KINETIC STUDIES ON CATALYTIC METHANATION BY MEANS OF A CONCENTRATION-CONTROLLED RECYCLE REACTOR.

The rate behavior of multi-step reaction systems is difficult to model. Concentration-controlled investigations in a recycle reactor provide new tools for this purpose, e. g. the possibility to decompose a network into single reaction steps. Methanation of carbon monoxide over a supported Ni catalyst could be shown to be accompanied to a considerable extent by the shift reaction, and to a lesser extent by direct hydrogenation of carbon dioxide. Deactivation of the catalyst was measured at definite gas compositions. The two main steps show different responses to deactivation: Separable kinetics was found only for the methanation step. Power law rate equations were fitted to the rate data of the individual reaction steps to represent the main features of their kinetic behavior. Some aspects of deactivation kinetics are also discussed.