Effect of Cesium and Phosphate Addition to Mo/V/W Mixed Oxide Catalysts for the Gas Phase Oxidation of Methacrolein to Methacrylic Acid

The present study investigates modified Mo/V/W mixed oxides as a possible alternative for state of the art heteropoly acid catalysts (HPA) in partial oxidation methacrolein (MAC) to methacrylic (MAA). Even though HPAs show an excellent activity and MAA selectivity, their long-term stability is unsatisfying, rendering catalyst inoperable after runtimes roughly 6 months. consisting M1 hexagonal (Mo,V,W)Ox-phase (h-phase) varying proportions were by impregnation with aqueous solutions containing cesium phosphate ions. All samples characterized respect specific surface area, crystallinity, elemental phase composition. catalytic performance MAC was investigated using continuously operated reaction unit tubular fixed bed reactor. Impregnation ions subsequent heating triggers transformation oxide into Keggin-type HPA, whereby h-phase more reactive than M1. HPA accompanied change properties, i.e., selectivity considerably improved. Compared synthesized directly, however, obtained exhibit no advantages, be it activity, or stability.