Thermal decomposition of precursors and physicochemical characteristics of titania supported vanadia catalysts

Abstract

Titania supported vanadia catalysts (2.5, 5, and 11 wt.% V 2O 5) were prepared by a wet impregnation technique and their thermal behavior, morphology as well as redox properties were examined by thermal analysis methods thermogravimetry (TGA), differential scanning calorimetry (DSC), temperature programmed-evolved gas analysis with mass spectroscopy, (EGA-MS), scanning electron microscopy (SEM), and temperature programmed reduction (TPR). The two Eurocat samples EL10V1 and EL10V8 containing 1 and 8 wt.% V 2O 5 were also characterized using the same techniques. Thermal decomposition of vanadium oxide precursors (ammonium vanadyl oxalate) supported on TiO 2 as evidenced by thermal analysis, occurs in three successive steps, which are influenced by the surrounding atmosphere (oxidative, reductive, and inert). The presence of tower-like vanadia crystals in the sample with the highest vanadia loading (11 wt.% V 2O 5) was identified by SEM. The H 2–TPR experiments revealed that the reduction temperature is a factor of the vanadia loading and the type of support. Vanadia species supported on Norton titania are more reducible that those supported on Eurocat titania.