Effect of zinc addition on catalytic properties of PtSnK/γ-Al2O3 catalyst for isobutane dehydrogenation

The effect of zinc addition on the catalytic properties of PtSnK/γ-Al2O3 catalyst for isobutane dehydrogenation has been investigated by reaction tests and some physicochemical characterizations such as nitrogen adsorption, H2 chemisorption, H2–TPD, NH3–TPD, TPR, TEM and TPO. It was found that suitable addition of Zn (0.2 and 0.4 wt.%) to PtSnK/γ-Al2O3 catalyst could not only increase the platinum dispersion by geometric effect, but also decrease the carbon depositions. In these cases, the presence of zinc strengthened the interactions between Sn species and the support, thus inhibiting the reduction of Sn species. Among the catalysts studied, the PtSnKZn(0.4%)/Al catalyst exhibited the best performance in terms of isobutane conversion and stability. However, when the content of Zn was excessive, the interfacial character between metal and support, and the character of Pt metal had been changed. The formation of PtZn alloy resulted in the loss of catalytic activity and stability, while had a promoting effect for the reaction selectivity.

► The presence of Zn improves the platinum dispersion by geometric effect.
► Zinc strengthens the interactions between Sn species and the support.
► Excessive content of Zn changes the character of Pt and the interfacial properties.
► The addition of 0.4 wt.% Zn results in the best catalytic performances.