The effect of lanthanum in dehydrogenation of propane on Pt-Sn bimetallic catalysts

Four catalysts, H2PtCl6-5SnCl2/γ-Al2O3 (cat-1), { H2PtCl6-5SnCl2 + xLaCl3 } / γ-Al2O3 (cat-2), (Me4N)[Pt(SnCl3)5]/ γ-Al2O3 (cat-3), and {(Me4N)[Pt(SnCl3)5] + xLaCl3} / γ-Al2O3 (cat-4) were prepared and their catalytic activities and stabilities in dehydrogenation of propane were investigated. It has been shown that the stabilities of the Pt-Sn bimetallic catalysts were improved by introducing lanthanum into the catalysts either by the conventional impregnation method with Pt- and Sn-containing salts or by using precursors derived from Pt-Sn bimetallic clusters. Results from XPS analysis indicated that addition of lanthanum could inhibit the reduction of tin in the catalysts, especially in cat-2. The distribution of pore capacity in a used cat-2 was mainly in the large and medium size range, but in a used cat-1 the distribution was mainly in the small to medium size range. Thermal gravimetric analysis (TGA) showed that weight loss in the used cat-1 was much more than that in the used cat-2. The results suggested that introducing lanthanum into the Pt-Sn bimetallic catalysts could effectively prevent them from coking.