0-8.0 MPa, the urea conversion rate is 44.0-46.8%, and the methyl methyl carbamate selectivity is 30.7-36.8%. Using dibutyltin oxide as a catalyst has no significant effect on the preparation method of methyl methyl carbamate using methanol, dimethyl carbonate, and urea as raw materials.

Claims

1. A method for preparing methyl methyl carbamate, wherein: include: Mixing methyl methyl carbamate and zinc acetate to perform a first chemical reaction to obtain an ionic liquid catalyst; Methanol, dimethyl carbonate and urea are mixed and subjected to a second chemical reaction under the catalysis of the ionic liquid catalyst to obtain methyl methyl carbamate.

2. The method for preparing methyl methyl carbamate according to claim 1, wherein The temperature of the first chemical reaction is 100-150° C., and the time is 60-150 minutes.

3. The method for preparing methyl methyl carbamate according to claim 1, wherein The molar ratio of the methyl methyl carbamate to the zinc acetate is 6 to 10:

1.

4. The method for preparing methyl methyl carbamate according to claim 1, 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.

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

6. The method for preparing methyl methyl carbamate according to claim 1, wherein During the second chemical reaction, gaseous by-products in the reaction product system are discharged.

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