Catalysis in Molten Ionic Media

This chapter deals with catalysis in molten salts and ionic liquids, which are introduced and reviewed briefly, while an in-depth review of the oxidation catalyst used for the manufacturing of sulfuric acid and cleaning of flue gas from electrical power plants is the main topic of the chapter. The historical development of the process during the last 100 years is described briefly; it is noteworthy that the liquid nature of the catalyst medium was not recognized before the early 1940s. The catalyst system appears quite complicated due to the complex nature of the melt components, which are not identified easily. It has been shown that the melt consists of vanadium oxosulfato complexes in the oxidation states III-V in an alkali pyrosulfate solvent. However, many basic data for alkali pyrosulfates and oxosulfato vanadates have turned out to be either nonexisting or unreliable. As a result, the fundamental research described in this chapter involves (i) the synthesis of compounds and pure chemicals; (ii) the determination of basic physical and chemical data as melting point, density, heat capacity, and so on; (iii) the construction of phase diagrams; (iv) the determination of the crystal structure of vanadium compounds, of which the majority are identified as catalyst deactivation products; and (v) studies of molecular structure and catalytic activity. Finally, the reaction mechanism is highlighted, which represents the state of the art of that catalytic process by 2013. © 2013 Elsevier Inc. All rights reserved.