Method for preparing triphenylphosphine from chlorodiphenylphosphine by removing dichlorophenylphosphine during heat treatment

Abstract

The present invention relates to a method for preparing triphenylphosphine, comprising performing heat treatment on a chlorodiphenylphosphine starting material at a temperature of 280-420°C to prepare triphenylphosphine, wherein at least part of dichlorophenylphosphine is removed in the heat treatment process.

Description

Process for the preparation of triphenylphosphine from diphenylphosphine chloride by removing phenyldichlorophosphine during heat treatment TECHNICAL FIELD

[0001] The present invention relates to a process for the preparation of triphenylphosphine by heat treatment of a diphenylphosphine chloride raw material, wherein at least part of the phenyldichlorophosphine is removed during the heat treatment. TECHNICAL BACKGROUND

[0002] Triphenylphosphine has a wide range of applications in the field of chemical industry, and is an important fine chemical synthesis catalyst; a catalyst for petroleum processing; a new type of biocatalysis technology and catalyst; a new type of high-efficiency catalyst for environmental protection; a new type of catalyst for organic synthesis; a new type of high-efficiency catalyst for polyolefins; a new material for catalyst carriers and various new types of cocatalyst materials; can also be used as a functional fine chemical; a new type of papermaking special chemical; a new type of oilfield chemical suitable for protective exploitation and enhanced oil recovery; a new type of surfactant; a high-performance, water-based functional coating and additive; a new type of textile dyeing and finishing agent; a high-performance environmentally friendly adhesive; a new type of safe and environmentally friendly pigment and dye; a high-performance environmentally friendly leather chemical. Triphenylphosphine can also be used as an intermediate for the synthesis of various important chemical products, such as β-carotene, cefprozil, and cefdinir.

[0003] The main synthesis methods for industrial production of triphenylphosphine include (1) the Grignard method (sodium method) using high-speed stirring to make metallic sodium and reacting with chlorobenzene and phosphorus trichloride to produce triphenylphosphine. This method is technically demanding, especially the sodium sand making equipment, which needs to solve the problem of sodium dispersion and avoid the presence of water during operation, because highly active sodium can react violently with water and cause explosion. Therefore, there is a high safety risk in the production process. (2) The Grignard reagent method (Grignard method), which uses phenylmagnesium halide and phosphorus trichloride as raw materials, and heats the reactants to produce triphenylphosphine with a small amount of by-product triphenylphosphine oxide. This method has the disadvantages of high cost, low yield, and poor economic benefit. (3) The Friedel-Crafts method, which produces triphenylphosphine sulfide by reacting thiophosphonic chloride with benzene in the presence of excess aluminum trichloride, and then uses iron filings or sodium naphthalene for desulfurization (reduction) to obtain triphenylphosphine. However, the triphenylphosphine produced by reduction with iron powder has poor quality and yellowish color, and the use of aluminum trichloride and iron powder as catalysts generates a large amount of solid waste, which is difficult to dispose and pollutes the environment. (4) The triphenylphosphine oxide reduction method, but the reducing agent used in the triphenylphosphine oxide reduction method is expensive.

[0004] In summary, there is an urgent need to develop a green and environmentally friendly, low-cost, high-quality, and simple method for synthesizing triphenylphosphine. SUMMARY

[0005] The present application aims to provide a method for preparing triphenylphosphine, which is green, safe, low in cost, high in quality and simple in operation, and the method does not need to use solvent or cosolvent and raw materials are easy to obtain.

[0006] The technical solutions of achieving the above-mentioned objects of the present application can be summarized as follows:

[0007] 1. A method for preparing triphenylphosphine, comprising heat-treating a diphenylphosphine chloride raw material at a temperature of 280-420°C to prepare triphenylphosphine, wherein at least part of the phenyldichlorophosphine is removed during the heat-treatment.

[0008] 2. The method according to embodiment 1, wherein at least 20% by weight, preferably at least 40% by weight, more preferably at least 60% by weight, even at least 75% by weight of the phenyldichlorophosphine is removed during the heat-treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

[0009] 3. The method according to embodiment 1 or 2, wherein 20-98% by weight, preferably 40-95% by weight, more preferably 60-95% by weight of the phenyldichlorophosphine is removed during the heat-treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

[0010] 4. The method according to any one of embodiments 1-3, wherein at least 80% by weight, preferably at least 90% by weight, more preferably at least 98% by weight, even more preferably at least 99.5% by weight of the chlorobenzene and phosphorus trichloride is removed during the heat-treatment, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat-treatment and the removed chlorobenzene and phosphorus trichloride.

[0011] 5. The method according to any one of embodiments 1-4, wherein not more than 50% by weight, preferably not more than 40% by weight, for example not more than 30% by weight of the diphenylphosphine chloride is removed during the heat-treatment, based on the total amount of diphenylphosphine chloride present in the reaction mixture after completion of the heat-treatment and the removed diphenylphosphine chloride.

[0012] 6. The method according to any one of embodiments 1-5, wherein the content of phenyldichlorophosphine in the diphenylphosphine chloride raw material is not more than 35% by weight, preferably not more than 30% by weight, more preferably not more than 20% by weight, still more preferably not more than 15% by weight, especially not more than 8% by weight, particularly not more than 3% by weight, most preferably not more than 1% by weight, for example not more than 0.5% by weight, based on the total weight of the diphenylphosphine chloride raw material.

[0013] 7. The process according to any one of embodiments 1 to 6, wherein the content of the diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 65 wt.-%, preferably at least 70 wt.-%, more preferably at least 80 wt.-%, even more preferably at least 88 wt.-%, still more preferably at least 95 wt.-%, such as at least 98 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0014] 8. The process according to any one of embodiments 1 to 7, wherein the heat treatment temperature is 290 to 400 °C, preferably 300 to 400 °C, more preferably 300 to 350 °C.

[0015] 9. The process according to any one of embodiments 1 to 8, wherein the heat treatment temperature is especially 300 to 320 °C, most preferably 310 to 320 °C.

[0016] 10. The process according to any one of embodiments 1 to 9, wherein the time of the heat treatment is at least 1.5 hours, preferably 1.5 to 12 hours, more preferably 1.5 to 8 hours, especially 2 to 6 hours, most preferably 3 to 6 hours.

[0017] 11. The process according to any one of embodiments 1 to 10, wherein the content of phosphorus trichloride in the diphenylchlorophosphine starting material is not more than 5 wt.-%, preferably not more than 2 wt.-%, more preferably not more than 1 wt.-%, such as not more than 0.5 wt.-% or not more than 0.1 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0018] 12. The process according to any one of embodiments 1 to 11, wherein the process comprises heat treating the diphenylchlorophosphine starting material at a temperature of 310 to 320 °C for a time of 3 to 6 hours, and

[0019] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 98 wt.-%, the content of phenyldichlorophosphine is not more than 1 wt.-%, and the content of phosphorus trichloride is not more than 0.1 wt.-% (preferably free of phosphorus trichloride), based on the total weight of the diphenylchlorophosphine starting material.

[0020] 13. The process according to any one of embodiments 1 to 12, wherein the phenyldichlorophosphine is removed by distillation, preferably atmospheric distillation.

[0021] 14. The process according to any one of embodiments 1 to 13, further comprising repeating the heat treatment as defined in any one of embodiments 1 to 5, 8 to 10 and 13 for 1 to 5 times, preferably 1 to 4 times, more preferably 2 or 3 times, after the heat treatment has been completed.

[0022] 15. The process according to embodiment 14, which comprises, before repeating the heat treatment, adding additional diphenylphosphine chloride to the reaction mixture obtained after the last heat treatment, preferably the amount of diphenylphosphine chloride added is at least 5 wt.%, preferably at least 10 wt.% or at least 20 wt.%, for example 10-80 wt.% based on the total weight of the reaction mixture obtained after the last heat treatment.

[0023] 16. The process according to embodiment 14 or 15, wherein the time of each heat treatment is 1.5-2.5 hours or 3-6 hours.

[0024] 17. The process according to any one of embodiments 1-16, wherein during the heat treatment at least 75 wt.% of the phenyldichlorophosphine is removed based on the total amount of phenyldichlorophosphine present in the reaction mixture after the heat treatment is completed and the removed phenyldichlorophosphine, and the time of the heat treatment is 3-6 hours,

[0025] or

[0026] during the heat treatment at least 75 wt.% of the phenyldichlorophosphine is removed based on the total amount of phenyldichlorophosphine present in the reaction mixture after the heat treatment is completed and the removed phenyldichlorophosphine, and the reaction mixture obtained after the heat treatment is completed is repeated 1-5 times with a heat treatment as defined in any one of embodiments 1-5, 8-10 and 13 and the sum of the time of the heat treatment and the time of the repeated heat treatments is 4-20 hours or 4-10 hours.

[0027] The advantages of the present application are as follows:

[0028] (1) The process of the present application is green, safe, low cost, high quality and simple to operate.

[0029] (2) The process of the present application uses diphenylphosphine chloride as raw material, without the need to add other cosolvents, and the raw material is simple and easy to obtain.

[0030] (3) Diphenylphosphine chloride is a liquid, easy to operate, without the need to use solvents, avoiding solvent pollution.

[0031] (4) By removing phenyldichlorophosphine during the heat treatment, the present application can obtain triphenylphosphine with higher yield and higher triphenylphosphine / raw material weight ratio. The price of triphenylphosphine is much higher than that of diphenylphosphine chloride, so the process of the present application has very high industrial value. In addition, by removing phenyldichlorophosphine during the heat treatment, the temperature of the heat treatment can be reduced, thereby reducing energy consumption and risk. DETAILED DESCRIPTION

[0032] The present invention relates to a process for the preparation of triphenylphosphine comprising heat-treating a diphenylphosphine chloride starting material at a temperature in the range of 280-420°C to produce triphenylphosphine, wherein at least part of the phenyldichlorophosphine is removed during said heat-treatment.

[0033] The inventors of the present invention found that phenyldichlorophosphine is produced during the heat-treatment of diphenylphosphine chloride and that the diphenylphosphine chloride starting material can also contain phenyldichlorophosphine. By removing at least part of the phenyldichlorophosphine from the system during the heat-treatment, the yield of triphenylphosphine is further improved.

[0034] In one embodiment, during said heat-treatment, at least 20 wt% (e.g. 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 98 wt%, 99 wt% or 100 wt%), preferably at least 40 wt%, more preferably at least 60 wt%, even at least 75 wt%, of the phenyldichlorophosphine is removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

[0035] In one embodiment, during said heat-treatment, 20-98 wt% (e.g. 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt% or 98 wt%), preferably 40-95 wt%, more preferably 60-95 wt%, e.g. 70-95 wt%, 80-95 wt%, 80-93 wt% or 80-90 wt%, of the phenyldichlorophosphine is removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

[0036] During the heat-treatment some light components, such as chlorobenzene and phosphorus trichloride, are produced. By removing at least part of these light components, the yield of triphenylphosphine is further improved.

[0037] In one embodiment, during said heat-treatment, at least 80 wt% or at least 85 wt%, preferably at least 90 wt% or 95 wt%, more preferably at least 98 wt%, even more preferably at least 99.5 wt% or 100 wt%, of the chlorobenzene and phosphorus trichloride is removed, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat-treatment and the removed chlorobenzene and phosphorus trichloride. Preferably, all of the chlorobenzene and phosphorus trichloride is removed.

[0038] In one embodiment, not more than 50 wt.-% (e.g. 45 wt.-%, 40 wt.-%, 35 wt.-%, 30 wt.-%, 25 wt.-%, 20 wt.-%, 15 wt.-%, 10 wt.-%, 5 wt.-%, 2 wt.-%, 1 wt.-%), preferably not more than 40 wt.-%, e.g. not more than 30 wt.-%, of diphenylchlorophosphine is removed during the heat treatment, based on the total amount of diphenylchlorophosphine present in the reaction mixture after completion of the heat treatment and removed diphenylchlorophosphine.

[0039] For example, 1 to 50 wt.-%, preferably 2 to 40 wt.-%, e.g. 5 to 30 wt.-% or 10 to 25 wt.-%, of diphenylchlorophosphine is removed during the heat treatment, based on the total amount of diphenylchlorophosphine present in the reaction mixture after completion of the heat treatment and removed diphenylchlorophosphine.

[0040] In one embodiment, the content of phenyldichlorophosphine in the diphenylchlorophosphine starting material is not more than 35 wt.-% (e.g. 32 wt.-%, 30 wt.-%, 28 wt.-%, 26 wt.-%, 25 wt.-%, 22 wt.-%, 20 wt.-%, 18 wt.-%, 15 wt.-%, 12 wt.-%, 10 wt.-%, 8 wt.-%, 5 wt.-%, 3 wt.-%, 2 wt.-%, 1 wt.-%, 0.5 wt.-% or 0.1 wt.-%), preferably not more than 30 wt.-% or 28 wt.-%, more preferably not more than 22 wt.-% or 20 wt.-%, still more preferably not more than 15 wt.-%, especially not more than 8 wt.-%, in particular not more than 3 wt.-%, most preferably not more than 1 wt.-%, e.g. not more than 0.5 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0041] In one embodiment, the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 65 wt.-% (e.g. 68 wt.-%, 70 wt.-%, 75 wt.-%, 80 wt.-%, 85 wt.-%, 88 wt.-%, 90 wt.-%, 91 wt.-%, 92 wt.-%, 93 wt.-%, 95 wt.-%, 98 wt.-%, 99 wt.-%, 99.5 wt.-% or 99.9 wt.-%), preferably at least 70 wt.-%, more preferably at least 80 wt.-%, even more preferably at least 88 wt.-%, still more preferably at least 95 wt.-%, e.g. at least 98 wt.-% or 99 wt.-% or 99.5 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0042] In one embodiment, the phosphorus trichloride content of the diphenylchlorophosphine starting material is no more than 5 wt% (e.g. 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.2 wt%, 0.1 wt% or 0.05 wt%), preferably no more than 2 wt%, more preferably no more than 1 wt%, e.g. no more than 0.5 wt% or no more than 0.1 wt%, based on the total weight of the diphenylchlorophosphine starting material. In one embodiment, the diphenylchlorophosphine starting material is free of phosphorus trichloride.

[0043] In one embodiment, the triphenylphosphine content of the diphenylchlorophosphine starting material is no more than 6 wt% (e.g. 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.2 wt% or 0.1 wt%), preferably no more than 5 wt%, more preferably no more than 1 wt%, e.g. no more than 0.5 wt% or no more than 0.1 wt%, based on the total weight of the diphenylchlorophosphine starting material.

[0044] According to the present application, the heat treatment temperature is in the range of 280-420°C, e.g. 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 345°C, 350°C, 355°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C or 420°C. In one embodiment, the heat treatment temperature is in the range of 290-400°C, preferably 300-400°C, more preferably 300-350°C. In a preferred embodiment, the heat treatment temperature is in particular in the range of 300-320°C, especially 310-320°C.

[0045] In one embodiment, the heat treatment is carried out at normal pressure. If desired, the heat treatment can also be carried out at negative or elevated pressure. For example, the heat treatment is carried out at a pressure of -5 Kpa or less (i.e. 5 Kpa or less below atmospheric pressure), -10 Kpa or less, -20 Kpa or less, -50 Kpa or less, or -80 Kpa or less. Alternatively, the heat treatment can be carried out at a pressure of (gauge pressure) at least 0.05 MPa (e.g. 0.08 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa), at least 0.08 MPa, or at least 0.1 Mpa. In one embodiment, the heat treatment is carried out at a pressure of -80 Kpa to 4 MPa, or -20 Kpa to 2 Mpa, or -10 Kpa to 1 Mpa, or -10 Kpa to 0.5 Mpa, or atmospheric pressure to 0.5 Mpa.

[0046] In one embodiment, the heat treatment is performed for at least 1.5 hours (e.g. 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours), preferably 1.5-12 hours, more preferably 1.5-8 hours, especially 1.5-6 hours or 3-6 hours or 1.5-3 hours.

[0047] In one embodiment, the heat treatment is performed with stirring. The stirring rate can for example be 50-700 r / min, e.g. 100-600 r / min, or 200-500 r / min or 300-450 r / min.

[0048] The diphenylphosphine chloride starting material can be preheated before the stirring, e.g. to 40-90 °C, preferably to 50-80 °C, e.g. 60-80 °C.

[0049] In one embodiment, the product mixture obtained from the process comprises triphenylphosphine, phenyldichlorophosphine, and diphenylphosphine chloride, and optionally chlorobenzene and phosphorus trichloride.

[0050] According to the present application, the phenyldichlorophosphine can be removed by distillation, preferably atmospheric distillation.

[0051] According to the present application, the light components (such as chlorobenzene and phosphorus trichloride) can be removed by distillation, preferably atmospheric distillation.

[0052] In one embodiment, at least part of the phenyldichlorophosphine is removed continuously during the heat treatment.

[0053] In a preferred embodiment of the present application, the process of the present application further comprises repeating the heat treatment as defined above 1-5 times, preferably 1-4 times, more preferably 2 or 3 times, after the reaction mixture obtained after the heat treatment is completed. For example, if the heat treatment is repeated once, the process of the present application comprises the heat treatment and the repeated heat treatment 1; if the heat treatment is repeated twice, the process of the present application comprises the heat treatment, the repeated heat treatment 1 and 2; if the heat treatment is repeated three times, the process of the present application comprises the heat treatment, the repeated heat treatment 1, 2 and 3; if the heat treatment is repeated four times, the process of the present application comprises the heat treatment, the repeated heat treatment 1, 2, 3 and 4; and if the heat treatment is repeated five times, the process of the present application comprises the heat treatment, the repeated heat treatment 1, 2, 3, 4 and 5.

[0054] The conditions of each heat treatment can be the same or different, preferably the conditions (such as time, temperature, amount of phenyldichlorophosphine removed, amount of chlorobenzene and phosphorus trichloride removed and amount of diphenylphosphine chloride removed) of the repeated heat treatments have the preferred meanings described above.

[0055] For example, the repeated heat treatment can be carried out at 300-400°C, preferably 300-350°C, especially 300-320°C, most preferably 310-320°C; and / or

[0056] The repeated heat treatment can be carried out for a period of 1.5-8 hours, preferably 1.5-8 hours, especially 1.5-6 hours or 3-6 hours or 1.5-3 hours; and / or

[0057] During the repeated heat treatment, at least 40 wt%, more preferably at least 60 wt%, even more preferably at least 75 wt% of the phenyldichlorophosphine is removed, and / or

[0058] During the repeated heat treatment, at least 90 wt%, more preferably at least 98 wt%, even more preferably at least 99.5 wt% of the chlorobenzene and phosphorus trichloride is removed, and / or

[0059] During the repeated heat treatment, no more than 40 wt%, for example no more than 30 wt% or 10-25 wt% of the diphenylchlorophosphine is removed,

[0060] wherein the wt% is based on the total weight of the reaction mixture as described above.

[0061] In a preferred embodiment, the process of the present application comprises, prior to the repeated heat treatment, additional addition of diphenylchlorophosphine to the reaction mixture obtained after completion of the previous heat treatment, preferably the amount of diphenylchlorophosphine added is at least 5 wt% (e.g. 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or 90 wt%), preferably at least 10 wt% or at least 20 wt%, for example 10-80 wt% or 10-60 wt% or 20-60 wt%, based on the total weight of the reaction mixture obtained after completion of the previous heat treatment. In case the repeated heat treatment is carried out more than once, for example 2, 3, 4 or 5 times, the amount of diphenylchlorophosphine added can be the same or different each time. The content of triphenylphosphine in the product can be further increased by additional addition of diphenylchlorophosphine to the reaction mixture obtained after completion of the previous heat treatment.

[0062] In case the heat treatment is repeated, the time of each heat treatment (including the heat treatment and the repeated heat treatment) can be 1.5-2.5 hours or 3-6 hours, preferably 1.5-2.5 hours.

[0063] According to the present application, in case the heat treatment is performed repeatedly, a shorter heat treatment time can be employed, for example 1.5 to 2.5 hours (e.g. 1.8 hours, 2 hours or 2.2 hours). The repeated heat treatment can result in a higher triphenylphosphine yield at the same or a similar total heat treatment time as compared to the case where the heat treatment is not repeated. Alternatively, the repeated heat treatment can result in the same or a similar triphenylphosphine yield at a shorter total heat treatment time as compared to the case where the heat treatment is not repeated.

[0064] In one embodiment, the content of phenyldichlorophosphine in the reaction mixture after completion of the heat treatment is not more than 8 wt.-% (e.g. 7 wt.-%, 6 wt.-%, 5 wt.-%, 4 wt.-%, 3 wt.-%, 2 wt.-% or 1 wt.-%), preferably not more than 6 wt.-% or not more than 4 wt.-% or not more than 3 wt.-% or not more than 2 wt.-%, for example 0.5 to 8 wt.-%, or 1 to 6 wt.-%, or 1 to 5 wt.-%, or 1 to 4 wt.-%, or 1 to 3 wt.-%, based on the total weight of the reaction mixture after completion of the heat treatment.

[0065] In one embodiment, the total content of chlorobenzene and phosphorus trichloride in the reaction mixture after completion of the heat treatment is not more than 5 wt.-%, preferably not more than 3 wt.-%, more preferably not more than 1 wt.-%, in particular not more than 0.5 wt.-%, based on the total weight of the reaction mixture after completion of the heat treatment. It is particularly preferred that the reaction mixture after completion of the heat treatment is free of chlorinated and trichlorinated phosphorus.

[0066] In one embodiment, the content of triphenylphosphine in the reaction mixture after completion of the heat treatment is at least 20 wt.-% (e.g. 21 wt.-%, 25 wt.-%, 30 wt.-%, 35 wt.-%, 40 wt.-%, 50 wt.-%, 60 wt.-%, 70 wt.-% or 80 wt.-%), preferably at least 30 wt.-% or at least 35 wt.-%, even at least 40 wt.-%, for example 20 to 80 wt.-%, 30 to 70 wt.-%, 35 to 70 wt.-%, 40 to 70 wt.-%, based on the total weight of the reaction mixture after completion of the heat treatment.

[0067] In one embodiment, the weight ratio of the amount of triphenylphosphine in the reaction mixture after completion of the heat treatment to the total amount of diphenylchlorophosphine in the diphenylchlorophosphine starting material can be at least 0.15 (e.g. 0.16, 0.18, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55 or 0.6), preferably at least 0.15 or at least 0.2 or at least 0.25, even at least 0.3 or 0.4, for example 0.15 to 0.6, 0.2 to 0.6 or 0.2 to 0.5 or 0.25 to 0.45 or 0.35 to 0.45.

[0068] The weight ratio of the content of phenyldichlorophosphine in the reaction mixture after completion of the heat treatment, the total content of chlorobenzene and phosphorus trichloride, the content of triphenylphosphine, and / or the amount of triphenylphosphine to the total amount of diphenylchlorophosphine in the diphenylchlorophosphine starting material in the context of the present disclosure can refer to the reaction mixture obtained after a single heat treatment or to the reaction mixture obtained after repeated heat treatments.

[0069] In a preferred embodiment, the process of the present application further comprises repeating the heat treatment as defined above 1 to 5 times, preferably 1 to 4 times, more preferably 2 or 3 times, to the reaction mixture obtained after completion of the heat treatment, wherein the content of triphenylphosphine in the final reaction mixture is at least 40 wt.-% (e.g. 50 wt.-%, 60 wt.-%, 70 wt.-% or 80 wt.-%), preferably at least 50 wt.-% or at least 60 wt.-%, e.g. 40 to 80 wt.-%, 50 to 70 wt.-%, based on the total weight of the reaction mixture after completion of the heat treatment.

[0070] In a preferred embodiment, the process of the present application further comprises repeating the heat treatment as defined above 1 to 5 times, preferably 1 to 4 times, more preferably 2 or 3 times, to the reaction mixture obtained after completion of the heat treatment, wherein the weight ratio of the amount of triphenylphosphine in the final reaction mixture to the total amount of diphenylchlorophosphine in the diphenylchlorophosphine starting material can be at least 0.3 (e.g. 0.35, 0.38, 0.40, 0.45, 0.50, 0.55 or 0.6), preferably at least 0.35 or at least 0.38, e.g. 0.3 to 0.6, 0.35 to 0.6 or 0.3 to 0.5 or 0.35 to 0.45.

[0071] In one embodiment, the process comprises heat treating the diphenylchlorophosphine starting material at a temperature of 280 to 420 °C, wherein at least part of the phenyldichlorophosphine is removed during the heat treatment, the heat treatment is carried out for a time of 1.5 to 12 hours, and

[0072] The content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 65 wt.-%, the content of phenyldichlorophosphine is not more than 30 wt.-%, and the content of phosphorus trichloride is not more than 5 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0073] In one embodiment, the process comprises heat treating the diphenylchlorophosphine starting material at a temperature of 290 to 400 °C, wherein at least 20 wt.-% of the phenyldichlorophosphine is removed during the heat treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the removed phenyldichlorophosphine, and

[0074] The content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 70 wt.-%, the content of phenyldichlorophosphine is not more than 20 wt.-%, and the content of phosphorus trichloride is not more than 2 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0075] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 300 to 350°C, wherein during the heat-treatment at least 20 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine,

[0076] The heat-treatment is carried out for a period of at least 1.5 hours, and

[0077] The content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 70 wt.-%, the content of phenyldichlorophosphine is not more than 20 wt.-%, and the content of phosphorus trichloride is not more than 2 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0078] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 300 to 350°C, wherein during the heat-treatment at least 20 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine,

[0079] During the heat-treatment at least 80 wt.-% of chlorobenzene and phosphorus trichloride are removed, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat-treatment and the removed chlorobenzene and phosphorus trichloride.

[0080] The heat-treatment is carried out for a period of at least 1.5 hours, and

[0081] The content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 70 wt.-%, the content of phenyldichlorophosphine is not more than 20 wt.-%, and the content of phosphorus trichloride is not more than 2 wt.-%, based on the total weight of the diphenylchlorophosphine starting material.

[0082] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 300 to 350°C, wherein during the heat-treatment at least 20 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine,

[0083] During the heat-treatment at least 90 wt.-% of chlorobenzene and phosphorus trichloride are removed, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat-treatment and the removed chlorobenzene and phosphorus trichloride,

[0084] the time of the heat treatment is 1.5 to 12 hours, and

[0085] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 80% by weight, the content of phenyldichlorophosphine is not more than 15% by weight, and the content of phosphorus trichloride is not more than 1% by weight, based on the total weight of the diphenylchlorophosphine starting material.

[0086] In one embodiment, the process comprises heat treating a diphenylchlorophosphine starting material at a temperature of 300 to 350°C, wherein during the heat treatment at least 40% by weight of phenyldichlorophosphine is removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed,

[0087] during the heat treatment at least 90% by weight of chlorobenzene and phosphorus trichloride is removed, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat treatment and the chlorobenzene and phosphorus trichloride removed,

[0088] wherein during the heat treatment not more than 50% by weight of diphenylchlorophosphine is removed, based on the total amount of diphenylchlorophosphine present in the reaction mixture after completion of the heat treatment and the diphenylchlorophosphine removed,

[0089] the time of the heat treatment is 1.5 to 12 hours, and

[0090] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 80% by weight, the content of phenyldichlorophosphine is not more than 15% by weight, and the content of phosphorus trichloride is not more than 1% by weight, based on the total weight of the diphenylchlorophosphine starting material.

[0091] In one embodiment, the process comprises heat treating a diphenylchlorophosphine starting material at a temperature of 300 to 320°C, wherein during the heat treatment at least 60% by weight of phenyldichlorophosphine is removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed,

[0092] during the heat treatment at least 98% by weight of chlorobenzene and phosphorus trichloride is removed, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat treatment and the chlorobenzene and phosphorus trichloride removed,

[0093] wherein during the heat treatment not more than 40% by weight of diphenylchlorophosphine is removed, based on the total amount of diphenylchlorophosphine present in the reaction mixture after completion of the heat treatment and the diphenylchlorophosphine removed,

[0094] the time of the heat treatment is 1.5 to 8 hours, and

[0095] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 95 wt.-%, the content of phenyldichlorophosphine is not more than 3 wt.-%, the content of phosphorus trichloride is not more than 0.1 wt.-% (preferably the diphenylchlorophosphine starting material is free of phosphorus trichloride), based on the total weight of the diphenylchlorophosphine starting material.

[0096] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0097] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0098] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0099] the heat-treatment is carried out for a period of 1.5 to 6 hours, and

[0100] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 95 wt.-%, the content of phenyldichlorophosphine is not more than 3 wt.-%, the content of phosphorus trichloride is not more than 0.1 wt.-% (preferably the diphenylchlorophosphine starting material is free of phosphorus trichloride), based on the total weight of the diphenylchlorophosphine starting material.

[0101] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0102] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0103] In one embodiment, the process comprises heat-treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C, wherein during the heat-treatment at least 75 wt.-% of phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the phenyldichlorophosphine removed,

[0104] the heat-treatment is carried out for a period of 1.5 to 2.5 hours,

[0105] the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 95 wt.-%, the content of phenyldichlorophosphine is not more than 3 wt.-%, the content of phosphorus trichloride is not more than 0.1 wt.-% (preferably the diphenylchlorophosphine starting material is free of phosphorus trichloride), based on the total weight of the diphenylchlorophosphine starting material, and

[0106] the process comprises repeating the heat treatment as defined above 1 to 5 times, preferably 1 to 4 times, more preferably 2 or 3 times, after the reaction mixture obtained after completion of the heat treatment, and, especially before repeating the heat treatment, additionally adding diphenylchlorophosphine to the reaction mixture obtained after completion of the last heat treatment, preferably the amount of diphenylchlorophosphine added is at least 5 wt.-%, preferably at least 10 wt.-% or at least 20 wt.-%, for example 10 to 80 wt.-%, based on the total weight of the reaction mixture obtained after completion of the last heat treatment.

[0107] In one embodiment, during the heat treatment at least 75 wt.-% of the phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed, and the heat treatment is carried out for a time of 3 to 6 hours,

[0108] In one embodiment, during the heat treatment at least 75 wt.-% of the phenyldichlorophosphine are removed, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed, and the reaction mixture obtained after completion of the heat treatment is repeated 1 to 5 times as defined above and the sum of the time of the heat treatment and the time of the repeated heat treatment is 4 to 20 hours or 4 to 10 hours.

[0109] The process according to the application is carried out under the protection of an inert gas, for example nitrogen. Before carrying out the process according to the application, the reactor is replaced with an inert gas, for example nitrogen, for example 2 to 5 times, preferably 3 to 5 times.

[0110] The product mixture of the process according to the application can be separated by work-up, for example by distillation.

[0111] In one embodiment, the diphenylphosphine chloride raw material can be prepared by using chlorobenzene and yellow phosphorus as raw materials. The obtained reaction mixture generally contains light components such as chlorobenzene and phosphorus trichloride, and phenyldichlorophosphine, diphenylphosphine chloride and triphenylphosphine. In the reaction mixture, the amount of triphenylphosphine is generally not more than 6% by weight, for example 1-6% by weight or 2-6% by weight, based on the total weight of phenyldichlorophosphine, diphenylphosphine chloride and triphenylphosphine. The reaction is carried out at a high temperature (for example 300-500°C or 300-400°C) and an elevated pressure (for example 0.01-8.0 MPa or 0.01-6.0 MPa, preferably autogenous pressure). The diphenylphosphine chloride raw material of the present application can be prepared by removing chlorobenzene, phosphorus trichloride and most of the phenyldichlorophosphine from the reaction mixture, or can be prepared by additionally adding diphenylphosphine chloride to the product mixture enriched in diphenylphosphine chloride obtained after removing chlorobenzene, phosphorus trichloride and most of the phenyldichlorophosphine from the reaction mixture.

[0112] In this technical solution, since the diphenylphosphine chloride does not need to be specially purified, the purification cost is saved.

[0113] Examples

[0114] The features of the present application are further illustrated by the following examples, but the present application is not limited thereto. In the examples, the specific conditions not mentioned are carried out according to the conventional conditions. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market. In the examples, the pressure is indicated as the gauge pressure.

[0115] Raw materials:

[0116] Diphenylphosphine chloride: Hubei Guron Technology Co., Ltd., purity ≥ 99.5%, triphenylphosphine content 0.1%-0.3%, without phosphorus trichloride.

[0117] Content determination:

[0118] Each component is analyzed by gas chromatography, and quantified by the correction normalization method.

[0119] Example 1 (comparative):

[0120] The 5L synthesis reactor was replaced with nitrogen three times, 500g of diphenylphosphine chloride was added to the synthesis reactor, the valve of the reactor was closed, the stirring was started, the stirring rate was 350-400r / min, the temperature was raised to a maximum of 300°C for 2.0h after 70-80min, the maximum pressure during the reaction was 0.05MPa, and the reaction produced 495g of reaction liquid, including 21g of phenyldichlorophosphine, 431g of diphenylphosphine chloride and 41g of triphenylphosphine, and the triphenylphosphine accounted for 8.3wt%.

[0121] Example 2:

[0122] The 5L synthesis reactor was replaced with nitrogen three times, 500g of diphenyl phosphine chloride was added into the synthesis reactor, the reactor valve was not closed, the stirring was started, the stirring rate was 350-400r / min, the temperature was raised to the highest 300-310°C for 70-80min, after 1h of heat preservation, the distillate began to distill, then the distillate was collected by normal pressure distillation for 4h, 15g of distillate was collected, including 2g of light components (chlorobenzene, phosphorus trichloride), 8g of phenyldichlorophosphine, and 4g of diphenyl phosphine chloride. The reaction in the reactor produced 458g of reaction liquid (bottom material), including 24g of phenyldichlorophosphine, 334g of diphenyl phosphine chloride, and 97g of triphenyl phosphine, the triphenyl phosphine accounted for 21.1wt% and did not contain light components (chlorobenzene and phosphorus trichloride).

[0123] Example 3:

[0124] The 5L synthesis reactor was replaced with nitrogen three times, 800g of diphenyl phosphine chloride was added into the synthesis reactor, the reactor valve was not closed, the stirring was started, the stirring rate was 350-400r / min, the temperature was raised to the highest 310-320°C for 70-80min, after 1h of heat preservation, the distillate began to distill, then the distillate was collected by normal pressure distillation for 4h, 232g of distillate was collected, including 5g of light components (chlorobenzene, phosphorus trichloride), 87g of phenyldichlorophosphine, and 130g of diphenyl phosphine chloride. The reaction in the reactor produced 564g of reaction liquid (bottom material), including 16g of phenyldichlorophosphine, 328g of diphenyl phosphine chloride, and 216g of triphenyl phosphine, the triphenyl phosphine accounted for 38.3wt% and did not contain light components (chlorobenzene and phosphorus trichloride).

[0125] Example 4:

[0126] The 5L synthesis reactor was replaced with nitrogen three times, 800g of diphenyl phosphine chloride was added into the synthesis reactor, the reactor valve was not closed, the stirring was started, the stirring rate was 350-400r / min, the temperature was raised to the highest 310-320°C for 70-80min, after 1h of heat preservation, the distillate began to distill, then the distillate was collected by normal pressure distillation for 5h, 273g of distillate was collected, including 4g of light components (chlorobenzene, phosphorus trichloride), 91g of phenyldichlorophosphine, and 168g of diphenyl phosphine chloride. The remaining 520g of bottom material in the reactor included 12g of phenyldichlorophosphine, 283g of diphenyl phosphine chloride, and 220g of triphenyl phosphine, the triphenyl phosphine accounted for 42.4wt% and did not contain light components (chlorobenzene and phosphorus trichloride).

[0127] The above 520 g of the starting material and 280 g of diphenylphosphine chloride were added into a synthesis reactor, the valve of the reactor was not closed, the stirring was started with a stirring rate of 350-400 r / min, the temperature was raised to a maximum of 310-320 °C after 70-80 min, and then the distillate started to distill after 1 h of heat preservation, and then the distillate was collected by normal pressure distillation for 5 h, 151 g of distillate was collected, including 7 g of light components (chlorobenzene and phosphorus trichloride), 76 g of phenyldichlorophosphine, and 61 g of diphenylphosphine chloride. The remaining 645 g of the starting material in the reactor included 12 g of phenyldichlorophosphine, 228 g of diphenylphosphine chloride, and 404 g of triphenylphosphine, accounting for 62.6 wt% of triphenylphosphine and containing no light components (chlorobenzene and phosphorus trichloride).

[0128] The above 520 g of the starting material and 280 g of diphenylphosphine chloride were added into a synthesis reactor, the valve of the reactor was not closed, the stirring was started with a stirring rate of 350-400 r / min, the temperature was raised to a maximum of 310-320 °C after 70-80 min, and then the distillate started to distill after 1 h of heat preservation, and then the distillate was collected by normal pressure distillation for 5 h, 151 g of distillate was collected, including 7 g of light components (chlorobenzene and phosphorus trichloride), 76 g of phenyldichlorophosphine, and 61 g of diphenylphosphine chloride. The remaining 645 g of the starting material in the reactor included 12 g of phenyldichlorophosphine, 228 g of diphenylphosphine chloride, and 404 g of triphenylphosphine, accounting for 62.6 wt% of triphenylphosphine and containing no light components (chlorobenzene and phosphorus trichloride).

[0129] Example 5:

[0130] The 5 L synthesis reactor was replaced with nitrogen for three times, 800 g of diphenylphosphine chloride was added into the synthesis reactor, the valve of the reactor was not closed, the stirring was started with a stirring rate of 350-400 r / min, the temperature was raised to a maximum of 310-320 °C after 70-80 min, and then the distillate started to distill after 1 h of heat preservation, and then the distillate was collected by normal pressure distillation for 2 h, 114 g of distillate was collected, including 4 g of light components (chlorobenzene and phosphorus trichloride), 56 g of phenyldichlorophosphine, and 50 g of diphenylphosphine chloride. The remaining 685 g of the starting material in the reactor included 10 g of phenyldichlorophosphine, 505 g of diphenylphosphine chloride, and 160 g of triphenylphosphine, accounting for 23.4 wt% of triphenylphosphine and containing no light components (chlorobenzene and phosphorus trichloride).

[0131] The above 685 g of the raw material and 115 g of diphenylphosphine chloride are added into a synthesis reactor, the valve of the reactor is not closed, the stirring is started with a stirring rate of 350-400 r / min, the temperature is raised to the maximum of 310-320 °C after 70-80 min, and then the distillation is collected for 2 h after 1 h of heat preservation, and 180 g of distillate is collected, wherein the light components (chlorobenzene and phosphorus trichloride) are 5 g, the phenyldichlorophosphine is 65 g, and the diphenylphosphine chloride is 100 g. The remaining 620 g of the raw material in the reactor contains 5 g of phenyldichlorophosphine, 327 g of diphenylphosphine chloride, and 283 g of triphenylphosphine, and the triphenylphosphine accounts for 45.6 wt% and does not contain light components (chlorobenzene and phosphorus trichloride).

[0132] The above 620 g of the raw material and 180 g of diphenylphosphine chloride are added into a synthesis reactor, the valve of the reactor is not closed, the stirring is started with a stirring rate of 350-400 r / min, the temperature is raised to the maximum of 310-320 °C after 70-80 min, and then the distillation is collected for 2 h after 1 h of heat preservation, and 79 g of distillate is collected, wherein the light components (chlorobenzene and phosphorus trichloride) are 4 g, the phenyldichlorophosphine is 43 g, and the diphenylphosphine chloride is 24 g. The remaining 720 g of the raw material in the reactor contains 4 g of phenyldichlorophosphine, 276 g of diphenylphosphine chloride, and 425 g of triphenylphosphine, and the triphenylphosphine accounts for 59.0 wt% and does not contain light components (chlorobenzene and phosphorus trichloride).

[0133] The above 720 g of the raw material and 80 g of diphenylphosphine chloride are added into a synthesis reactor, the valve of the reactor is not closed, the stirring is started with a stirring rate of 350-400 r / min, the temperature is raised to the maximum of 310-320 °C after 70-80 min, and then the distillation is collected for 2 h after 1 h of heat preservation, and 42 g of distillate is collected, wherein the light components (chlorobenzene and phosphorus trichloride) are 4 g, the phenyldichlorophosphine is 25 g, and the diphenylphosphine chloride is 11 g. The remaining 756 g of the raw material in the reactor contains 7 g of phenyldichlorophosphine, 236 g of diphenylphosphine chloride, and 494 g of triphenylphosphine, and the triphenylphosphine accounts for 65.3 wt% and does not contain light components (chlorobenzene and phosphorus trichloride).

[0134] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A process for the preparation of triphenylphosphine comprising heat-treating a diphenylphosphine chloride starting material at a temperature of 280-420°C to produce triphenylphosphine, wherein at least part of the phenyldichlorophosphine is removed during the heat-treatment.

2. The process according to claim 1, wherein at least 20 wt.%, preferably at least 40 wt.%, more preferably at least 60 wt.%, even at least 75 wt.% of the phenyldichlorophosphine is removed during the heat-treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

3. The process according to claim 1 or 2, wherein 20-98 wt.%, preferably 40-95 wt.%, more preferably 60-95 wt.% of the phenyldichlorophosphine is removed during the heat-treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat-treatment and the removed phenyldichlorophosphine.

4. The process according to any one of claims 1-3, wherein at least 80 wt.%, preferably at least 90 wt.%, more preferably at least 98 wt.%, even more preferably at least 99.5 wt.% of the chlorobenzene and phosphorus trichloride is removed during the heat-treatment, based on the total amount of chlorobenzene and phosphorus trichloride present in the reaction mixture after completion of the heat-treatment and the removed chlorobenzene and phosphorus trichloride.

5. The process according to any one of claims 1-4, wherein not more than 50 wt.%, preferably not more than 40 wt.%, such as not more than 30 wt.% of the diphenylphosphine chloride is removed during the heat-treatment, based on the total amount of diphenylphosphine chloride present in the reaction mixture after completion of the heat-treatment and the removed diphenylphosphine chloride.

6. The process according to any one of claims 1-5, wherein the content of phenyldichlorophosphine in the diphenylphosphine chloride starting material is not more than 35 wt.%, preferably not more than 30 wt.%, more preferably not more than 20 wt.%, still more preferably not more than 15 wt.%, especially not more than 8 wt.%, in particular not more than 3 wt.%, most preferably not more than 1 wt.%, such as not more than 0.5 wt.%, based on the total weight of the diphenylphosphine chloride starting material.

7. The process according to any one of claims 1-6, wherein the content of the diphenylphosphine chloride in the diphenylphosphine chloride starting material is at least 65 wt.%, preferably at least 70 wt.%, more preferably at least 80 wt.%, even more preferably at least 88 wt.%, still more preferably at least 95 wt.%, such as at least 98 wt.%, based on the total weight of the diphenylphosphine chloride starting material.

8. The process according to any one of claims 1-7, wherein the heat-treatment temperature is 290-400°C, preferably 300-400°C, more preferably 300-350°C.

9. The process according to any one of claims 1-8, wherein the heat-treatment temperature is especially 300-320°C, most preferably 310-320°C.

10. The process according to any one of claims 1-9, wherein the heat-treatment is carried out for a time of at least 1.5 hours, preferably 1.5-12 hours, more preferably 1.5-8 hours, especially 2-6 hours, most preferably 3-6 hours.

11. The process according to any one of claims 1 to 10, wherein the content of phosphorous trichloride in the diphenylchlorophosphine starting material is not more than 5 wt.%, preferably not more than 2 wt.%, more preferably not more than 1 wt.%, such as not more than 0.5 wt.% or not more than 0.1 wt.%, based on the total weight of the diphenylchlorophosphine starting material.

12. The process according to any one of claims 1 to 11, wherein the process comprises heat treating the diphenylchlorophosphine starting material at a temperature of 310 to 320°C for a time of 3 to 6 hours, and the content of diphenylchlorophosphine in the diphenylchlorophosphine starting material is at least 98 wt.%, the content of phenyldichlorophosphine is not more than 1 wt.% and the content of phosphorous trichloride is not more than 0.1 wt.% (preferably free of phosphorous trichloride), based on the total weight of the diphenylchlorophosphine starting material.

13. The process according to any one of claims 1 to 12, wherein the phenyldichlorophosphine is removed by distillation, preferably atmospheric distillation.

14. The process according to any one of claims 1 to 13, further comprising repeating the heat treatment as defined in any one of claims 1 to 5, 8 to 10 and 13 one to five times, preferably one to four times, more preferably two or three times, to the reaction mixture obtained after completion of the heat treatment.

15. The process according to claim 14, comprising adding additional diphenylchlorophosphine to the reaction mixture obtained after completion of the last heat treatment before repeating the heat treatment, preferably in an amount of at least 5 wt.%, preferably at least 10 wt.% or at least 20 wt.%, such as 10 to 80 wt.%, based on the total weight of the reaction mixture obtained after completion of the last heat treatment.

16. The process according to claim 14 or 15, wherein the time of each heat treatment is 1.5 to 2.5 hours or 3 to 6 hours.

17. The process according to any one of claims 1 to 16, wherein at least 75 wt.% of the phenyldichlorophosphine is removed during the heat treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed, and the time of the heat treatment is 3 to 6 hours, or wherein at least 75 wt.% of the phenyldichlorophosphine is removed during the heat treatment, based on the total amount of phenyldichlorophosphine present in the reaction mixture after completion of the heat treatment and the phenyldichlorophosphine removed, and the reaction mixture obtained after completion of the heat treatment is repeated the heat treatment as defined in any one of claims 1 to 5, 8 to 10 and 13 one to five times and the sum of the time of the heat treatment and the time of the repeated heat treatments is 4 to 20 hours or 4 to 10 hours. ​ ​