Propane dehydrogenation on mixed Ga/Cr oxide pillared zirconium phosphate materials

Porous Ga/Cr mixed oxides were prepared by calcination at 673 K of mixed hy droxooligomers intercalated within the layers of alpha-zirconium phosphate using a colloidal suspension of the phosphate previously swelled with vapor s of n-propylamine; The catalytic activity of pillared materials for the de hydrogenation of propane under oxidative and nonoxidative conditions has be en investigated in a flow apparatus. Under nonoxidative conditions at 823 K , the initial activity varies between 1.56 mu mol of propene . g(-1). s(-1) for the sample Ga/Cr 70/30 and 2.62 mu mol of propene . g(-1). s(-1) for t he sample Ga/Cr 50/50, all catalysts being highly selective to propene. The observed initial deactivation was due to coke originated from side reactio ns on active sites. Under oxidative conditions, the catalytic activity at 6 73 K, after 5 h of reaction, varies between 0.45 and 1.22 mu mol of propene . g(-1). s(-1) and the deactivation was inappreciable. In all cases, the o bserved high activity is attributed to the presence of Cr(III) with coordin ation vacancies that, in an inert atmosphere, can activate propane molecule s, yielding propene and hydrogen; while under oxidative conditions is capab le of activating oxygen, by a labile coordination between the metal ion and oxygen, and its subsequent transfer to propane yielding propene and water.