Method for preparing sodium diisobutyl dithiophosphinate by using microreactor
By initiating stepwise free radical addition and nucleophilic substitution reactions through photothermal synergy in microreactors, the problems of easy clogging and high by-product levels in microreactors were solved, achieving high-yield and high-purity production of sodium diisobutyldithiophosphonate and improving the utilization efficiency of phosphine.
Patent Information
- Application Number
- CN202511417424.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-02-13
AI Technical Summary
Microreactors are prone to clogging in free radical addition reactions, resulting in a high proportion of byproducts, which leads to a decrease in product yield and purity. Furthermore, traditional methods have low utilization efficiency for phosphine byproducts.
A stepwise free radical addition reaction initiated by photothermal synergy was carried out in a microreactor. Combining a pre-activation zone, a transition zone, and a main reaction zone, isobutylene was dissolved using supercritical carbon dioxide. The initiator concentration and reaction temperature were controlled, and byproducts were separated. Sodium diisobutyldithiophosphonate was prepared by nucleophilic substitution reaction.
It improved the yield of diisobutylphosphine, suppressed the formation of byproducts, avoided microreactor clogging, and achieved safe, reliable, and efficient production with high product purity, low cost, and high phosphine utilization rate.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a method for preparing sodium diisobutyl dithiophosphinate by using a micro-reactor. BACKGROUND
[0002] In the production process of sodium hypophosphite, phosphine tail gas is an inevitable by-product. At present, the conventional treatment method for the phosphine by-product is to synthesize organic phosphorus compounds such as flame retardants, bactericides, organic intermediates, etc. by using the phosphine tail gas as raw material. For example, sodium diisobutyl dithiophosphinate (DTPINa) is an important industrial chemical, which can be used as a flotation collector, a lubricating oil additive, a chemical synthesis intermediate, etc. The conventional synthesis process of sodium diisobutyl dithiophosphinate is to first synthesize diisobutyl phosphine by a free radical addition reaction of phosphine and isobutene, and then to generate sodium diisobutyl dithiophosphinate by a substitution reaction.
[0003] The free radical addition reaction is the key to the synthesis. In order to further improve the reaction efficiency, micro-reactors gradually replace conventional reaction kettles in experiments and industries. The micro-reactor (also known as a micro-channel reactor) is a continuous flow reaction equipment with a feature size of microns to millimeters. The micro-channel network is precisely processed inside, so that the reactants flow, mix and react continuously in the micro-channel network. The micro-reactor has advantages of safety, high efficiency, environmental protection, energy saving, etc. Therefore, the use of the micro-reactor in the free radical addition reaction is beneficial to improving the yield of diisobutyl phosphine. However, the micro-reactor has the disadvantage of easy clogging, especially in the free radical addition reaction. The proportion of by-products such as monoisobutyl phosphine, triisobutyl phosphine and oxidation by-products is high, which not only causes the yield and purity of the product to decrease, but also is the root cause of the clogging of the micro-reactor. SUMMARY
[0004] In view of this, the application aims to provide a method for preparing sodium diisobutyl dithiophosphinate by using a micro-reactor, and aims to solve at least one technical problem in the background art.
[0005] The application is implemented in the following manner: The application provides a method for preparing sodium diisobutyl dithiophosphinate by using a micro-reactor, which comprises the following steps: S1, phosphine gas is sequentially subjected to impurity removal pretreatment, pre-cooling and drying, and deep cooling to obtain high-purity liquid phosphine; S2, liquid phosphine and isobutene are used as raw materials, an initiator is added, and a photo-thermal synergistic initiated free radical addition reaction is performed in a micro-reactor to synthesize diisobutyl phosphine; the micro-reactor comprises a straight-through pre-activation zone, a transition reaction zone and a main reaction zone; S3, diisobutyl phosphine is separated by rectification; S4, under the conditions of pressurization and heating, the diisobutyl phosphine and the sodium hydroxide solution are added to the sulfur source solution, a nucleophilic substitution reaction occurs, and the reaction is preserved to prepare the sodium diisobutyl dithiophosphinate.
[0006] Further, the free radical addition reaction specifically includes: S21, after part of the isobutene is pre-cooled into a liquid state, the isobutene is mixed with an initiator solution to prepare solution A; the part of the isobutene is 40% to 45% of the total amount of the isobutene; and the remaining isobutene is dissolved in a solvent to prepare solution B; S22, solution A is mixed with liquid phosphine in a mixer arranged at the inlet end of a pre-activation zone, under ultraviolet irradiation and low temperature of-10℃ to 5℃, the mixture stays in the pre-activation zone for a first time; S23, the reaction product of S22 enters a transition reaction zone pre-set to 25℃ to 35℃, stays for a second time under ultraviolet irradiation; S24, the reaction product of S23 is synchronously added to a main reaction zone pre-heated to 70℃ to 150℃ with solution B, and stays for a third time.
[0007] Further, the first time is 2min to 5min; the second time is 5min to 10min; and the third time is 10min to 30min.
[0008] Further, the amount of the liquid phosphine exceeds 3% to 10% of the theoretical amount.
[0009] Further, the initiator is azobisisobutyronitrile, azobisisoamyl nitrile or azobisisoheptyl nitrile. Further, the solvent for dissolving the isobutene is supercritical carbon dioxide.
[0010] Further, before the micro-reactor starts to react, the micro-reactor is purged and pressure-kept for leak detection with high-purity inert gas.
[0011] Further, the phosphine gas is a by-product of sodium hypophosphite production; and the impurity removal pretreatment is used to remove water vapor, yellow phosphorus vapor and solid impurities contained in the by-product of sodium hypophosphite production, so as to finally obtain the purified phosphine gas.
[0012] Further, the temperature of the pre-cooled and dried is-20℃ to-40℃.
[0013] Further, the specific steps for rectifying and separating the diisobutyl phosphine are as follows: the gas in the micro-reactor is discharged, the liquid mixture after the reaction is subjected to normal pressure distillation and reduced pressure distillation, and the mono-isobutyl phosphine, diisobutyl phosphine and tri-isobutyl phosphine are separated.
[0014] Compared with the prior art, the present application has the following beneficial effects: 1.The present application uses sodium hypophosphite production by-product phosphine as raw material, and prepares sodium diisobutyl dithiohypophosphite through free radical addition reaction and substitution reaction, wherein the free radical addition reaction is carried out in a microreactor and adopts a step-by-step operation of photo-thermal synergistic initiation, effectively improving the yield of the target product diisobutyl phosphine, inhibiting the generation of by-products, and avoiding the blockage of the microreactor.
[0015] 2.Compared with the traditional high-pressure reaction kettle, the microchannel reaction has the advantages of fast reaction speed, easy precise control, few side reactions, safety and reliability, high product purity, low cost, high utilization rate of phosphine and many other advantages; compared with the traditional reactor, the microchannel reaction does not have the uncontrollable effect of scale-up and the safety risk of scale-up, and only needs to increase the number in parallel, that is, the so-called "scale-up by number" can be realized.
[0016] 3.The present application uses sodium hypophosphite production by-product phosphine as raw material, and through impurity removal and secondary purification by low-temperature treatment, the phosphine is frozen to a liquid state, and the purity of the purified phosphine reaches 99%.
[0017] 4.The free radical addition in the present application undergoes a low-temperature pre-activation zone and a medium-temperature transition zone before thermal reaction, improving the safety and controllability of the reaction. In addition, the pre-activation zone and the transition zone are irradiated with ultraviolet light to weakly activate the initiator, and then a certain first step addition occurs in the pre-activation zone and the transition zone, that is, monoisobutyl phosphine is generated, while excessive initiation is avoided, which causes the reaction to be uncontrollable.
[0018] 5.In the main reaction zone of the free radical addition in the present application, supercritical carbon dioxide is used to dissolve isobutene, creating a homogeneous reaction environment, which is conducive to the full and rapid contact between isobutene and phosphine in the subsequent main reaction zone, thereby making the reaction rate close to its intrinsic kinetic limit, greatly shortening the reaction time and improving the yield.
[0019] 6.In the free radical addition step of the present application, the raw materials are added separately, and the initiator, excess phosphine and insufficient isobutene are added first, which is to ensure that there is a very high concentration of phosphine around the free radical intermediate during the first step addition and the subsequent second step addition, so that it preferentially takes H atoms and "terminates", rather than reacting with the third molecule of isobutene to generate triisobutyl phosphine, thereby reducing the content of by-products. DETAILED DESCRIPTION
[0020] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with examples. It should be understood that the specific implementation cases described herein are only used to explain the present application, and are not used to limit the present application. The parameter ranges mentioned in the present specification include the end point values of the parameter ranges, and the rest of the parameter ranges include the end point values.
[0021] The method for preparing sodium diisobutyl dithiophosphinate by using a microreactor comprises steps S1 to S4.
[0022] S1, the phosphine gas is sequentially subjected to impurity removal pretreatment, precooling and drying, and deep cooling to obtain high-purity liquid phosphine.
[0023] The phosphine gas of the present application is a by-product of sodium hypophosphite production, which contains water vapor, yellow phosphorus vapor and solid impurities, and the purpose of the impurity removal pretreatment is to remove the above-mentioned impurities. The specific impurity removal process can be adjusted according to the actual industrial impurity situation. The conventional impurity removal steps are as follows: the phosphine-containing tail gas enters a spray gas washing tower, is cleaned by alkali liquor spraying to remove yellow phosphorus vapor and part of solid impurities in the gas; enters a gas cabinet to adjust the gas flow, and after coming out of the gas cabinet, is washed by a two-stage Venturi scrubber to mainly remove particulate matters in the gas; is then washed by a packed tower; finally, is subjected to cyclone gas-liquid separation and wire mesh demister to reduce liquid entrainment in the gas; and finally, the purified phosphine gas is obtained. In specific implementation, the impurity removal steps can be adjusted according to actual needs, which are not limited to the above-mentioned steps.
[0024] The purpose of the precooling and drying is to remove the residual water vapor in the purified phosphine gas, and the precooling and drying temperature is -20℃ to -40℃.
[0025] The purpose of the deep cooling is to form high-purity liquid phosphine. After being subjected to low-temperature treatment at -84℃ or below by liquid nitrogen, the phosphine gas becomes liquid, realizing the re-separation and purification of the phosphine from non-condensable gases.
[0026] S2, liquid phosphine and isobutene are used as raw materials, an initiator is added, and a free radical addition reaction is carried out in a microreactor to synthesize diisobutyl phosphine.
[0027] The microreactor comprises a straight-through pre-activation zone, a transition reaction zone and a main reaction zone. Before the microreactor starts to react, the microreactor is purged and pressure-maintained for leak detection by using high-purity inert gas (such as helium, argon, etc.). S2 specifically comprises S21-S24.
[0028] S21, part of the isobutene is pre-cooled to liquid state and mixed with an initiator solution to prepare solution A; the part of the isobutene is 40% to 45% of the total amount of isobutene; and the remaining isobutene is dissolved in a solvent to prepare solution B.
[0029] The initiator is azobisisobutyronitrile, azobisisopentyl nitrate or azobisisoheptyl nitrate; the initiator dosage is 0.5% to 5% of the molar dosage of phosphine, preferably 1% to 3%, and the specific dosage can be adjusted according to the actual needs. The isobutene and initiator in this step are treated with anhydrous water, and the solvent of the initiator solution is an anhydrous inert solvent allowed in the art, such as n-hexane or cyclohexane, etc. The mass concentration of the initiator in the initiator solution is about 0.5% to 2%, and n-hexane is selected as the anhydrous inert solvent in the following examples, and azobisisobutyronitrile is selected as the initiator, and the concentration is 0.5%, but not limited thereto.
[0030] The solvent for dissolving isobutene is supercritical carbon dioxide. In a specific implementation, supercritical carbon dioxide (scCO2) is a special fluid state at a specific temperature (> 31.1°C) and pressure (> 7.39 MPa). Compared with directly using isobutene, the advantage of using supercritical carbon dioxide to dissolve isobutene as a reaction raw material is that supercritical carbon dioxide dissolves isobutene to form a uniform supercritical fluid phase, thereby creating a homogeneous reaction environment, which is conducive to the full and rapid contact between isobutene and phosphine in the subsequent main reaction zone, thereby making the reaction rate close to its intrinsic kinetic limit, greatly shortening the reaction time and improving the yield. In addition, the reaction of isobutene and phosphine is an exothermic reaction, and isobutene is a gas under normal conditions. The safety is low during the exothermic reaction process. The present application greatly improves the safety by dissolving it in supercritical carbon dioxide, and supercritical carbon dioxide has very high heat capacity and thermal conductivity, which can quickly absorb and disperse the heat released during the reaction, effectively eliminating the heat concentration in the micro-reactor channel, thereby inhibiting the side reactions and temperature runaway accidents caused by excessive temperature.
[0031] The step of dissolving isobutene in a solvent is to pump isobutene into a container of supercritical carbon dioxide. The specific dosage ratio can be adjusted according to the temperature and pressure conditions, and a homogeneous phase is generally formed. In the following examples, isobutene and supercritical carbon dioxide are mixed at 50°C and 15 MPa, and isobutene accounts for about 20% of the total moles of the mixture.
[0032] In a specific implementation, the initiator generates free radicals under high temperature / ultraviolet irradiation, the free radicals attack phosphine (PH3), take away a hydrogen atom to generate a phosphine radical (-PH2), and then undergo a radical addition reaction with isobutene. The possible products in this process are: mono-isobutyl phosphine, di-isobutyl phosphine, and tri-isobutyl phosphine. Among them, the reaction formula of phosphine and isobutene to synthesize di-isobutyl phosphine is: PH3+2CH2=C(CH3)2→H-P[CH2CH(CH3)2]2. In a theoretical case, the molar ratio of phosphine to isobutene is 1:2. In order to reduce the excessive alkylation to generate tri-isobutyl phosphine, the amount of phosphine is 3% to 10% more than the theoretical amount, and the molar ratio of phosphine to isobutene is 1.03 to 1.1:2.
[0033] The microreactor has excellent mass and heat transfer efficiency, improves the efficiency of the radical addition reaction, and improves the selectivity. Compared with a conventional reaction kettle, the reaction time is greatly reduced. The initiator is a thermal initiator. If it is directly introduced into the heating reaction stage, the rapid gasification of liquid phosphine, liquid isobutene and other raw materials will cause abnormal pressure in the reactor and is not easy to control. Therefore, the present application undergoes a low-temperature pre-activation zone (i.e., S22) and a medium-temperature transition zone (i.e., S23) before the thermal reaction, thereby improving the safety and controllability of the reaction. In addition, the pre-activation zone and the transition zone apply ultraviolet irradiation to weakly activate the initiator, and then a certain first step addition occurs in the pre-activation zone and the transition zone, i.e., mono-isobutyl phosphine is generated.
[0034] S22, solution A is mixed with liquid phosphine in a mixer provided at the inlet end of the pre-activation zone. Under ultraviolet irradiation and at a low temperature of -10°C to 5°C, the mixture stays in the pre-activation zone for a first time.
[0035] In a specific implementation, the mixer is preferably a Y-shaped mixer or a T-shaped mixer; the first time is 2 min to 5 min, for example, it can be 2 min, 3 min, or 5 min; but it is not limited to the listed values, and other values not listed in the value range are also applicable; the temperature of isobutene in solution A and liquid phosphine is relatively low, and after they are mixed with solution A, the temperature in this step is relatively low.
[0036] In this step, all the initiators, excess phosphine and insufficient isobutene are added, so as to ensure that there is a very high concentration of phosphine around the free radical intermediate in the first step addition and the subsequent second step addition, so that it preferentially takes away the H atom and is "terminated", rather than reacting with the third molecule of isobutene to generate tri-isobutyl phosphine.
[0037] S23, the reaction product of S22 enters a transition reaction zone pre-set to 25°C to 35°C, stays for a second time under ultraviolet irradiation, and then enters the heating reaction stage. The second time is 5 min to 10 min, for example, can be 5 min, 8 min, 10 min; but not limited to the listed values, other values not listed in the range of values are also applicable.
[0038] The reaction product of S24, S23 is added to the main reaction zone preheated to 70 DEG C to 150 DEG C synchronously with solution B, and is kept for a third time.
[0039] The temperature of the main reaction zone is 70 DEG C to 150 DEG C, for example, can be 70 DEG C, 90 DEG C, 100 DEG C, 120 DEG C, 150 DEG C; but not limited to the listed values, other values not listed in the range of values are also applicable. Preferably 70 DEG C to 90 DEG C, higher safety in this temperature range.
[0040] The third time is 10 min to 30 min, for example, can be 10 min, 20 min, 30 min; but not limited to the listed values, other values not listed in the range of values are also applicable.
[0041] S3, rectification separation of diisobutyl phosphorus; the specific steps are: first, the gas in the microreactor is discharged, the liquid mixture after reaction is first normal pressure gradient distillation (first 30 DEG C to 40 DEG C, then 60 DEG C to 70 DEG C) to remove the solvent, and then vacuum distillation to separate monoisobutyl phosphorus, diisobutyl phosphorus and triisobutyl phosphorus.
[0042] The conditions of vacuum distillation can be adjusted according to actual needs, not limited to this, the following examples are used: using an oil bath as the heat source of the distillation device, first slowly start the vacuum pump to reduce the system pressure to the required value, slowly increase the oil bath temperature, distill under the condition of about 10 mmHg to 20 mmHg, 30 DEG C to 50 DEG C, mainly collect light component monoisobutyl phosphorus; then gradually increase the oil bath temperature, and further adjust the vacuum degree as needed, distill under the condition of about 30 mmHg to 50 mmHg, 90 DEG C to 110 DEG C, mainly collect diisobutyl phosphorus; finally, then gradually increase the oil bath temperature, and further adjust the vacuum degree as needed, distill under the condition of about 5 mmHg to 10 mmHg, 130 DEG C to 150 DEG C, the time node of each stage distillation is ended when the distillation component no longer increases.
[0043] S4, under the conditions of pressurization and heating, diisobutyl phosphorus and sodium hydroxide solution are added to the sulfur source solution to occur nucleophilic substitution reaction, and diisobutyl sodium dithiophosphinate is prepared by keeping the reaction.
[0044] In a reaction kettle, sulfur (purity 98%) and a proper amount of deionized water are added, and under stirring, diisobutyl phosphine prepared in S3 and liquid alkali (mass concentration 32%) are slowly metered and added, the molar ratio of diisobutyl phosphine to sulfur is controlled to be 1:1, the reaction temperature is controlled to be 75-85°C, the pressure is controlled to be 0-10 bar, after the metered material is added, the material is finally adjusted to pH 7-8 with liquid alkali, and the temperature is kept for 3-3.5 hours, to generate a diisobutyl dithiophosphinic acid sodium solution (DTPINa).
[0045] Example 1 The method for preparing diisobutyl dithiophosphinic acid sodium by using a microreactor comprises steps S1-S4.
[0046] S1, phosphine tail gas, a byproduct of sodium hypophosphite production, enters a spray washing tower and is cleaned by alkali spraying; the gas flow is adjusted in a gas cabinet, after coming out of the gas cabinet, the gas is washed by using a two-stage Venturi scrubber; then the gas is washed by a packed tower; finally, the gas is separated by a cyclone gas-liquid separator and a wire mesh demister, to obtain purified phosphine gas, the phosphine gas is pre-cooled and dried at about -30°C, and finally deeply cooled to liquid phosphine.
[0047] S2, raw materials are configured according to a molar ratio of phosphine:isobutene=1.1:2, the molar amount of azobisisobutyronitrile is 2% of the molar amount of phosphine, about 45% of isobutene is pre-cooled (for example, at -10°C) to be liquid, mixed with the azobisisobutyronitrile solution to be solution A, and the remaining about 55% of isobutene is dissolved in supercritical carbon dioxide to be solution B; a microreactor including a straight-through pre-activation zone, a transition reaction zone and a main reaction zone is used as a device for the free radical addition reaction of this step, and the microreactor is purged and pressure-kept and leak-tested by using high-purity inert gases helium and argon; solution A is mixed with liquid phosphine in a Y-type mixer arranged at the inlet end of the pre-activation zone, under ultraviolet irradiation and at a low temperature of -10°C to 5°C, the mixture is kept in the pre-activation zone for about 3 min, then enters the transition reaction zone preheated to 30°C, and is kept for about 8 min under ultraviolet irradiation; the reaction product and solution B are synchronously added to the main reaction zone preheated to 80°C, and are kept for 20 min.
[0048] S3, after the free radical addition reaction, the microreactor is depressurized to discharge the gas inside, and the liquid mixture after the reaction is distilled at normal pressure gradient (first at 30-40°C, then at 60-70°C) to remove the solvent; then, vacuum distillation is performed, using an oil bath as the heat source of the distillation device, first slowly starting the vacuum pump to reduce the system pressure to the required value, slowly increasing the oil bath temperature, and distilling at about 10-20 mmHg and 30-50°C to collect the main light component monoisobutyl phosphine; then gradually increasing the oil bath temperature and further adjusting the vacuum degree as needed, and distilling at about 30-50 mmHg and 90-110°C to collect the main component diisobutyl phosphine, which is analyzed by gas chromatography, and the purity of diisobutyl phosphine is greater than 99%; finally, the oil bath temperature is gradually increased, and the system pressure is further reduced as needed, and distillation is carried out at about 5-10 mmHg and 130-150°C to separate monoisobutyl phosphine, diisobutyl phosphine, and triisobutyl phosphine.
[0049] S4, in the reaction kettle, sulfur (purity 98%) and appropriate amount of deionized water are added, and under stirring, diisobutyl phosphine prepared in S3 and liquid alkali (mass concentration 32%) are slowly metered and added, the molar ratio of diisobutyl phosphine to sulfur is controlled at 1:1, the reaction temperature is controlled at 75-85°C, and the pressure is controlled at 0-10 bar, after the metered material is added, the material is finally adjusted to pH 7-8 with liquid alkali, and the temperature is kept for 3 hours to generate a diisobutyl dithiophosphinic acid sodium solution (DTPINa).
[0050] Example 2 The method for preparing diisobutyl dithiophosphinic acid sodium using a microreactor comprises steps S1-S4.
[0051] S1, same as example 1.
[0052] S2, according to the molar ratio, the raw materials are prepared with a molar ratio of phosphine to isobutene of 1.03:2, the molar amount of azobisisobutyronitrile is 2% of the phosphine, about 40% of the isobutene is pre-cooled (e.g. -10°C) to a liquid state, mixed with the azobisisobutyronitrile solution to form solution A, and the remaining about 60% of the isobutene is dissolved in supercritical carbon dioxide to form solution B; the microreactor including a straight-through pre-activation zone, a transition reaction zone and a main reaction zone is used as the device for the free radical addition reaction of this step, and the microreactor is purged and pressure-tested with high-purity inert gases helium and argon; first, solution A and liquid phosphine are mixed in a T-shaped mixer at the inlet end of the pre-activation zone, and after mixing, they are kept in the pre-activation zone for about 5 min under ultraviolet irradiation and low temperature of -10-5°C; then they enter the preheated to 25°C transition reaction zone, and stay for about 10 min under ultraviolet irradiation; the reaction product and solution B are added simultaneously to the preheated to 70°C main reaction zone, and stay for 25 min.
[0053] S3, same as example 1.
[0054] S4, same as example 1.
[0055] Example 3 The method for preparing sodium diisobutyl dithiophosphinate by using a microreactor comprises steps S1 to S4.
[0056] S1, same as example 1.
[0057] S2, raw materials are prepared according to a molar ratio of phosphine:isobutene = 1.05:2, the molar amount of azobisisobutyronitrile is 2% of that of phosphine, about 43% of isobutene is pre-cooled (for example, at -10°C) to be in a liquid state, mixed with the azobisisobutyronitrile solution to form solution A, and the remaining about 57% of isobutene is dissolved in supercritical carbon dioxide to form solution B; a microreactor comprising a straight-through pre-activation zone, a transition reaction zone and a main reaction zone is used as a device for the free radical addition reaction of this step, and the microreactor is purged and pressure-maintained and leak-tested with high-purity inert gases helium and argon; solution A is first mixed with liquid phosphine in a T-shaped mixer arranged at the inlet end of the pre-activation zone, and after mixing, the mixture is kept in the pre-activation zone for about 5 min under ultraviolet irradiation and at a low temperature of -10°C to 5°C; then the mixture enters the transition reaction zone preheated to 35°C and stays for about 5 min under ultraviolet irradiation; the reaction product and solution B are synchronously added to the main reaction zone preheated to 90°C, and kept for 15 min.
[0058] S3, same as example 1.
[0059] S4, same as example 1.
[0060] Comparative Example 1 This comparative example is based on example 1, and the reaction of the microreactor in step S2 is set to one-time addition instead of stepwise addition, and the other steps and conditions are the same as those in example 1.
[0061] In S2 of this comparative example, raw materials are prepared according to a molar ratio of phosphine:isobutene = 1.1:2, the molar amount of azobisisobutyronitrile is 2% of that of phosphine, and the microreactor is purged and pressure-maintained and leak-tested with high-purity inert gases helium and argon; isobutene and initiator azobisisobutyronitrile are introduced into the microchannel reactor, and purified phosphine is introduced into the microchannel reactor to react under the conditions of a temperature of 80°C, a pressure of 0-25 bar and a residence time of 60 min.
[0062] Comparative Example 2 This comparative example is based on example 1, and the ultraviolet irradiation in the reactions of the pre-activation zone and the transition reaction zone in step S2 is deleted, and the other steps and conditions are the same as those in example 1.
[0063] S2 of the present comparative example is specifically as follows: raw materials are prepared according to a molar ratio of phosphine:isobutene = 1.1:2, the molar amount of azobisisobutyronitrile is 2% of that of phosphine, about 45% of isobutene is pre-cooled (for example, at -10°C) to be in a liquid state, mixed with the azobisisobutyronitrile solution to form solution A, and the remaining about 55% of isobutene is dissolved in supercritical carbon dioxide to form solution B; a microreactor including a straight-through pre-activation zone, a transition reaction zone and a main reaction zone is used as a device for the radical addition reaction in this step, and the microreactor is purged and pressure-maintained and leak-tested with high-purity inert gas helium or argon; solution A is first mixed with liquid phosphine in a Y-shaped mixer arranged at the inlet end of the pre-activation zone, and after mixing at a low temperature of -10°C to 5°C, it is left in the pre-activation zone for about 3 min; then it enters the transition reaction zone preheated to 30°C and stays for about 8 min; the reaction product and solution B are synchronously added to the main reaction zone preheated to 80°C, and left for 20 min.
[0064] Comparative Example 3 In the present comparative example, the remaining isobutene in step S2 is directly used instead of being dissolved in supercritical carbon dioxide, that is, isobutene is directly introduced into the main reaction zone instead of solution B prepared by dissolving isobutene in supercritical carbon dioxide, and other steps and conditions are the same as those in Example 1.
[0065] Comparative Example 4 In the present comparative example, the microreactor in step S2 is replaced by a conventional reaction kettle, and other steps and conditions are the same as those in Example 1.
[0066] The contents of mono-isobutyl phosphine, di-isobutyl phosphine and tri-isobutyl phosphine in the product after the gradient distillation of the liquid mixture after reaction in S2 of Example 1 to Example 3 and Comparative Example 1 to Comparative Example 4 under normal pressure are tested by gas chromatography-mass spectrometry (GC-MS), and the balance is impurities; in addition, the yield of the final product sodium diisobutyl dithiophosphinate solution (DTPINa) is measured (calculated based on isobutene).
[0067] Table 1
[0068] As can be seen from the data in Table 1, in the radical addition reaction, the present example effectively suppresses the generation of by-products mono-isobutyl phosphine and tri-isobutyl phosphine, improves the yield of the target product di-isobutyl phosphine, and thus effectively improves the yield of the final product sodium diisobutyl dithiophosphinate solution (DTPINa).
[0069] Comparative Example 4 uses a conventional reaction device, and the yield of the target product di-isobutyl phosphine is less than 50%, and Comparative Document 1 uses a microreactor, and the yield of the target product di-isobutyl phosphine is improved to more than 50%, but it is still much lower than that of the present example.
[0070] The yields of the target product diisobutyl phosphine in Comparative Example 2 and Comparative Example 3, in which ultraviolet irradiation and dissolution of the raw material isobutene are cancelled respectively, are slightly decreased, but are still higher than those in Comparative Document 1. The plugging of the microreactor in Step S2 in Test Examples 1 to 3 and Comparative Examples 1 to 3 was tested. High-precision pressure sensors were installed at the inlet and outlet of the microreactor to monitor and record the pressure difference (△P) between the two ends of the microreactor in real time. The relative change rate of △P during operation was calculated. The results of the relative change rate of △P after each and continuous multiple operations are shown in Table 2.
[0071] ; It refers to the stable pressure difference between the inlet and outlet of the microreactor after the system runs stably during the initial reaction process; It refers to the stable pressure difference between the inlet and outlet of the microreactor after the system runs stably during the n-th reaction process. In order to avoid the normal fluctuation of the pressure difference caused by the addition of raw materials in S24 interfering with the results, 、 It refers to the pressure difference after the addition of all raw materials and the stable operation of the system. If the pressure drop △P remains stable and unchanged, it indicates that the microreactor is not plugged. If the pressure drop △P starts to rise, it indicates that plugging occurs. The greater the relative change rate of △P, the more serious the plugging.
[0072] Table 2
[0073] As can be seen from the data in Table 1, in the free radical addition reaction, the relative change rate of △P is less than 4% when the microreactor is continuously operated for 20 times, and the relative change rate of △P is less than 6% when the microreactor is continuously operated for 25 times, which is far below the standard for stopping and cleaning. In a conventional case, the warning value of the relative change rate of △P is 10%, and the trigger threshold for stopping and flushing is 15% to 25%.
[0074] In Comparative Example 1, only about 10 times of operation is performed, which exceeds the warning value and reaches the trigger threshold for stopping and flushing.
[0075] The plugging effect of Comparative Example 2 and Comparative Example 3 is better than that of Comparative Example 1, but is obviously inferior to Example 1. When about 20 times of operation is performed to reach the warning value, and about 25 times of operation is performed to reach the trigger threshold for stopping and flushing.
[0076] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.
Claims
1. A method for preparing sodium diisobutyldithiophosphonate using a microreactor, characterized in that, The method includes the following steps: S1, phosphine gas is subjected to impurity removal pretreatment, pre-cooling and drying, and deep cooling in sequence to obtain high-purity liquid phosphine; S2, using liquid phosphine and isobutylene as raw materials, with the addition of an initiator, to synthesize diisobutylphosphine through a photothermal synergistic free radical addition reaction in a microreactor; the microreactor includes a through-flow pre-activation zone, a transition reaction zone, and a main reaction zone; S3, distillation separation of diisobutylphosphide; S4, under pressure and heating conditions, diisobutylphosphine and sodium hydroxide solution are added to a sulfur source solution, and a nucleophilic substitution reaction occurs. The reaction is then maintained at a certain temperature to prepare sodium diisobutyldithiophosphonate.
2. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 1, wherein the free radical addition reaction specifically includes: S21, a portion of the isobutylene is pre-cooled into a liquid state and then mixed with an initiator solution to obtain solution A; the portion of isobutylene is 40%~45% of the total isobutylene; the remaining isobutylene is dissolved in a solvent to obtain solution B. S22, Solution A and liquid phosphine are mixed in a mixer located at the inlet of the pre-activation zone. Under ultraviolet irradiation and a low temperature of -10℃ to 5℃, the mixture remains in the pre-activation zone for the first time. The reaction products of S23 and S22 enter the pre-set transition reaction zone at 25℃~35℃ and remain there for a second time under ultraviolet irradiation. The reaction products of S24 and S23 are added simultaneously with solution B to the main reaction zone, which is preheated to 70℃~150℃, and remain there for the third time.
3. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 2, characterized in that, The first time is 2 min to 5 min; the second time is 5 min to 10 min; and the third time is 10 min to 30 min.
4. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 2, characterized in that, The amount of liquid phosphine used exceeds the theoretical amount by 3% to 10%.
5. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 2, characterized in that, The initiator is azobisisobutyronitrile, azobisisovalerate, or azobisisoheptanenitrile.
6. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 2, characterized in that, The solvent for dissolving isobutylene is supercritical carbon dioxide.
7. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 2, characterized in that, Before the microreactor reaction begins, the microreactor is purged and pressure-tested for leaks using high-purity inert gas.
8. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 1, characterized in that, The phosphine gas is a byproduct of sodium hypophosphite production; the impurity removal pretreatment is used to remove water vapor, yellow phosphorus vapor and solid impurities contained in the sodium hypophosphite production byproduct, and finally obtain purified phosphine gas.
9. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 1, characterized in that, The pre-cooling and drying temperature is -20℃ to -40℃.
10. The method for preparing sodium diisobutyldithiophosphonate using a microreactor according to claim 1, characterized in that, The specific steps for distillation separation of diisobutylphosphide are as follows: first, the gas in the microreactor is discharged, and the liquid mixture after the reaction is subjected to atmospheric pressure distillation and vacuum distillation to separate monoisobutylphosphide, diisobutylphosphide and triisobutylphosphide.