Chapter 4: Propane-Selective Oxidation to Acrylic Acid

Acrylic acid synthesis is currently based on propylene generated mainly by high-temperature processes, such as steam reforming or fluid catalytic cracking using petroleum feedstock. The development of novel catalysts for direct oxidation of propane to acrylic acid can have significant economic impact due to the abundance and lower costs of propane. Selectivity is an essential issue with regard to efficient exploitation of fossil resources and abatement of greenhouse-gas emissions. Direct conversion of propane to acrylic acid is challenging in view of the catalyst particularly because allylic C–H bonds in propylene-derived intermediates are more easily activated compared to the nonpolar C–H bonds in propane. The abundance and spatial arrangement of active sites that simultaneously bring about H-abstraction and O-insertion are required. Various types of catalysts that selectively oxidize propane to acrylic have been reported. High selectivity to acrylic acid has been achieved over chemically and structurally complex multicomponent oxides, like quinternary Mo–V–Te–Nb mixed oxides, which are characterized by high crystallinity, well-defined crystal structures, and high selectivity at comparatively high conversion. An attempt is undertaken to examine critically relations between synthesis of multimetal oxides, their bulk structure, surface termination, and dynamics in the feed of the reactants aiming at a deeper understanding of the essential aspects that determine selectivity in oxidation catalysis.