Textural, Structural and Catalytic Properties of CrO/SiO Catalysts

Abstract

Four chromia/silica samples containing 5–30 wt% Cr III were prepared by impregnation methods and calcined at 773–1173 K. Nickel, molybdenum and vanadium oxide-impregnated Cr 2 O 3 /SiO 2 samples were also prepared by impregnation and were subjected to the same thermal treatment. The textural parameters of all the samples prepared were determined from the adsorption of nitrogen at 77 K, while X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques were used to elucidate their structures. The catalytic properties of the solids so prepared in the catalytic cracking of cumene were investigated using a pulse microcatalytic technique. The surface areas evaluated for the various Cr 2 O 3 /SiO 2 samples studied were found to decrease gradually on increasing their Cr III content, the calcination temperature and on addition of Ni, Mo and V oxides. DTA and XRD studies demonstrated the absence of any interaction between the SiO 2 and Cr 2 O 3 , with the latter being the only phase capable of detection by these techniques. Samples impregnated with Ni, Mo and V ions also showed no interaction between these ions and Cr 2 O 3 and SiO 2 , with only the corresponding oxides being detected. The results obtained for the catalysis studies also indicated that the cracking of cumene depended on the metal content, impregnant cations and thermal treatment of the solids employed.