Supported VPO Catalysts for Maleic Anhydride by Atomic Layer Deposition.

The preparation of vanadium-phosphate catalysts by Atomic Layer Deposition (ALD) was studied for application to selective oxidation of n-butane to maleic anhydride (MA). Modification of bulk V2O5 by ALD with trimethylphosphate significantly increased the selectivity to MA but the catalyst performance was still much worse than that observed for bulk vanadium phosphate (VPO). Silica-supported VPO was then prepared by ALD of P and V and compared to a VPO/SiO2 catalyst prepared by impregnation. Raman spectra showed that the ALD-prepared materials were more homogeneous, and temperature-programmed desorption of 2-propanol demonstrated that the VPO phase covered the silica more uniformly when deposited by ALD. However, the bulk VPO catalyst remained the most selective for MA. Possible reasons for why the supported catalysts showed lower performance are discussed and suggestions made for improving these catalysts. [ABSTRACT FROM AUTHOR]