The decomposition of formic acid was studied on supported Rh catalysts in a flow reactor at 380-520 K. The dominant process in the decomposition was the dehydrogenation reaction which followed first-order kinetics. The values of activation energy of the reaction fell in the range 66-83 kJ mol-1. The activity of the catalysts, based on the turnover frequencies, decreased in the order Rh TiO2> Rh Al2O3> Rh MgO ≈ Rh SiO2. The presence of CO in the gas stream markedly inhibited the reaction. The effect of different treatments of the catalysts was also examined. In situ infrared spectroscopic measurements revealed that weakly held HCOOH, adsorbed CO, and formate species were present on the catalyst surfaces during the reaction. Evidence is presented to show that the surface formate is located not on the Rh, but rather on the support. The stability of this formate species was investigated by temperature-programmed desorption. It is assumed that the dissociative adsorption of HCOOH is the slowest step in the catalytic decomposition of formic acid.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry