Dehydrogenation of alkane to light olefin over PtSn/O-Al203 catalyst: Effects of Sn loading

Abstract

Pt0.5Snx,10-Al203 catalysts with different amount of tin (0.5, 0.75, 1.0 and 1.5 wt%) were prepared by a co-impregnation method. Propane dehydrogenation was performed at 873 K and a GHSV of 53,000 mL/(gcat h). The Pt0.5/0-Al2 03 catalyst showed severe deactivation in alkane dehydrogenation reaction. The Sn addition decreased the cracking products of C1-C2 and the Pt0.5 SI10.75 catalyst with the highest Pt dispersion showed the highest C3= yield and C3= selectivity, n-Butane dehydrogenation was performed at 823 K and a GHSV of 18,000 ml./(gca] h). Similarly to propane dehydrogenation, the Sn addition to the Pt0.510-Al203 catalyst decreased the cracking products of C, -C3. However, the Pt0.55n1.0 showed the highest n-C4= yield and the catalyst was steadily deactivated even at 823 K differently from propane dehydrogenation at 873 K. The small amount of Sn addition improved the C3= and n-C4= selectivity by blocking the cracking sites of Pt catalyst. The PtSn alloy formed after the reduction at 500 C. The PtSn formation can enhance the C3= and n-C4= selectivity. The Pt dispersion on the Pt0.510-Al2 03 catalyst increased with the Sn addition up to 0.75 wt%. The highest Pt metal dispersion was observed on the Pt0.55110.75 catalyst. The conclusion was given to the Sn effects on the increase of Pt dispersion to enhance the activity as well as on the electronic and geometric effect of PtSn alloy to increase the stability and olefin selectivity. 2013 Elsevier B.V. All rights reserved.