Method for preparing phosphorane through pyrolysis of sodium hypophosphite based on raw material pretreatment

Abstract

The invention provides a method for preparing phosphorane by pyrolyzing sodium hypophosphite based on raw material pretreatment, the pretreatment method comprises the following steps: carrying out mechanical activation and dry granulation on sodium hypophosphite, and firstly, carrying out intermittent ball milling treatment on sodium hypophosphite powder in an inert atmosphere to form primary activated sodium hypophosphite; and then granulating by the steps of tabletting, crushing, screening and the like to obtain the granular sodium hypophosphite with the particle size of 0.8-1.2 mm, the porosity of 20-35% and the bulk density of 0.75-0.95 g / cm < 3 >. According to the pyrolysis method, on the basis of pretreatment, staged heating is carried out, a pyrolysis reaction is carried out under inert gas protection, the product phosphine is subjected to multi-stage condensation and low-temperature rectification purification, and then high-purity phosphine gas is obtained, the pyrolysis starting temperature can be remarkably reduced, the phosphine release rate and yield are increased, side reactions and impurity entrainment are reduced, and the method is suitable for industrial production. The method has the advantages of high raw material utilization rate, centralized and controllable pyrolysis reaction, high product purity and the like, and is suitable for efficient and safe preparation of phosphorane.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phosphine preparation, and particularly relates to a method for preparing phosphine by pyrolysis of sodium hypophosphite based on raw material pretreatment. BACKGROUND

[0002] Phosphine (PH3) is an important industrial raw material, widely used in electronics, chemical industry, medicine and other fields, especially in the semiconductor industry. Because phosphine has strong reducing property, and is flammable and toxic, safety and purity are very important in the preparation and recovery process.

[0003] At present, the methods for preparing phosphine mainly include calcium phosphide hydrolysis method, white phosphorus and alkali metal reaction method, electrolysis method and hypophosphite pyrolysis method. Among them, the pyrolysis of sodium hypophosphite (NaH2PO2) to prepare phosphine is paid more and more attention because of its easy-to-get raw material, low cost and simple operation. The reaction can generate phosphine and by-product phosphate under heating conditions, and the main reaction is as follows: 2NaH2PO2→ Na2HPO4+ PH3↑.

[0004] The existing sodium hypophosphite pyrolysis process generally has the following technical problems. The raw material is usually in powder form, has strong hygroscopicity, and is easy to agglomerate and clog during storage and reaction, causing uneven heating, local overheating, affecting the pyrolysis efficiency and phosphine yield. In addition, the internal structure of the raw material is dense, lacking effective gas escape channels, which easily leads to poor gas release, local temperature rise, easy to induce side reactions, generate solid by-products with complex structure such as pyrophosphate, reduce the selectivity of the main reaction, and may also block the reaction system, affecting the continuity and stability of the equipment operation. SUMMARY

[0005] The purpose of the present application is to provide a method for preparing phosphine by pyrolysis of sodium hypophosphite based on raw material pretreatment, to at least solve the problem of hygroscopicity of sodium hypophosphite powder raw material, avoid clogging during pyrolysis reaction, and the local overheating of agglomerates affecting the pyrolysis efficiency and inducing side reactions, and ensure the stable operation of the process equipment.

[0006] In one aspect, the present application provides a raw material pretreatment method for preparing phosphine by pyrolysis of sodium hypophosphite, which comprises the following steps: S100 mechanically activating sodium hypophosphite to obtain primary activated sodium hypophosphite; S200 granulating the primary activated sodium hypophosphite to obtain granular sodium hypophosphite; The mechanical activation is ball milling.

[0007] Preferably, the ball milling process is carried out in an inert gas environment, and is intermittent ball milling, with 2-10 minutes of ball milling, 2-5 minutes of standing, 5-10 cycles, and a rotation speed of 300-500 rpm.

[0008] Preferably, the granulation method comprises: S201 tabletting the primary activated sodium hypophosphite; S202 crushing and sieving the tabletting product to obtain granular sodium hypophosphite.

[0009] Preferably, the granular sodium hypophosphite has a D50 of 0.8-1.2 mm and a porosity of 20%-35%.

[0010] Preferably, the granular sodium hypophosphite has a bulk density of 0.75-0.95 g / cm 3 .

[0011] In another aspect, the present application provides a method for preparing phosphine by pyrolysis of sodium hypophosphite, wherein a raw material pretreatment method is used to treat the sodium hypophosphite raw material before pyrolysis, and the method for preparing phosphine by pyrolysis comprises the following steps: S300 pre-drying the granular sodium hypophosphite; S400 placing the dried granular sodium hypophosphite in a reactor and heating under an inert gas atmosphere to perform a pyrolysis reaction; S500 multi-stage condensation collection of the phosphine gas generated by pyrolysis; S600 purification of the collected phosphine by rectification to obtain a high-purity phosphine product.

[0012] Preferably, the pyrolysis is divided into four stages, specifically comprising: S401 raw material preheating stage, with a temperature of 80-110℃, a heating rate of 25-30℃ / min, and a holding time of 30-60 min; S402 activated heating stage, with a temperature of 110-160℃, a heating rate of 20-25℃ / min; S403 pyrolysis stage, with a temperature of 160-200℃, a heating rate of 10-15℃ / min, and a holding time of 60-120 min; S404 supplementary heating and finishing stage, with a temperature of 200-210℃, a heating rate of 5-10℃ / min, and a holding time of 10-15 min.

[0013] Preferably, the multi-stage condensation is provided with three-stage condensation, with a first-stage condensation temperature of 0--20℃, a second-stage condensation temperature of -90--30℃, and a third-stage condensation temperature of -90℃ or lower.

[0014] Preferably, the rectification step adopts two-stage low-temperature rectification columns, the first rectification column has a top temperature of -110 to -100 DEG C, the second rectification column has a top temperature of -90 to -85 DEG C, and the rectification pressure is controlled at 0.1 to 0.3 MPa.

[0015] Advantages: The application provides a method for preparing phosphine by pyrolysis of sodium hypophosphite based on raw material pretreatment. On the one hand, by pretreating sodium hypophosphite powder raw material, a combined pretreatment mode of mechanical activation and dry granulation is introduced, the problem of easy caking and agglomeration of the powder raw material in the existing process is solved, the problem of uneven heating in the subsequent pyrolysis reaction process is further avoided, the occurrence of side reactions is reduced, and thus the pyrolysis efficiency and product purity are improved. The mechanical activation can effectively disperse the agglomerated sodium hypophosphite raw material, at the same time, the ball milling mode can introduce lattice defects, increase the pyrolysis reactivity, reduce the initial pyrolysis temperature, and further improve the pyrolysis efficiency, so as to ensure complete pyrolysis of sodium hypophosphite at a lower temperature. In addition, the dry granulation makes the raw material form particles with a certain particle size range and pore structure, which can improve the heating uniformity of the raw material in the pyrolysis process, avoid local overheating and coking, provide micro channels for the phosphine product, and reduce the risk of side reactions caused by the phosphine product not being discharged in time. Through the synergistic treatment of ball milling and dry granulation, the reactivity of the sodium hypophosphite raw material is improved, the sodium hypophosphite can be heated more uniformly in the pyrolysis reaction process, and at the same time, the gas discharge capacity is also improved, which further improves the pyrolysis efficiency and avoids the occurrence of side reactions.

[0016] On the other hand, by reasonably controlling the heating rate and the holding time of each stage, the pyrolysis reaction process is more stable, the release of phosphine is more uniform and controllable, the local overheating and the occurrence of side reactions caused by local overheating are effectively inhibited, and thus the yield and purity of phosphine are improved. Further, a method combining multi-stage condensation and low-temperature rectification is used to treat the product, which improves the recovery rate and purity of phosphine. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 The process flow chart of Example 1. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to sub-ranges falling within the specified range. In this context, individual points within a range should be considered as being included within that range, and individual points can be combined to form new ranges, which are to be considered as being included within the present disclosure.

[0020] The application will be further described with reference to the drawings and examples, but the scope of the application is not limited to the content.

[0021] The application provides a raw material pretreatment method for preparing phosphine by pyrolysis of sodium hypophosphite, and the method comprises the following steps: S100 mechanically activating sodium hypophosphite to obtain primary activated sodium hypophosphite; S200 granulating the primary activated sodium hypophosphite to obtain granular sodium hypophosphite; The mechanical activation is ball milling treatment, the ball milling treatment is carried out in an inert gas environment, and the ball milling treatment is intermittent ball milling, ball milling is performed for 2-10 min, the system is allowed to stand for 2-5 min, the cycle is 5-10 times, and the rotation speed is 300-500 rpm.

[0022] In the application, sodium hypophosphite is mechanically activated by ball milling, the purpose is to improve the physical structure of sodium hypophosphite powder and improve the pyrolysis reaction performance. Sodium hypophosphite raw material is a hygroscopic powder solid, is easy to agglomerate, and affects the stability and efficiency of the subsequent reaction, therefore, in the ball milling process, inert gas is introduced into the reaction system, and air in the reaction system is exhausted, so that the raw material can be prevented from agglomerating due to moisture absorption, and the inert gas is continuously introduced to take away the heat generated in the ball milling process, thereby further ensuring the purity and conversion efficiency of the final product.

[0023] Further, the ball milling is intermittent operation, which can prevent the raw material from being agglomerated or decomposed too early due to too rapid temperature rise caused by continuous operation. In the ball milling, inert ball milling media such as zirconia is selected.

[0024] After ball milling, the crystal structure of sodium hypophosphite changes at the micro level, the collision and friction of ball milling cause dislocation, cracks or boundary defects in the crystal lattice, a large number of surface active sites are formed, the surface activity is increased, and the pyrolysis starting temperature is reduced by 5-10℃ compared with untreated raw material.

[0025] Further, after ball milling, the particle size of the powder particles is smaller and more uniform, which is more conducive to tabletting.

[0026] Preferably, the granulation method comprises: S201 tabletting the primary activated sodium hypophosphite; S202 crushing and sieving the tablet product to obtain granular sodium hypophosphite.

[0027] Preferably, the D50 of the granular sodium hypophosphite is 0.8-1.2 mm, the D50 can be 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm; the porosity is 20%-35%, the porosity can be 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%.

[0028] Preferably, the bulk density of the granular sodium hypophosphite is 0.75-0.95 g / cm 3 , the bulk density can be 0.76 g / cm 3 , 0.77 g / cm 3 , 0.78 g / cm 3 , 0.79 g / cm 3 , 0.80 g / cm 3 , 0.81 g / cm 3 , 0.82 g / cm 3 , 0.83 g / cm 3 , 0.84 g / cm 3 , 0.85 g / cm 3 , 0.86 g / cm 3 , 0.87 g / cm 3 , 0.88 g / cm 3 , 0.89 g / cm 3 , 0.90 g / cm 3 , 0.91 g / cm 3 , 0.92 g / cm 3 , 0.93 g / cm 3 , 0.94 g / cm 3 , 0.95 g / cm 3 .

[0029] In the present application, the primary activated sodium hypophosphite powder is loaded into a mold, and is formed into a tablet in a tabletting device under pressure, preferably, a stainless steel tabletting mold with a mold diameter of 50-100 mm is used, and the tablet is pressed under a pressure of 5-10 MPa for 30-60 s. In the tabletting process, no binder or auxiliary agent is added to ensure the purity of the system and avoid the introduction of impurities affecting the subsequent pyrolysis process. Preferably, the thickness of the tablet is 2-5 mm. In detail, the tabletting process can improve the subsequent particle shaping efficiency, and the dense structure formed by tabletting can reduce the flying powder, at the same time, the tabletting can enhance the surface hardness, which is conducive to controlling the particle breakage size.

[0030] Further, the tablet product is crushed, coarse crushing is carried out by using a knife or roll crushing device, and granular sodium hypophosphite raw material between 0.5-3 mm is formed, then the crushing product is classified by using a standard screen, sieving is carried out by using a 14-20 mesh screen, and 0.8-1.2 mm particles are collected to obtain granular sodium hypophosphite. The fine powder after screening is re-tableted, and the large particles can be further crushed and sieved to ensure that granular sodium hypophosphite of the target size is obtained. The reason for selecting D50 as 0.8-1.2 mm is that, in this particle size range, sodium hypophosphite has a suitable bulk density and gas escape channel, which can improve the uniformity of heating and the pyrolysis efficiency. When the particle size is less than 0.8 mm, it is still easy to form a ball during pyrolysis, and when the particle size is greater than 1.5 mm, it will lead to poor heat transfer efficiency and is not conducive to the diffusion of gas, resulting in the accumulation of product phosphane inside the raw material and the difficulty in dispersing, and the particle size is too large, which will lead to insufficient local reaction and induce the occurrence of side reactions.

[0031] Further, the porosity of the granular sodium hypophosphite is between 20%-35%, which is helpful for the smooth release of phosphane product, reduces the risk of side reactions caused by gas retention, and also improves the permeability of the particle bed in the pyrolysis reactor and the uniformity of heat transfer. In addition, the bulk density of the granular sodium hypophosphite is controlled to be 0.75-0.95 g / cm 3 range, which is also an important condition to ensure the smooth release of phosphane product. Under this bulk density, the granular sodium hypophosphite structure is loose but not loose, has good gas channel, ensures the heat transfer contact area, and can improve the efficiency and stability of the pyrolysis reaction.

[0032] The present application pretreats the sodium hypophosphite powder raw material by mechanical activation and dry granulation. The mechanical activation significantly improves the surface activity of the raw material, reduces the decomposition initiation temperature of sodium hypophosphite by 5-10℃, effectively reduces the occurrence of side reactions, and ensures that sodium hypophosphite can be completely reacted to improve the pyrolysis efficiency. By dry granulation, the porosity, particle size distribution and bulk density of the granular sodium hypophosphite are controlled, so that the reaction raw material has good filling performance and gas outlet channel in the reactor, further improves the escape efficiency of the product phosphane and the uniformity of heat transfer, and the granular sodium hypophosphite after granulation maintains good mechanical stability during pyrolysis, further inhibits the agglomeration and coking of the raw material, and compared with the original powder, the granular sodium hypophosphite can also reduce the entrainment of dust and by-products, avoid the entry of powdery material into the condensing area, and cause blockage or impurity entrainment. The pretreated raw material provides a solid foundation for the efficient, safe and controllable pyrolysis process of sodium hypophosphite. Further, the present application also provides a method for preparing phosphane by pyrolyzing sodium hypophosphite, which comprises the following steps: S300 pre-drying the granular sodium hypophosphite; S400 drying granular sodium hypophosphite and pyrolyzing the granular sodium hypophosphite in a reactor under an inert gas atmosphere; S500 collecting phosphine gas generated by pyrolysis through multi-stage condensation; S600 purifying the collected phosphine through rectification to obtain high-purity phosphine product.

[0033] In detail, the granular sodium hypophosphite is hot-air dried at 80-100℃ for 30-60 min, and inert gas is introduced into the reaction system to avoid early oxidation while discharging trace amounts of crystal water.

[0034] Preferably, the pyrolysis is divided into four stages, specifically including: S401 preheating the raw material at a temperature of 80-110℃ at a heating rate of 25-30℃ / min for 30-60 min; S402 activating and heating at a temperature of 110-160℃ at a heating rate of 20-25℃ / min; S403 pyrolysis at a temperature of 160-200℃ at a heating rate of 10-15℃ / min for 60-120 min; S404 heating and ending at a temperature of 200-210℃ at a heating rate of 5-10℃ / min for 10-15 min.

[0035] In detail, the granular sodium hypophosphite is hot-air dried at 80-100℃ for 30-60 min, and inert gas is introduced into the reaction system to avoid early oxidation while discharging trace amounts of crystal water.

[0036] Further, the multi-stage condensation is provided with three stages of condensation, the first stage of condensation is at a temperature of 0--20℃, the second stage of condensation is at a temperature of -90--30℃, and the third stage of condensation is at a temperature of -90℃ or lower.

[0037] In detail, the phosphine gas generated by pyrolysis is collected by multi-stage condensation, the first stage condensation temperature is 0-20℃, ice salt water or ordinary refrigerant is used, this stage of condensation is mainly to preliminarily cool the phosphine mixed gas, condense and remove most of the water vapor, to prevent icing, blockage and other problems in the subsequent low-temperature condensation system. The second stage condensation uses dry ice / acetone cold bath or liquid nitrogen jacket indirect cooling, this stage is the main condensation stage of phosphine, the boiling point of phosphine is -87.7℃, at this temperature interval, most of the phosphine will condense, realizing the concentrated recovery of the main product. The third stage condensation temperature is below -90℃, using liquid nitrogen direct cooling method, to capture the residual phosphine, further improve the recovery rate, at the same time, the third stage condensation section can be used as a buffer protection zone of the condensation system, to prevent the impact of high peak gas flow, and improve the stability and safety of the condensation system.

[0038] Further, the rectification step uses two-stage low-temperature rectification columns, the first rectification column top temperature is -110 to -100℃, the second rectification column top temperature is -90 to -85℃, and the rectification pressure is controlled at 0.1-0.3MPa.

[0039] In detail, after multi-stage condensation, the phosphine crude gas collected by condensation is sent to a pre-cooling tank at -90℃, the pressure is maintained at 0.1-0.3MPa, moderate pressurization is conducive to the liquefaction of phosphine, then the pre-cooled phosphine crude liquid is introduced into a two-stage rectification system for further purification. The first rectification column has a feed temperature of -90℃, a top temperature of -110 to -100℃, a bottom temperature maintained at -90 to -80℃, and an operating pressure of 0.1-0.3MPa. The reflux ratio of the column is set to 1.5-2.5, and the preliminary separation of phosphine and low-boiling substances is realized by condensation reflux control. The phosphine distillate at the bottom of the first rectification column is further sent to the second rectification column for purification of high-purity phosphine, the second rectification column has a feed temperature of -90 to -80℃, a top temperature controlled at -90 to -85℃, a bottom temperature maintained at -80 to -70℃, and an operating pressure of 0.1-0.3MPa. The second rectification column further separates phosphine and volatile components, thereby obtaining high-purity phosphine product.

[0040] In the two-stage rectification process, the gas escaping from the top of the column is mainly hydrogen, containing a trace amount of phosphine. To ensure safety and environmental emissions, the tail gas at the top of the column needs to be treated with an alkaline oxidizing washing liquid, preferably using an alkaline solution of NaClO2 or KMnO4 to oxidize PH3 into non-toxic stable phosphate, the washed tail gas can be treated by high-temperature combustion tower or safely released through a vacuum exhaust system.

[0041] Example 1 S100 Mechanical activation treatment is performed on sodium hypophosphite to obtain primary activated sodium hypophosphite; sodium hypophosphite powder is placed in a ball mill tank, zirconium oxide inert ball milling medium is added, high-purity nitrogen is introduced under a closed condition, and intermittent ball milling treatment is performed; the ball milling conditions are as follows: ball milling for 5 min, standing for 3 min, 6 cycles, rotation speed of 400 rpm, and ambient temperature of 25°C; S200 The primary activated sodium hypophosphite is granulated to obtain granular sodium hypophosphite; the milled powder is loaded into a tablet press die, a pressure of 7 MPa is applied for 40 s to obtain a tablet pressing product. After tablet pressing, a knife crusher is used for crushing, a 14-20 mesh screen is used for sieving, and 0.8-1.2 mm particles are collected to obtain granular sodium hypophosphite. The D50 is 1.0 mm, the bulk density is measured to be 0.85 g / cm 3 , and the porosity is measured to be 28%.

[0042] S300 The granular sodium hypophosphite is pre-dried: the granular sodium hypophosphite is placed in a hot air drying oven, the temperature is controlled at 90°C, and drying is performed under nitrogen protection for 45 min to remove the crystal water.

[0043] S400 The dried granular sodium hypophosphite is placed in a reactor and heated under an inert gas atmosphere to perform a pyrolysis reaction, 40 mL / min of nitrogen is introduced and heated, and the reactor sequentially reaches the following reaction stages: S401 Raw material preheating stage: the temperature increasing rate is 25°C / min, the temperature is increased to 100°C and held for 45 min; S402 Activation heating stage: the temperature increasing rate is increased to 20°C / min and increased to 160°C; S403 Pyrolysis stage: the temperature increasing rate is adjusted to 12°C / min, the temperature is increased to 190°C and held for 90 min; S404 Heat supplement stage: the temperature is increased to 200°C and held for 10 min.

[0044] Nitrogen is continuously introduced during the pyrolysis process to maintain an inert atmosphere and carry away product gas.

[0045] S500 The phosphine gas generated by pyrolysis is collected by multi-stage condensation: the output phosphine gas sequentially passes through a three-stage condensation system: First stage condensation: the temperature is controlled at 0°C, ice salt water cooling is used, and water vapor is removed; Second stage condensation: the temperature is controlled at -78°C, a dry ice-acetone cooling bath is used, and most of the phosphine is condensed; Third stage condensation: the temperature is controlled at -196°C, liquid nitrogen is directly cooled, and residual phosphine is captured.

[0046] S600 The collected phosphine is purified by rectification to obtain a high-purity phosphine product: The phosphane crude liquid collected by the condensing system was sent to a pre-cooling tank at -90°C for pretreatment, and the control pressure was 0.2 MPa.

[0047] The operating conditions of the first rectifying column were as follows: feed temperature -90°C, top temperature -105°C, bottom temperature -85°C, pressure 0.2 MPa, and reflux ratio 2.0; The operating conditions of the second rectifying column were as follows: feed temperature -85°C, top temperature -88°C, bottom temperature -75°C, and pressure 0.2 MPa.

[0048] The top escaping gas was washed by a basic solution containing NaClO2 to oxidize the residual PH3, and the remaining gas was discharged into a combustion tail gas system.

[0049] Finally, high-purity phosphane products with a purity of >99.5% were obtained, which met the requirements of electronic-grade applications, and the phosphane yield was 92%.

[0050] Examples 2-12 The steps of preparing phosphane from sodium hypophosphite were the same as in Example 1, and the differences are shown in the following table:

[0051] In Examples 1-8, the purity of phosphane was higher than 97%, and the highest was 99.5%, and the yield was 85%-92%. The main pyrolysis stage was at a temperature of 190°C-198°C, the pyrolysis process was stable, the side reaction was small, the gas release was smooth, and almost no agglomeration and coking of the raw materials occurred.

[0052] In Examples 9-12, when the porosity was too high, the particle structure was too loose, the thermal contact efficiency was reduced, part of the raw materials was not heated enough, leading to incomplete pyrolysis; when the porosity was too low, the gas channel was limited, the phosphane escape was blocked, and the side reaction occurred due to the phosphane not escaping in time; both too high and too low porosity would lead to a decrease in the purity and yield of phosphane, and the holding temperature of the pyrolysis stage would also increase.

[0053] When the bulk density was too low, the material was not tightly packed, and was not uniformly heated, at the same time, the phosphane gas escape path was chaotic, and the aggregation of phosphane was easy to occur, leading to the occurrence of side reactions; when the bulk density was too high, the bed was too dense, making it difficult for the gas to penetrate, and there was local heat accumulation and slight coking; both too high and too low porosity would lead to a decrease in the purity and yield of phosphane, and the holding temperature of the pyrolysis stage would also increase.

[0054] Example 13-14, the ball milling conditions were adjusted, resulting in an increase in pyrolysis temperature, insufficient ball milling, resulting in fewer lattice defect sites of sodium hypophosphite, which cannot achieve the effect of reducing the pyrolysis temperature, the reaction proceeds slowly, and during the pyrolysis process, the raw materials are not fully decomposed, resulting in a decrease in phosphine purity and yield; when the ball milling is excessive, the raw material temperature is too high, resulting in premature agglomeration and local sintering of sodium hypophosphite, further leading to a decrease in phosphine purity and yield.

[0055] Comparative Example 1 The sodium hypophosphite was granulated to obtain granular sodium hypophosphite; the ball-milled powder was loaded into a tablet press die, and a pressure of 8 MPa was applied for 40 s to obtain a tablet product. After tabletting, a knife crusher was used for crushing, and a 14-20 mesh screen was used for sieving to collect particles of 0.8-1.2 mm to obtain granular sodium hypophosphite. The bulk density was measured to be 0.43 g / cm 3 , and the porosity was measured to be 55%.

[0056] The granular sodium hypophosphite was pre-dried: the granular sodium hypophosphite was placed in a hot air drying oven, the temperature was controlled at 90°C, and dried for 45 minutes under nitrogen protection to remove the crystal water.

[0057] The dried granular sodium hypophosphite was placed in a reactor and heated under an inert gas atmosphere to perform a pyrolysis reaction, 40 mL / min of nitrogen was introduced and heated, and the reactor reached the following reaction stages in turn: S401 raw material preheating stage: the temperature was raised at a rate of 26°C / min, and after the temperature was raised to 100°C, it was kept for 45 min; S402 activation heating stage: the temperature was raised at a rate of 20°C / min to 160°C; S403 pyrolysis stage: the temperature was raised at a rate of 12°C / min to 210°C, and kept for 90 min; S404 heat supplement stage: the temperature was raised to 220°C and kept for 10 min.

[0058] Nitrogen was continuously introduced during the pyrolysis process to maintain an inert atmosphere and remove product gas.

[0059] The phosphine gas produced by pyrolysis was collected by multi-stage condensation, and the output phosphine gas passed through a three-stage condensation system in turn: First stage condensation: the temperature was controlled at 0°C, ice salt water cooling was used, and water vapor was removed; Second stage condensation: the temperature was controlled at -78°C, dry ice-acetone cooling bath was used, and most of the phosphine was condensed; Third stage condensation: the temperature was controlled at -196°C, liquid nitrogen was used for direct cooling, and residual phosphine was captured.

[0060] The collected phosphine is purified by rectification to obtain a high-purity phosphine product: The crude phosphine liquid collected by the condensing system is sent to a -90℃ pre-cooling tank for pretreatment, and the control pressure is 0.2 MPa.

[0061] The operating conditions of the first rectification tower are as follows: feed temperature -90℃, tower top temperature -105℃, tower bottom -85℃, pressure 0.2 MPa, and reflux ratio 2.0; The operating conditions of the second rectification tower are as follows: feed temperature -85℃, tower top temperature -88℃, tower bottom -75℃, and pressure 0.2 MPa.

[0062] The tower top escaping gas is washed by being introduced into an alkaline solution containing NaClO2 to oxidize residual PH3, and the remaining gas is introduced into a combustion tail gas system for discharge.

[0063] Finally, a phosphine product with a purity of >97.3% and a phosphine yield of 76% is obtained.

[0064] In Comparative Example 1, the ball milling pretreatment procedure is absent, and after tabletting, the bulk density is low, the powder is loose, easy to agglomerate, the bulk is not compact, the porosity is large, most of the pores are inter-particle pores, the permeability is poor, the original powder structure is loose, but the internal micropores are less, in the pyrolysis process, there is a local overheating phenomenon, and the main decomposition temperature of sodium hypophosphite is higher than that of Example 1, resulting in a decrease in the purity of the final phosphine product.

[0065] Comparative Example 2 The sodium hypophosphite is subjected to mechanical activation treatment to obtain primary activated sodium hypophosphite; the sodium hypophosphite powder is placed in a ball mill tank, zirconium oxide inert ball milling medium is added, high-purity nitrogen gas is introduced under sealed conditions, and intermittent ball milling treatment is performed; the ball milling conditions are as follows: ball milling for 8 min, standing for 5 min, 8 cycles, rotation speed 300 rpm, and ambient temperature 25℃; The primary activated sodium hypophosphite is subjected to pre-drying: the granular sodium hypophosphite is placed in a hot air drying oven, the temperature is controlled at 90℃, and the drying is performed under nitrogen protection for 45 min to remove the crystal water.

[0066] The dried primary activated sodium hypophosphite is placed in a reactor, heated under an inert gas atmosphere, and subjected to pyrolysis reaction; 40 mL / min of nitrogen gas is introduced and heated, and the reactor sequentially reaches the following reaction stages: S401 raw material preheating stage: the temperature is raised at a rate of 30℃ / min, and after the temperature is raised to 100℃, the temperature is maintained for 45 min; S402 activated temperature rising stage: the temperature rising rate is increased to 25℃ / min, and the temperature is raised to 160℃; S403 pyrolysis stage: the temperature rising rate is adjusted to 10℃ / min, the temperature is raised to 205℃, and the temperature is maintained for 90 min; S404: heating to 210℃ and holding for 10 min.

[0067] Nitrogen gas is continuously supplied during pyrolysis to maintain inert atmosphere and carry away product gas.

[0068] The phosphine gas generated by pyrolysis is collected by multi-stage condensation. The generated phosphine gas passes through three-stage condensation system in turn: First-stage condensation: temperature control at 0℃, ice-salt water cooling is used to remove water vapor; Second-stage condensation: temperature control at -78℃, dry ice-acetone cooling bath is used to condense most of the phosphine; Third-stage condensation: temperature control at -196℃, liquid nitrogen direct cooling is used to capture residual phosphine.

[0069] The collected phosphine is purified by rectification to obtain high-purity phosphine product: The crude phosphine liquid collected by the condensation system is sent to a -90℃ pre-cooling tank for pretreatment, and the control pressure is 0.2 MPa.

[0070] First rectification column operating conditions: feed temperature -90℃, overhead temperature -105℃, bottom temperature -85℃, pressure 0.2 MPa, reflux ratio 2.0; Second rectification column operating conditions: feed temperature -85℃, overhead temperature -88℃, bottom temperature -75℃, pressure 0.2 MPa.

[0071] The overhead escaping gas is washed with an alkaline solution containing NaClO2 to oxidize residual PH3, and the remaining gas enters the combustion tail gas system for discharge.

[0072] Finally, the phosphine product with a purity of >93.6% and a phosphine yield of 75% is obtained.

[0073] Comparative Example 2 lacks the pretreatment process of dry granulation compared to Example 1. Only the particle size after ball milling is small, and the pyrolysis process is prone to agglomeration and coking. Local overheating occurs, the pyrolysis reaction temperature is high, gas retention leads to an increase in side reactions, and the yield of phosphine is significantly reduced. Sodium hypophosphite powder appears in the condensation system.

[0074] Comparative Example 3 Pre-drying of sodium hypophosphite: granular sodium hypophosphite is placed in a hot air drying oven, the temperature is controlled at 90℃, and dried for 45 minutes under nitrogen protection to remove crystal water.

[0075] The dried and once-activated sodium hypophosphite is placed in a reactor and heated under an inert gas atmosphere. Nitrogen gas is supplied at 40 mL / min and heated. The reactor reaches the following reaction stages in turn: S401 raw material preheating stage: the temperature was raised at a rate of 28°C / min, and the temperature was kept at 100°C for 45 min after the temperature was raised to 100°C; S402 activation temperature raising stage: the temperature raising rate was increased to 25°C / min, and the temperature was raised to 150°C; S403 pyrolysis stage: the temperature raising rate was adjusted to 18°C / min, the temperature was raised to 215°C, and the temperature was kept at 215°C for 90 min; S404 heat supplement stage: the temperature was raised to 220°C, and the temperature was kept at 220°C for 10 min.

[0076] Nitrogen was continuously supplied during the pyrolysis process to maintain an inert atmosphere and carry away product gas.

[0077] The phosphine gas generated in the pyrolysis process was collected by multi-stage condensation, and the generated phosphine gas passed through three-stage condensation systems in turn: First-stage condensation: the temperature was controlled at 0°C, ice salt water cooling was used, and water vapor was removed; Second-stage condensation: the temperature was controlled at -78°C, dry ice-acetone cooling bath was used, and most of the phosphine was condensed; Third-stage condensation: the temperature was controlled at -196°C, liquid nitrogen direct cooling was used, and residual phosphine was captured.

[0078] The collected phosphine was purified by rectification to obtain high-purity phosphine product: The crude phosphine liquid collected by the condensation system was sent to a -90°C pre-cooling tank for pretreatment, and the control pressure was 0.2 MPa.

[0079] First rectification column operating conditions: feed temperature -90°C, overhead temperature -105°C, bottom temperature -85°C, pressure 0.2 MPa, reflux ratio 2.0; Second rectification column operating conditions: feed temperature -85°C, overhead temperature -88°C, bottom temperature -75°C, pressure 0.2 MPa.

[0080] The overhead escaping gas was washed with an alkaline solution containing NaClO2 to oxidize residual PH3, and the remaining gas was discharged into the combustion tail gas system.

[0081] Finally, the phosphine product was obtained, with a purity of >90.4% and a phosphine yield of 65%.

[0082] In Comparative Example 3, no raw material pretreatment was performed, and the sodium hypophosphite powder was directly used for pyrolysis. Due to the uneven particle size distribution of the sodium hypophosphite powder, the powder was loose and easily absorbed moisture and formed clumps. In the pyrolysis process, coking problems caused by uneven heat transfer were obvious. The pyrolysis reaction temperature was high, and there were many by-products. A large amount of raw material powder appeared in the condensation system, and the purity and yield of the final phosphine product were low.

[0083] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A raw material pretreatment method for preparing phosphine by pyrolysis of sodium hypophosphite, characterized in that: The method comprises the following steps: S100 performs mechanical activation treatment on sodium hypophosphite to obtain primary activated sodium hypophosphite; S200 granulating the once-activated sodium hypophosphite to obtain granular sodium hypophosphite; The mechanical activation is ball milling; the D50 of the granular sodium hypophosphite is 0.8-1.2 mm, the porosity is 20%-35%, and the bulk density is 0.75-0.95 g / cm 3 .

2. The raw material pretreatment method according to claim 1, characterized in that: The granulation method comprises: S201 compresses the once activated sodium hypophosphite into tablets; S202 crushes the tablet product and then sieves it to obtain granular sodium hypophosphite.

3. The raw material pretreatment method according to claim 1, characterized in that: The granular sodium hypophosphite has a D50 of 0.9 to 1.1 mm, a porosity of 25% to 33%, and a bulk density of 0.80 to 0.92 g / cm 3 .

4. The raw material pretreatment method according to claim 1, characterized in that: The granular sodium hypophosphite has a D50 of 0.10-1.1 mm, a porosity of 28%-30%, and a bulk density of 0.85-0.90 g / cm 3 .

5. The raw material pretreatment method according to claim 1, characterized in that: The ball milling treatment is carried out in an inert gas environment. The ball milling treatment is intermittent ball milling, ball milling for 2 to 10 minutes, standing for 2 to 5 minutes, and circulating 5 to 10 times at a rotation speed of 300 to 500 rpm.

6. The raw material pretreatment method according to claim 5, characterized in that: Ball mill for 4 to 8 minutes, let it stand for 3 to 5 minutes, and cycle 6 to 8 times at a speed of 400 to 500 rpm.

7. A method for preparing phosphine by pyrolysis of sodium hypophosphite, characterized in that: Before pyrolysis, the sodium hypophosphite raw material is treated by the raw material pretreatment method according to any one of claims 1 to 6. The method for preparing phosphine by pyrolysis comprises the following steps: S300 pre-drying the granular sodium hypophosphite; In step S400, the dried granular sodium hypophosphite is placed in a reactor and heated under an inert gas atmosphere to perform a thermal decomposition reaction; S500 collects the phosphine gas produced by pyrolysis through multi-stage condensation; S600 purifies the collected phosphine by distillation to obtain high-purity phosphine product.

8. The method for preparing phosphine by pyrolysis according to claim 7, characterized in that: The pyrolysis is divided into four stages, specifically including: In the S401 raw material preheating stage, the temperature is 80-110°C, the heating rate is 25-30°C / min, and the holding time is 30-60min; During the S402 activation heating stage, the temperature is between 110 and 160°C, and the heating rate is 20 to 25°C / min; In the S403 pyrolysis stage, the temperature is 160-200°C, the heating rate is 10-15°C / min, and the holding time is 60-120min; In the final stage of S404 supplementary heating, the temperature is between 200 and 210°C, the heating rate is 5 to 10°C / min, and the holding time is 10 to 15 minutes.

9. The method for preparing phosphine by pyrolysis according to claim 7, characterized in that: The multi-stage condensation is provided with three stages of condensation, the first stage condensation temperature is 0 to -20°C, the second stage condensation temperature is -90 to -30°C, and the third stage condensation temperature is below -90°C.

10. The method for preparing phosphine by pyrolysis according to any one of claim 7, characterized in that: The distillation step adopts a two-stage low-temperature distillation tower, the top temperature of the first distillation tower is -110 to -100°C, the top temperature of the second distillation tower is -90 to -85°C, and the distillation pressure is controlled at 0.1 to 0.3 MPa.

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