Background and overview[1]
Diphenyl phosphate is an important pharmaceutical and pesticide intermediate. The currently reported preparation method is benzene and phosphorus trichloride using benzene as the solvent and aluminum trichloride as the acidifying agent to make phenylphosphorus dichloride, and phenylphosphorus dichloride using aluminum trichloride as the catalyst. A disproportionation reaction is carried out to produce diphenylphosphorus chloride. The diphenylphosphorus chloride is oxidized to diphenylphosphorus oxychloride by oxygen at cryogenic temperatures, and then hydrolyzed into diphenylphosphoric acid. However, the existing synthesis process of diphenylphosphoric acid is highly polluting and requires high equipment performance. The total yield is only 30% and the cost is high.
Preparation[1]
A preparation method of diphenylphosphoric acid specifically includes the following steps:
1) Put 208g toluene and 184g (1.2mol) phosphorus oxychloride into a 1000ml four-neck bottle, cool it to 15°C with ice water, and add dropwise 208g toluene and 219g (3mol) antioxidant between 15 and 25°C. rd) Diethylamine mixture, after adding dropwise, keep it at 15-25°C for 3 hours; the reaction principle of this step is as follows:
2) Filter the material after the reaction in step 1) to recover the reaction product diethylamine hydrochloride. The diethylamine hydrochloride can be processed into diethylamine as raw material for reuse, and then the filtrate is distilled under normal pressure and recovered The solvent toluene was continued to be distilled under reduced pressure to obtain 205 g (1.08 mol) of dichlorophosphoryl diethylamine as a fraction at 132-136°C and -0.096 MPa. The reaction yield was 90%.
3) Mix 2g tetrahydrofuran, 2g chlorobenzene, and 0.5ml bromobenzene to prepare the initiator material for later use.
4) Mix 140g chlorobenzene, 100g tetrahydrofuran, and 65g toluene in a 500ml bottle to make a mixed solution.
5) Add 27g (1.125mol) magnesium strips into a 1000ml dry reaction bottle, stir and heat, heat to 50°C and stop heating, use residual heat to reach the heating temperature of 60~70°C, add the initiator prepared in step 3) Conduct Grignard reaction with the material and observe whether the reaction is triggered in the reaction bottle. If a large amount of white smoke is produced in the reaction bottle and the temperature rises rapidly, it means that the reaction has been triggered.
6) Step 5) When the temperature in the reaction bottle stops rising, add the mixed solution obtained in step 4) dropwise. Keep it at 100~110℃ and add it dropwise. The maximum should not exceed 120℃ and the minimum should not be lower than 90℃. After the dropwise addition is completed, the reaction is maintained at 90 to 110°C for 2 hours. After the reaction is completed, the temperature is lowered to 55°C.
7) Mix 205g (1.08mol) dichlorophosphoryl diethylamine obtained in step 2) and 65g toluene to prepare a mixed solution. When the temperature drops to 55°C after the reaction in step 6), add the mixture dropwise liquid, control the dripping temperature of the mixed liquid to 55~65℃, after the dropwise addition is completed, keep the reaction at 55~65℃ for 3 hours, and collect the reaction product;
8) Add 100g hydrochloric acid and 230g (12.8mol) water to a 2000ml four-necked flask, stir and control the temperature inside the four-necked flask to 30-40°C, and dropwise add the reaction product collected in step 7) into the four-necked flask. After the addition is completed, the temperature is raised to 70~80°C and refluxed for 4 hours; the reaction principle is as follows:
Cool and filter, collect the solid material and dry it to obtain 178g (0.92mol) of the product diphenylphosphoric acid. The yield of the Grignard reaction and hydrolysis reaction in steps 5) to 8) is 85%. The total reaction yield of this product diphenyl phosphoric acid is 76.6% based on phosphorus oxychloride.
