Characterization and reactivity of vanadium oxide supported on TiO2-SiO2 mixed oxide support

A TiO2-SiO2 support, 90Ti-Si, containing 90 wt.% TiO2 was synthesized by the sol-gel method. Several supported vanadium oxide (vanadia) catalysts, xV90Ti-Si (x = 2-12.5 wt.%) were synthesized by incipient wetness impregnation method using this support. The catalysts and support were characterized and probed with the propane oxidative dehydrogenation (ODH) reaction. The support possesses no rutile phase and retains 30-40% of its initial surface area even after calcination at 1073 K. The surface area loss is accelerated in the presence of vanadia and the rutile phase appears below 1073 K. Surface vanadia species are present for the supported vanadia catalysts calcined at 673 K and the propane ODH activity and propene yield increases with vanadia loading. The ODH activity of the 2V90Ti-Si sample at 673 K is retained even after the catalyst is pre-calcined at 1023 K. Interestingly, the activity of the 4V90Ti-Si sample at 673 K reaches a maximum at an intermediate pre-calcination temperature. The higher vanadia loading samples deactivate with an increase in calcination temperature. The ODH reactivity reveals that the propene yield at iso-conversion increases with loading. Analysis of kinetic parameters also reveals that the rate constant ratio increases with vanadia loading.