Effect of CaO on decarboxylation of stearic acid over Pt/C catalyst

The effects of CaO addition and temperature on decarboxylation of stearic acid over Pt/C catalyst in subcritical water were investigated. The conversion of stearic acid increased dramatically, while the selectivity to heptadecane hardly changed with the addition of CaO. At 330 ℃ the conversion of stearic acid reached a maximum with Ca/stearic mol ratio of 0.5. Moreover, Pt/C catalyzed decarboxylation of stearic acid in subcritical water exhibited first-order kinetics. It was proposed that dissociative stearic acid was adsorbed on Pt/C catalyst, forming surface octadecanoate species and adsorbed H. The C-C bond dissociated via H insertion, resulting in the formation of heptadecane and CO₂. The addition of CaO promoted the dissociation of stearic acid. As a result, the amount of adsorbed octadecanoate increased and the reaction was accelerated.