Method for synthesising trifluoroethylene from chlorotrifluoroethylene

摘要

The present invention relates to the preparation of trifluoroethylene (VF3 or TrFE) by hydrogenolyzis of chlorotrifluoroethylene (CTFE) in the gaseous phase over a group VIII metal catalyst deposited on a support. This method can be used to obtain VF3 in an economical manner in conditions which minimize the risk of explosion of this molecule. Using a catalyst containing a group VIII metal and, more specifically, containing Pd deposited on a support and a specific series of steps of separation and purification makes it possible to obtain excellent CTFE conversion rates and high selectivity in VF3 at atmospheric pressure and at low temperatures.

主权项

1. A process for the manufacture of trifluoroethylene (VF3) from chlorotrifluoroethylene (CTFE), said process comprising the following stages, carried out at atmospheric pressure:
i) introducing, into a reactor having a jacket filled with a heat-exchange fluid, the temperature of which is maintained at between 25 and 50° C., a gas mixture A composed of hydrogen, CTFE and optionally an inert gas over a bed of catalyst based on a metal from Group VIII deposited on a support, the H2/CTFE molar ratio ranging from 0.5/1 to 2/1, resulting, after a sufficient contact time, in the achievement of a gas mixture B composed of reaction products comprising VF3 and organic byproducts, and also unconsumed H2, said inert gas and unconsumed CTFE and hydracids; ii) removing the hydracids present in the mixture B by washing with water, followed by washing with a dilute base and then drying, resulting in the recovery of a gas mixture C composed of reaction products comprising VF3 and organic byproducts, and also unconsumed H2, said inert gas and unconsumed CTFE; iii) passing the gas mixture C through a countercurrentwise column of a solvent, at a temperature lower than ambient temperature, resulting in obtaining, on the one hand, of the hydrogen and the inert gas and, on the other hand, of a mixture composed of organic products dissolved in said solvent; iv) desorbing, by heating to boiling point, the organic products dissolved in the solvent in order to obtain, on the one hand, the solvent, which will be recycled to the absorption, and, on the other hand, a mixture D composed of the reaction products devoid of hydrogen and of inert gas; v) distilling said mixture D of organic products, resulting in the recovery of the VF3 at the column top and of a mixture E at the column bottom composed of unconverted CTFE and also reaction byproducts.