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 hydroxooligomers intercalated within the layers of alpha-zirconium phosphate using a colloidal suspension of the phosphate previously swelled with vapors of n-propylamine; The catalytic activity of pillared materials for the dehydrogenation of propane under oxidative and nonoxidative conditions has been 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 the sample Ga/Cr 50/50, all catalysts being highly selective to propene. The observed initial deactivation was due to coke originated from side reactions on active sites. Under oxidative conditions, the catalytic activity at 673 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 observed high activity is attributed to the presence of Cr(III) with coordination vacancies that, in an inert atmosphere, can activate propane molecules, yielding propene and hydrogen; while under oxidative conditions is capable of activating oxygen, by a labile coordination between the metal ion and oxygen, and its subsequent transfer to propane yielding propene and water.