Effects of Mg, Ca, and K Addition on Pt-Sn/γ-Al2O3 for Propane Dehydrogenation

In the present study, the applicability of a bimetallic Pt-Sn/Al2O3 in propane dehydrogenation with different promoters, namely, Ca, Mg, and incorporation of Mg-K and Ca-K was studied. The catalysts were prepared by the sequential impregnation of γ-alumina support and characterized by TPD, SEM, XRD, and UV analysis. The propane conversion and propylene selectivity were evaluated under representative industrial conditions. The results showed that the Pt-Sn-Mg-K/γ-Al2O3 catalyst had a better performance in terms of propane conversion and propylene selectivity and yield, due to the partially neutralized and synergistic effect of Mg and K (probably by increasing the platinum dispersion and preventing side reaction and coke formation). TPD results also showed the effects of all these promoters (Ca, Mg, Ca-K and Mg-K) on the reduction of acidic sites of the catalyst, which are favorable sites for cracking reaction and coke formation. In the meantime, Ca is more effective in reducing strong acidic sites, but also Mg is more effective in reducing weak and medium-strength acid sites. Therefore, alkaline-earth metals and also using them with potassium could reduce side reaction products and lead to a more selective reaction to propylene, and improve catalyst performance compared to industrial catalysts.