Effect of Transition Metal lons on Cyclohexene Formation over Zeolite Catalyst

Abstract

Oxidative dehydrogenation of cyclohexane was investigated at 180. v2900C over several kinds of X, Y and mordenite type zeolites of which Na were ion exchanged with transition metal ions. The: metal ions employed in this study were Cr(III), Cr(III), Fe(III), Co(III), Cu(1), Cu(III)and Tl(1). This reaction was observed over Na and Cq type Y zeolite catalysts, but carbon. dioxide was fermed in preference to cyclohexene or benzene. Oxidative dehydrogenation was.., . accelerated by exchange with the transition metal ions, especially by Fe(III), which were found to adsorb oxygen. The catalysts exchanged with the other metal ions showed a similar catalytic action as of Na type Y zeolite with rather lower activity. A pretty good selectivity with respect to partial dehydrogenatfon of cyclohexane to cyclohexene was obtained, in the presence of steam, over X and Y type zeolites exchanged with Fe(III)io s. Mordenite catalysts showed no catalytic activity for this reaction. The Fe(II)X catalyst was the most excellent of all catalysts used in this study, and the selectivity for dehydrogenation of cyclohexane to cyclohexene and benzene was increased with an increase in the degree of ion exchange, while combustion reaction was decreased.