Characterization and catalytic behavior in the n-butane dehydrogenation of trimetallic InPtSn/MgAl2O4 catalysts

Abstract

This paper deals with the characterization and catalytic dehydrogenation behavior of trimetallic InPtSn catalysts with different Sn content (from 0.12 wt% up to 1.08 wt%) supported on MgAl2O4. The support was initially impregnated with In, followed by a co-impregnation with Pt and Sn. The Pt and In contents in all catalysts were 0.30 wt% and 0.28 wt%, respectively. Besides, two catalysts with a Sn content of 0.37 wt% were prepared by two different methods: (a) successive impregnation (first Pt, second Sn) and (b) impregnation with PtSn complex, [(CH3)4N]2[PtCl2(SnCl3)2]. Experiments of n-butane dehydrogenation reaction were carried out both in continuous flow equipment and in pulse equipment. The catalysts were characterized by TPR, XPS and test reactions of the metallic phase. Trimetallic catalysts display high activity and selectivity to butenes and low deactivation during the n-butane dehydrogenation reaction. In order to analyze the influence of the preparation method on the catalytic performance, the better trimetallic catalyst was selected. It was observed that the different impregnation methods of Pt and Sn lead to trimetallic catalysts with similar catalytic behaviors between them. The characterization studies indicate the existence of geometric effects of In and Sn on Pt sites that produce a dilution of the Pt surface, and also a strong interaction between the three metals, which could lead to alloy formation. These facts positively influence the catalytic performance, thus increasing the activity, the selectivity to butenes and the stability of the metallic phase.