Dispersion and activity of vanadia supported on phosphate modified silica

Abstract

Silica was modified by phosphoric acid impregnation and was used as a support in the preparation of supported vanadium oxide catalysts. The prepared catalysts were characterised by low-temperature oxygen chemisorption. X-ray diffraction and electron spin resonance techniques. Activities of the catalysts for the partial oxidation of methanol were also studied. These results suggest a higher dispersion of the active vanadia phase even at highly loaded vanadium oxide on phosphate modified silica compared to conventional V2O5 catalysts supported on unmodified silica. Phosphate modified silica supported V2O5 catalysts showed a high selectivity towards formaldehyde at a reaction temperature of 175 °C. The high HCHO selectivity is in conformity with ESR spectral analysis of these catalysts which showed a stronger V=O bond strength when compared to unmodified SiO2 supported vanadia catalysts.