Microfibrous Entrapment of Small Catalyst Particulates for High Contacting Efficiency Removal of Trace Co from Reformates at Low Temperatures for Pem Fuel Cells

Preferential oxidation (PROX) of CO is the most efficient way to remove CO from reformate streams for PEM fuel cells. Pt/Al2O3 has long been used for this purpose. Pt/Al2O3 catalysts are effective for preferential oxidation of CO only at temperatures above 150°C, and the maximum CO conversion usually takes place at around 200°C. In this study, promotion of Pt/Al2O3 with transition metals results in enhanced catalytic activity and selectivity in the temperature range from 25 to 150C. A high void and tailorable sintered microfibrous carrier consisting of 5vol% 4 and 8μm diameter Ni fibers is used to entrap 15vol% of 150-250μm diameter Al2O3 particulates. SEM images show that the alumina support particulates are uniformly entrapped within the matrix. Promoter and platinum are then dispersed onto the microfibrous entrapped alumina support particles by incipient-wetness. In-situ FTIR investigations have been employed to reveal the reaction mechanism / pathway of PROX using the promoted Pt/Al2O3 at low temperatures. The transition metal oxide promoters provide active oxygen for selective CO oxidation. The transition metal promoter appears to provide a separate non-competitive site for O2 activation. On the other hand, data collected over un-promoted Pt/Al2O3 indicates both oxygen and CO competition for surface Pt sites resulting in strong CO inhibition at lower temperatures.