New Trends of Alkali Promotion in Heterogeneous Catalysis: Electrochemical Promotion with Alkaline Ionic Conductors

Abstract

Chemical promotion obtained with the addition of alkalis to a metal supported catalyst induces effects on the catalytic activity very similar to those of electrochemically supplied alkali ions trough the concept of electrochemical promotion of catalysis. Despite of the functional identity and the origin between two ways of promotion analyzed here (chemical and electrochemical), which follow the same general rules, the usefulness of the latter is clear. In this review the most important and recent contributions of Electrochemical Promotion with alkaline ionic conductors (Na+ and K+ conductors) in heterogeneous catalysis have been analyzed. The possibility of in situ controlling the alkali promoter coverage on the catalyst under working conditions lead to new opportunities from both: fundamental and more applied point of view. The optimization of catalytic activity and selectivity, the activation of a catalyst at lower reaction temperatures, the permanent electro-promotional effect or the regeneration of a catalyst at fixed reaction conditions are some of the novel contributions discussed here. Due to the wide use of alkali ions as electronic promoters in heterogeneous catalysis the aim of this review is to bring closer this fascinating and novel phenomenon to the catalysis scientific community.