The Catalytic Decomposition of 2-Propanol over the Silica-Manganese(II), -Zinc(II) and -Magnesium(II) Prepared by the Homogeneous Method

Abstract

The catalytic dehydration and dehydrogenation of 2-propanol over thesilica-manganeset (II), -zinc(II)and-magnesium(II), which were prepared by the method of precipitation from homogeneous solution were compared with those over usual coprecipitated metals.Dehydration took place to a large extent over the catalysts prepared by the homogeneous method, while dehydrogenate did only toa small extent at 300Cover the catalysts prepared by the both methods. The catalytic dehydration activities on the homogeneous catalysts were much higher than those on the coprecipitated catalysts, and the order of activity was Mg(II) Zn(II) Mn(II).Kinetics studies using a fiow reactor indicated that the dehydration and the dehydrogenation were of both first-order irreversible reactions. From theArrhepius plots the activation energies for the dehydration Over the homogeneoussilica-manganese(E), -zinc(II) and -magnesium(E), were found to be 16.0, 17.9 and20.6kcal/mol.m2, respectively.From the consideration, of the changes of relative activities by adding various amounts of KOH and of the differences of thepH titration curves for the catalysts and silica gel, it was concludedthat the active sites of the dehydration were. Lewis acid site, vi2., the metals with the vacant orbitals which combined with the silica gel and those of the dehydrogenation were the electron pair donor or the oxygen atom of the metallic oxide bended to the silica gel.