Low-energy-consumption tetramethyl ammonium bicarbonate preparation process

Abstract

The invention provides a low-energy-consumption preparation process of tetramethylammonium bicarbonate, and relates to the technical field of chemical synthesis. The preparation process comprises the following steps: inputting trimethylamine, dimethyl carbonate and a solvent methanol into a reactive distillation tower, carrying out a quaternization reaction to generate methyl carbonate tetramethylammonium, and carrying out a hydrolysis reaction on a first liquid phase obtained by rectification and water vapor to generate TMAB; the reacted material is input into a methanol removal tower for rectification, an obtained second gas phase is heated and pressurized, one part of the second gas phase is input into a subsequent methanol recovery tower, the other part of the second gas phase exchanges heat with water to generate steam, the steam is input into a tower kettle of the methanol removal tower, and high-purity methanol is extracted from the side of the methanol recovery tower. The number of reaction equipment is reduced, and the energy utilization rate is increased; the steam grade is improved by utilizing a heat pump technology, and steam latent heat is integrated between the methanol removal tower and the methanol recovery tower through thermal coupling, so that the overall process energy consumption is remarkably reduced while the product quality is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and particularly relates to a preparation process of tetramethylammonium hydrogencarbonate with low energy consumption. Background Art

[0002] Tetramethylammonium hydroxide (TMAH), with the chemical formula C4H 13 NO, is an important organic strong base, and can be used as a developer and etchant in the field of the electronics industry, as well as an ultra-pure cleaning agent in the chemical mechanical polishing process of integrated circuits. In the application process, TMAH has extremely high requirements for purity. The early silver oxide method and the electrolysis of tetramethylammonium chloride to prepare tetramethylammonium hydroxide have disadvantages such as many impurity ions, high cost, and strong corrosiveness to equipment. Moreover, toxic gas chlorine will be generated during the electrolysis of tetramethylammonium chloride. In recent years, the process of preparing tetramethylammonium hydroxide with tetramethylammonium hydrogencarbonate (TMAB) as the raw material has been widely used. TMAH is obtained by ion-exchange membrane electrolysis of an aqueous solution of TMAB. This process can effectively reduce the content of impurity ions, reduce the corrosiveness of equipment, and avoid the emission of chlorine gas as a toxic and harmful gas.

[0003] The raw material TMAB can be synthesized through two-step reactions: (1) Quaternization reaction: Using trimethylamine and dimethyl carbonate as raw materials, tetramethylammonium methyl carbonate is prepared through a quaternization reaction in the solvent methanol; (2) Hydrolysis reaction: Tetramethylammonium methyl carbonate undergoes a hydrolysis reaction when encountering water to generate TMAB. The specific chemical reaction equations are as follows:

[0004] (CH3)3N + (CH3O)2CO → (CH3)4NOCOOCH3,

[0005] (CH3)4NOCOOCH3 + H2O → (CH3)4NOCOOH + CH3OH.

[0006] During the TMAB preparation process, methanol is the solvent used in the reaction system and is also a by-product generated by the synthesis reaction. In the process of electrolyzing TMAB to prepare TMAH, there is no longer a purification device for removing organic substances. Only relying on the barrier of the ion-exchange membrane in the electrolytic cell to prevent methanol molecules from migrating to the product cathode chamber. Therefore, in order to ensure that the methanol content in the TMAH product is ≤ 40 ppm, the methanol content in the raw material TMAB solution needs to be as low as possible. Therefore, in order to obtain a high-purity TMAB solution, it is necessary to separate methanol, unreacted trimethylamine, and dimethyl carbonate from the TMAB aqueous solution and prepare qualified methanol by-products for external sale.

[0007] In Patent CN217568669U, TMAB is synthesized by connecting two reaction kettles in series, and a two-stage distillation tank and a rectifying column are used to couple and separate trimethylamine, methanol, etc. during the synthesis process. However, the series kettle reactor adopted in this method has high equipment investment and high energy consumption, and actual operation has confirmed that components such as trimethylamine and dimethyl carbonate cannot be effectively separated from the methanol product only through the distillation tank, which will seriously affect the quality and sales of the by-product methanol.

[0008] Patent CN107281994A proposes a device and method for synthesizing TMAB by connecting a circulating tubular reactor in series with a tubular reactor. This method uses a two-stage double-effect falling film evaporator to flash a mixed material such as TMAB, methanol, and trimethylamine to obtain a mixed solution of methanol, dimethyl carbonate, and trimethylamine, which is recycled to the reaction device, and at the same time, a methanol solution and a product of tetramethylammonium bicarbonate are generated. In this method, it is difficult for the tubular reactor to overcome problems such as uneven mixing at the initial stage of the reaction and difficulty in timely removing the reaction heat, and a large amount of methanol aqueous solution will be generated during the evaporation process, which is difficult to be completely recycled under this reaction system and requires further in-depth treatment, and the overall process energy consumption is relatively high.

[0009] Patent CN208407002U proposes a tower reaction structure for synthesizing dimethyl carbonate. The reaction tower is divided into upper and lower parts: the lower part realizes circulating mixing through an external pump on the circulation loop, and controls the reaction temperature through an external condenser to improve the mass transfer and heat transfer effect. At the same time, the circulation speed of the pump is controlled to ensure that the upper part of the reaction tower adopts a plug flow mode from bottom to top, so that the reaction fully reacts and discharges at the top of the tower. However, this method does not propose a preliminary separation method for methanol, trimethylamine, and dimethyl carbonate during the quaternization reaction.

[0010] Patent CN221267175U proposes a new separation and purification device for methanol, trimethylamine, and dimethyl carbonate. A side-line methanol product extraction port is arranged in the middle and upper part of the methanol separation tower, and the extracted methanol product does not contain trimethylamine impurities, which greatly improves the quality of the methanol product. However, the energy utilization rate of this overall process is relatively low.

[0011] In summary, the existing preparation processes of tetramethylammonium bicarbonate have technical problems such as high equipment investment, high energy consumption, and low product purity. Summary of the Invention

[0012] In view of the deficiencies in the prior art, the present invention discloses a low-energy-consumption preparation process for tetramethylammonium bicarbonate, which can solve the problems of high equipment investment, high energy consumption, and low product purity existing in the existing preparation processes of tetramethylammonium bicarbonate.

[0013] In order to achieve the above technical objectives, the present invention proposes a low-energy-consumption preparation process for tetramethylammonium bicarbonate, and this process includes the following steps:

[0014] (1) Trimethylamine, dimethyl carbonate and solvent methanol are fed into a reactive distillation column to undergo a quaternization reaction to produce tetramethylammonium methyl carbonate. A first gas phase and a first liquid phase are respectively withdrawn from the top and the bottom of the reactive distillation column.

[0015] (2) The first liquid phase undergoes a hydrolysis reaction with water to obtain a material to be separated containing tetramethylammonium bicarbonate.

[0016] (3) The material to be separated is rectified in a methanol removal column to obtain a second liquid phase and a second gas phase. The second liquid phase is an aqueous solution of tetramethylammonium bicarbonate. The second gas phase is divided into two parts after being heated and pressurized: one part is fed into a subsequent methanol recovery column, and the other part exchanges heat with water to generate steam, and the steam is fed into the bottom of the methanol removal column. After heat exchange and condensation, a part of the material is returned to the methanol removal column, and the other part is fed into the methanol recovery column.

[0017] (4) High-purity methanol is withdrawn from the side of the methanol recovery column, and a dilute methanol solution is withdrawn from the bottom of the column.

[0018] In the above technical solution, a reactive distillation column is used for continuous quaternization reaction. While the quaternization reaction releases heat, preliminary separation of unreacted raw materials and solvents in the column is achieved. The overall equipment occupies a small area and has a low equipment investment. It overcomes the disadvantages of high equipment cost and large floor area of traditional multi-kettle series reactors, and avoids the deficiencies such as high reaction pressure and difficult heat removal in tubular reactors. Examples and comparative examples of the present invention show that in the quaternization reaction and hydrolysis reaction stages, the present invention can reduce the comprehensive energy consumption by about 7.41% - 21.34%.

[0019] In the above technical solution, a heat pump technology is used to heat and pressurize the second gas phase withdrawn from the top of the methanol removal column to improve the steam quality at the top of the column, and part of the second gas phase after heating and pressurizing is used to generate steam. By directly feeding the steam as a heat source into the methanol removal column for heating, the methanol can be efficiently recovered by utilizing its different distributions in water vapor and aqueous solution. Using steam heating effectively reduces the heating requirement of the reboiler at the bottom of the methanol removal column. Compared with reboiler heat exchange, direct steam heating can enhance the interference effect on the bottom material of the column, with uniform heating and enhanced heat transfer. Examples and comparative examples of the present invention show that the comprehensive energy consumption of the methanol removal column in the low-energy consumption preparation process of tetramethylammonium bicarbonate of the present invention can be reduced by 89.97% - 93.28%.

[0020] In the above technical solution, part of the second gas phase after heating and pressurizing is directly fed into a subsequent methanol recovery column as a heat source, and can be directly fed into the bottom of the methanol recovery column as superheated gas feed, reducing the steam consumption of the reboiler in the methanol recovery column, and reducing the comprehensive energy consumption of the methanol recovery column by 72.58% - 91.1%.

[0021] The present invention integrates the energy of the heat pump distillation technology with the separation process of the post-reaction materials, significantly reducing the overall energy consumption of the preparation technology of tetramethylammonium hydrogencarbonate. The comprehensive energy consumption of the methanol separation process is reduced by 62.19% - 70.87%. Methanol in the TMAB aqueous solution is removed by steam stripping at the bottom of the methanol removal column, and the methanol content in the obtained TMAB aqueous solution is ≤ 30 ppm, meeting the requirements of the subsequent electrolysis process.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The low-energy consumption preparation process of tetramethylammonium hydrogencarbonate of the present invention has low energy consumption, less equipment investment, and high raw material utilization rate. High-purity TMAB can be continuously produced and high-purity methanol products can be recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 Shows a structural diagram of the low-energy consumption preparation process of tetramethylammonium hydrogencarbonate of the present invention;

[0025] Wherein, Figure 1 Including the following reference numerals: 1 - reactive distillation column, 11 - first heat exchanger, 12 - second reflux drum, 13 - first reboiler, 2 - static mixer, 3 - methanol removal column, 31 - steam generator, 32 - first reflux drum, 33 - steam compressor, 4 - methanol recovery column, 41 - second heat exchanger, 42 - third reflux drum, 43 - second reboiler.

[0026] Figure 2 Shows a structural diagram of the preparation process of tetramethylammonium hydrogencarbonate in Comparative Example 1.

[0027] Wherein, Figure 2 Including the following reference numerals: 51 - first reaction kettle, 52 - second reaction kettle, 53 - third reaction kettle, 61 - water heater, 62 - static mixing device, 71 - first falling film evaporator, 72 - second falling film evaporator, 73 - preparation tank, 8 - methanol removal tower, 9 - methanol recovery tower. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0029] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention belongs. In the present invention, the terms "first", "second", and "third" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", and "third" may explicitly or implicitly include one or more of such features.

[0030] In the description of this specification, the descriptions referring to terms such as "further example", "optional example", "example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic descriptions of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0031] The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0032] The present invention provides a low - energy - consumption preparation process of tetramethylammonium hydrogencarbonate, and this process includes the following steps:

[0033] (1) Trimethylamine, dimethyl carbonate, and the solvent methanol are fed into a reactive distillation column for a quaternization reaction to generate tetramethylammonium methyl carbonate. A first gas phase and a first liquid phase are respectively withdrawn from the top and the bottom of the reactive distillation column.

[0034] (2) The first liquid phase undergoes a hydrolysis reaction with water to obtain a material to be separated containing tetramethylammonium hydrogencarbonate.

[0035] (3) The material to be separated is rectified in a methanol removal column to obtain a second liquid phase and a second gas phase. The second liquid phase is an aqueous solution of tetramethylammonium hydrogencarbonate. The second gas phase is divided into two parts after being heated and pressurized: one part is fed into a subsequent methanol recovery column, and the other part exchanges heat with water to generate steam, and this steam is fed into the bottom of the methanol removal column. After heat exchange and condensation, a part of the material is returned to the methanol removal column, and the other part is fed into the methanol recovery column.

[0036] (4) High - purity methanol is side - drawn from the methanol recovery column, and a dilute methanol solution is withdrawn from the bottom of the column.

[0037] Figure 1 A device structure diagram of the low - energy - consumption preparation process of tetramethylammonium hydrogencarbonate according to the present invention is shown. As Figure 1 shown, this device includes a reactive distillation column 1, a static mixer 2, a methanol removal column 3, and a methanol recovery column 4, wherein:

[0038] The reactive distillation column 1 is connected to a dimethyl carbonate input pipe, a trimethylamine and solvent methanol input pipe, and the liquid-phase discharge port is connected to the first feed port of the static mixer 2;

[0039] The second feed port of the static mixer 2 is connected to a hot water input pipe, and its discharge port is connected to the feed port of the methanol removal column 3;

[0040] The gas-phase discharge port of the methanol removal column 3 is connected to the inlet of the steam compressor 33. A first branch connected to the outlet of the steam compressor 33 is connected to the methanol recovery column 4, and a second branch connected to the outlet of the steam compressor 33 is connected to the first reflux tank 32 through the heat medium channel of the steam generator 31. A third branch connected to the outlet of the first reflux tank 32 is connected to the feed port of the methanol recovery column 4, and a fourth branch connected to the outlet of the first reflux tank 32 is connected to the top of the methanol removal column 3. Pure water exchanges heat through the refrigerant channel of the steam generator 31 and outputs water vapor, and this water vapor is input into the bottom of the methanol removal column 3 through a pipeline.

[0041] The methanol recovery column 4 is provided with a side draw port for extracting high-purity methanol, and the bottom of the column is provided with a liquid discharge port for extracting a dilute methanol solution.

[0042] In the above device, the bottom of the reactive distillation column 1 is provided with a first reboiler 13 for providing heat source; the methanol recovery column 4 is provided with a second reboiler 43 for providing heat source, and this reboiler and the second gas phase after temperature and pressure increase input into the methanol recovery column 4 partially provide heat source for the methanol recovery column 4. In addition, those skilled in the art can set devices or components for promoting the flow of the logistics on the logistics pipeline as needed, such as circulation pumps, etc., and the protection scope of the present invention is not limited thereby.

[0043] In a further example of the present invention, the molar ratio of dimethyl carbonate, trimethylamine and solvent methanol in step (1) can be selected as 1:(0.8 - 1.2):(1.5 - 4).

[0044] In a further example of the present invention, the operating temperature of the reactive distillation column 1 can be selected as 80°C - 200°C, preferably 105°C - 180°C; the operating pressure can be selected as 0.5 - 0.9 MpaA, preferably 0.6 - 0.8 MPaA.

[0045] In a further example of the present invention, the number of theoretical plates of the reactive distillation column 1 can be selected as 36 - 68, and the reflux ratio can be selected as 1 - 2; the feed position of dimethyl carbonate can be selected as the tray at 1 / 5 - 1 / 4 from the top of the column, and the feed positions of trimethylamine and methanol can be selected as the trays at 1 / 5 - 1 / 3 from the bottom of the column.

[0046] In a further example of the present invention, the first gas phase returns to the reactive distillation column 1. The first gas phase includes a part of methanol and unreacted trimethylamine and dimethyl carbonate. By returning this part of the material to the reactive distillation column 1 for continuous reaction, the raw material utilization rate is improved.

[0047] Optionally, the first gas phase is heat-exchanged and condensed with pure water input into the system and then returns to the reactive distillation column 1, so that the thermal energy of the first gas phase can be recycled; further optionally, the pure water heat-exchanged with the first gas phase generates hot water, and this hot water is used for the hydrolysis reaction in step (2). Figure 1 An example is shown in which the gas phase outlet of the reactive distillation column 1 is heat-exchanged through the heat medium channel of the first heat exchanger 11 and then input into the second reflux tank 12, and then returns to the reactive distillation column 1; the pure water is heat-exchanged through the refrigerant channel of the first heat exchanger 11 and outputs hot water, and this part of the hot water is input into the second feed port of the static mixer 2 for the hydrolysis reaction of methyl carbonate tetramethylammonium.

[0048] In a further example of the present invention, the temperature of the hydrolysis reaction can be selected as 105-135 °C, preferably 110 °C-130 °C; the operating pressure can be selected as 0.1-0.2 MPaA, preferably 0.1-0.15 MPaA.

[0049] In a further example of the present invention, the hydrolysis reaction is carried out in the static mixer 2. The first liquid phase and hot water are respectively input into the static mixer 2. After the hydrolysis reaction is completed, the material to be separated is output from the static mixer 2.

[0050] In a further example of the present invention, the concentration of tetramethylammonium bicarbonate in the material to be separated is 35 wt%-45 wt%, preferably 38 wt%-41 wt%. Adjusting the tetramethylammonium bicarbonate in the material to be separated to a suitable concentration is beneficial to the methanol content in the TMAB aqueous solution ≤ 30 ppm, thus meeting the subsequent electrolysis requirements, and at the same time minimizing the separation energy consumption.

[0051] In a further example of the present invention, pure water and / or the dilute methanol solution withdrawn from the bottom of the methanol recovery column 4 is used as a diluent to adjust the concentration of tetramethylammonium bicarbonate in the material to be separated. In the specific process, pure water and / or the dilute methanol solution can be selected as the diluent according to needs to adjust the concentration of tetramethylammonium bicarbonate in the material to be separated, improving the raw material utilization rate.

[0052] Optionally, when pure water and the dilute methanol solution are used as diluents, the dilute methanol solution accounts for 60%-75% of the volume of the diluent. The use of an appropriate amount of the dilute methanol solution can improve the operability of the process and reduce the process cost.

[0053] In a further example of the present invention, the operating temperature of the methanol removal column 3 can be selected from 60°C to 95°C, preferably 63°C to 85°C; the operating pressure can be selected from 0.025 to 0.06 MPaA, preferably 0.025 to 0.04 MPaA.

[0054] In a further example of the present invention, the number of theoretical plates of the methanol removal column 3 is 20 to 30, the feed position is at the tray 1 / 4 to 1 / 3 from the top of the column, and the reflux ratio is 0.3 to 0.5.

[0055] In a further example of the present invention, after the second gas phase is heated and pressurized, the temperature is 120°C to 230°C, preferably 140°C to 190°C; the pressure is 0.08 to 0.15 MPaA, preferably 0.08 to 0.10 MPaA.

[0056] In a further example of the present invention, the operation of heating and pressurizing the second gas phase is carried out by a steam compressor.

[0057] In a further example of the present invention, 15% to 25% of the second gas phase after heating and pressurizing is input into the subsequent methanol recovery column 4. By distributing the second gas phase after heating and pressurizing, the heat energy consumption of the methanol removal column 3 and the methanol recovery column 4 can be regulated, and the separation purity of the target product and methanol in the overall process can be improved.

[0058] In a further example of the present invention, the temperature of the material obtained after heat exchange and condensation can be selected from 70 to 95°C, preferably 70 to 80°C.

[0059] In a further example of the present invention, in the material obtained after heat exchange and condensation, 32% to 52% of the material by mass percentage is returned to the methanol removal column 3.

[0060] In a further example of the present invention, pure water exchanges heat with the second gas phase after heating and pressurizing to obtain steam at 0.06 to 0.1 MPaA, and this part of the steam will be directly input into the methanol removal column 3 as a heat source.

[0061] In a further example of the present invention, the operating temperature of the methanol recovery column 4 can be selected from 60°C to 110°C, preferably 63°C to 100°C; the operating pressure can be selected from 0.1 to 0.15 MPaA, preferably atmospheric pressure.

[0062] In a further example of the present invention, the number of theoretical plates of the methanol recovery column 4 is 60 to 70, the reflux ratio is 10 to 50; the feed position of the second liquid phase is at the tray 1 / 2 to 3 / 4 from the top of the column, and the second gas phase after heating and pressurizing is fed into the bottom of the column; the side line position of high-purity methanol is at the tray 1 / 5 to 1 / 4 from the top of the column.

[0063] In a further example of the present invention, a third gas phase is withdrawn from the top of the methanol recovery column 4; the third gas phase is a material of trimethylamine and dimethyl carbonate, and this third gas phase can be optionally returned to the reactive distillation column 1. Optionally, Figure 1 It is shown that the condensate obtained after the third gas phase is condensed by the second heat exchanger 41 is input into the third reflux drum 42, and one branch of the third reflux drum 42 returns to the methanol recovery column 4, and the other branch returns to the reactive distillation column 1.

[0064] In the above technical solution, the first liquid phase is a material containing a small amount of methanol, trimethylamine, dimethyl carbonate and tetramethylammonium methyl carbonate. The second liquid phase is a material of methanol, water, trimethylamine, dimethyl carbonate, etc. The methanol content in the aqueous solution of TMAB withdrawn from the bottom of the methanol removal column 3 is ≤30 ppm, which meets the requirements of the subsequent electrolysis process to prepare high-purity TMAH. The concentration of the high-purity methanol withdrawn from the side of the methanol recovery column 4 can reach 99.5 wt% to 99.9 wt%, preferably 99.8 wt% to 99.9 wt%, and the recovered methanol can be directly recycled. The methanol concentration of the dilute methanol aqueous solution withdrawn from the bottom of the methanol recovery column 4 is 0.03 wt% to 0.5 wt%, and it can be used as a diluent to adjust the concentration of TMAB in the material to be separated.

[0065] Example 1

[0066] This example demonstrates a low-energy consumption process for preparing tetramethylammonium bicarbonate under specific working conditions. It should be noted that this example is only a better demonstration and does not limit the protection scope of the present invention thereby.

[0067] A low-energy consumption process for preparing tetramethylammonium bicarbonate specifically includes the following steps:

[0068] Step (1): Trimethylamine, dimethyl carbonate and solvent methanol are fed into reactive distillation column 1, where a quaternization reaction occurs to produce tetramethylammonium methyl carbonate, yielding a first gas phase and a first liquid phase. Among them, the reactive distillation column 1 is set with 48 theoretical plates and a reflux ratio of 1.5; the feeding position of dimethyl carbonate is the 12th theoretical plate (counting from top to bottom), and the feeding positions of trimethylamine and solvent methanol are the 36th theoretical plate. The feeding molar ratio of dimethyl carbonate, trimethylamine and solvent methanol is 1:1.03:2, and the total feeding amount is 108.84 kg / h. The top temperature of the reactive distillation column 1 is 117.6 °C, and the pressure is 0.6 MPaA. The first gas phase containing unreacted dimethyl carbonate, trimethylamine and solvent methanol is withdrawn from the top of the column at a rate of 27.71 kg / h; the temperature of the reaction section is 117.7 - 132.4 °C, and the pressure is 0.6 MPaA. Dimethyl carbonate and trimethylamine undergo countercurrent contact reaction in the reaction section; the temperature of the column bottom is 169.6 °C, and the pressure is 0.6 MPaA. The first liquid phase is withdrawn from the column bottom at a rate of 81.13 kg / h; the first liquid phase is a mixed material containing a mixture of tetramethylammonium methyl carbonate, and the yield of tetramethylammonium methyl carbonate is 97.7%.

[0069] Step (2): Tetramethylammonium methyl carbonate and hot water are mixed in static mixer 2 and then undergo a hydrolysis reaction to produce a material to be separated containing TMAB and methanol. The operating conditions of static mixer 2 are 120 °C and atmospheric pressure. This step also includes using the dilute methanol solution and / or pure water withdrawn from the bottom of subsequent methanol recovery column 4 as a diluent to adjust the concentration of TMAB in the material to be separated.

[0070] Step (3): The material to be separated is fed into the methanol removal column 3 at a rate of 108.10 kg / h for rectification. The methanol removal column 3 is set with 24 theoretical plates, and the feed position is the 9th theoretical plate. The operating conditions at the top of the methanol removal column 3 are 69.8 °C and 0.04 MPaA. The top of the methanol removal column 3 is connected to the steam compressor 33 through a pipeline. The steam temperature and pressure are increased to 195.6 °C and 0.12 MPaA by using heat pump technology to obtain the second gas phase after temperature and pressure increase. A part of the second gas phase after temperature and pressure increase is input into the subsequent methanol recovery column 4 as the heat source for methanol recovery rectification, and the other part is circulated into the heat medium channel of the steam generator 31 as the heat source. Pure water is heated and evaporated in the refrigerant channel of the steam generator 31 to obtain steam. This part of the steam is fed into the bottom of the methanol removal column 3 as the heat source and is used for the stripping of methanol in the bottom liquid. The condensation temperature of the condensed material is 83.7 °C. A part of the second liquid phase is refluxed to the top of the methanol removal column 3 to maintain a reflux ratio of 0.3, and the other part of the second liquid phase is transported into the subsequent methanol recovery column 4 for further purification and recovery of methanol. The temperature at the bottom of the methanol removal column 3 is 82.8 °C, and the pressure is 0.04 MPaA. An aqueous solution of 60 wt% TMAB (methanol content is 15 ppm) is withdrawn from the bottom of the column at a rate of 111.48 kg / h.

[0071] Step (4): The methanol recovery column 4 is set with 60 theoretical plates, and the reflux ratio is 14. The gas-phase feed port is located on the 59th theoretical plate, and the liquid-phase feed port is located on the 40th theoretical plate. The temperature at the top of the recovery column is 64.4 °C, and the pressure is 0.103 MPaA. The third gas phase containing trimethylamine, dimethyl carbonate, and methanol is withdrawn from the top of the column at a rate of 6.24 kg / h. After condensation, it is returned to the reactive distillation column 1 for reuse. The methanol product outlet of the methanol recovery column 4 is located on the 12th theoretical plate, and methanol product with a mass fraction of 99.5 wt% is withdrawn at a rate of 17.11 kg / h. The temperature at the bottom of the methanol recovery column 4 is 96.5 °C, and the pressure is 0.103 MPaA. A dilute methanol aqueous solution with a methanol mass fraction of 0.05 wt% is withdrawn from the bottom of the column at a rate of 32.47 kg / h. This part of the dilute methanol solution is used as a diluent to mix with the material to be separated to adjust its TMAB concentration.

[0072] Comparative Example 1

[0073] Comparative Example 1 uses Figure 2The device shown is used for the preparation of tetramethylammonium hydrogencarbonate. During the process: dimethyl carbonate, trimethylamine and solvent methanol are fed into the first reaction kettle 51 and undergo quaternization reaction through the second reaction kettle 52 and the third reaction kettle 53 connected in series. The reacted material is fed into the first-stage falling film evaporator 71 for gas-liquid separation. The obtained gas-phase material is returned to the first reaction kettle 51, and the liquid-phase material undergoes hydrolysis reaction with pure water heated by the water heater 61 in the static mixing device 62; the material after hydrolysis reaction is fed into the second-stage falling film evaporator 72 for gas-liquid separation. The obtained gas-phase material is fed into the methanol recovery tower 9, and the liquid-phase material is fed into the preparation tank 73 and then fed into the methanol removal tower 8 after being diluted with pure water; the TMAB solution is taken out from the bottom of the methanol removal tower 8. After the overhead product material is condensed, part of it is refluxed and part of it is fed into the methanol recovery tower 9; methanol products are taken out from the side of the methanol recovery tower 9, the overhead product is returned to the first reaction kettle 51, and the bottom product is used to be fed into the preparation tank 73.

[0074] The specific process includes the following steps:

[0075] Step (1), in the three-stage series reaction kettle, the molar ratio of dimethyl carbonate, trimethylamine and solvent methanol in the feed is 1:1.03:2, and the feed rate is 108.84 kg / h; the control conditions of the reaction kettle are 110-130 °C and 0.6 MPaA. After reaction, the yield of tetramethylammonium methyl carbonate is 97.4%; the mixed solution of tetramethylammonium methyl carbonate generated by the reaction is fed into the first-stage falling film evaporator 71. After evaporation, dimethyl carbonate, trimethylamine and solvent methanol are directly recycled; the operating conditions of the first-stage falling film evaporator 71 are 0.11 MPaA and 105 °C; the remaining tetramethylammonium methyl carbonate is mixed with hot water for hydrolysis and then fed into the second-stage falling film evaporator 72. Saturated steam at 0.35 MPaA is introduced under a pressure of 0.11 MPaA to maintain the temperature of the TMAB mixed solution at 120 °C; the gas-phase extraction rate of the second-stage falling film evaporator 72 is 28.73 kg / h. After partial condensation, it is recycled to the synthesis section as a reaction solvent, and the rest is directly sent to the methanol recovery tower 9 as a heat source; the liquid-phase extract of the second-stage falling film evaporator 72 is sent to the preparation tank 73, pure water and the bottom product solution of the methanol recovery tower 9 are introduced to adjust the TMAB concentration to 40%, and then it is transported to the methanol removal tower 8, and the transport flow rate is 166.92 kg / h.

[0076] Step (2): The methanol removal column 8 is set with 24 theoretical plates, and the feed position is the 9th theoretical plate. The operating conditions at the top of the column are 71.5 °C and 0.04 MPaA. The steam extraction rate at the top of the column is 72.33 kg / h. The steam pipeline is directly connected to the condenser. Part of the condensate is refluxed to the top of the methanol removal column 8 to maintain a reflux ratio of 0.3 for the methanol removal column 8. The remaining condensate is transported to the methanol recovery column 9 for further purification and recovery of methanol. The operating conditions at the bottom of the methanol removal column 8 are 79.8 °C and 0.04 MPaA. An aqueous solution of 60 wt% TMAB (methanol content is 68 ppm) is withdrawn from the bottom of the column at a rate of 111.22 kg / h.

[0077] Step (3): The methanol recovery column 9 is set with 60 theoretical plates and a reflux ratio of 35. The gas-phase feed inlet is located at the 59th theoretical plate, and the liquid-phase feed inlet is located at the 40th theoretical plate. The operating conditions at the top of the methanol recovery column 9 are 65.8 °C and 0.103 MPaA. A mixture of trimethylamine, dimethyl carbonate, and methanol is withdrawn from the top of the column at a rate of 0.32 kg / h. After condensation, it is returned to the synthesis system for reuse in the reaction. The methanol product outlet of the methanol recovery column 9 is located at the 12th theoretical plate, and methanol products with a mass fraction of 99.5 wt% are withdrawn at a rate of 15.50 kg / h. The operating conditions at the bottom of the methanol recovery column 9 are 96.5 °C and 0.103 MPaA. A dilute aqueous methanol solution with a methanol mass fraction of 0.05 wt% is withdrawn from the bottom of the column at a rate of 35.15 kg / h, and this part of the dilute aqueous methanol solution is input into the preparation tank 73.

[0078] Furthermore, the present invention compared the energy consumption at each stage and the overall energy consumption between Example 1 and Comparative Example 1, and the results are shown in Table 1.

[0079] Table 1

[0080]

[0081] It can be verified from Table 1 that in the quaternization reaction and hydrolysis reaction stages (Comparative Example 1 also includes the preliminary separation by the film evaporator of the secondary falling film device), compared with Comparative Example 1, the comprehensive energy consumption of the reaction and hydrolysis device in Example 1 is reduced by 21.34%; in the methanol removal stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol removal column 3 in Example 1 is reduced by 93.13%; in the methanol recovery stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol recovery column 4 in Example 1 is reduced by 72.58%. Generally speaking, compared with Comparative Example 1, the comprehensive energy consumption in the preparation process of TMAB in Example 1 is reduced by 65.73%, demonstrating significant energy-saving and consumption-reducing advantages.

[0082] Example 2

[0083] This embodiment demonstrates another preparation process of tetramethylammonium hydrogencarbonate under specific working conditions. It should be noted that this embodiment is only a better demonstration and does not limit the protection scope of the present invention hereby.

[0084] A preparation process of tetramethylammonium hydrogencarbonate with low energy consumption specifically comprises the following steps:

[0085] Step (1), the reaction distillation column 1 is set with 48 theoretical plates and a reflux ratio of 1.5; the feeding position of dimethyl carbonate is the 12th theoretical plate, and the feeding positions of trimethylamine and solvent methanol are the 36th theoretical plate. The feeding molar ratio of dimethyl carbonate, trimethylamine and solvent methanol is 1:1.03:2, and the total feeding amount is 108.84 kg / h; the temperature at the top of the reaction distillation column 1 is 127.9 °C, and the pressure is 0.8 MPaA. 29.59 kg / h of unreacted first gas phase (dimethyl carbonate, trimethylamine and solvent methanol) is taken out from the top of the column; the reaction section temperature of the reaction distillation column 1 is 128.2 - 142.7 °C, and the pressure is 0.8 MPaA. Dimethyl carbonate and trimethylamine react by countercurrent contact in the reaction section; the operating temperature at the bottom of the reaction column is 178.7 °C, and the pressure is 0.8 MPaA. The first liquid phase is taken out from the bottom of the column at a rate of 79.25 kg / . The first liquid phase is a mixed material containing tetramethylammonium methyl carbonate, and the yield of tetramethylammonium methyl carbonate is 98.6%;

[0086] Step (2), the first liquid phase and hot water are mixed in the static mixer 2 and then undergo a hydrolysis reaction to generate a material to be separated containing TMAB and methanol. The operating conditions of the static mixer 2 are 120 °C and normal pressure. This step also includes using the dilute methanol solution and / or pure water taken out from the bottom of the subsequent methanol recovery column 4 as a diluent to adjust the concentration of TMAB in the material to be separated.

[0087] Step (3): The material to be separated is fed into the methanol removal column 3 at a rate of 106.22 kg / h. The methanol removal column 3 is set with 24 theoretical plates, and the feeding position is the 9th theoretical plate. The operating conditions at the top of the methanol removal column 3 are 69.1 °C and 0.04 MPaA. The steam pipeline at the top of the column is connected to the steam compressor 33. The temperature and pressure of the steam are increased to 195.0 °C and 0.12 MPaA by using heat pump technology to obtain the second gas phase after temperature and pressure increase. A part of the second gas phase after temperature and pressure increase is input into the subsequent methanol recovery column 4 as the heat source of the methanol recovery distillation system, and the other part is circulated into the heat medium channel of the steam generator 31 as the heat source. Pure water is heated and evaporated in the refrigerant channel of the steam generator 31 and then fed into the bottom of the methanol removal column 3 as the heat source of the methanol removal column 3 and used for the stripping of methanol in the bottom liquid. The condensation temperature of the condensed material is 83.7 °C. Part of the condensate flows back to the top of the methanol removal column 3 to maintain a reflux ratio of 0.3, and the other part of the condensate is transported into the methanol recovery column 4 for further purification and recovery of methanol. The operating conditions at the bottom of the methanol removal column 3 are 82.8 °C and 0.04 MPaA. An aqueous solution of 60 wt% TMAB (methanol content is 14 ppm) is withdrawn from the bottom of the column at a rate of 112.51 kg / h.

[0088] Step (4): The methanol recovery column 4 is set with 60 theoretical plates, the reflux ratio is 14, the gas-phase feed inlet is located at the 59th theoretical plate, and the liquid-phase feed inlet is located at the 40th theoretical plate. The operating conditions at the top of the column are 64.4 °C and 0.103 MPaA. A third gas phase containing trimethylamine, dimethyl carbonate and methanol is withdrawn from the top of the column at a rate of 5.56 kg / h, and after condensation, it is returned to the reactive distillation column 1 for re-reaction and utilization. The methanol product outlet of the methanol recovery column 4 is located at the 12th theoretical plate, and the methanol product with a mass fraction of 99.5 wt% is withdrawn at a rate of 16.03 kg / h. The operating conditions at the bottom of the methanol recovery column 4 are 96.5 °C and 0.103 MPaA. A dilute aqueous methanol solution with a methanol mass fraction of 0.05 wt% is withdrawn from the bottom of the column at a rate of 31.89 kg / h. This part of the dilute methanol solution is used as a diluent to mix with the material to be separated to adjust its TMAB concentration.

[0089] Furthermore, the present invention compares the energy consumption at each stage and the overall energy consumption between Example 2 and Comparative Example 1, and the results are shown in Table 2.

[0090] Table 2

[0091]

[0092] It can be confirmed from Table 2 that in the quaternization reaction and hydrolysis reaction stages (the preliminary separation by the falling film evaporator of the secondary falling film device is also included in Comparative Example 1), compared with Comparative Example 1, the comprehensive energy consumption of the reaction and hydrolysis device in Example 2 decreased by 7.41%; in the methanol removal stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol removal column 3 in Example 2 decreased by 93.28%; in the methanol recovery stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol recovery column 4 in Example 2 decreased by 74.07%. Generally speaking, compared with Comparative Example 1, the comprehensive energy consumption in the preparation process of TMAB in Example 1 decreased by 62.19%, showing significant advantages in energy conservation and consumption reduction.

[0093] Example 3

[0094] This example provides a low-energy consumption preparation process of tetramethylammonium bicarbonate under specific conditions. The steps (1) and (2) of this process are the same as those in Example 1, and the step (3) is as follows:

[0095] Step (3), the material to be separated is fed into the methanol removal column 3 at a rate of 108.10 kg / h. The methanol removal column 3 is set with 24 theoretical plates, and the feeding position is the 9th theoretical plate; the operating conditions at the top of the column are 59.3 °C and 0.025 MPaA. The second gas phase extracted is input into the steam compressor 33, and the steam temperature and pressure are increased to 240.6 °C and 0.12 MPaA by using the heat pump technology to obtain the second gas phase after temperature and pressure increase; a part of the second gas phase after temperature and pressure increase is input into the subsequent methanol recovery column 4 as the heat source of the methanol recovery distillation system, and the other part is circulated and input into the heat medium channel of the steam generator 31 as the heat source. Pure water is heated and evaporated through the refrigerant channel of the steam generator 31 to obtain steam. This part of the steam is input into the bottom of the methanol removal column 3 as the heat source and is used for the stripping of methanol in the bottom liquid. The condensation temperature of the condensed material is 83.7 °C. Part of the second liquid phase is refluxed to the top of the methanol removal column 3 to maintain a reflux ratio of 0.3, and the other part of the second liquid phase is transported into the methanol recovery column 4 for further purification and recovery of methanol; the operating conditions at the bottom of the methanol removal column 3 are 71.4 °C and 0.025 MPaA, and an aqueous solution of 60 wt% TMAB (methanol content is 15 ppm) is extracted from the bottom of the column at a rate of 111.48 kg / h.

[0096] Step (4), the operation and condition control of the methanol recovery column 4 in this example are the same as those in Example 1.

[0097] Comparative Example 2

[0098] This comparative example provides a preparation process of tetramethylammonium bicarbonate. The step (1) in this process is the same as that in Comparative Example 1, and the step (2) is as follows:

[0099] Step (2): The methanol removal column 8 is set with 24 theoretical plates, and the feed position is the 9th theoretical plate. The operating conditions at the top of the column are 63.8 °C and 0.025 MPaA. The steam extraction rate at the top of the column is 72.33 kg / h. The steam pipeline is directly connected to the condenser. Part of the condensate is refluxed to the top of the removal column to maintain a reflux ratio of 0.3 for the removal column. The remaining condensate is transported to the methanol recovery column 9 for further purification and methanol recovery. The operating conditions at the bottom of the methanol removal column 8 are 71.4 °C and 0.025 MPaA. An aqueous solution of 60 wt% TMAB (methanol content is 68 ppm) is withdrawn from the bottom of the column at a rate of 111.22 kg / h.

[0100] Step (3): The operation and condition control of the methanol recovery column 9 are the same as those in Comparative Example 1.

[0101] Furthermore, the present invention compared the energy consumption at each stage and the overall energy consumption between Example 3 and Comparative Example 2, and the results are shown in Table 3.

[0102] Table 3

[0103]

[0104] It can be verified from Table 3 that in the quaternization reaction and hydrolysis reaction stages (Comparative Example 2 also includes the preliminary separation by the film evaporator of the secondary falling film device), compared with Comparative Example 2, the comprehensive energy consumption of the reaction and hydrolysis device in Example 3 is reduced by 21.34%; in the methanol removal stage, compared with Comparative Example 2, the comprehensive energy consumption of the methanol removal column 3 in Example 3 is reduced by 89.97%; in the methanol recovery stage, compared with Comparative Example 2, the comprehensive energy consumption of the methanol recovery column 4 in Example 3 is reduced by 91.10%. Generally speaking, compared with Comparative Example 2, the comprehensive energy consumption in the preparation process of TMAB in Example 3 is reduced by 70.87%, demonstrating a significant advantage in energy conservation and consumption reduction.

[0105] Example 4

[0106] This example provides a low-energy consumption preparation process of tetramethylammonium bicarbonate under specific working conditions. Steps (1) and (2) of this process are the same as those in Example 1, and step (3) is as follows:

[0107] Step (3): The material to be separated is fed into the methanol removal column 3 at a rate of 108.10 kg / h. The methanol removal column 3 is set with 24 theoretical plates, and the feeding position is the 9th theoretical plate. The operating conditions at the top of the column are 69.8 °C and 0.04 MPaA. The steam pipeline at the top of the column is connected to the steam compressor 33. The temperature and pressure of the steam are increased to 214.7 °C and 0.14 MPaA by using heat pump technology to obtain the second gas phase after temperature and pressure increase. A part of the second gas phase after temperature and pressure increase is input into the subsequent methanol recovery column 4 as the heat source for methanol recovery rectification, and the other part is circulated into the heat medium channel of the steam generator 31 as the heat source. Pure water is heated and evaporated through the refrigerant channel of the steam generator 31 to obtain steam. This part of the steam is fed into the bottom of the methanol removal column 3 as the heat source and is used for the stripping of methanol in the bottom liquid. The condensation temperature of the condensed material is 87.9 °C. Part of the second liquid phase is refluxed to the top of the methanol removal column 3 to maintain a reflux ratio of 0.3, and the other part of the second liquid phase is transported into the methanol recovery column 4 for further purification and recovery of methanol. The operating conditions at the bottom of the methanol removal column 3 are 82.8 °C and 0.04 MPaA. The bottom of the column withdraws 60 wt% TMAB aqueous solution (methanol content is 15 ppm) at a rate of 111.48 kg / h.

[0108] Step (4): The operation and condition control of the methanol recovery column 4 in this embodiment are the same as those in Embodiment 1.

[0109] Furthermore, the present invention compares the energy consumption at each stage and the overall energy consumption between Example 4 and Comparative Example 1, and the results are shown in Table 4.

[0110] Table 4

[0111]

[0112] It can be confirmed from Table 4 that in the quaternization reaction and hydrolysis reaction stages (Comparative Example 1 also includes the preliminary separation by the film evaporator of the secondary falling film device), compared with Comparative Example 1, the comprehensive energy consumption of the reaction and hydrolysis device in Example 4 is reduced by 21.34%; in the methanol removal stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol removal column 3 in Example 4 is reduced by 92.36%; in the methanol recovery stage, compared with Comparative Example 1, the comprehensive energy consumption of the methanol recovery column 4 in Example 4 is reduced by 79.51%. Generally speaking, compared with Comparative Example 1, the comprehensive energy consumption in the preparation process of TMAB in Example 4 is reduced by 68.02%, which shows significant energy-saving and consumption-reducing advantages in large-scale industrial production.

[0113] It should be noted that the above content is a further detailed description of the present invention in combination with specific implementation manners, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple improvements can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A low-energy consumption tetramethylammonium bicarbonate preparation process, characterized in that: The following steps are involved: (1) trimethylamine, dimethyl carbonate and solvent methanol are fed into a reactive distillation tower to undergo quaternization reaction to generate methyl carbonate tetramethylammonium; Extracting a first gas phase and a first liquid phase from the top and bottom of the reactive distillation tower respectively; (2) the first liquid phase undergoes a hydrolysis reaction with water to obtain a material to be separated comprising tetramethylammonium bicarbonate; (3) The material to be separated is distilled in a methanol removal tower to obtain a second liquid phase and a second gas phase, wherein the second liquid phase is a tetramethylammonium bicarbonate aqueous solution, and the second gas phase is divided into two parts after being heated and pressurized: one part is input into a subsequent methanol recovery tower, and the other part is heat-exchanged with water to generate steam, and the steam is input into the bottom of the methanol removal tower. After heat exchange and condensation, a part of the material is returned to the methanol removal tower, and the other part is input into the methanol recovery tower; (4) High-purity methanol is extracted from the side of the methanol recovery tower and dilute methanol solution is extracted from the bottom of the tower.

2. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: In the step (1), the molar ratio of dimethyl carbonate, trimethylamine and solvent methanol is 1:(0.8-1.2):(1.5-4).

3. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The operating temperature of the reactive distillation tower is 80°C to 200°C, preferably 105°C to 180°C; the operating pressure is 0.5 to 0.9 MPaA, preferably 0.6 to 0.8 MPaA.

4. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The number of theoretical plates of the reactive distillation tower is 36 to 68, and the reflux ratio is 1 to 2; the feed position of the dimethyl carbonate is a plate 1 / 5 to 1 / 4 away from the top of the tower, and the feed position of the trimethylamine and methanol is a plate 1 / 5 to 1 / 3 away from the bottom of the tower.

5. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The first gas phase returns to the reactive distillation tower; Preferably, the first gas phase is condensed by heat exchange with pure water input into the system and then returns to the reactive distillation tower; Further preferably, pure water is used for the hydrolysis reaction in step (2) after heat exchange with the first gas phase.

6. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The temperature of the hydrolysis reaction is 105-135°C, preferably 110-130°C; the operating pressure is 0.1-0.2MPaA, preferably 0.1-0.15MPaA; And / or, the hydrolysis reaction is carried out in a static mixer.

7. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The concentration of tetramethylammonium bicarbonate in the material to be separated is 35wt% to 45wt%, preferably 38wt% to 41wt%; Preferably, pure water and / or the dilute methanol solution is used as a diluent to adjust the concentration of tetramethylammonium bicarbonate in the material to be separated; Preferably, when pure water and the dilute methanol solution are used as diluents, the dilute methanol solution accounts for 60% to 75% of the volume of the diluent.

8. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The operating temperature of the methanol removal tower is 60°C to 95°C, preferably 63°C to 85°C; the operating pressure is 0.025 to 0.06 MPaA, preferably 0.025 to 0.04 MPaA; And / or, the number of theoretical plates of the methanol removal tower is 20 to 30, the feed position is a plate 1 / 4 to 1 / 3 away from the top of the tower, and the reflux ratio is 0.3 to 0.

5.

9. The low-energy consumption tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: In the step (3), after the temperature and pressure of the second gas phase are increased, the temperature is 120°C to 230°C, preferably 140°C to 190°C; the pressure is 0.08 to 0.15 MPaA, preferably 0.08 to 0.10 MPaA; And / or, the second gas phase temperature and pressure increasing operation is performed by a steam compressor; and / or, 15% to 25% of the second gas phase after temperature and pressure increase is input into a subsequent methanol recovery tower; And / or, the temperature of the material obtained after heat exchange condensation is 70 to 95° C., preferably 70 to 80° C.; And / or, of the materials obtained after heat exchange and condensation, 32% to 52% by mass of the materials are returned to the methanol removal tower; And / or, the pressure of the steam is 0.06-0.1 MPaA.

10. The low-energy tetramethylammonium bicarbonate preparation process according to claim 1, characterized in that: The operating temperature of the methanol recovery tower is 60°C to 110°C, preferably 63°C to 100°C; the operating pressure is 0.1 to 0.15 MPaA, preferably normal pressure; And / or, the number of plates of the methanol recovery tower is 60 to 70, and the reflux ratio is 10 to 50; the feeding position of the second liquid phase is a plate 1 / 2 to 3 / 4 away from the top of the tower, and the second gas phase after temperature and pressure increase is fed to the bottom of the tower; the side line position of high-purity methanol is a plate 1 / 5 to 1 / 4 away from the top of the tower; And / or, a third gas phase is extracted from the top of the methanol recovery tower, and the third gas phase is returned to the reactive distillation tower.

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