Production of CO-free H2 from formic acid. A comparative study of the catalytic behavior of Pt metals on a carbon support

Abstract

The vapor-phase decomposition of formic acid was investigated over Pt metals supported on inert carbon Norit with the aim of producing CO-free H2. FTIR spectroscopic studies revealed that formic acid dissociated on Pt metals at 220–240K, but the formate species formed was stable only below 300–350K. Decomposition of formic acid started at and above 350K on all catalysts and was complete at 473–523K. Kinetic studies on Pt/Norit demonstrated that the decomposition was a zero-order process with an activation energy of 70.7kJ/mol. Although dehydrogenation was the predominant process at lower temperatures, CO-free H2 was not produced on any catalyst. The highest selectivity of 98.3–99% for H2 formation was attained on Ir/Norit. For all catalysts, the selectivity was improved considerably by the addition of water to formic acid. The production of CO-free H2 was achieved only on supported Ir at 383–473K. Similarly, as regards the H2 yield the outstanding catalyst was Ir/Norit, followed by Pt/Norit.