A method for preparing trialkylphosphine from liquid phosphine

Abstract

The present invention relates to a method for preparing trialkylphosphine from liquid phosphine, wherein low-temperature liquid phosphine and liquid olefin are successively added to a premixing kettle, mixed evenly and then heated to a target temperature as a premixed raw material for standby use, and then the premixed raw material and initiator solution are respectively added to a reactor containing a bottom material through a static pipeline mixer, the system temperature in the reactor is controlled to initiate a free radical addition reaction, and the reaction material is continuously extracted through a decompression extraction device, and the extracted material is subjected to rectification and separation to obtain the target product trialkylphosphine. The present invention uses purified low-temperature liquid phosphine as a raw material, not only realizing the high added value utilization of the phosphine tail gas, a byproduct of sodium hypophosphite, but also creating conditions for the liquid phase continuous reaction of phosphine and olefin, and avoiding the use and recovery of organic reaction solvents such as toluene.

Description

Technical Field

[0001] The invention relates to a method for preparing trialkyl phosphine by utilizing liquid phosphine, a byproduct in the production process of sodium hypophosphite. Background Art

[0002] Trialkylphosphine is an important and widely used organic phosphine intermediate, which can be mainly used to synthesize quaternary phosphonium salts, trialkylphosphine oxide and other products. Among them, quaternary phosphonium salts are a series of high-grade and high-efficiency algaecides and fungicides, which have many advantages such as high efficiency, high speed and broad spectrum; trialkylphosphine oxide (TRPO) is a lanthanide and actinide extractant, and is also used to separate and extract organic acids as food additives. Taking tri-n-butylphosphine as an example, the quaternary phosphonium salt synthesized from it is a broad-spectrum, high-efficiency and low-toxic antimicrobial agent, and is also a surfactant with excellent performance, with low foaming and wide applicable pH range. At the same time, the complexes formed by tri-n-butylphosphine and many transition metal elements are very important catalysts, as olefin polymerization catalysts, dibenzyl alcohol carbonylation catalysts, polybutadiene aminomethylation catalysts, unsaturated steroid selective hydrogenation catalysts, etc.; in addition, tri-n-butylphosphine can also be used as a phase transfer catalyst, which is widely used in medicine and pesticide synthesis. The preparation methods of trialkylphosphines mainly include phosphine-olefin method, Grignard reagent-phosphorus trichloride method, alkyl halide-sodium phosphide method, trialkylphosphine oxide reduction method and the like.

[0003] Among these synthetic routes, the most promising for industrialization is the phosphine method. The process of preparing alkyl phosphines by addition reaction of phosphine with olefins under the action of an initiator is the shortest, with the lowest cost, the highest yield and the least by-products. For example, Yu Weifa et al. (CN200810117469.8), Peter Hasting et al. (CN201110057830.4), Dai Xuanwu et al. (CN201910570079.4) and Li Juan (CN202010892732.1) used phosphine and olefins to synthesize trialkyl phosphines.

[0004] The process of synthesizing organic phosphorus products by reacting phosphine with olefins was developed as early as the 1950s, but the source of phosphine has always been the key to the process, among which the yellow phosphoric acid process and the phosphorous acid pyrolysis process are the main ones. In addition, the by-product phosphine produced by the sodium hypophosphite process is another important source, but the by-product phosphine tail gas contains up to 60% hydrogen and a small amount of nitrogen by volume. Such phosphine can only synthesize organic phosphorus products with low yield and uneconomically, and the reaction pressure is as high as 8 to 10 MPa. Therefore, how to take advantage of the industrial cost advantage of the by-product liquid phosphine of sodium hypophosphite, combine the characteristics of the raw materials, design and optimize the process, reduce the use of solvents and separation and recovery, reduce the reaction pressure, realize continuous reaction, improve the reaction safety, and realize the safe, efficient and economical synthesis of organic phosphine products is the problem to be solved by the present invention. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing trialkyl phosphine by using the purified liquid phosphine byproduct of sodium hypophosphite in order to solve the above problems.

[0006] The present invention provides a method for preparing trialkylphosphine using liquid phosphine as a raw material, comprising the following steps:

[0007] (1) First, the purified low-temperature liquid phosphine is transported to a pre-cooled premixing kettle. After the feeding of the liquid phosphine is completed, stirring is started and the liquid olefin is transported to the premixing kettle. After the feeding of the phosphine and the olefin is completed, the temperature is raised and the stirring and mixing are continued until the temperature reaches the target temperature. Then, the premixed materials and the initiator solution are respectively added to an addition reactor containing a bottom material through a static pipeline mixer. The temperature of the system in the reactor is controlled to initiate the addition reaction. Then, the reaction materials are continuously withdrawn through a pressure reduction withdrawal device to obtain a reaction discharge containing the target product trialkylphosphine.

[0008] (2) The vacuum extraction device releases a small amount of gaseous phosphine and olefins that have not reacted completely, and discharges the liquid reaction mixture containing trialkyl phosphine to the distillation system. The vacuum extraction device is connected to a pressure relief buffer tank for safe pressure relief, and the extraction pressure is controlled to 0.1 ~ 0.2MPa before discharging; in addition, the pressure relief buffer tank can also be used as an emergency pressure relief buffer tank for emergency discharge of phosphine and olefins when the addition reaction is abnormal and the pressure or temperature in the reactor exceeds the set value, and is discharged to the phosphine tail gas incineration system through a closed pipeline.

[0009] In step (1), the premixing kettle is precooled by a high and low temperature heat transfer oil integrated machine before feeding, so that the temperature inside the kettle reaches -30 ~ -40 ° C;

[0010] The temperature of low-temperature liquid phosphine is -60 ~ -80℃, and the feed pressure is 0.1 ~ 0.8MPa; after the liquid phosphine feed is completed, the temperature in the premixing kettle is -30 ~ -50℃;

[0011] The temperature of the liquid olefin is room temperature, the olefin feed pressure is 0.6 ~ 1.6MPa, and after the olefin feed is completed, the temperature in the premixing kettle is -10 ~ -30℃;

[0012] After the feeding of phosphine and olefins is completed, the material temperature in the premixing kettle is controlled by heating to be 25 ~ 35℃ and the pressure in the kettle is 1.0 ~ 2.0MPa. Under the above conditions, phosphine and olefins are evenly mixed in the liquid phase.

[0013] The initiator is any one of azobisisobutyronitrile, azobisisovaleronitrile and azobisisoheptanenitrile;

[0014] The initiator solvent used in the initiator solution is one of trialkylphosphine, dialkylphosphine and monoalkylphosphine or a mixture of several of them, and the concentration of the initiator solution is 2-4%; the solvent trialkylphosphine, dialkylphosphine or monoalkylphosphine comes from the separated product of the subsequent distillation process.

[0015] The above premixed materials and initiator solution are continuously added to the addition reactor containing the bottom material through a static pipeline mixer to ensure that the feeding process is continuous liquid phase feeding, so that the subsequent reaction is easier to carry out and the reaction efficiency is higher;

[0016] The filling volume of the bottom material in the addition reactor is 60-80% of the effective volume of the reactor, and the bottom material is a mixture of trialkylphosphine, dialkylphosphine and monoalkylphosphine prepared by batch reaction;

[0017] The feed flow of all raw materials continuously added through the static pipeline mixer is balanced with the withdrawal flow of the reaction materials continuously withdrawn through the pressure reduction withdrawal device to keep the material level in the reactor within the set range, and the average residence time of the withdrawn materials is controlled at 3.5 ~ 6h.

[0018] The technical scheme of the present invention has the following beneficial effects: utilizing the properties of low-temperature liquid phosphine produced as a byproduct of sodium hypophosphite, the feed pressure of phosphine and olefins is reduced, low-pressure liquid-phase mixing of phosphine and olefins is achieved, the use of a large amount of organic solvents is avoided, and conditions are created for a liquid-phase continuous reaction of phosphine and olefins; compared with a kettle-type batch reaction, the reaction pressure of the system is greatly reduced, the heat release in the reaction process is stable and easy to control, the temperature and pressure fluctuations of the reaction system are small, the risk of reaction runaway is significantly reduced, and the safety of the reaction is greatly improved; at the same time, the problems of equipment metal fatigue and low production efficiency caused by frequent cooling and heating of the reactor in the batch production process are avoided, and the production efficiency and safety reliability are significantly improved. DETAILED DESCRIPTION

[0019] Example 1 Preparation of reaction base material for synthesizing tri-n-butylphosphine by continuous reaction method

[0020] First, the temperature in the 100L premix kettle is controlled at -30 ~ -40℃ by the high and low temperature heat transfer oil integrated machine, and then 8.0kg of phosphine is added, the temperature of phosphine is controlled at -70 ~ -80℃, and the feed pressure is controlled at 0.2 ~ 0.5MPa; stirring is turned on, and then 39kg of n-butene is added by a diaphragm metering pump, and the feed pressure is controlled at 0.4 ~ 0.7MPa. After the feeding is completed, the temperature in the premix kettle is -20 ~ -30℃; the temperature in the premix kettle is controlled at 25 ~ 35℃ and the pressure is 1.0 ~ 1.5MPa by the heat transfer oil system, and all the above premixed materials are added to the 100L addition reactor by the diaphragm metering pump. After the feeding is completed, the temperature in the addition reactor is controlled at 82 ~ 85℃ and the pressure is 3.0 ~ 3.5MPa; after the temperature and pressure are stabilized, 6.0kg of tri-n-butylphosphine solution of azobisisovaleronitrile is slowly added through a diaphragm metering pump, the dropwise addition time is 3~4h, the concentration of the initiator solution is 2%, and the initiator solution is added and the reaction is continued for 1h. After the reaction is completed, the pressure in the kettle is 1.0~1.5MPa. The above-mentioned material containing tri-n-butylphosphine synthesized by the intermittent reaction method has an average composition of 3~5% n-butene, 1~3% mono-n-butylphosphine, 5~10% di-n-butylphosphine, and 80~85% tri-n-butylphosphine.

[0021] In the present invention, it is used as the reaction base material for synthesizing tri-n-butylphosphine by continuous reaction method. During the addition reaction, when phosphine and n-butene are premixed and fed, and then heated to the target reaction temperature through the heat transfer oil system, the pressure in the addition reactor is as high as 3-4MPa. At the same time, the addition reaction is an exothermic reaction. If the heat released by the reaction cannot be removed in time through the circulating cooling system, or the initiator solution is accelerated too fast, the temperature of the reaction system may be out of control, thereby accelerating the addition reaction, causing the reaction system to be out of control, and the temperature and pressure to rise abnormally. If the above situation occurs in the present invention, the following emergency interlocking measures will be taken: (1) Immediately stop feeding the initiator solution; (2) Start the emergency cooling system; (3) Start the safety relief system, and gradually release the pressure in the reactor to a safe and controllable range through the automatic safety relief valve. The safety relief system is equipped with a 5000L pressure relief buffer tank and an exhaust gas incineration system. The pressure relief buffer tank can buffer the relief pressure to within 20KPa, and then slowly release it to the exhaust gas incineration system.

[0022] Example 2 Synthesis of tri-n-butylphosphine by continuous reaction method

[0023] First, the reaction base material required for synthesizing tri-n-butylphosphine by continuous reaction method was prepared according to the method in Example 1, and kept warm for later use.

[0024] The temperature in the 100L premix kettle was controlled at -30 ~ -40°C by a high and low temperature heat transfer oil integrated machine, and then 8.0kg of phosphine was added, the temperature of phosphine was controlled at -70 ~ -80°C, and the feed pressure was controlled at 0.2 ~ 0.5MPa; stirring was turned on, and 37kg of n-butene was added using a diaphragm metering pump, and the feed pressure was controlled at 0.4 ~ 0.7MPa. After the feeding was completed, the temperature in the premix kettle was -20 ~ -30°C; the temperature in the premix kettle was controlled at 25 ~ 35°C and the pressure was controlled at 1.0 ~ 1.5MPa by a heat transfer oil system, and it was used after the temperature and pressure were stable; the temperature in the addition reactor containing the reaction base material was controlled at 85 ~ 88°C by a heat transfer oil system (relative to Example 1, the system pressure here is after the intermittent reaction is completed, the system pressure itself is 1.0 ~ 1.5MPa (pressure is the saturated vapor pressure of the raw materials such as phosphine and isobutylene that have not been completely reacted)), after the temperature stabilizes, the above-mentioned premixed materials and initiator solution are continuously added to the addition reactor through a static pipeline mixer, wherein the initiator solution is a tri-n-butylphosphine solution of azobisisovaleronitrile with a concentration of 2.2%; the feed flow rate of the premixer material is 14.2L / h, and the feed flow rate of the initiator solution is 1.3L / h; then the pressure reduction extraction device is used to continuously extract the initiator solution from the addition reactor. The material is discharged, the discharge flow rate is 15.5L / h, and the average residence time of the discharged material is 4.5h; the material is discharged after the pressure is released to 0.1~0.2MPa through the pressure reducing device and the pressure relief buffer tank, and the addition reaction completed material containing mono-n-butylphosphine, di-n-butylphosphine and tri-n-butylphosphine is obtained; the average composition is as follows through gas chromatography analysis: n-butene 3~5%, mono-n-butylphosphine 3~5%, di-n-butylphosphine 10~15%, tri-n-butylphosphine 75~80%. Average residence time*continuous discharge flow rate=addition reactor bottom material volume (default is fixed value); the sum of continuous feed flow rate=continuous discharge flow rate (maintaining the reactor liquid level stable).

[0025] Since the addition reaction is an exothermic reaction, if the heat released by the reaction cannot be removed in time through the thermal oil temperature control system, or the raw material feeding speed is too fast, it is possible to cause the temperature of the reaction system to get out of control, thereby accelerating the addition reaction, causing the reaction system to get out of control, and the temperature and pressure to rise abnormally. In the patent of this invention, if the above situation occurs, the following emergency interlocking measures will be taken: (1) Immediately stop feeding the premixed materials and initiator solution; (2) Start the emergency cooling system; (3) Start the safety relief system, and gradually release the pressure in the reactor to a safe and controllable range through the automatic safety relief valve. The safety relief system is equipped with a 5000L pressure relief buffer tank and an exhaust gas incineration system. The pressure relief buffer tank can buffer the relief pressure to within 10KPa, and then slowly release it to the exhaust gas incineration system.

[0026] Example 3 Synthesis of tri-n-butylphosphine by continuous reaction method

[0027] First, the reaction base material required for synthesizing tri-n-butylphosphine by continuous reaction method was prepared according to the method in Example 1, and kept warm for later use.

[0028] The temperature in the 100L premix kettle was controlled at -30 ~ -40℃ by the high and low temperature heat transfer oil integrated machine, and then 8.0kg of phosphine was added, the temperature of phosphine was controlled at -60 ~ -70℃, and the feed pressure was controlled at 0.3 ~ 0.6MPa; stirring was started, and 39kg of n-butene was added using a diaphragm metering pump, and the feed pressure was controlled at 0.5 ~ 0.8MPa. After the feeding was completed, the temperature in the premix kettle was -15 ~ -25℃; the temperature in the premix kettle was controlled at 25 ~ 35℃, pressure at 1.0~1.5MPa, and standby after the temperature and pressure are stable; the temperature in the addition reactor filled with the reaction base material is controlled at 85~88℃ through the heat transfer oil system, and after the temperature is stable, the above-mentioned premixed materials and initiator solution are continuously added to the addition reactor through a static pipeline mixer, wherein the initiator solution is a di-n-butylphosphine solution of azobisisovaleronitrile with a concentration of 3%; the feed flow rate of the premixed reactor material is 11.6L / h, and the feed flow rate of the initiator solution is 1.1L / h; and then the reduction The pressure extraction device continuously extracts materials from the addition reactor, with an extraction flow rate of 12.7L / h and an average residence time of the extracted materials of 5.5h. During the material extraction process, the pressure is released to 0.1~0.2MPa through a pressure reducing device and a pressure relief buffer tank, and then the material is discharged to obtain an addition reaction completed material containing mono-n-butyl phosphine, di-n-butyl phosphine and tri-n-butyl phosphine. The average composition thereof is as follows through gas chromatography analysis: 3~5% of n-butene, 1~3% of mono-n-butyl phosphine, 5~10% of di-n-butyl phosphine and 80~85% of tri-n-butyl phosphine.

[0029] Example 4 Synthesis of tri-n-butylphosphine by continuous reaction method

[0030] First, the reaction base material required for synthesizing tri-n-butylphosphine by continuous reaction method was prepared according to the method in Example 1, and kept warm for later use.

[0031] The temperature in the 100L premix kettle was controlled at -30 ~ -40℃ by the high and low temperature heat transfer oil integrated machine, and then 8.0kg of phosphine was added, the temperature of phosphine was controlled at -60 ~ -70℃, and the feed pressure was controlled at 0.3 ~ 0.6MPa; stirring was started, and 41kg of n-butene was added using a diaphragm metering pump, and the feed pressure was controlled at 0.5 ~ 0.8MPa. After the feeding was completed, the temperature in the premix kettle was -15 ~ -25℃; the temperature in the premix kettle was controlled at 25 ~ 35℃ and the pressure at 1.0 ~ 1.5MPa by the heat transfer oil system, and it was used for standby after the temperature and pressure were stable; the temperature in the addition reactor containing the reaction base material was controlled at 85 ~ 88°C, after the temperature stabilizes, the above-mentioned premixed materials and initiator solution are continuously added to the addition reactor through a static pipeline mixer, with a concentration of 4.0%, wherein the initiator is azobisisovaleronitrile, and the initiator solvent is a mixed solvent of mono-n-butylphosphine and di-n-butylphosphine (ratio is 1:3); the feed flow rate of the premixed reactor material is 11.6L / h, and the feed flow rate of the initiator solution is 1.1L / h; then the material is continuously withdrawn from the addition reactor through a decompression withdrawal device, with a withdrawal flow rate of 12.7L / h, and the average residence time of the withdrawn material is 5.5h; during the material withdrawal process, the pressure is released to 0.1~0.2MPa through a decompression device and a pressure relief buffer tank, and then the material is discharged to obtain an addition reaction completed material containing mono-n-butylphosphine, di-n-butylphosphine and tri-n-butylphosphine; the average composition thereof is analyzed by gas chromatography as follows: n-butene 5~10%, mono-n-butylphosphine 1~3%, di-n-butylphosphine 3~7%, and tri-n-butylphosphine 80~85%.

[0032] Example 5 Synthesis of tri-n-butylphosphine by continuous reaction method

[0033] The method steps are the same as those in Example 3, except that the concentration of the initiator solution is 1.5%. The average composition of the produced material is analyzed by gas chromatography as follows: 3-5% n-butene, 5-10% mono-n-butyl phosphine, 10-15% di-n-butyl phosphine, and 70-75% tri-n-butyl phosphine; if the concentration of the initiator solution is too low, the yield of the target product tri-n-butyl phosphine of the addition reaction will be significantly lower than that in Example 3, and the average yield will decrease by 10-15%.

[0034] Example 6 Synthesis of tri-n-butylphosphine by continuous reaction method

[0035] The method steps are the same as those in Example 3, except that the concentration of the initiator solution is 4.5%. The average composition of the extracted material is analyzed by gas chromatography as follows: 3-5% n-butene, 0-2% mono-n-butyl phosphine, 5-10% di-n-butyl phosphine, and 80-85% tri-n-butyl phosphine; if the concentration of the initiator solution is too high, the yield of the target product tri-n-butyl phosphine of the addition reaction is at the same level as that of Example 3, but with the increase of the initiator concentration, the addition reaction speed increases. Since the reaction is a violent exothermic reaction, it is easy to have overtemperature and overpressure phenomena, resulting in overload operation of the temperature control system, or starting the interlock to stop feeding, and re-feeding after the temperature returns to normal; or starting the emergency discharge to cause the system to stop in an emergency. If the concentration of the initiator solution is too high, not only the difficulty of reaction control will increase, but also the increase in initiator consumption will also increase production costs.

[0036] Example 7 Synthesis of tri-n-butylphosphine by continuous reaction method

[0037] The method steps are the same as those in Example 3, and the average residence time of the material continuously produced from the addition reactor only by the decompression production device is 3 hours. The average composition of the produced material is analyzed by gas chromatography as follows: 5-10% n-butene, 5-10% mono-n-butyl phosphine, 15-20% di-n-butyl phosphine, and 65-70% tri-n-butyl phosphine; if the average residence time of the produced material is less than 3.5 hours, which is too short, the yield of the target product tri-n-butyl phosphine of the addition reaction will be significantly lower than that in Example 3, and the average yield will decrease by 15-20%.

[0038] Example 8 Synthesis of tri-n-butylphosphine by continuous reaction method

[0039] The method steps are the same as those in Example 3, and the average residence time of the material continuously extracted from the addition reactor only by the decompression extraction device is 7 hours. The average composition of the extracted material is analyzed by gas chromatography as follows: 2-3% of n-butene, 1-3% of mono-n-butyl phosphine, 10-15% of di-n-butyl phosphine, and 81-86% of tri-n-butyl phosphine; if the average residence time of the extracted material is greater than 6 hours, which is too long, the yield of the target product of the addition reaction, tri-n-butyl phosphine, is at the same level as that in Example 3, but as the average residence time of the extracted material increases, the production efficiency is bound to decrease, with an average decrease of 20-30%.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution, improvement, etc. made without exceeding the technical solution described in the claims shall be included in the protection scope of the present invention.

Claims

1. A method for preparing trialkylphosphine from liquid phosphine, characterized in that: The following steps are involved: (1) First, low-temperature liquid phosphine is transported to a pre-cooled premixing kettle. After the liquid phosphine is fed, stirring is started and liquid olefin is transported to the premixing kettle. The olefin is any one of n-butene, isobutylene and propylene. After the phosphine and olefin are fed, the temperature is raised and stirring is continued. After the mixture is evenly mixed and reaches the target temperature, the mixture is kept warm for standby use. (2) respectively mixing the above-mentioned premixed raw materials and initiator solution uniformly through a static pipeline mixer and continuously adding them into an addition reaction kettle filled with a bottom material, controlling the system temperature in the reaction kettle to initiate the addition reaction, and then continuously withdrawing the reaction materials through a pressure reduction withdrawal device to obtain a reaction discharge containing the target product trialkylphosphine; The initiator solvent used in the initiator solution is one or a mixture of trialkylphosphine, dialkylphosphine, monoalkylphosphine; The filling volume of the bottom material in the addition reactor is 60-80% of the effective volume of the reactor. The bottom material is a mixture of trialkylphosphine, dialkylphosphine and monoalkylphosphine prepared by intermittent reaction. The sum of the feed flow rates of phosphine, olefin premix and initiator solution is balanced with the withdrawal flow through the pressure reduction withdrawal device to keep the material level in the reactor within the set range. The average residence time of the withdrawn material is controlled at 3.5-6h.

2. The method according to claim 1, characterized in that In step (1), the premixing kettle is precooled by a high and low temperature heat transfer oil integrated machine before feeding, so that the temperature inside the kettle reaches -30 ~ -40 °C.

3. The method according to claim 1, characterized in that In step (1), the temperature of the low-temperature liquid phosphine is -60 to -80°C, and the feed pressure is 0.1 to 0.8 MPa; after the liquid phosphine is fed, the temperature in the kettle is -30 to -50°C.

4. The method according to claim 1, characterized in that: In step (1), the temperature of the liquid olefin is room temperature, the feed pressure is 0.6 to 1.6 MPa, and after the liquid olefin feed is completed, the temperature in the kettle is -10 to -30°C.

5. The method according to claim 1, characterized in that After the phosphine and olefin feeding in step (1) is completed, the material temperature in the kettle is heated to control the temperature to 25-35°C and the pressure in the kettle to 1.0-2.0 MPa.

6. The method according to claim 1, characterized in that In step (2), the temperature in the reactor is controlled according to the temperature-half-life curve of the initiator. When azobisisobutyronitrile or azobisisovaleronitrile is used as the initiator, the temperature in the reactor is 85-88°C and the pressure in the reactor is 1.0-2.5 MPa; when azobisisoheptanenitrile is used as the initiator, the temperature in the reactor is 70-73°C and the pressure in the reactor is 1.0-2.0 MPa.

7. The method according to claim 1, characterized in that In step (1), the molar ratio of liquid phosphine to olefin is 1:2.8 to 1:3.1, and the mass ratio of the amount of initiator added to the amount of phosphine added is 1.5 to 3%.

8. The method according to claim 1, characterized in that The initiator used in the initiator solution in step (2) is any one of azobisisobutyronitrile, azobisisovaleronitrile and azobisisoheptanenitrile.

9. The method according to claim 1, characterized in that: The concentration of the initiator solution in step (2) is 2-4%.