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 carbid e has been studied for the reforming reaction of 2-methylpentane in a great excess of hydrogen (P-H2/P-HC = 150). The oxygen surface concent ration has been measured by the ratio of the signal area of the O-1s a nd the W-4f levels as determined by X-ray photoelectron spectroscopy. Two kinds of processes are observed: cracking and isomerization reacti ons. The introduction of oxygen at T = 350 degrees C leads to a deep d ecrease of the cracking reaction kinetics; about two orders of magnitu de. The tungsten carbide, strongly selective for cracking reactions in absence of oxygen, becomes very selective for isomer production in th e presence of oxygen.