Manufacture of phosphorus oxychloride

Phosphous oxychloride is produced in a continuous process by introducing phosphorus trichloride and a gas containing free oxygen separately into a liquid heel composed of POCl3 and unreacted PCl3, the POCl3 being present in the liquid heel in an amount of at least 70 wt. per cent at all times throughout the process. The reaction is carried out at 15 DEG -70 DEG C. and atmospheric to 30 p.s.i.g. pressure with air, O2-enriched air, or O2. The liquid heel is withdrawn from surge tank 1 (whence product containing 80-90% POCl3 is withdrawn at 8), through 2 by circulating pump 3 and PCl3 is added at 5. O2 is added to the discharge at 6 and the mixture passes through water-cooled pipe reactor 4. The volume ratio of liquid to gas at the inlet 6 is 2/1 to 4,2/1, and the time in the reactor is 0,05-0,5 mins. The reaction mixture is returned to surge tank 1. The flow in the pipe reactor should be turbulent and the minimum liquid velocity in the first 5-8 vol. per cent of the reactor should be 8-11 ft./sec. Velocity in the remainder of the reactor is 4-6 ft./sec. and this difference in flow velocity is obtained by variation in pipe diameter. A simple heat-exchanger jacketed reaction kettle equipped with an agitator (Fig. 1, not shown) is also described where PCl3 is fed in just below the surface of the liquid heel, and O2 is fed in through a distributer at the bottom. Specification 727,950 is referred to.