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

Abstract

The vapor-phase decomposition of formic acid was studied over Au supported on various materials, with the aim of producing CO-free H2. With regards to the decomposition and H2 formation, Au/SiO2 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 SiO2, CeO2, and carbon Norit, dehydrogenation predominated, whereas on Al2O3, ZSM-5, and TiO2-supported Au, dehydration of formic acid was favored. Pure CO-free H2 was obtained on Au/SiO2 and Au/CeO2 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/SiO2, located exclusively on Au particles. The decomposition of HCOOH over Au/SiO2 followed zero-order kinetics. The activat...