Selective hydrogenolysis of dichlorodifluoromethane on carbon covered alumina supported palladium catalyst

Abstract

γ-Alumina is modified by carbon coverage and the resulting carbon covered alumina is used in the preparation of supported Pd catalysts with varying Pd loadings. The prepared catalysts have been characterized by BET surface area, CO-chemisorption, X-ray diffraction and temperature programmed reduction (TPR). The catalytic activities of these catalysts have been tested for the selective hydrogenolysis of dichlorodifluoromethane to difluoromethane. TPR studies reveal that fresh Pd/CCA catalysts at lower Pd loading (up to 4 wt.%) exhibit features of Pd/Al 2O 3 (decomposition of β-PdH x ) along with Pd/C (reaction of Cl − with hydrogen) and beyond 4 wt.%, only Pd/C features are observed. TPR of spent catalysts reveal the increase in the intensity of β-PdH x with increase in Pd loading indicating the reorganization of Pd particles during the course of hydrogenolysis reaction. TPR of CCA and active carbon supports showed that the nature of carbon is somewhat different in CCA and active carbon. XRD data has shown that some amount of uncovered alumina is converted into its hydroxide fluoride. High selectivity to HFC-32 (∼95%) over 4 wt.% Pd/CCA catalyst at a reaction temperature of 220 °C is attributed to the beneficial role of carbon coverage on γ-alumina.