Decomposition and Reforming of Formic Acid on Supported Au Catalysts: Production of CO-Free H2

The vapor-phase decomposition of formic acid was studied over Au supported on various materials, with the aim of producing CO-free H 2 . With regards to the decomposition and H 2 formation, Au/SiO 2 was found to be the most active catalyst. The reaction started at 373 K and was complete at 523 K. Depending on the nature of the supports, significant differences were experienced in the reaction pathways. On Au deposited on SiO 2, CeO 2, and carbon Norit, dehydrogenation predominated, whereas on Al 2 O 3, ZSM-5, and TiO 2 -supported Au, dehydration of formic acid was favored. Pure CO-free H 2 was obtained on Au/SiO 2 and Au/CeO 2 at and below 473 K. No changes in activity or selectivity were observed within ∼10 h. For most of the catalysts, the selectivity was improved by the addition of water to formic acid. In situ infrared spectroscopic studies revealed the formation of formate species even on Au/SiO 2, located exclusively on Au particles. The decomposition of HCOOH over Au/SiO 2 followed zero-order kinetics. The activation energy for the decomposition was 60.7 kJ mol –1, and that for H 2 production was 58.5 kJ mol –1 .