ACTIVATION AND DEACTIVATION OF COBALT CATALYSTS IN THE HYDROGENATION OF CARBON-DIOXIDE

Activation and deactivation of Co foils during hydrogenation of carbon dioxide have been studied in dependence on pretreatment of the cataly st and time on stream, temperature and composition of the educt gas. M odifications of the surface due to activation and deactivation have be en investigated by means of a combination of various methods, includin g temperature programmed processes as well as Auger electron spectrosc opy and electron microscopy. Both oxidation/reduction of the surface a nd incorporation of oxygen and carbon in the bulk lead to marked chang es in the surface structure and a considerable increase in surface are a. The catalytic activity of the oxidized surface concerning the hydro genation of CO2 is small, but increases strongly with reduction. Deact ivation is accompanied with structural changes and proved to be revers ible. Chemical poisoning was only observed after addition of hydrogen sulfide to the educt gas.