Catalytic activity and XPS surface determination of tungsten carbide for hydrocarbon reforming. Influence of the oxygen

The influence of oxygen on the catalytic properties of tungsten carbide has been studied for the reforming reaction of 2-methylpentane in a great excess of hydrogen. The oxygen surface concentration has been measured by the ratio of the signal area of the O_1s and the W_4f levels as determined by X-ray photoelectron spectroscopy. Two kinds of processes are observed: cracking and isomerization reactions. The introduction of oxygen at T=350°C leads to a deep decrease of the cracking reaction kinetics; about two orders of magnitude. The tungsten carbide, strongly selective for cracking reactions in absence of oxygen, becomes very selective for isomer production in the presence of oxygen.