Effect of indium in trimetallic Pt/Al2O3SnIn–Cl naphtha-reforming catalysts

Trimetallic Pt/Al2O3SnIn–Cl naphtha-reforming catalysts were characterized by 119Sn Mössbauer spectroscopy, TPR, CO chemisorption, FTIR of adsorbed CO and NH3-TPD. TPR traces indicate that indium facilitates tin reduction and strongly interacts with platinum as well. 119Sn Mössbauer spectroscopy results show that addition of even small amount of In (0.06 wt.%) leads to the formation of a Pt3Sn alloy. At higher indium loadings, higher amounts of PtxSn alloys of almost equal Pt and Sn atomic concentrations were detected. Indium also decreases the overall CO chemisorption capacity and provokes a modification of Pt electronic properties at the highest In loadings. A decrease in the acidity of the support in trimetallic catalysts is also observed by NH3-TPD upon indium addition. These results correlate well with those from n-heptane-reforming reaction, showing that indium decreases catalyst’s overall conversion and selectivity to C1 and C3–C4 paraffins and increases isomerization selectivity.