Process and system for efficiently preparing dimethyl phosphite and control system

Abstract

In order to reduce the use amount of raw material methanol, improve the atom utilization rate and reduce byproduct chloromethane and the like, the invention discloses a process, a system and a control system for efficiently preparing dimethyl phosphite, and belongs to the technical field of synthesis of intermediate dimethyl phosphite of pesticide glyphosate. Wherein water and methanol are jointly used as raw materials (one molecule of water is used for replacing one molecule of methanol), the use amount of methanol is reduced, meanwhile, the byproduct chloromethane is greatly reduced, and the atom utilization rate is increased; a continuous flow reactor, a gas-liquid separator and the like are adopted, so that the whole reaction system is in a state from normal pressure to micro-positive pressure, the negative pressure state of a traditional kettle type continuous reactor is replaced, the reaction system does not need to use a vacuum pump, and the power consumption is greatly reduced; in addition, by controlling temperature, pressure, flow and the like, continuity, orderliness and controllability of the preparation process are guaranteed.

Description

Technical Field

[0001] The invention relates to a process for preparing dimethyl phosphite, in particular to a process, system and control system for efficiently preparing dimethyl phosphite, and belongs to the technical field of production of dimethyl phosphite, an intermediate of the pesticide glyphosate. Background Art

[0002] The main use of dimethyl phosphite is to synthesize glyphosate. At present, the method for industrial synthesis of dimethyl phosphite is: the raw materials phosphorus trichloride and methanol are continuously added quantitatively, reacted under negative pressure conditions, and the generated hydrogen chloride is removed at the same time; finally, after deep deacidification and distillation, dimethyl phosphite is obtained. The reaction mechanism involved includes: methanol reacts with phosphorus trichloride to generate trimethyl phosphite and hydrogen chloride; trimethyl phosphite then quickly reacts with a molecule of hydrogen chloride to generate dimethyl phosphite and a molecule of methyl chloride. The overall reaction equation involved is as follows: PCl3+3CH3OH =H(O)P(OCH3)2+2 HCl↑+CH3Cl↑ The reaction mechanism includes: PCl3+3CH3OH=P(OCH3)3+3HCl P(OCH3)3+HCl=H(O)P(OCH3)2+CH3Cl Among them, 1 molecule of phosphorus trichloride consumes 3 molecules of methanol to generate 1 molecule of dimethyl phosphite, 2 molecules of hydrogen chloride and 1 molecule of methyl chloride. After the hydrogen chloride is absorbed by water to become hydrochloric acid, it can be used in the subsequent hydrolysis process of glyphosate synthesis; while methyl chloride needs to be purified and then sold as a by-product. In addition, there are only 2 methoxy groups in the product dimethyl phosphite. Among the 3 molecules of methanol consumed, 1 molecule of methanol is finally generated into methyl chloride, which makes the utilization rate of methanol molecules low. In addition, the by-product of methyl chloride requires additional purification, storage and other treatment of the by-product, which in turn increases the risk source and environmental pressure.

[0003] Although the prior art CN107488193A discloses "a new method for synthesizing dimethyl phosphite", it mainly uses yellow phosphorus as raw material to continuously produce dimethyl phosphite; "CN101870712A a method for producing dimethyl phosphite" mainly injects two reaction raw materials into the reaction chamber space in a high-speed spraying manner for mixed reaction to increase the reaction rate and reduce by-products; "CN114605469A a high-efficiency synthesis of dimethyl phosphite production process" reduces by-products through continuous graded reaction and atomization spraying; "CN114920772A a method for continuously preparing dimethyl phosphite and its application" adopts a continuous flow reactor, but there is still a large amount of by-product-methyl chloride, and the consumption of methanol is higher than 3 times the molar amount of phosphorus trichloride; in addition, it adopts negative pressure reaction conditions, which leads to gas expansion in the reactor, a decrease in the capacity of the continuous flow reactor, a larger volume of the subsequent tail gas system, high equipment investment, and high energy consumption. "CN108840884A A method for continuously synthesizing dialkyl phosphite in a continuous flow reactor" adopts a microchannel continuous reactor, and its preferred molar ratio has exceeded the methanol feed ratio in the existing dimethyl phosphite production technology. The residence time of 60-300s also fails to bring into play the mass transfer rate characteristics of the continuous flow reactor, and it has greater environmental pressure. Summary of the invention

[0004] In order to reduce the amount of raw material methanol, improve the atomic utilization rate, and at the same time, reduce the by-product of chloromethane, the present invention provides a process, system and control system for efficiently preparing dimethyl phosphite. Among them, water and methanol are used as raw materials together (one molecule of water replaces one molecule of methanol), which reduces the amount of methanol used, and at the same time, greatly reduces the by-product of chloromethane and improves the atomic utilization rate; and, a continuous flow reactor and a gas-liquid separator are used to make the entire reaction system in a state of normal pressure to slightly positive pressure, replacing the negative pressure state of the traditional kettle continuous reactor, that is, the reaction process does not require the use of a vacuum pump, which greatly reduces the power consumption; in addition, the reaction process can also be carried out under negative pressure, but a vacuum pump needs to be added, that is, the present invention has high adjustability to the required pressure, which can be set according to actual needs; Among them, the overall reaction equation involved is: PCl3+H2O+2CH3OH= H(O)P(OCH3)2+3HCl↑.

[0005] In order to achieve the above technical objectives, the following technical solutions are proposed: The first purpose of the technical solution is to provide: a process for efficiently preparing dimethyl phosphite, comprising the following steps: 1) First reaction: With the molar ratio of phosphorus trichloride to water being 1:0-1, phosphorus trichloride and water are introduced into a continuous flow reactor I, and the temperature in the continuous flow reactor I is controlled to be 30-80°C and the pressure to be -0.1-0.1MPa to obtain an intermediate product; 2) Second reaction: With the molar ratio of phosphorus trichloride to methanol being 1:2-4, methanol and the intermediate product obtained in step S1 are introduced into a continuous flow reactor II, and the temperature in the continuous flow reactor II is controlled to be 20-70° C. and the pressure to be -0.1-0.1 MPa to obtain a reaction solution; Wherein, during the entire reaction process of step 1) and step 2), the molar ratio of the total amount of water and methanol introduced to the amount of phosphorus trichloride introduced is controlled to be 3.1-4:1; the raw material - water can be specifically "deionized water"; 3) Gas-liquid separation: the reaction liquid obtained in step 2) is introduced into a gas-liquid separator, the temperature in the gas-liquid separator is controlled to be 20-70°C and the pressure to be -0.1-0.1 MPa, gas-liquid separation is performed, and gas I (a large amount of gas, which is hydrogen chloride gas containing a small amount of methyl chloride, methanol and vaporized dimethyl phosphite) and a separation liquid are obtained; After the gas I is condensed, it is passed into the atmospheric tail gas treatment system for water washing to obtain a large amount of by-product hydrochloric acid and a small amount of water-unabsorbed gas (mainly methyl chloride), which is discharged to the methyl chloride recovery system. Among them, the gas I is first condensed to reduce the phosphorus-containing substances entering the atmospheric tail gas treatment system, effectively reducing the phosphorus content of the by-product hydrochloric acid and improving the quality of hydrochloric acid; 4) Deacidification and separation: the separated liquid obtained in step 3) is introduced into the deacidification kettle, and the speed of the distributor in the deacidification kettle is controlled to be 30-120 r / min, the temperature to be 30-80° C. and the pressure to be -0.1-0.5 MPa, and separation is performed to obtain gas II (a small amount of gas. Mainly including vaporized dimethyl phosphite, methanol, hydrogen chloride gas, and a very small amount of chloromethane) and crude dimethyl phosphite; The gas II is introduced into the packed tower, and separated by the packed tower to obtain heavy components (mainly including dimethyl phosphite) and light components (methanol containing a small amount of hydrogen chloride and methyl chloride). The heavy components are refluxed into the deacidification kettle; the light components are recovered (condensed) and then used for the synthesis of dimethyl phosphite; the small amount of non-condensable gas (mainly including hydrogen chloride and methyl chloride) formed is introduced into the vacuum tail gas treatment system for water washing to obtain a small amount of by-product hydrochloric acid and a very small amount of water non-absorbent gas (mainly methyl chloride), and the very small amount of water non-absorbent gas is discharged into the methyl chloride recovery system. Among them, the gas II is introduced into the packed tower, and a condensation reflux is set at the top of the packed tower to avoid the entrainment of heavy components in the gas phase, effectively reduce the phosphorus content of the by-product hydrochloric acid in the subsequent vacuum tail gas treatment system, and improve the quality of hydrochloric acid. At the same time, a high content of anhydrous methanol can be obtained after recovery, which is directly reused in the synthesis process of dimethyl phosphite, achieving the purpose of reducing methanol consumption. That is, without increasing energy consumption, methanol consumption is reduced and the quality of by-product hydrochloric acid is improved; 5) Post-treatment: The crude dimethyl phosphite obtained in step 4) is post-treated to obtain dimethyl phosphite as a transparent liquid.

[0006] In this preparation process, on the one hand, by using water and methanol as raw materials, the amount of methanol is reduced, and at the same time, the by-product methyl chloride is greatly reduced; on the other hand, by using a continuous flow reactor and a gas-liquid separator, etc., and correspondingly treating and recycling the tail gas (gas I, gas II) formed, it is finally ensured that this preparation process is no longer like the traditional process - a large amount of non-condensable gas needs to be treated by the vacuum unit before being discharged to the methyl chloride recovery system. The load of the vacuum unit in this preparation process is reduced by multiples, which can greatly reduce equipment investment and energy consumption. In addition, in this preparation process, the reaction temperature involved is controlled by the cooling system matched with the continuous flow reactor; the reaction pressure involved is controlled by the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator.

[0007] The second object of the technical scheme is to provide: a system for efficiently preparing dimethyl phosphite, comprising a continuous flow reactor I, a continuous flow reactor II, a gas-liquid separator, a deacidification kettle, a packed tower and a tail gas treatment system (including a normal pressure tail gas treatment system and a vacuum tail gas treatment system); Continuous flow reactor I: connected to a phosphorus trichloride storage tank through a phosphorus trichloride inlet pipe, the phosphorus trichloride inlet pipe is provided with a phosphorus trichloride delivery pump, a phosphorus trichloride flowmeter and a phosphorus trichloride regulating valve, and the discharge port on the continuous flow reactor I is connected to the continuous flow reactor II; A water storage tank is also connected via a water inlet pipe, and a water delivery pump, a water flow meter and a water regulating valve are arranged on the water inlet pipe; Continuous flow reactor II: located at the rear side of the station of continuous flow reactor I, continuous flow reactor II is connected to a methanol storage tank through a methanol inlet pipe, the methanol inlet pipe is provided with a methanol delivery pump, a methanol flow meter and a methanol regulating valve, and the discharge port on continuous flow reactor II is connected to a gas-liquid separator; Gas-liquid separator: It is located at the rear side of the station of the continuous flow reactor II. The gas-liquid separator is provided with a liquid level gauge and a pressure transmitter. The liquid outlet on the gas-liquid separator is connected to the deacidification kettle through a liquid down pipe I. A liquid down regulating valve is provided on the liquid down pipe I. In addition, the gas outlet on the gas-liquid separator is connected to the heat exchanger I through a gas phase outlet pipe, a pressure regulating valve is provided on the gas phase outlet pipe, the condensate outlet on the heat exchanger I is connected to the gas-liquid separator through a condensate pipeline, and the heat exchanger I is arranged at a high position relative to the gas-liquid separator; the gas outlet on the heat exchanger is connected to the atmospheric pressure tail gas treatment system, and the atmospheric pressure tail gas treatment system includes a washing tower; a continuous passage for condensation and reflux of methanol and dimethyl phosphite in gas I is formed between the gas outlet on the gas-liquid separator, the gas phase outlet pipe, the heat exchanger I, the condensate outlet on the heat exchanger I and the condensate pipeline; Deacidification kettle: It is located at the rear side of the station of the gas-liquid separator. A distributor is provided in the deacidification kettle, which is connected to the lower liquid pipe I. The gas outlet on the deacidification kettle is connected to the middle or lower part of the packing tower through an exhaust pipe, and the bottom of the packing tower is connected to the deacidification kettle through a reflux pipe. A continuous passage for condensation and reflux of the heavy components in gas II is formed between the gas outlet on the deacidification kettle, the exhaust pipe, the packing tower and the reflux pipe. The upper part of the packing tower is connected with a heat exchanger II, and the heat exchanger II is connected with a receiving tank. The gas outlet on the receiving tank is connected with a vacuum tail gas treatment system; the vacuum tail gas treatment system is connected with a vacuum unit to ensure that the deacidification kettle works under negative pressure conditions; the liquid outlet on the receiving tank is connected with the packing tower, and the liquid outlet on the receiving tank is connected with a methanol storage tank; A dimethyl phosphite intermediate tank is provided at the rear side of the deacidification kettle station, and the lower liquid pipe II of the deacidification kettle extends to the middle or bottom of the dimethyl phosphite intermediate tank to ensure the formation of a liquid seal. Preferably, the level difference between the bottom of the deacidification kettle and the bottom of the dimethyl phosphite intermediate tank is controlled at 10 to 15 meters to ensure that the deacidification kettle can work continuously under negative pressure to achieve continuous operation of the entire system.

[0008] Furthermore, the phosphorus trichloride inlet pipe, the water inlet pipe and the methanol inlet pipe are all provided with a pressure sensor and a temperature sensor I.

[0009] Furthermore, the distributor includes a cylindrical distribution trough, which is connected to the motor through a rotating shaft, that is, the motor drives the distribution trough to perform centrifugal motion; the lower liquid pipe I extends into the deacidification kettle to the top of the distribution trough, and the separation liquid is passed into the distribution trough. Under the action of centrifugal force, the separation liquid moves outward along the surface of the distribution trough, and then flies out of the distribution trough, evenly adheres to the inner wall of the deacidification kettle, and flows downward. It is heated during the flow process, and the low-boiling substances are vaporized, thereby finally completing the material separation with high efficiency and high quality.

[0010] The third object of the technical scheme is to provide: a control system for efficiently preparing dimethyl phosphite, comprising a DCS controller, a phosphorus trichloride flowmeter and a phosphorus trichloride regulating valve arranged on the phosphorus trichloride inlet pipe between the phosphorus trichloride storage tank and the continuous flow reactor I, a water flowmeter and a water regulating valve arranged on the water inlet pipe between the water storage tank and the continuous flow reactor I, a methanol flowmeter and a methanol regulating valve arranged on the methanol inlet pipe between the methanol storage tank and the continuous flow reactor II, a liquid level meter and a pressure transmitter arranged on the gas-liquid separator, a pressure regulating valve arranged on the gas phase outlet pipe of the gas-liquid separator, a lower liquid regulating valve arranged on the lower liquid pipe I between the gas-liquid separator and the deacidification kettle, a motor connected to the distributor, and a temperature sensor II arranged on the jacket of the deacidification kettle; The phosphorus trichloride flowmeter, phosphorus trichloride regulating valve, water flowmeter, water regulating valve, methanol flowmeter, methanol regulating valve, liquid level meter, lower liquid regulating valve, pressure transmitter, pressure regulating valve, motor and temperature sensor II are all connected to the DCS controller; Among them, the phosphorus trichloride flow meter and the phosphorus trichloride regulating valve are interlocked by electrical signals; The water flow meter and the water regulating valve are interlocked by electrical signals; The methanol flow meter and the methanol regulating valve are interlocked by electrical signals; The liquid level meter and the lower liquid regulating valve are interlocked through electrical signals; The pressure transmitter and the pressure regulating valve are interlocked through electrical signals.

[0011] Furthermore, the phosphorus trichloride inlet pipe, the water inlet pipe and the methanol inlet pipe are all provided with a pressure sensor and a temperature sensor I, and the pressure sensor and the temperature sensor I are both connected to the DCS controller.

[0012] In this technical solution, the mechanism and reaction structures involved include: The reactions of phosphorus trichloride with water and methanol are all exothermic and violent. If not precisely controlled, side reactions are likely to occur, such as: Phosphorus trichloride reacts with water to form unstable intermediate transition products and hydrogen chloride: PCl3+H2O=(OH)PCl2+HCl, but if not properly controlled, it will lead to the following reactions: (OH)PCl2+H2O=(OH)2PCl+HCl, and (OH)2PCl+H2O=(OH)3P+HCl, where (OH)3P is phosphorous acid, which is a stable structure; The reaction product of phosphorus trichloride and water can be directly reacted with methanol to obtain dimethyl phosphite: (OH)PCl2+2CH3OH=(OH)P(OCH3)2+2HCl. However, if it is not properly controlled, it will lead to the following reactions: (OH)P(OCH3)2+HCl=(OH)2P(OCH3) +CH3Cl, and (OH)2P(OCH3) +HCl=(OH)3P+CH3Cl.

[0013] To this end, it is necessary to control the corresponding reaction process and discharge the corresponding intermediates / products in time.

[0014] The positional relationships involved in this technical solution, such as "between", "on", "rear side of the workstation", "middle", "lower", "bottom", "upper part", and "outside", are defined according to the situations under actual usage conditions. They are conventional terms in this technical field and are also conventional terms used by technical personnel in this field in actual use.

[0015] The beneficial technical effects brought about by adopting this technical solution are: 1. The present invention uses water and methanol as raw materials (one molecule of water replaces one molecule of methanol), thereby reducing the amount of methanol used. At the same time, due to the presence of a small amount of side reaction, although a small amount of methyl chloride is still formed, the atomic utilization rate of methanol is greatly improved compared with the traditional process; Second, the present invention adopts a continuous flow reactor to ensure the orderliness, controllability and sustainability of the reaction system. By adjusting the pressure regulating valve on the gas phase outlet pipe connected to the gas outlet on the gas-liquid separator, the entire reaction system is kept at normal pressure to slightly positive pressure, replacing the negative pressure state of the traditional kettle continuous reactor. The reaction system does not require a vacuum pump, which greatly reduces power consumption. At the same time, the equipment requirements are not harsh, reducing equipment costs and reducing tail gas equipment investment. 3. The present invention uses a deacidification kettle with a special structure to distribute the dimethyl phosphite reaction liquid through a distributor, and splashes to the inner wall of the gas-liquid separator under the action of centrifugal force to form a liquid film and descend. At the same time, the low-boiling substances in the reaction liquid are gasified by the steam in the jacket, and the residual hydrogen chloride is taken out of the system with the low-boiling substances, thereby achieving the effect of deacidification, effectively reducing the phosphorus content of the by-product hydrochloric acid in the subsequent tail gas washing system, and improving the quality of the hydrochloric acid. At the same time, a high content of methanol can be recovered and directly reused, thereby achieving the purpose of reducing methanol consumption, that is, without increasing energy consumption, reducing methanol consumption, improving the quality of by-product hydrochloric acid, and ensuring the sustainability of the synthesis process of dimethyl phosphite; Fourth, compared with the traditional process, the present invention greatly reduces the amount of by-product chloromethane generated, increases the collection time of by-product chloromethane on the production line, thereby reducing the possibility of the impact of large inventory of by-product chloromethane on glyphosate production, and improves the stability of the production system and the overall impact resistance of the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A process flow chart of the present invention; Figure 2 It is a device connection diagram involved in the present invention; Figure 3 This is a control principle diagram of the present invention; Figure 4 The present invention relates to a gas chromatogram of dimethyl phosphite; Figure 5 This is a physical picture of the product dimethyl phosphite involved in the present invention; Among them, in the figure: 1, continuous flow reactor I, 2, continuous flow reactor II, 3, gas-liquid separator, 4, deacidification kettle, 5, packed tower, 6, atmospheric tail gas treatment system, 7, phosphorus trichloride inlet pipe, 8, phosphorus trichloride storage tank, 9, phosphorus trichloride delivery pump, 10, phosphorus trichloride flow meter, 11, phosphorus trichloride regulating valve, 12, water inlet pipe, 13, water storage tank, 14, water delivery pump, 15, water flow meter, 16, water regulating valve, 17, methanol inlet pipe, 18, methanol storage tank, 19, methanol delivery pump, 20, methanol flow meter, 21, methanol regulating Valve, 22. Liquid level gauge, 23. Pressure transmitter, 24. Downstream liquid pipe I, 25. Downstream liquid regulating valve, 26. Gas phase outlet pipe, 27. Heat exchanger I, 28. Pressure regulating valve, 29. Condensate pipeline, 31. Distributor, 32. Exhaust pipe, 33. Reflux pipe, 34. Heat exchanger II, 35. Receiving tank, 36. Vacuum unit, 37. Dimethyl phosphite intermediate tank, 38. Downstream liquid pipe II, 39. Pressure sensor, 40. Temperature sensor I, 42. Temperature sensor II, 43. Motor, 44. Deacidification kettle jacket, 45. Vacuum tail gas treatment system. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The invention reduces the amount of raw material methanol, improves the atomic utilization rate, and reduces by-product chloromethane and the like, providing a process for efficiently preparing dimethyl phosphite, wherein phosphorus trichloride and water are respectively metered and continuously introduced into a continuous flow reactor, and then reacted with methanol, the reaction liquid passes through a gas-liquid separator, the tail gas enters a washing tower for absorption to prepare hydrochloric acid, a small amount of non-condensable gas enters a chloromethane system as chloromethane, and the separated liquid enters a vacuum deacidification system to remove hydrogen chloride therein.

[0019] This is illustrated by the following example.

[0020] Example 1 This embodiment provides: a process for efficiently preparing dimethyl phosphite, which specifically comprises the following steps: Phosphorus trichloride at a flow rate of 40 kg / min and water at a flow rate of 5.2 kg / min are continuously added to the continuous flow reactor I, and the reaction temperature in the continuous flow reactor I is controlled to be 60° C. Then, the obtained intermediate product and methanol at a flow rate of 21.7 kg / min are continuously added to the continuous flow reactor II, and the reaction temperature in the continuous flow reactor II is controlled to be 40° C. Subsequently, the obtained reaction liquid is passed into the gas-liquid separator, and the reaction is controlled at normal pressure through the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator; The liquid level of the gas-liquid separator is controlled as low as possible through the liquid discharge valve of the gas-liquid separator, and the liquid continuously flows into the deacidification kettle. Under the negative pressure condition of 5 to 10 Kpa absolute pressure, the deacidification and post-treatment are carried out at 50 to 60° C. Finally, the obtained dimethyl phosphite is quantitatively detected, and the yield is about 87%.

[0021] Example 2 This embodiment provides: a process for efficiently preparing dimethyl phosphite, which specifically comprises the following steps: Phosphorus trichloride at a flow rate of 40 kg / min and water at a flow rate of 3.9 kg / min are continuously added to the continuous flow reactor I, and the reaction temperature in the continuous flow reactor I is controlled to be 50° C.; then, the obtained intermediate product and methanol at a flow rate of 24 kg / min are continuously added to the continuous flow reactor II, and the reaction temperature in the continuous flow reactor II is controlled to be 35° C. Subsequently, the obtained reaction liquid is passed into the gas-liquid separator, and the reaction is controlled at normal pressure through the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator; The liquid level of the gas-liquid separator is controlled as low as possible through the liquid discharge valve of the gas-liquid separator, and the liquid continuously flows into the deacidification kettle. Under the negative pressure condition of 5 to 10 Kpa absolute pressure, the deacidification and post-treatment are carried out at 50 to 60°C; finally, the obtained dimethyl phosphite is quantitatively detected, and the yield is about 90%.

[0022] Example 3 This embodiment provides: a process for efficiently preparing dimethyl phosphite, which specifically comprises the following steps: Phosphorus trichloride at a flow rate of 40 kg / min and water at a flow rate of 2.6 kg / min are continuously added to the continuous flow reactor I, and the reaction temperature in the continuous flow reactor I is controlled to be 50° C.; then, the obtained intermediate product and methanol at a flow rate of 26.4 kg / min are continuously added to the continuous flow reactor II, and the reaction temperature in the continuous flow reactor II is controlled to be 35° C. Subsequently, the obtained reaction liquid is passed into the gas-liquid separator, and the reaction is controlled at normal pressure through the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator; The liquid level of the gas-liquid separator is controlled as low as possible through the liquid discharge valve of the gas-liquid separator, and the liquid continuously flows into the deacidification kettle. Under the negative pressure condition of 5 to 10 Kpa absolute pressure, the deacidification and post-treatment are carried out at 50 to 60° C. Finally, the obtained dimethyl phosphite is quantitatively detected, and the yield is about 92%.

[0023] Example 4 This embodiment provides: a process for efficiently preparing dimethyl phosphite, which specifically comprises the following steps: Phosphorus trichloride at a flow rate of 40 kg / min and water at a flow rate of 2.6 kg / min are continuously added to the continuous flow reactor I, and the reaction temperature in the continuous flow reactor I is controlled to be 50° C.; then, the obtained intermediate product and methanol at a flow rate of 28 kg / min are continuously added to the continuous flow reactor II, and the reaction temperature in the continuous flow reactor II is controlled to be 35° C. Subsequently, the obtained reaction liquid is passed into the gas-liquid separator, and the reaction is controlled at normal pressure through the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator; The liquid level of the gas-liquid separator is controlled as low as possible through the liquid discharge valve of the gas-liquid separator, and the liquid continuously flows into the deacidification kettle. Under the negative pressure condition of 5 to 10 Kpa absolute pressure, the deacidification and post-treatment are carried out at 50 to 60°C; finally, the obtained dimethyl phosphite is quantitatively detected, and the yield is about 94%.

[0024] Example 5 This embodiment provides: a process for efficiently preparing dimethyl phosphite, such as Figure 1 As shown, the specific steps include: 1) First reaction: With the molar ratio of phosphorus trichloride to water being 1:0-1, phosphorus trichloride and water are introduced into a continuous flow reactor I, and the temperature in the continuous flow reactor I is controlled to be 30-80°C and the pressure to be -0.1-0.1MPa to obtain an intermediate product; 2) Second reaction: With the molar ratio of phosphorus trichloride to methanol being 1:2-4, methanol and the intermediate product obtained in step S1 are introduced into a continuous flow reactor II, and the temperature in the continuous flow reactor II is controlled to be 20-70° C. and the pressure to be -0.1-0.1 MPa to obtain a reaction solution; Wherein, during the entire reaction process of step 1) and step 2), the molar ratio of the total amount of water and methanol introduced to the amount of phosphorus trichloride introduced is controlled to be 3.1-4:1; the raw material - water can be specifically "deionized water"; 3) Gas-liquid separation: the reaction liquid obtained in step 2) is introduced into a gas-liquid separator, the temperature in the gas-liquid separator is controlled to be 20-70°C and the pressure to be -0.1-0.1 MPa, gas-liquid separation is performed, and gas I (a large amount of gas, which is hydrogen chloride gas containing a small amount of methyl chloride, methanol and vaporized dimethyl phosphite) and a separation liquid are obtained; After the gas I is condensed, it is passed into the atmospheric tail gas treatment system for water washing to obtain a large amount of by-product hydrochloric acid and a small amount of water-unabsorbed gas (mainly methyl chloride), which is discharged to the methyl chloride recovery system. Among them, the gas I is first condensed to reduce the phosphorus-containing substances entering the atmospheric tail gas treatment system, effectively reducing the phosphorus content of the by-product hydrochloric acid and improving the quality of hydrochloric acid; 4) Deacidification and separation: the separated liquid obtained in step 3) is introduced into the deacidification kettle, and the speed of the distributor in the deacidification kettle is controlled to be 30-120 r / min, the temperature to be 30-80° C. and the pressure to be -0.1-0.5 MPa, and separation is performed to obtain gas II (a small amount of gas. Mainly including vaporized dimethyl phosphite, methanol, hydrogen chloride gas, and a very small amount of chloromethane) and crude dimethyl phosphite; The gas II is introduced into the packed tower, and separated by the packed tower to obtain heavy components (mainly including dimethyl phosphite) and light components (methanol containing a small amount of hydrogen chloride). The heavy components are refluxed into the deacidification kettle; the light components are recovered (condensed) and used for the synthesis of dimethyl phosphite; the small amount of non-condensable gas (mainly including hydrogen chloride and methyl chloride) formed is introduced into the vacuum tail gas treatment system for water washing to obtain a small amount of by-product hydrochloric acid and a very small amount of water non-absorbent gas (mainly methyl chloride), and the very small amount of water non-absorbent gas is discharged into the methyl chloride recovery system. Among them, the gas II is introduced into the packed tower, and a condensation reflux is set at the top of the packed tower to avoid the entrainment of heavy components in the gas phase, effectively reduce the phosphorus content of the by-product hydrochloric acid in the subsequent vacuum tail gas treatment system, and improve the quality of hydrochloric acid. At the same time, a high content of anhydrous methanol can be obtained after recovery, which is directly reused in the synthesis process of dimethyl phosphite, achieving the purpose of reducing methanol consumption. That is, without increasing energy consumption, methanol consumption is reduced and the quality of by-product hydrochloric acid is improved; 5) Post-treatment: The crude dimethyl phosphite obtained in step 4) is post-treated to obtain dimethyl phosphite (such as Figure 4 As shown), it is a transparent liquid (such as Figure 5 as shown).

[0025] In this preparation process, on the one hand, by using water and methanol as raw materials, the amount of methanol is reduced, and at the same time, the by-product methyl chloride is greatly reduced; on the other hand, by using a continuous flow reactor and a gas-liquid separator, etc., and correspondingly treating and recycling the tail gas (gas I, gas II) formed, it is finally ensured that this preparation process is no longer like the traditional process - a large amount of non-condensable gas needs to be treated by the vacuum unit before being discharged to the methyl chloride recovery system. The load of the vacuum unit in this preparation process is reduced by multiples, which can greatly reduce equipment investment and energy consumption. In addition, in this preparation process, the reaction temperature involved is controlled by the cooling system matched with the continuous flow reactor; the reaction pressure involved is controlled by the pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator.

[0026] Example 6 This embodiment provides: a system for efficiently preparing dimethyl phosphite, such as Figure 2-3 As shown, it includes a continuous flow reactor Ⅰ1, a continuous flow reactor Ⅱ2, a gas-liquid separator 3, a deacidification kettle 4, a packed tower 5 and a tail gas treatment system (including a normal pressure tail gas treatment system 6 and a vacuum tail gas treatment system 45); The continuous flow reactor I1 is connected to a phosphorus trichloride storage tank 8 through a phosphorus trichloride inlet pipe 7, on which a phosphorus trichloride delivery pump 9, a phosphorus trichloride flowmeter 10 and a phosphorus trichloride regulating valve 11 are provided, and the discharge port on the continuous flow reactor I1 is connected to the continuous flow reactor II2; it is also connected to a water storage tank 13 through a water inlet pipe 12, on which a water delivery pump 14, a water flowmeter 15 and a water regulating valve 16 are provided; Continuous flow reactor II 2: arranged at the rear side of the station of continuous flow reactor I 1, continuous flow reactor II 2 is connected to a methanol storage tank 18 via a methanol inlet pipe 17, a methanol delivery pump 19, a methanol flowmeter 20 and a methanol regulating valve 21 are arranged on the methanol inlet pipe 17, and the discharge port on the continuous flow reactor II 2 is connected to the gas-liquid separator 3; Gas-liquid separator 3: arranged at the rear side of the station of continuous flow reactor II 2, the gas-liquid separator 3 is provided with a liquid level meter 22 and a pressure transmitter 23, the liquid outlet on the gas-liquid separator 3 is connected to the deacidification kettle 4 through a liquid down pipe I 24, and a liquid down regulating valve 25 is provided on the liquid down pipe I 24; In addition, the gas outlet on the gas-liquid separator 3 is connected to the heat exchanger I 27 through the gas phase outlet pipe 26, and the gas phase outlet pipe 26 is provided with a pressure regulating valve 28. The condensate outlet on the heat exchanger I 27 is connected to the gas-liquid separator 3 through the condensate pipeline 29, and the heat exchanger I 27 is arranged at a high position relative to the gas-liquid separator 3; the gas outlet on the heat exchanger I 27 is connected to the atmospheric tail gas treatment system 6, and the atmospheric tail gas treatment system 6 includes a washing tower; a continuous passage for condensation and reflux of methanol and dimethyl phosphite in the gas I is formed between the gas outlet on the gas-liquid separator 3, the gas phase outlet pipe 26, the heat exchanger I 27, the condensate outlet on the heat exchanger I 27 and the condensate pipeline 29; Deacidification kettle 4: It is arranged at the rear side of the station of gas-liquid separator 3. A distributor 31 is arranged in the deacidification kettle 4. The distributor 31 is connected with the lower liquid pipe Ⅰ24. The gas outlet on the deacidification kettle 4 is connected with the middle or lower part of the packing tower 5 through the exhaust pipe 32. The bottom of the packing tower 5 is connected with the deacidification kettle 4 through the reflux pipe 33. A continuous passage for condensation and reflux of the heavy components in the gas Ⅱ is formed between the gas outlet on the deacidification kettle 4, the exhaust pipe 32, the packing tower 5 and the reflux pipe 33. The upper part of the packing tower 5 is connected with the heat exchanger Ⅱ34, and the heat exchanger Ⅱ34 is connected with the receiving tank 3. 5. The gas outlet on the receiving tank 35 is connected to the vacuum tail gas treatment system 45; the vacuum tail gas treatment system 45 is connected to the vacuum unit 36 ​​to ensure that the gas-liquid separator 3 and the deacidification kettle 4 work under negative pressure conditions; the liquid outlet on the receiving tank 35 is connected to the packing tower 5, and the liquid outlet on the receiving tank 35 is connected to the methanol storage tank 18; a dimethyl phosphite intermediate tank 37 is provided at the rear side of the station of the deacidification kettle 4, and the lower liquid pipe II 38 of the deacidification kettle 4 extends to the middle or bottom of the dimethyl phosphite intermediate tank 37 to ensure the formation of a liquid seal. Preferably, the level difference between the bottom end of the deacidification kettle 4 and the bottom of the dimethyl phosphite intermediate tank 37 is controlled at 10 to 15 meters to ensure that the deacidification kettle 4 can work continuously under negative pressure to achieve continuous operation of the entire system.

[0027] In addition, the phosphorus trichloride inlet pipe 7, the water inlet pipe 12 and the methanol inlet pipe 17 are all provided with a pressure sensor 39 and a temperature sensor I 40.

[0028] Among them, the distributor 31 includes a cylindrical distribution trough, and the distributor 31 is connected to the motor 43 through a rotating shaft, that is, the motor 43 drives the distribution trough to perform centrifugal motion; the lower liquid pipe Ⅰ24 extends into the deacidification kettle 4 to the top of the distribution trough, and passes the separation liquid into the distribution trough. Under the action of centrifugal force, the separation liquid moves outward along the surface of the distribution trough, and then flies out of the distribution trough, evenly adheres to the inner wall of the deacidification kettle 4, and flows downward. It is heated during the flow process, and the low-boiling substances are vaporized, and finally the material separation is completed efficiently and with high quality.

[0029] Example 7 This embodiment provides: a control system for efficiently preparing dimethyl phosphite, such as Figure 3 As shown, it includes a DCS controller, a phosphorus trichloride flowmeter 10 and a phosphorus trichloride regulating valve 11 arranged on the phosphorus trichloride inlet pipe 7 between the phosphorus trichloride storage tank 8 and the continuous flow reactor Ⅰ1, a water flowmeter 15 and a water regulating valve 16 arranged on the water inlet pipe 12 between the water storage tank 13 and the continuous flow reactor Ⅰ1, a methanol flowmeter 20 and a methanol regulating valve 21 arranged on the methanol inlet pipe 17 between the methanol storage tank 18 and the continuous flow reactor Ⅱ2, a liquid level meter 22 and a pressure transmitter 23 arranged on the gas-liquid separator 3, a pressure regulating valve 28 arranged on the gas phase outlet pipe 26 of the gas-liquid separator 3, a lower liquid regulating valve 25 arranged on the lower liquid pipe Ⅰ24 between the gas-liquid separator 3 and the deacidification kettle 4, a motor 43 connected to the distributor 31, and a temperature sensor Ⅱ42 arranged on the jacket 44 of the deacidification kettle; The phosphorus trichloride flowmeter 10, the phosphorus trichloride regulating valve 11, the water flowmeter 15, the water regulating valve 16, the methanol flowmeter 20, the methanol regulating valve 21, the liquid level meter 22, the lower liquid regulating valve 25, the pressure transmitter 23, the pressure regulating valve 28, the motor 43 and the temperature sensor II 42 are all connected to the DCS controller; Among them, the phosphorus trichloride flow meter 10 and the phosphorus trichloride regulating valve 11 are interlocked by electrical signals; The water flow meter 15 and the water regulating valve 16 are interlocked by electrical signals; The methanol flow meter 20 and the methanol regulating valve 21 are interlocked by electrical signals; The liquid level meter 22 and the lower liquid regulating valve 25 are interlocked through electrical signals; The pressure transmitter 23 and the pressure regulating valve 28 are interlocked via electrical signals.

[0030] Furthermore, the phosphorus trichloride inlet pipe 7, the water inlet pipe 12 and the methanol inlet pipe 17 are all provided with a pressure sensor 39 and a temperature sensor I40, and the pressure sensor 39 and the temperature sensor I40 are both connected to the DCS controller.

[0031] Comparative Example 1 This comparative example uses a continuous flow reactor to examine the reaction yield of phosphorus trichloride and anhydrous methanol. Specifically, it includes: Phosphorus trichloride at a flow rate of 40 kg / min and anhydrous methanol at a flow rate of 31 kg / min are respectively introduced into a continuous flow reactor, the reaction temperature is controlled at 20°C, and the reaction is controlled at normal pressure through a pressure regulating valve on a gas-liquid separator. The materials then continuously enter a deacidification kettle, and deacidification and post-treatment are carried out at 50-60°C under a negative pressure condition of 5-10 KPa absolute pressure. Finally, the obtained dimethyl phosphite is quantitatively detected, and the yield is about 93%.

[0032] It can be seen that: under the premise of using a continuous flow reactor, the yield of dimethyl phosphite synthesized by replacing part of the methanol with a small amount of water can reach the level of dimethyl phosphite synthesized by using only anhydrous methanol, which confirms that it is feasible to synthesize dimethyl phosphite by replacing methanol with a small amount of water in a special reactor and supporting equipment.

[0033] Discussion Example 1 In this example, anhydrous methanol and phosphorus trichloride were reacted in a four-necked flask to synthesize dimethyl phosphite.

[0034] Put 107 g of anhydrous methanol with a content of 99% into a four-necked flask, start the low-temperature water circulation of the condensing reflux tube, then start the stirring and vacuum pump, the methanol refluxes stably at about 20°C, and then add 138.2 g of 99.5% phosphorus trichloride dropwise, and place the reaction bottle in an ice water device at the same time, control the reaction temperature at 19-21°C, and control the system pressure not higher than -0.095 MPa by the phosphorus trichloride addition speed. After the phosphorus trichloride is added dropwise, replace the ice water bath with an oil bath for heating, control the material temperature in the reaction bottle at 50-60°C, stir for 5 minutes, sample and detect the content of dimethyl phosphite in the reaction bottle, and calculate the dimethyl phosphite yield to be about 80%.

[0035] Discussion Example 2 In this example, a glass flask is used as a reactor to discuss the use of water to replace part of the methanol to synthesize dimethyl phosphite.

[0036] In a 4-necked flask, 75 g of anhydrous methanol with a content of 99% was added, and 18 g of deionized water was added. The low-temperature water circulation of the condensing reflux tube was turned on, and then the stirring and vacuum pump were turned on. The methanol-water system refluxed stably at about 20°C, and then 138.2 g of 99.5% phosphorus trichloride was added dropwise. At the same time, the reaction bottle was placed in an ice water device, and the reaction temperature was controlled at 19-21°C. The pressure of the system was controlled not to be higher than -0.095 MPa by the phosphorus trichloride addition speed. After the phosphorus trichloride was added dropwise, the ice water bath was replaced with an oil bath for heating, and the material temperature in the reaction bottle was controlled at 50-60°C. Stir for 5 minutes, sampled and tested the content of dimethyl phosphite in the reaction bottle, and the yield of dimethyl phosphite was calculated to be about 65%.

[0037] Discussion Example 3 In this discussion example, the reaction priority is determined by the intensity of the reaction between phosphorus trichloride and methanol and the reaction between phosphorus trichloride and water.

[0038] 1. Put an appropriate amount of anhydrous methanol into a test tube, then drop phosphorus trichloride into it. The reaction will be violent and produce a large amount of gas. 2. Add an appropriate amount of deionized water into a test tube, then drop phosphorus trichloride into it, and gas will be generated, but the phosphorus trichloride will obviously sink to the bottom of the water quickly. As the reaction proceeds, the phosphorus trichloride will gradually disappear. It shows that judging from the reaction phenomenon, phosphorus trichloride easily reacts with methanol, and the reaction rate of phosphorus trichloride with water is significantly lower than the reaction rate of phosphorus trichloride with methanol.

[0039] Through the discussion of Examples 1-3, it can be seen that when anhydrous methanol and phosphorus trichloride are used to react to prepare dimethyl phosphite, the yield of the batch method is only 80%, which is significantly lower than the current industrialized continuous process. The reason is that the material residence time is inconsistent, resulting in too many side reactions. When the same reaction device is used to replace methanol with part of water for the reaction, the yield is even lower, because phosphorus trichloride is more likely to react with methanol first, and the generated ester is more likely to react with water under acidic conditions and be hydrolyzed. In addition, untimely deacidification also causes an increase in side reactions, so the overall yield is not high.

Claims

1. A process for efficiently preparing dimethyl phosphite, characterized in that: The steps include: S1: introducing phosphorus trichloride and water into a continuous flow reactor I at a molar ratio of phosphorus trichloride to water of 1:0-1, controlling the temperature in the continuous flow reactor I to be 30-80° C. and the pressure to be -0.1-0.1 MPa, to obtain an intermediate product; S2: In a molar ratio of phosphorus trichloride to anhydrous methanol of 1:2-4, anhydrous methanol and the intermediate product obtained in step S1 are introduced into a continuous flow reactor II, and the temperature in the continuous flow reactor II is controlled to be 20-70° C. and the pressure is -0.1-0.1 MPa to obtain a reaction solution; Wherein, during the entire reaction process of step S1 and step S2, the molar ratio of the total amount of water and anhydrous methanol introduced to the amount of phosphorus trichloride introduced is 3.1 to 4:1; S3: passing the reaction liquid obtained in step S2 into a gas-liquid separator to perform gas-liquid separation to obtain a separated liquid; S4: passing the separated liquid obtained in step S3 into a deacidification kettle for separation to obtain a crude dimethyl phosphite; post-processing to obtain dimethyl phosphite.

2. The process for efficiently preparing dimethyl phosphite according to claim 1, characterized in that: In step S3, the temperature in the gas-liquid separator is controlled to be 20-70°C and the pressure to be -0.1-0.1 MPa.

3. The process for efficiently preparing dimethyl phosphite according to claim 2, characterized in that: In step S3, after gas-liquid separation, gas I is obtained; gas I is condensed and then passed into a normal pressure tail gas treatment system for water washing to obtain by-product hydrochloric acid and water-unabsorbed gas, and the water-unabsorbed gas is discharged to a chloromethane recovery system.

4. The process for efficiently preparing dimethyl phosphite according to claim 1, characterized in that: In step S4, the speed of the distributor in the deacidification kettle is controlled to be 30-120 r / min, the temperature to be 30-80° C., and the pressure to be -0.1-0.5 MPa.

5. The process for efficiently preparing dimethyl phosphite according to claim 4, characterized in that: In step S4, after separation, gas II is obtained; gas II is introduced into a packed tower, and separated by the packed tower to obtain a heavy component and a light component; The heavy components are directly refluxed into the deacidification kettle; After the light component is recovered, its content is tested; then, it is used as direct anhydrous methanol for the preparation of dimethyl phosphite.

6. A system for efficiently preparing dimethyl phosphite, characterized in that: A system used in the process according to any one of claims 1 to 5, comprising a continuous flow reactor I (1), a continuous flow reactor II (2), a gas-liquid separator (3) and a deacidification reactor (4); The continuous flow reactor I (1) is connected to a phosphorus trichloride storage tank (8) via a phosphorus trichloride inlet pipe (7), and a phosphorus trichloride delivery pump (9), a phosphorus trichloride flow meter (10) and a phosphorus trichloride regulating valve (11) are provided on the phosphorus trichloride inlet pipe (7); the upper discharge port of the continuous flow reactor I (1) is connected to the continuous flow reactor II (2); the continuous flow reactor I (1) is also connected to a water storage tank (13) via a water inlet pipe (12), and a water delivery pump (14), a water flow meter (15) and a water regulating valve (16) are provided on the water inlet pipe (12); The continuous flow reactor II (2) is arranged at the rear side of the station of the continuous flow reactor I (1). The continuous flow reactor II (2) is connected to a methanol storage tank (18) via a methanol inlet pipe (17). A methanol delivery pump (19), a methanol flow meter (20) and a methanol regulating valve (21) are arranged on the methanol inlet pipe (17). The upper discharge port of the continuous flow reactor II (2) is connected to a gas-liquid separator (3). The gas-liquid separator (3) is arranged at the rear side of the working station of the continuous flow reactor II (2). The gas-liquid separator (3) is provided with a liquid level meter (22) and a pressure transmitter (23). The liquid outlet of the gas-liquid separator (3) is connected to the deacidification kettle (4) through a liquid lower pipe I (24). The liquid lower pipe I (24) is provided with a liquid lower regulating valve (25). The deacidification kettle (4) is arranged at the rear side of the station of the gas-liquid separator (3). A distributor (31) is arranged in the deacidification kettle (4). The distributor (31) is connected to the lower liquid pipe I (24). A dimethyl phosphite intermediate tank (37) is arranged at the rear side of the station of the deacidification kettle (4). The lower liquid pipe II (38) of the deacidification kettle (4) extends to the middle or bottom of the dimethyl phosphite intermediate tank (37) to ensure the formation of a liquid seal.

7. The system for efficiently preparing dimethyl phosphite according to claim 6, characterized in that: The system further comprises a normal pressure tail gas treatment system (6); The gas outlet on the gas-liquid separator (3) is connected to the heat exchanger I (27) via a gas phase outlet pipe (26), a pressure regulating valve (28) is provided on the gas phase outlet pipe (26), the condensate outlet on the heat exchanger I (27) is connected to the gas-liquid separator (3) via a condensate pipeline (29), and the heat exchanger I (27) is arranged at a higher position relative to the gas-liquid separator (3), and a continuous passage for condensation and reflux of methanol and dimethyl phosphite in the gas I is formed between the gas outlet on the gas-liquid separator (3), the gas phase outlet pipe (26), the heat exchanger I (27), the condensate outlet on the heat exchanger I (27) and the condensate pipeline (29); the gas outlet on the heat exchanger I (27) is connected to the atmospheric pressure tail gas treatment system (6).

8. The system for efficiently preparing dimethyl phosphite according to claim 7, characterized in that: The system further comprises a packed tower (5); The upper gas outlet of the deacidification kettle (4) is connected to the middle or lower part of the packing tower (5) through an exhaust pipe (32), and the bottom of the packing tower (5) is connected to the deacidification kettle (4) through a reflux pipe (33). A continuous passage for condensing and refluxing heavy components in gas II is formed between the upper gas outlet of the deacidification kettle (4), the exhaust pipe (32), the packing tower (5) and the reflux pipe (33); The upper part of the packed tower (5) is connected to a heat exchanger II (34), and the heat exchanger II (34) is connected to a receiving tank (35). The gas outlet on the receiving tank (35) is connected to a vacuum tail gas treatment system (45); the liquid outlet on the receiving tank (35) is connected to the packed tower (5), and the liquid outlet on the receiving tank (35) is connected to a methanol storage tank (18).

9. The system for efficiently preparing dimethyl phosphite according to claim 8, characterized in that: The vacuum tail gas treatment system (45) comprises a washing tower, and the vacuum tail gas treatment system (45) is connected to a vacuum unit (36).

10. The system for efficiently preparing dimethyl phosphite according to claim 6, characterized in that: The height difference between the bottom of the deacidification kettle (4) and the bottom of the dimethyl phosphite intermediate tank (37) is controlled to be 10 to 15 m.

11. The system for efficiently preparing dimethyl phosphite according to claim 5, characterized in that: The phosphorus trichloride inlet pipe (7), the water inlet pipe (12) and the methanol inlet pipe (17) are all provided with a pressure sensor (39) and a temperature sensor I (40).

12. A control system for efficiently preparing dimethyl phosphite, characterized in that: A control system used in the process according to any one of claims 1 to 5, the control system comprising a DCS controller and a phosphorus trichloride flowmeter (10) and a phosphorus trichloride regulating valve (11) provided on the phosphorus trichloride inlet pipe (7) between the phosphorus trichloride storage tank (8) and the continuous flow reactor I (1), the phosphorus trichloride flowmeter (10) and the phosphorus trichloride regulating valve (11) both being connected to the DCS controller; The phosphorus trichloride flow meter (10) and the phosphorus trichloride regulating valve (11) are interlocked via an electrical signal.

13. The control system for efficiently preparing dimethyl phosphite according to claim 12, characterized in that: The control system further comprises a water flow meter (15) and a water regulating valve (16) arranged on the water inlet pipe (12) between the water storage tank (13) and the continuous flow reactor I (1), and the water flow meter (15) and the water regulating valve (16) are both connected to the DCS controller; The water flow meter (15) and the water regulating valve (16) are interlocked via an electrical signal.

14. The control system for efficiently preparing dimethyl phosphite according to claim 13, characterized in that: The control system further comprises a methanol flow meter (20) and a methanol regulating valve (21) disposed on the methanol inlet pipe (17) between the methanol storage tank (18) and the continuous flow reactor II (2), and the methanol flow meter (20) and the methanol regulating valve (21) are both connected to the DCS controller; The methanol flow meter (20) and the methanol regulating valve (21) are interlocked via an electrical signal.

15. The control system for efficiently preparing dimethyl phosphite according to claim 14, characterized in that: The control system further comprises a liquid level meter (22) and a pressure transmitter (23) provided on the gas-liquid separator (3), a pressure regulating valve (28) provided on the gas phase outlet pipe (26) of the gas-liquid separator (3), a lower liquid regulating valve (25) provided on the lower liquid pipe I (24) between the gas-liquid separator (3) and the deacidification kettle (4), and a motor (43) connected to the distributor (31) in the gas-liquid separator (3); The liquid level meter (22), the pressure transmitter (23), the pressure regulating valve (28), the lower liquid regulating valve (25) and the motor (43) are all connected to the DCS controller; The liquid level meter (22) and the lower liquid regulating valve (25) are interlocked via an electrical signal; The pressure transmitter (23) and the pressure regulating valve (28) are interlocked via an electrical signal.

16. The control system for efficiently preparing dimethyl phosphite according to claim 15, characterized in that: The control system further comprises a temperature sensor II (42) arranged on the jacket (44) of the deacidification reactor, and the temperature sensor II (42) is connected to the DCS controller.

17. The control system for efficiently preparing dimethyl phosphite according to claim 16, characterized in that: The phosphorus trichloride inlet pipe (7), the water inlet pipe (12) and the methanol inlet pipe (17) are all provided with a pressure sensor (39) and a temperature sensor I (40), and the pressure sensor (39) and the temperature sensor I (40) are both connected to the DCS controller.

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