Daikin Kogyo Co., Ltd.

Yohnosuki Ohsaka

Heikitsu Sonoyama

A process for preparing high purity tetrafluoromethane which comprises the steps of (a) passing a gaseous mixture of chlorotrifluoromethane and hydrogen fluoride in a molar proportion of 1:1 to 1:10 through a catalyst layer of chromium oxyfluoride at a temperature of 380.degree. to 420.degree. C. under a pressure of 1 to 5 atm with a space velocity of 10 to 150 hr.sup.-1, (b) washing the gaseous reaction mixture obtained in the foregoing step (a) with water or an aqueous alkaline solution so as to remove acidic materials therefrom, (c) passing the resultant gaseous mixture with hydrogen fluoride in an amount of 0.2 to 10 mole to 1 mole of the combined amount of chlorotrifluoromethane and tetrafluoromethane in the gaseous mixture through a catalyst layer of chromium oxyfluoride at a temperature of 380.degree. to 420.degree. C. under a pressure of 1 to 5 atm with a space velocity of 10 to 300 hr.sup.-1 and (d) washing the gaseous reaction mixture obtained in the foregoing step (c) with water or an aqueous alkaline solution so as to remove acidic materials therefrom, optionally followed by effecting the same operations as in the latter two steps repeatedly one or more times until a desired purity of tetrafluoromethane is obtained.

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Osaka, Japan

Yohnosuki Ohsaka