CHARACTERIZATION BY TEMPERATURE-PROGRAMMED REDUCTION AND BY TEMPERATURE-PROGRAMMED OXIDATION (TPR-TPO) OF CHROMIUM(III) OXIDE-BASED CATALYSTS - CORRELATION WITH THE CATALYTIC ACTIVITY FOR HYDROFLUOROALKANE SYNTHESIS

The catalytic activity of chromium (III) oxide for the fluorination of CF3CH2Cl (HCFC 133a) is proportional to the number of reversibly oxid ized sites. The proportionality coefficient depends on the atmosphere employed during the pretreatment of the catalyst. The temperature-prog rammed reduction and temperature-programmed oxidation experiments cons titute a simple technique that allows the number of reversibly oxidize d chromium atoms to be measured. The method of preparation of the chro mium hydroxide has little effect on the catalytic properties of chromi um (III) oxide. The activation atmosphere and the temperature are esse ntial parameters in the formation of chromium (III) oxide from hydroxi de. Indeed, the most active chromium (III) oxide for the fluorination of CF3CH2Cl is obtained by thermal treatment of hydroxide at 380 degre es C under nitrogen. (C) 1995 Academic Press, Inc.