CONVERSION UNDER HYDROGEN OF DICHLORODIFLUOROMETHANE OVER BIMETALLIC PALLADIUM CATALYSTS

The conversion of difluorodichloromethane under hydrogen has been stud ied in the ps phase between 413 and 473 K at atmospheric pressure over graphite supported Pd, PdK, PdFe, PdCo and PdAg catalysts reduced at 523 K. Neither a stoichiometric phase, nor a solid solution was detect ed in these catalysts. In CF2Cl2 hydrogenation at low CF2Cl2 pressure (P(CF2Cl2) /P(H2) < 0.3), CH2F2 and CH4 represent more than 95% of the products. However, at high CF2Cl2 Pressure (P(CF2Cl2)/P(H2) > 2), and over PdFe/graphite or PdCo/graphite catalysts, high selectivities for the coupling product CF2CF2 were obtained. This is probably due to th e occurrence of some mixed sites between Pd and Fe or Co. The kinetics of the reaction indicates adsorption competition between CF2Cl2 and H -2 for the active sites, which can be described by an halogenation/deh alogenation mechanism of the palladium surface by CF2Cl2 and hydrogen respectively.