CATALYST CHARACTERIZATION BY A PROBE REACTION - EFFECT OF TIN ADDITION IN PTSN AL2O3/

Ethylene hydrogenation as a probe reaction was used to characterize Pt Sn/Al2O3 catalysts. The effects of the amount of tin and the impregnat ion order of platinum and tin on the activity for ethylene hydrogenati on, the hydrogen number and the hydrogen uptake were studied. Two seri es of catalysts were prepared by two different successive impregnation s of aqueous solutions of platinum and tin compounds. The platinum con tent was constant at 0.5 wt.-% and the tin content was varied over the range 0.0 to 0.45 wt.-%. The presence of tin caused a decrease in bot h the ethylene hydrogenation activity and the hydrogen number values i n the two series of bimetallic catalysts. Hydrogen uptake decreased on the Pt-Sn catalysts and increased on the Sn-Pt catalysts when the ato mic Sn/Pt ratio was increased. As shown in the literature, these resul ts can be related to a chemical change of the platinum due to the pres ence of tin either by forming Pt-Sn clusters or by interaction between platinum and tin ions on the alumina surface.