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

Ethylene hydrogenation as a probe reaction was used to characterize PtSn/Al2O3 catalysts. The effects of the amount of tin and the impregnation order of platinum and tin on the activity for ethylene hydrogenation, the hydrogen number and the hydrogen uptake were studied. Two series of catalysts were prepared by two different successive impregnations of aqueous solutions of platinum and tin compounds. The platinum content 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 both the ethylene hydrogenation activity and the hydrogen number values in the two series of bimetallic catalysts. Hydrogen uptake decreased on the Pt-Sn catalysts and increased on the Sn-Pt catalysts when the atomic Sn/Pt ratio was increased. As shown in the literature, these results can be related to a chemical change of the platinum due to the presence of tin either by forming Pt-Sn clusters or by interaction between platinum and tin ions on the alumina surface.