Oxydehydrogenation of ethylbenzene to styrene over metal pyrophosphates: 2. Microbalance studies of carbon deposition and burnoff

Abstract

A flow microbalance was used to measure the deposition of carbon from styrene and ethylbenzene and also the burnoff of carbon in oxygen in order to determine the role of carbon in the Oxydehydrogenation of ethylbenzene. Small amounts of oxygen enhance the rate of carbon deposition from styrene and the rate approaches zero at a carbon loading which corresponds closely with a graphitic monolayer. On selective catalysts, carbon burns at the same rate as that of graphite, whereas on nonselective catalysts it burns significantly faster. In the presence of styrene vapor, the rate of production of carbon oxides increases with increasing carbon levels. Reaction models indicate that in the presence of styrene vapor, carbon itself does not burn readily, but it does catalyze the burning of styrene and is the actual catalyst for the Oxydehydrogenation of ethylbenzene.