Method and device for separating methyl phosphine dichloride

Abstract

The invention discloses a method and a device for separating methyl phosphine dichloride, and belongs to the technical field of chemical intermediate separation, a reaction gas phase component enters a pre-separation zone of a dividing wall column, methane and hydrogen chloride are evaporated from the top of the dividing wall column, and the methane and the hydrogen chloride are recycled after passing through a tower top condenser; and discharging methyl phosphine dichloride and phosphorus trichloride from the bottom of the dividing wall column, and further separating. Chloralkane and a small amount of impurities are extracted from an extraction port of the dividing wall column; the device consists of a dividing wall column and comprises a pre-separation area, an extraction area, a rectifying section and a stripping section, according to the method, the process safety and the added value are improved; the MDP yield is improved, the separation effect is better, impurities are separated more cleanly, and the stability of a reaction system is improved in the circulating process; the dividing wall column is adopted, multi-component separation is achieved, system energy consumption is further reduced, and the method is suitable for large-scale industrial production and is efficient and environmentally friendly.

Description

Technical Field

[0001] This application belongs to the field of chemical intermediate separation technology, and in particular relates to a method and apparatus for separating methylphosphine dichloride. Background Technology

[0002] Methylphosphonic acid (MDP) serves as a key intermediate for the highly efficient, low-toxicity, non-selective herbicide glufosinate and non-halogenated methylphosphite flame retardants. Glufosinate is an excellent alternative to paraquat, exhibiting superior speed of action and weed resistance mitigation compared to glyphosate. Non-halogenated flame retardants offer advantages such as low dosage, high flame retardant efficiency, low smoke, low toxicity, and wide applicability. Therefore, research into the efficient and low-cost production of methylphosphonic acid is receiving increasing attention.

[0003] Currently, methylphosphonic acid can be synthesized using a solid-phase method with phosphorus trichloride and aluminum trichloride, or by high-temperature cracking of methane and phosphorus trichloride in the presence of carbon tetrachloride. The former generates a large amount of solid waste, while the latter has the advantages of less waste and higher atom economy, but it consumes more energy because the conversion rate of phosphorus trichloride is only about 20%, and a large amount of chloroalkane byproducts are generated during the reaction, requiring further separation.

[0004]

[0005]

[0006] US4104304A discloses a method for preparing methylphosphine dichloride by reacting methane and phosphorus trichloride. Methane and phosphorus trichloride react with carbon tetrachloride at a temperature of 500-650 °C. After the reaction mixture is rapidly cooled, the gaseous phase containing methane and hydrogen chloride is fed into a scrubbing tower. The hydrogen chloride is absorbed by the alkaline solution, and the methane at the top of the tower is dried and reused. The liquid phase is then subjected to distillation, and the entrained gaseous phase is reused.

[0007] CN114539315A discloses a method for preparing methylphosphine dichloride, in which methane and phosphorus trichloride gas are catalytically reacted in a quartz glass tube of a fixed-bed reactor to obtain MDP. The tail gas obtained is also absorbed by water, and the excess methane is dried, compressed and then recycled into the reaction system.

[0008] The above method achieves the reuse of methane gas and phosphorus trichloride raw materials as much as possible. However, water-containing materials are used in the hydrogen chloride recovery process. Methylphosphine dichloride is prone to generating a large amount of acid mist when it comes into contact with water, which increases the process risk. The generated salt-containing waste is difficult to treat and increases environmental protection costs. Furthermore, the chloroalkane impurities generated in the reaction process are not completely removed, which affects the yield and system stability in the recycling system. Summary of the Invention

[0009] The purpose of this application is to provide a method and apparatus for separating methylphosphine dichloride, so as to solve the technical problems in the prior art that require the addition of alkaline solution or water-containing materials to absorb chlorine, resulting in incomplete separation of impurities and excessive waste.

[0010] To achieve the above objectives, the technical solution adopted in this application is: to provide a method for separating methylphosphine dichloride, specifically including the following steps: The gaseous components of the reaction enter the pre-separation zone of the partition tower. Methane and hydrogen chloride are distilled off from the top of the partition tower and reused after passing through the top condenser. Methylphosphine dichloride and phosphorus trichloride are discharged from the bottom of the partition tower for further separation. Chlorinated alkanes and impurities are collected from the outlet on the right side of the partition tower.

[0011] In one embodiment, The gaseous components of the reaction, by mass percentage, include 25-35% methane, 10-15% methylphosphine dichloride, 45-55% phosphorus trichloride, 1.5-2.5% chloroalkanes, and 3-5% hydrogen chloride.

[0012] In one embodiment, The feed temperature of the gaseous components of the reaction is 5-55 ℃, and the pressure is 0.1-1.0 MPaG.

[0013] In one embodiment, The temperature at the top of the adjacent tower is -110 to -130 ℃, and the pressure is 0.20-0.70 MPaG; the temperature at the bottom of the tower is 100-125 ℃, and the pressure is 0.22-0.72 MPaG.

[0014] This application also provides a separation device for methyl dichloride, including a partition wall column, a pre-separation zone and a collection zone in the middle of the partition wall column, a rectification section in the upper part of the partition wall column, a collector below the rectification section, a stripping section in the lower part of the partition wall column, a top condenser connected to the top of the partition wall column, and a bottom reboiler connected to the bottom of the partition wall column. The theoretical number of plates in the adjacent tower is 30-50.

[0015] In one embodiment, A partition plate is installed between the pre-separation zone and the extraction zone. The theoretical number of plates in the rectification section is 10-30, and the theoretical number of plates in the stripping section is 10-30.

[0016] In one embodiment, The collector has a first reflux zone and a second reflux zone on both sides; the reflux ratio of the pre-separation zone is 0.5-0.75.

[0017] In one embodiment, The top condenser has a top reflux feed inlet connected to the adjacent tower on one side of its bottom, and a top hydrogen chloride liquid phase outlet on the other side; the top condenser has a top methane gas phase outlet on one side; the top reflux ratio of the adjacent tower is 0.3-0.5.

[0018] In one embodiment, The bottom reboiler supplies rising steam to the collector, and the ratio of the steam mass flow rate of the collector is 0.5-0.8; the bottom reboiler is connected to the adjacent tower and has a bottom heavy component discharge port.

[0019] In one embodiment, The pre-separation zone is equipped with a reaction gas inlet, and the production zone is equipped with a side-stream chloroalkane outlet. The reaction gas inlet is located 1 / 2 to 2 / 3 of the tray below the pre-separation zone, and the side-stream chloroalkane outlet is located 1 / 3 to 1 / 2 of the tray from top to bottom in the production zone.

[0020] This application provides a method for separating methylphosphonic acid dichloride. This method eliminates the need for alkali absorption of hydrogen chloride, reducing the possibility of water entering the system and improving process safety. The obtained pure hydrogen chloride can be used to prepare high-value-added products such as triethyl orthoformate, or to prepare high-concentration hydrochloric acid for reuse, thus increasing added value. The removal of chloroalkanes makes the returned methane purer, increasing the MDP yield and improving the separation effect. This method achieves cleaner impurity separation and improves the stability of the reaction system during recycling. Using a single diverter tower, multiple components can be separated. By utilizing the low temperature at the top of the tower, system energy consumption is further reduced, making it suitable for large-scale industrial production, highly efficient, and environmentally friendly. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the separation device.

[0023] Explanation of symbols in the diagram: A. Pre-separation zone; B. Production zone; C. Rectifying section; D. Stripping section; 1. Reactant gas phase inlet; 2. First reflux zone; 3. Top reflux inlet; 4. Top hydrogen chloride liquid phase outlet; 5. Side stream chloroalkanes outlet; 6. Bottom heavy component outlet; 7. Second reflux zone; 8. Top methane gas phase outlet; 9. Divider plate; 10. Top condenser; 11. Bottom reboiler; 12. Collector. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0025] Example 1 A method for separating methylphosphine dichloride specifically includes the following steps: A gaseous reaction component (mass percentage, the same below) containing 30% methane, 13.9% methylphosphine dichloride, 50% phosphorus trichloride, 2.1% chloroalkanes, and 4% hydrogen chloride enters the pre-separation zone A of the partition tower at a rate of 825 kg / h, with a feed temperature of 10 ℃ and a pressure of 0.5 MPaG. The light components, methane and hydrogen chloride, rise to the rectification section C under the action of bottom steam. The liquid in the rectification section C falls onto collector 12, and the collected liquid is redistributed to both sides of the partition plate 9. The liquid in the first reflux zone 2 falls into the pre-separation zone A, and the liquid in the second reflux zone 7 falls into the collection zone B. The reflux ratio is 0.6 (first reflux zone 2 / (first reflux zone 2 + second reflux zone 7)). The partition plate 9 is positioned at the same level as the reflux ratio, that is, the cross-sectional length of the pre-separation zone A is 0.6 times the tower diameter. Steam is introduced into the bottom of the column, the bottom temperature is 108 ℃, and the pressure is 0.5 MPaG. The heavy component outlet 6 at the bottom of the column discharges at a rate of 527.18 kg / h. The discharge includes 21.75% MDP and 78.25% phosphorus trichloride. MDP and phosphorus trichloride are further separated by a distillation column. Phosphorus trichloride is separated from the top of the column, and MDP is separated from the bottom of the column, thus obtaining pure MDP. The tower top temperature is -120 ℃, and the pressure is 0.5 MPaG. The light components at the top of the tower are condensed and then separated into gas and liquid phases. The gas phase methane outlet 8 at the top of the tower discharges at a rate of 248.17 kg / h, and the discharge includes 99.70% methane and 0.3% hydrogen chloride. The methane is dried and reused. The liquid phase hydrogen chloride outlet 4 at the top of the tower discharges at a rate of 32.30 kg / h, and the discharge includes 99.88% hydrogen chloride, 0.12% methane and other components. The hydrogen chloride and methane can be stored as by-products to produce high value-added products. The side-stream chloroalkanes outlet 5 discharges at a rate of 17.36 kg / h, and the discharge includes 99.80% chloroalkanes and 0.20% minor impurities. The chloroalkanes and impurities are then incinerated.

[0026] Example 2 A method for separating methylphosphine dichloride specifically includes the following steps: A gaseous reaction component (mass percentage, the same below) containing 30% methane, 13.9% methylphosphine dichloride, 50% phosphorus trichloride, 2.1% chloroalkanes, and 4% hydrogen chloride enters the pre-separation zone A of the diverter column at a rate of 825 kg / h, with a feed temperature of 40 ℃ and a pressure of 0.8 MPaG. The light components, methane and hydrogen chloride, rise to the rectification section C under the action of bottom steam. The liquid in the rectification section C falls onto collector 12, and the collected liquid is redistributed to both sides of the divider plate 9. The liquid in the first reflux zone 2 falls into the pre-separation zone A, and the liquid in the second reflux zone 7 falls into the collection zone B. The reflux ratio is 0.7 (first reflux zone 2 / (first reflux zone 2 + second reflux zone 7)). The division position of the divider plate 9 is consistent with the reflux ratio, that is, the cross-sectional length of the pre-separation zone A accounts for 0.7 of the column diameter. The theoretical number of plates in the diverter column is 50, the number of plates in the rectification section C is 20, and the number of plates in the stripping section D is 20. Steam is introduced into the bottom of the column, the bottom temperature is 125 ℃, and the pressure is 0.7 MPaG. The heavy component outlet 6 at the bottom of the column discharges at a rate of 527.18 kg / h. The discharge includes 23.93% MDP and 76.07% phosphorus trichloride. MDP and phosphorus trichloride are further separated by a distillation column. Phosphorus trichloride is separated from the top of the column, and MDP is separated from the bottom of the column, thus obtaining pure MDP. The tower top temperature is -125 ℃, and the pressure is 0.7 MPaG. The light components at the top of the tower are condensed and then separated into gas and liquid phases. The gas phase methane outlet 8 at the top of the tower discharges at a rate of 248.17 kg / h, and the discharge includes 99.84% methane and 0.16% hydrogen chloride. The methane is dried and reused. The liquid phase hydrogen chloride outlet 4 at the top of the tower discharges at a rate of 32.30 kg / h, and the discharge includes 99.77% hydrogen chloride, 0.23% methane and others. The hydrogen chloride and methane can be stored as by-products to produce high value-added products. The side-stream chloroalkanes outlet 5 discharges at a rate of 17.36 kg / h, and the discharge includes 99.80% chloroalkanes and 0.20% minor impurities. The chloroalkanes and impurities are then incinerated.

[0027] Example 3 The difference between this embodiment and Example 1 is that the composition of the gas phase component is: 25% methane, 10% methylphosphine dichloride, 45% phosphorus trichloride, 1.5% chloroalkanes, and 3% hydrogen chloride; the rest of the operations are the same.

[0028] Example 4 The difference between this embodiment and Example 1 is that the composition of the gas phase reaction component is: 35% methane, 15% methylphosphine dichloride, 55% phosphorus trichloride, 2.5% chloroalkanes, and 5% hydrogen chloride; the rest of the operations are the same.

[0029] Example 5 The difference between this embodiment and Example 1 is that the feed temperature of the gaseous reaction component is 5 °C and the pressure is 0.1 MPaG; the rest of the operations are the same.

[0030] Example 6 The difference between this embodiment and Example 1 is that the feed temperature of the gaseous reaction component is 55 °C and the pressure is 1.0 MPaG; the rest of the operations are the same.

[0031] Example 7 The difference between this embodiment and Embodiment 1 is that the top temperature of the tower is -110 ℃ and the pressure is 0.20 MPaG; the rest of the operations are the same.

[0032] Example 8 The difference between this embodiment and Embodiment 1 is that the top temperature of the tower is -130 ℃ and the pressure is 0.70 MPaG; the rest of the operations are the same.

[0033] Example 9 The difference between this embodiment and Embodiment 1 is that the bottom temperature of the tower is 100 ℃ and the pressure is 0.22 MPaG; the rest of the operations are the same.

[0034] Example 10 The difference between this embodiment and Embodiment 1 is that the bottom temperature of the tower is 125 ℃ and the pressure is 0.72 MPaG; the rest of the operations are the same.

[0035] Example 11 A separation device for methylphosphine dichloride, such as Figure 1 As shown, the system includes a partition column, with a pre-separation zone A and a collection zone B in the middle, a rectification section C in the upper part of the partition column, and a collector 12 below the rectification section C; a stripping section D in the lower part of the partition column; a top condenser 10 connected to the top of the partition column, and a bottom reboiler 11 connected to the bottom of the partition column; the theoretical number of plates in the partition column is 30-50.

[0036] Specifically, the adjacent column has 40 trays, the rectification section C has 12 trays, the stripping section D has 13 trays, the pre-separation zone A and the extraction zone B have 15 trays, and the reaction gas inlet 1 is located on the 8th tray of the pre-separation zone A. A partition plate 9 is provided between the pre-separation zone A and the production zone B; a reaction gas inlet 1 is provided on the pre-separation zone A, and a side-stream chloroalkane outlet 5 is provided on the production zone B. The reaction gas inlet 1 is located 1 / 2 to 2 / 3 of the tray below the pre-separation zone A, and the side-stream chloroalkane outlet 5 is located 1 / 3 to 1 / 2 of the tray from top to bottom in the production zone B. Collector 12 is located between trays 10-30. Collector 12 is a disc distributor that redistributes the distilled liquid. A first reflux zone 2 and a second reflux zone 7 are respectively provided on both sides of collector 12. The liquid in collector 12 flows into the first reflux zone 2 and the second reflux zone 7 respectively. The reflux ratio of pre-separation zone A is 0.6. The top condenser 10 has a top reflux feed inlet 3 connected to the adjacent tower on one side of its bottom, and a top hydrogen chloride liquid phase outlet 4 on the other side; the top methane gas phase outlet 8 is provided on one side of the top condenser 10; the top reflux ratio of the adjacent tower is 0.4 (top reflux feed inlet 3 / top hydrogen chloride liquid phase outlet 4). The bottom reboiler 11 provides rising steam to the collector 12, and the ratio of the steam mass flow rate of the collector 12 is 0.6; the bottom reboiler 11 is connected to the adjacent column and has a bottom heavy component discharge port 6.

[0037] Example 12 The difference between this embodiment and embodiment 11 is that the adjacent column has 30 trays, the rectification section C has 10 trays, the stripping section D has 10 trays, the pre-separation zone A and the extraction zone B have 10 trays, and the reaction gas inlet 1 is located on the 5th tray of the pre-separation zone A; the reflux ratio of the pre-separation zone A is 0.5, and the rest of the operation is the same.

[0038] Example 13 The difference between this embodiment and embodiment 11 is that the adjacent column has 50 trays, the rectification section C has 30 trays, the stripping section D has 10 trays, the pre-separation zone A and the extraction zone B have 10 trays each, and the reaction gas inlet 1 is located on the 5th tray of the pre-separation zone A; the reflux ratio of the pre-separation zone A is 0.75, and the rest of the operation is the same.

[0039] Example 14 The difference between this embodiment and embodiment 13 is that the rectifying section C has 10 trays and the stripping section D has 30 trays; the rest of the operations are the same.

[0040] Example 15 The difference between this embodiment and embodiment 11 is that the reflux ratio at the top of the adjacent tower is 0.3, and the ratio of the steam mass flow rate of the collector is 0.5; the rest of the operations are the same.

[0041] Example 16 The difference between this embodiment and embodiment 11 is that the reflux ratio at the top of the adjacent tower is 0.5, and the ratio of the steam mass flow rate of the collector is 0.8; the rest of the operations are the same.

[0042] This application provides a method for separating methylphosphine dichloride. The reaction gas phase components enter the pre-separation zone of a partition wall column. Methane and hydrogen chloride are distilled off from the top of the partition wall column and reused after passing through a top condenser. Methylphosphine dichloride and phosphorus trichloride are discharged from the bottom of the partition wall column for further separation. Chloroalkanes and impurities are collected from the outlet on the right side of the partition wall column. The apparatus consists of a partition wall column, including a pre-separation zone, a collection zone, a rectification section, and a stripping section. The method for separating methylphosphine dichloride in this application does not require the use of alkaline solution to absorb hydrogen chloride, reducing the possibility of water entering the system. This method improves process safety; the obtained pure hydrogen chloride can be used to prepare high-value-added products such as triethyl orthoformate, or to prepare high-concentration hydrochloric acid for reuse, thus increasing added value; the removal of chloroalkanes makes the returned methane purer, resulting in higher MDP yield and better separation effect; the method achieves cleaner impurity separation and improves the stability of the reaction system during recycling; using a single diverter tower achieves multi-component separation, and by utilizing the low temperature at the top of the tower, the system energy consumption is further reduced, making it suitable for large-scale industrial production, highly efficient and environmentally friendly.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0044] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A process for the isolation of methylphosphine dichloride, characterized in that, Specifically comprising the following steps: The reaction gas phase component enters the pre-separation zone of the dividing wall column, methane and hydrogen chloride are distilled out from the top of the dividing wall column, and are reused after passing through the overhead condenser; methyl dichlorophosphine and phosphorus trichloride are discharged from the bottom of the dividing wall column, and are separated and distilled to obtain methyl dichlorophosphine; chloroalkane and impurities are discharged from the sampling outlet of the dividing wall column.

2. The process for separating methyl phosphinic dichloride according to claim 1, characterized in that, The reaction gas phase component comprises, in terms of mass percentage, 25-35 % methane, 10-15 % methyl dichlorophosphine, 45-55 % phosphorus trichloride, 1.5-2.5 % chloroalkane, and 3-5 % hydrogen chloride.

3. The process of claim 1, wherein the process is characterized by, The feeding temperature of the reaction gas phase component is 5-55 ℃, and the pressure is 0.1-1.0 MPaG.

4. The process of claim 1, wherein the process is characterized by, The temperature at the top of the dividing wall column is -110~-130 ℃, and the pressure is 0.20-0.70 MPaG; the temperature at the bottom is 100-125 ℃, and the pressure is 0.22-0.72 MPaG.

5. A separation apparatus for methyl dichlorophosphine comprising a dividing wall column, characterized in that, The middle part of the dividing wall column is provided with a pre-separation zone and a sampling zone, the upper part of the dividing wall column is provided with a rectification section, and a collector is arranged below the rectification section; the lower part of the dividing wall column is provided with a stripping section; the top end of the dividing wall column is connected with an overhead condenser, and the bottom end of the dividing wall column is connected with a bottom reboiler; the theoretical plate number of the dividing wall column is 30-50.

6. A device for separating methyl phosphine dichloride according to claim 5, characterized in that A partition plate is arranged between the pre-separation zone and the sampling zone, the theoretical plate number of the rectification section is 10-30, and the theoretical plate number of the stripping section is 10-30.

7. A device for separating methyl phosphine dichloride according to claim 5, characterized in that First and second reflux zones are respectively arranged on the two sides of the collector; the reflux ratio of the pre-separation zone is 0.5-0.

75.

8. The apparatus of claim 5, wherein the apparatus is characterized by: One side of the bottom of the overhead condenser is provided with an overhead reflux feeding port in communication with the dividing wall column, and the other side is provided with an overhead hydrogen chloride liquid phase discharge port; one side of the overhead condenser is provided with an overhead methane gas phase discharge port; the overhead reflux ratio of the dividing wall column is 0.3-0.

5.

9. The apparatus of claim 5, wherein the apparatus is characterized by: The bottom reboiler provides rising steam to the collector, the steam mass flow ratio of the collector is 0.5-0.8, and the bottom reboiler is in communication with the dividing wall column and is provided with a bottom heavy component discharge port.

10. The apparatus of claim 5, wherein the apparatus is characterized by: A reaction gas phase feeding port is arranged on the pre-separation zone, a side-line chloroalkane discharge port is arranged on the sampling zone, the reaction gas phase feeding port is arranged at 1 / 2-2 / 3 of the plate below the pre-separation zone, and the side-line chloroalkane discharge port is arranged at 1 / 3-1 / 2 of the plate from top to bottom in the sampling zone.

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