Deactivation of Pt Catalysts during Hydrothermal Decarboxylation of Butyric Acid

Abstract

Decarboxylation of fatty acids is a path to hydrocarbon fuels from renewable biomass resources. We explored the deactivation of Pt catalysts during the hydrothermal decarboxylation of butyric acid at 350 °C and 3000 psi in a continuous flow reactor. DRIFTS spectra of the used catalyst showing characteristic absorptions at 2900 and 1500 cm –1 suggested that unsaturated hydrocarbons are responsible for catalyst poisoning. The restoration of appreciable catalyst activity due to controlled oxidation indicated that coke had formed during the decarboxylation experiment. BET measurements showed that the Vulcan XC-72R carbon support pore volume decreased from 1.41 to 0.55 cm 3 /g. Thus, a combination of poisoning, coking, and pore structure changes in the carbon support caused the Pt/C catalyst to deactivate over a period of 24 h on stream. The first-order deactivation rate constant for Pt/C was 0.063 ± 0.006 h –1 . These results provide insight into interventions that may lead to prolonged catalyst activity for hydrothermal reactions.