Analysis of the catalytic activity induction and deactivation of PtIn/Mg(Al)O catalysts for propane dehydrogenation reaction
The catalytic activity induction and deactivation of PtIn/Mg(Al)O catalysts for propane dehydrogenation reaction are experimentally verified. Numerous physical–chemical characterizations are employed to probe the basis and structure–activity relationships, and a mechanism for the activity induction and deactivation is proposed with the help of a schematic diagram. XPS results prove that the valence state of In exhibits almost no change during the entire dehydrogenation reaction. In the activity induction period, the average metal particle size of the PtIn/Mg(Al)O catalyst presents a decreasing trend, and the specific surface area increases. Moreover, the crystal phase changes from primarily periclase (MgO) to dominantly meixnerite (Mg6Al2(OH)18·4H2O). Coke is mainly deposited on the carrier. Nevertheless, in the deactivation period, the metal particles tend to agglomerate and grow. The specific surface area decreases and crystal phase returns to the unique periclase crystal phase. A large amount of coke is formed over the catalyst and partially covers the active sites, which leads to the evident decrease of catalytic activity.