Method for feeding dimethyl phosphite by adopting microchannel reactor

Abstract

The invention relates to a method for feeding dimethyl phosphite by adopting a microchannel reactor, a process system comprises a microchannel reaction unit, a primary deacidification treatment unit and a post-system treatment unit, a methanol material inlet and a phosphorus trichloride material inlet are respectively arranged on two branch channels at one end of a microchannel, the other end of the microchannel is a product outlet, and the other end of the microchannel is a product outlet. The product outlet is connected with a top feed port of a first-stage deacidification kettle of the first-stage deacidification treatment unit through a pipeline, a bottom discharge port of the first-stage deacidification kettle is connected with a rear system, a heat-conducting medium cavity is formed among an upper heat-insulating plate, a lower heat-insulating plate and a shell, the upper heat-insulating plate is provided with a heat-conducting medium inlet, and the lower heat-insulating plate is provided with a heat-conducting medium outlet; the technological process comprises the following steps: S1, conveying methanol and phosphorus trichloride raw materials; s2, carrying out a reaction between the materials; s3, carrying out deacidification treatment; s4, purifying the dimethyl phosphite; through the advantages of the micro-channel reactor, the reaction efficiency and the product purity are improved, side reactions are reduced, and the method has a good industrial application prospect.

Description

Technical Field

[0001] This article belongs to the technical field of organophosphorus compound synthesis, specifically involving a method for feeding dimethyl phosphite using a microchannel reactor. Background Technology

[0002] Dimethyl phosphite (C2H7O3P) is a core intermediate in the synthesis of organophosphorus pesticides and is widely used in the production of various high-value-added pesticides such as dichlorvos and dimethoate. Against the backdrop of continuous growth in global agricultural demand, the market size of dimethyl phosphite has been expanding at an average annual rate of 8% to 10%. However, its industrial production has long been limited by technological bottlenecks, which has seriously restricted the high-quality development of the industry.

[0003] From the perspective of the chemical reaction itself, the synthesis of dimethyl phosphite is an esterification reaction of phosphorus trichloride (PCl3) and methanol (CH3OH): PCl3 + 3CH3OH → (CH3O)2HPO + 3HCl. This reaction is a typical rapid and strongly exothermic reaction. If the temperature is not properly controlled, local overheating will trigger a series of side reactions, such as the deep chlorination of methanol to form chloromethane (CH3Cl) and the further chlorination of dimethyl phosphite to form monochlorodimethyl phosphite (Cl(CH3O)2PO). These byproducts will not only reduce the purity of the product, but also increase the difficulty and cost of subsequent separation and purification.

[0004] In the existing technology system, the solution disclosed in patent CN105713037A is somewhat representative. This solution adopts a complex structure of a microchannel reactor connected in series with two-stage vacuum deacidification kettles, attempting to optimize the production process by precisely controlling the reaction temperature (28-35℃) and the deacidification temperature gradient (40-50℃ for the first-stage deacidification kettle and 70-80℃ for the second-stage deacidification kettle). Although this solution can improve the product purity to 98%, it has significant equipment and energy consumption defects. The two-stage deacidification system needs to maintain a high vacuum environment of -98 to -90 kPa, and the energy consumption of the vacuum unit accounts for more than 35% of the total power consumption of the system.

[0005] Another representative technology is the continuous flow process published by Liu Jianwu's team at Changzhou University. This process uses a pulsed variable diameter reactor (IFR) with a special microstructure to enhance mixing and mass transfer by changing the diameter of the flow channel. Under the condition of 60% methanol excess, the process achieved a yield of 92.6%. However, the recovery of excess methanol became a new problem. Since the boiling points of methanol and dimethyl phosphite are close (methanol boiling point 64.7℃, dimethyl phosphite boiling point 170℃), the methanol recovery process will increase the production cost by 25% to 30%, which will greatly compress the profit margin of enterprises.

[0006] In summary, existing technologies for the production of dimethyl phosphite generally suffer from problems such as complex equipment, high energy consumption, low raw material utilization, and insufficient reaction efficiency, making it difficult to meet the current industry's demand for efficient, low-consumption, and high-purity production processes. Therefore, developing a novel dimethyl phosphite production process is of significant practical importance. Summary of the Invention

[0007] To address the aforementioned issues, this paper proposes a method for feeding dimethyl phosphite using a microchannel reactor. The process system comprises a microchannel reaction unit, a primary deacidification unit, and a post-processing unit. The microchannel reaction unit includes a methanol inlet, a phosphorus trichloride inlet, a product outlet, a microchannel, an upper insulation plate, a lower insulation plate, a heat-conducting medium cavity, a heat-conducting medium inlet, a heat-conducting medium outlet, and a shell. The methanol inlet and phosphorus trichloride inlet are respectively located on two branch channels at one end of the microchannel, while the other end of the microchannel is the product outlet. The product outlet is connected to the top inlet of the primary deacidification reactor of the primary deacidification treatment unit via a pipeline. The bottom outlet of the primary deacidification reactor is connected to the downstream system. A heat-conducting medium cavity is formed between the upper and lower insulation plates and the shell. The upper insulation plate is provided with a heat-conducting medium inlet, and the lower insulation plate is provided with a heat-conducting medium outlet. By using this device, methanol and phosphorus trichloride can be rapidly mixed and reacted efficiently in the microchannel, which can significantly enhance the mass transfer efficiency, so that the reactants can be fully mixed and reacted in a short time, thereby improving the reaction rate and raw material conversion rate.

[0008] The microchannel reaction unit adopts an integrated temperature-controlled microchannel reactor with a temperature control accuracy of ±0.5℃. Through the temperature control function, the temperature of the reaction system can be precisely controlled to avoid the increase in the amount of by-products caused by local overheating. At the same time, the integrated design reduces the number of equipment connection nodes, reduces heat loss, and makes the temperature field distribution of the entire reaction process more uniform, providing a stable thermodynamic environment for the efficient reaction.

[0009] The methanol and phosphorus trichloride feed inlets are equipped with a precise ratio control system. This system monitors the feed rate of the two raw materials in real time through high-precision flow sensors, quickly adapts to external interference such as feed pressure fluctuations, and avoids incomplete reaction or increased by-products caused by raw material imbalance. This provides a precise material basis for the efficient conduct of subsequent reactions.

[0010] The shell is vertically connected between the upper and lower insulation plates, forming a sealed thermally conductive medium cavity. The thermally conductive medium cavity is equipped with microchannels, which enable precise control of the reaction temperature within the microchannels. At the same time, the optimized microchannel arrangement reduces flow dead zones, stabilizes the temperature within the microchannels, effectively reduces the amount of by-products generated, and improves product purity and reaction stability.

[0011] The product outlet is vertically connected to the feed flange at the top of the primary deacidification reactor via a DN25 pipe. The drain port at the bottom of the primary deacidification reactor is connected to the feed port of the buffer tank in the downstream system via a 45° inclined pipe. The vertical connection allows the material to enter the primary deacidification reactor with the help of gravity, reducing the material's retention in the pipe. The 45° inclined pipe connection at the bottom of the primary deacidification reactor to the buffer tank helps the deacidified material to enter the buffer tank smoothly under its own weight and the push of subsequent materials, avoiding the problems of material accumulation and increased flow resistance that may be caused by right-angle connections. It also provides structural protection for the continuous material transport in the entire process, ensuring that the material generated from the microchannel reaction unit can enter the downstream processing stage efficiently and stably.

[0012] The upper and lower insulation boards are covered with a 10mm thick ceramic fiber layer to encase the 316L stainless steel inner liner. The excellent thermal insulation performance of the ceramic fiber layer and the high strength and corrosion resistance of the 316L stainless steel inner liner ensure the structural stability under long-term high temperature and high pressure reaction environment, while reducing the loss of heat to the external environment and further improving energy utilization efficiency.

[0013] Beneficial effects:

[0014] This invention adopts a single-machine deacidification technology route, which reduces equipment investment costs by 32%, significantly reducing the initial investment pressure on enterprises. At the same time, the simplification of the equipment structure reduces the installation area by 45%, making it suitable for layout in factories with limited space and improving land utilization resources.

[0015] This invention eliminates the high-vacuum deacidification step in existing technologies and reduces methanol consumption through a precise proportioning control system, resulting in energy consumption per ton of product reduced to 155 kWh, a significant reduction compared to the 220 kWh per ton of product in existing technologies. Simultaneously, the optimized methanol consumption reduces steam consumption in subsequent distillation processes by 28%, further lowering energy consumption and improving energy efficiency. This aligns with current energy conservation and emission reduction policies, helping companies reduce production costs and enhance market competitiveness.

[0016] By adopting an integrated insulation board-shell structure, the insulation board and the lower insulation board are covered with a 10mm thick ceramic fiber layer to encase a 316L stainless steel inner liner. This reduces the weight of the equipment by 40% while maintaining thermal efficiency. This not only reduces the manufacturing and transportation costs of the equipment, but also reduces vibration and wear during operation, improves the operational stability and service life of the equipment, and reduces maintenance costs, thus providing a guarantee for the long-term stable production of enterprises.

[0017] By optimizing the structure of the microchannel reactor, the residence time of the material in the microchannel was extended, increasing the conversion rate of phosphorus trichloride to over 98% and significantly improving the reaction efficiency. Simultaneously, the increased conversion rate kept the amount of byproducts below 0.5%, effectively improving product purity. Furthermore, industrial pilot-scale data showed that under continuous operation for 500 hours, the product purity remained stably maintained within the range of 99.2%–99.5%, demonstrating high product quality stability and meeting the stringent quality requirements of industrial production.

[0018] By integrating equipment and optimizing processes, the production process is simplified, unnecessary operational steps are reduced, and the production cycle of a single batch is shortened to 60% of that of traditional processes, which greatly improves production efficiency. In the same production time, enterprises can produce more products, improve equipment utilization and economic benefits, and help enterprises respond quickly to market demands and expand market share. Attached Figure Description

[0019] Figure 1 A schematic diagram of a method for feeding dimethyl phosphite using a microchannel reactor;

[0020] In the diagram: 1. Methanol material inlet, 2. Phosphorus trichloride material inlet, 3. Heat transfer medium cavity, 4. Lower insulation plate, 5. Heat transfer medium outlet, 6. Shell, 7. Product outlet, 8. Upper insulation plate, 9. Heat transfer medium inlet, 10. Microchannel, 11. Primary deacidification reactor. Detailed Implementation

[0021] To enhance understanding of the present invention, the invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only for explaining the invention and do not constitute a limitation on the scope of protection of the invention.

[0022] Methanol material inlet 1, phosphorus trichloride material inlet 2, heat transfer medium cavity 3, lower insulation plate 4, heat transfer medium outlet 5, shell 6, product outlet 7, upper insulation plate 8, heat transfer medium inlet 9, microchannel 10, primary deacidification reactor 11.

[0023] like Figure 1 As shown;

[0024] A method for feeding dimethyl phosphite using a microchannel reactor, wherein the process system includes a microchannel reaction unit, a primary deacidification unit, and a post-processing unit. The microchannel reaction unit includes a methanol inlet 1, a phosphorus trichloride inlet 2, a product outlet 7, a microchannel 10, an upper insulation plate 8, a lower insulation plate 4, a heat-conducting medium cavity 3, a heat-conducting medium inlet 9, a heat-conducting medium outlet 5, and a shell 6. The methanol inlet 1 and phosphorus trichloride inlet 2 are respectively located on two branch channels at one end of the microchannel 10. The other end of the microchannel 10 is the product outlet 7, which is connected via a pipe to the top inlet of the primary deacidification vessel 11 in the primary deacidification unit. The bottom outlet of the primary deacidification vessel 11 is connected to the post-processing unit. The upper insulation plate 8, lower insulation plate 4, and shell 6 are connected... A heat-conducting medium cavity 3 is formed. The upper insulation plate 8 is provided with a heat-conducting medium inlet 9, and the lower insulation plate 4 is provided with a heat-conducting medium outlet 5. The microchannel reaction unit adopts an integrated temperature-controlled microchannel reactor with a temperature control accuracy of ±0.5℃. The methanol material inlet 1 and the phosphorus trichloride material inlet 2 are equipped with a precise ratio control system. The shell 6 is vertically connected between the upper insulation plate 8 and the lower insulation plate 4, sealing to form the heat-conducting medium cavity 3. The heat-conducting medium cavity 3 is provided with a microchannel 10. The product outlet 7 is vertically connected to the feed flange at the top of the primary deacidification vessel 11 through a DN25 pipe. The drain port at the bottom of the primary deacidification vessel 11 is connected to the feed port of the buffer tank in the downstream system through a 45° inclined pipe. The upper insulation plate 8 and the lower insulation plate 4 are covered with a 10mm thick ceramic fiber layer and a 316L stainless steel inner liner.

[0025] Implementation example;

[0026] S1. Prepare methanol and phosphorus trichloride raw materials according to theoretical values, wherein the amount of methanol raw material is 8% higher than the theoretical value. The methanol raw material is fed into the microchannel at a constant flow rate through methanol material inlet 1 via a flow controller; the phosphorus trichloride raw material is synchronously transported through phosphorus trichloride material inlet 2 via a metering pump.

[0027] S2. The heat transfer medium enters the heat transfer medium cavity 3 from the heat transfer medium inlet 9. When it flows through the area formed by the upper insulation plate 8 and the lower insulation plate 4, the temperature of the reaction zone is maintained at 25°C through heat exchange. Finally, the heat transfer medium is discharged from the heat transfer medium outlet 5 into the circulation system. The methanol raw material and the phosphorus trichloride raw material undergo an esterification reaction in the microchannel 10. The reaction takes 8 minutes and the conversion rate is 99.3%.

[0028] S3. The reaction products enter the primary deacidification reactor 11 through the product outlet 7. The temperature inside the primary deacidification reactor 11 is controlled at 50℃ and the pressure is controlled at -82kPa, with a deacidification efficiency of 99.7%.

[0029] S4. The deacidified liquid product is directly transported to the post-processing unit for distillation and purification to obtain dimethyl phosphite with a purity of 98.5%.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for feeding dimethyl phosphite using a microchannel reactor, characterized in that, The process system includes a microchannel reaction unit, a primary deacidification treatment unit, and a post-processing unit. The microchannel reaction unit includes a methanol material inlet, a phosphorus trichloride material inlet, a product outlet, a microchannel, an upper insulation plate, a lower insulation plate, a heat-conducting medium cavity, a heat-conducting medium inlet, a heat-conducting medium outlet, and a shell. The methanol material inlet and the phosphorus trichloride material inlet are respectively located on two branch channels at one end of the microchannel. The other end of the microchannel is the product outlet. The product outlet is connected to the top inlet of the primary deacidification reactor of the primary deacidification treatment unit through a pipe. The bottom outlet of the primary deacidification reactor is connected to the post-processing unit. A heat-conducting medium cavity is formed between the upper insulation plate, the lower insulation plate, and the shell. The upper insulation plate has a heat-conducting medium inlet, and the lower insulation plate has a heat-conducting medium outlet.

2. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 1, characterized in that, The microchannel reaction unit uses an integrated temperature-controlled microchannel reactor with a temperature control accuracy of ±0.5℃.

3. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 1, characterized in that, The methanol and phosphorus trichloride inlets are equipped with a precise proportioning control system.

4. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 1, characterized in that, The shell is vertically connected between the upper insulation plate and the lower insulation plate, forming a sealed heat-conducting medium cavity, which is provided with microchannels.

5. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 1, characterized in that, The product outlet is vertically connected to the feed flange at the top of the primary deacidification reactor via a DN25 pipe, and the drain outlet at the bottom of the primary deacidification reactor is connected to the feed inlet of the buffer tank in the downstream system via a 45° inclined pipe.

6. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 1, characterized in that, The upper and lower insulation boards are made of 10mm thick ceramic fiber layer covering a 316L stainless steel inner liner.

7. A method for feeding dimethyl phosphite using a microchannel reactor, characterized in that, The specific process flow is as follows; S1. Methanol feedstock is fed into the microchannel at a constant flow rate through the methanol material inlet and the flow controller; phosphorus trichloride feedstock is synchronously conveyed through the phosphorus trichloride material inlet and the metering pump. S2. Methanol and phosphorus trichloride raw materials undergo esterification reaction in the microchannel. The heat transfer medium enters the heat transfer medium cavity from the heat transfer medium inlet. When flowing through the area formed by the upper and lower insulation plates, the temperature of the reaction zone is maintained in the range of 20-35℃ through heat exchange. Finally, the heat transfer medium is discharged from the heat transfer medium outlet of the circulation system. S3. The reaction products enter the primary deacidification reactor through the product outlet, where hydrogen chloride gas is separated by pressure control. S4. The deacidified liquid product is directly transported to the post-processing unit for distillation and purification to obtain high-purity dimethyl phosphite.

8. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 7, characterized in that, The actual amount of methanol feedstock used is 5% to 10% higher than the theoretical value.

9. The method for feeding dimethyl phosphite using a microchannel reactor according to claim 7, characterized in that, The temperature inside the primary deacidification reactor is 50±2℃, and the pressure range is -85kPa to -80kPa.

Images