PtSn/θ-Al2O3 catalysts with different amount of potassium (0.4, 0.7, 0.95, 1.2 and 1.45 wt.%) were prepared by an impregnation method, and their catalytic activity in n-butane dehydrogenation was investigated at 823 K, an atmospheric pressure and a GHSV of 18,000 mL(g cat h)-1. The compositions listed in order of n-C 4= yields at 823 K were as follows: K0.95(PtSn) 1.5 > (PtSn)1.5 > K0.4(PtSn) 1.5 > K0.7(PtSn)1.5 > K 1.2(PtSn)1.5 > K1.45(PtSn)1.5 > K0.9(Pt)1.5. The K0.9(Pt)1.5 and K0.95(Sn)1.5 catalyst severely deactivated in n-butane dehydrogenation. The (PtSn)1.5 (without K) catalyst showed the highest n-butane conversion, while K0.95(PtSn)1.5 did the highest n-C4= yield. The small amount of potassium on bimetallic PtSn/θ-Al2O3 catalyst improved n-C 4= selectivity, but slightly decreased n-butane conversion, resulting in the increase of n-C4= yield. The effect of potassium was caused by blocking the acid sites of Pt catalyst. The TPR and HAADF STEM-EDS study suggested the reduction procedure of the Pt, Sn and K species. However, the higher loaded potassium (1.2 and 1.45 wt.%) doped (PtSn)1.5 catalysts were rather highly deactivated because the sizes of Pt particles were increased by weakening the interaction between Pt and Sn. The n-C4= selectivity of the (PtSn)1.5 catalyst increased with respect to the reaction, while that of the potassium doped catalysts maintained the high n-C4= selectivity from the beginning of the reaction. Also, different alkali metals (Ca, Na and Li) were tested for the comparison with K. The potassium doped catalyst showed the highest n-C4= yield among the other alkali metals for n-butane dehydrogenation.
Bibliographical noteFunding Information:
This work was supported by the basic research project of KIST and by Converging Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology ( 2011K000660 ).
- Effect of alkali metal
- PtSn alloy formation
- n-Butane dehydrogenation
ASJC Scopus subject areas