Selective oxidation of CO on Ru/γ-Al2O3 in methanol reformate at low temperatures

The preferential oxidation of CO (PROX) at low temperatures, 80-420 degreesC, over a Ru/-Al2O3 supported catalyst pretreated by a low temperature reduction (LTR) process was investigated over a range of CO partial pressures and 02 excess in a realistic methanol reformate reaction environment, in the presence of CO2 and H2O. Based on transmission electron microscopy (TEM) imaging the LTR pretreatment, which involves reduction in pure H-2 at 150 degreesC, does not lead to measurable particle growth (d(Ru) = 2.5 nm), in contrast to the calcination/reduction (CR) pretreatment at 350 degreesC used previously, which results in considerable particle sintering (d(Ru) = 11.2 nm). Kinetic parameters including the apparent activation energy (E approximate to 48 kJ/mol), reaction orders for CO (alpha(CO)) and for O-2 (alphaO(2)) and the selectivity for CO oxidation as well as the influence of the co-reactants CO2 and H2O were evaluated. The results show a significant activity and selectivities of around 55-60% both in idealized reformate, in the absence Of CO2 and H2O, and in realistic reformate, already at 80 degreesC. This and the negligible activity for the reverse water gas shift and the CO and CO2 methanation reaction under these reaction conditions make this catalyst suitable for application at low temperatures typical for operation of polymer electrolyte fuel cells (PEFCs), in contrast to the CR pretreated catalyst, where higher process temperatures are required. (C) 2004 Elsevier B.V. All rights reserved.