Time resolved ft-iras at high pressures: hydrogen assisted CO dissociation in the methanation reaction on Ru(001)

Abstract

Time-resolved Fourier Transform-Infrared Reflection Spectroscopy has been utilized to measure the kinetics of the dissociation of carbon monoxide on Ru(001) under reaction conditions of methanation, i.e. elevated pressures (1 to 100 torr) and temperatures (300 to 700 K). Following the decrease in intensity of the C-O stretching vibration, we can measure reaction rates and activation energy for the dissociation reaction. The absence of a significant frequency shift during reaction indicates the formation of carbon islands which prevent further CO adsorption. The presence of hydrogen is found to increase the dissociation rate of CO by more than two orders of magnitude. This “promotional” effect of the hydrogen is believed to be due to formation of water from oxygen and hydrogen, which prevents the recombination of dissociated CO and shifts the equilibrium between dissociation and recombination in favour of CO dissociation.