The Effect of Sn Content in a Pt/KIT-6 Catalyst Over its Performance in the Dehydrogenation of Propane

Propylene is one of the most important commodity chemicals. Its future demand is expected to exceed its production. Alternative routes to obtain this product need to be implemented. Dehydrogenation of propane assisted with catalyst is a promising route to meet demands. The Pt and Cr supported catalysts are amongst the most effective possibilities. However, Pt catalysts are preferred over Cr due to the toxic nature of Cr species. Despite the high performance of the Pt catalysts, they deactivate during reaction, mainly due to coke deposits blocking the active site and/or pores. This effect can be reduced with a support having high connectivity and surface area, like KIT-6. In this work the mesoporous silica KIT-6 was employed as support in a series of Pt-Sn catalysts. The influence of adding or increasing the weight % of Sn to Pt catalyst was studied. There were species of SnO and metallic Pt in the fresh catalysts. After reaction, it was found that in the catalysts with the lowest wt % of Sn (0.5), there were metallic Pt and a Pt-Sn alloy. In the rest of the used catalysts (containing 1.0, 1.5 and 2.0 wt % of Sn) the only detected specie was the Pt-Sn alloy. In the two most active catalysts (having 0.5 and 1.5 wt % of Sn), it was observed a difference of three times the quantity of coke deposited on the surface. The catalysts containing the highest coke deposits maintained its activity due to the high connectivity of the support.