Catalytic Activities for Methanol Decomposition on Praseodymium Oxides Doped with Platinum and Palladium

Abstract

Praseodymium oxides doped with small amounts of platinum and palladium (Pt/PrOx, Pd/PrOx) have been examined as a reforming catalyst for moderate temperature fuel cell systems. The catalysts were prepared by a wet process. The activity and the selectivity for the catalytic decomposition of methanol to hydrogen and carbon monoxide (H₂+CO) were studied in a flow reactor at a temperature range of 250-700°C. The activity of the catalysts increased with increasing the amount of the doped metals. The catalyst with 0.5% Pt, Pt/prOx (0.5%), had as a high activity as that of Pt/Al₂O₃ (0.5%), a commercial Pt catalyst supported on alumina. The reaction selectivity to H₂+CO on Pt/PrO₅ was much superior to that on Pt/Al₂O₃. Pd/PrOx showed both a high activity and a high selectivity at the reaction temperature below 400°C. For the reaction at a high temperature range above 500°C, the catalytic activity was reduced by the deposition of by-product carbon on the catalyst. The results of temperature-programed desorption (TPD) and mass spectrometries showed that the Pt/PrOx and Pd/PrOx catalysts scarecely form dimethyl ether and lead the high selectiv ity for the H₂, and CO formation.