THE EFFECT OF LANTHANUM IN DEHYDROGENATION OF PROPANE ON PT-SN BIMETALLIC CATALYSTS

Four catalysts, H2PtCl6-5SnCl(2)/gamma-Al2O3 (cat-1), {H2PtCl6-5SnCl(2 ) + xLaCl(3)}/gamma-Al2O3 (cat-2), (Me4N)[Pt(SnCl3)(5)]/gamma- Al2O3 ( cat-3), and {(Me4N)[Pt(SnCl3)(5)] + xLaCl(3)}/gamma-Al2O3 (cat-4) were prepared and their catalytic activities and stabilities in dehydrogen ation of propane were investigated. It has been shown that the stabili ties of the Pt-Sn bimetallic catalysts were improved by introducing la nthanum into the catalysts either by the conventional impregnation met hod with Pt-and Sn-containing salts or by using precursors derived fro m Pt-Sn bimetallic clusters. Results from XPS analysis indicated that addition of lanthanum could inhibit the reduction of tin in the cataly sts, 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. Ther mal 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 th at introducing lanthanum into the Pt-Sn bimetallic catalysts could eff ectively prevent them from coking.