Effect of zirconia additives on the activity of the Cr/SiO2 catalyst in isobutane dehydrogenation

A new approach to the preparation of modified silica-based supports is suggested to obtain Crcontaining catalysts for paraffin hydrocarbon dehydrogenation. CrO (x) /ZrO2, CrO (x) /SiO2, and CrO (x) /nZrO(2)-SiO2 (n = 0.5, 1.0, and 2.0 ZrO2 monolayers) catalysts have been synthesized by incipient-wetness impregnation. The catalysts have been characterized by X-ray diffraction, diffuse reflectance spectroscopy, and temperature-programmed reduction with hydrogen. Their catalytic properties were investigated in the reaction of isobutane dehydrogenation. The state of the supported chromium depends considerably on the nature of the support. The formation of Cr2O3 particles, which show low activity in the dehydrogenation reaction, takes place in the CrO (x) /SiO2 catalyst, while chromium in the CrO (x) /ZrO2 catalyst is in a highly dispersed, X-ray-amorphous state. The addition of ZrO2 to CrO (x) /SiO2 increases the amount of chromium in the highly dispersed Cr(V) and Cr(VI) states, thus enhancing the isobutane dehydrogenation activity of the catalyst.