Effect of pH on the catalytic performance of PtSn/B-ZrO2 in propane dehydrogenation

Abstract

Boron-modified ZrO2 (B-ZrO2) was synthesized under various pH values (9, 10, and 11) and used as the supports of PtSn catalysts (PtSn/B-ZrO2-x) for non-oxidative dehydrogenation of propane. The NH3-TPD and pyridine IR show that only Lewis acid is present and the acid strength increases with the synthesis pH. PtSn/B-ZrO2-10 exhibits the best catalytic performance with an initial propane conversion of 36% and a deactivation rate constant (kd) of 0.0127 h−1. The XPS results indicate that the electronic properties of Pt and SnOx are affected not only by their interaction but also by the interaction with support. After a careful analysis of the oxygen storage capacity and activity in CO oxidation, it is hypothesized that the interaction between Pt and Sn becomes stronger following the order: PtSn/B-ZrO2-9 < PtSn/B-ZrO2-11 < PtSn/B-ZrO2-10. The characterization with TPO and Raman on spent catalysts exhibits that more hydrogen deficient coke forms on the support and less coke deposits on the metal surface of PtSn/B-ZrO2-10. The results reveal that the interaction between Pt and Sn is influenced by their respective interaction with the support and a moderate interaction between the metal species and the support is desired.