Some surface and catalytic properties of V2O5-Cr2O3/SiO2, MoO3-Cr2O3/SiO2 and NiO-Cr2O3/SiO2 ternary solid catalysts

Ternary vanadia-chromia/silica, molybdena-chromia/silica and nickel oxide-c hromia/silica solid catalysts were prepared by the impregnation method. The ir structural characteristics were examined using differential thermal anal ysis (DTA) and X-ray diffraction techniques. The catalytic activities of th e prepared samples towards the conversion of isopropanol and cyclohexanol a nd the kinetics of these catalytic conversions were studied with the aid of a microcatalytic pulse technique. In addition, the surface acidities of se lected samples were measured From the percentage of propene produced by the poisoned catalysts. X-Ray diffraction and differential thermal analysis revealed that the only detectable phase was alpha -Cr2O3 with the presence of all other phases or spinel not being confirmed. The order of the surface acidities was found to lie in the sample sequence: 3 wt% V2O5-20 wt% Cr2O3/SiO2 > 3 wt% MoO3-20 w t% Cr2O3/SiO2 >20 wt% Cr2O3/SiO2 > 3 wt% NiO-20 wt% Cr2O3/SiO2, all samples having been precalcined at 500 degreesC. Catalytic conversion of isopropanol gave propene and acetone, whereas cyclo hexene, cyclohexanone and methylcyclopentene las an isomerization product) were produced from the catalytic conversion of cyclohexanol. The catalytic activity was found to be influenced considerably by the type of impregnatin g ion employed and by the precalcination temperature, and hence by the surf ace acidity of the examined catalysts. On the other hand, the Bassett-Habgo od and Kiperman equations could be applied in a satisfactory manner to the generation of the various reaction products. The calculated activation ener gies for the catalytic conversion of isopropanol and cyclohexanol were comp ared.