Mechanism of the deactivation of nickel catalysts by steam under pressure

Abstract

1. An investigation was made into the deactivating effect of steam on nickel catalysts in the course of their preparation by reduction with hydrogen under pressure. 2. It was shown that pretreatment of a mixture of nickelous oxide and carrier (Al2O3, MgO) with steam under pressure results in the formation of catalysts of low activity. Similar treatment of a reduced carriersupported nickel catalyst has a very much smaller effect on activity. 3. It was shown that steam treatment of a coprecipitated mixture of nickelous oxide and alumina ( or magnesia) under pressure results in a far-reaching irreversible change, namely recrystallization with great reduction in specific surface. 4. It is evident that the deactivation of reduced nickel catalysts by steam in the course of their use is due to the formation of nickelous oxide films or phases that rapidly recrystallize and are reduced with difficulty with formation of coarsely dispersed nickel. It is probable that the mechanism here proposed is applicable also to the deactivation of iron catalysts by water vapor.