Introductory study of multifunctional catalysts for ethanol and biogas vehicles

摘要

The long-term goal for the project is to develop highly efficient exhaust gas catalysts for heavy-duty vehicles fuelled by biobased motor fuels operating in urban traffic. In this report an experimental study of catalytic oxidation of ethanol in a laboratory flow reactor is presented. The miniature catalyst samples consisted of monolithic cordierite substrates onto which various combinations of washcoat material and active material were applied. The experimental conditions were chosen in order to simulate the composition of the exhaust from a diesel engine fuelled by neat ethanol. A series of precious metal-based catalysts has been tested where different metal loadings and different complex washcoat compositions have been evaluated. Earlier studies have been concentrated on model washcoats such as alumina, ceria, silica, and titania (see KFB Report 1997:40). The choice of materials for the complex washcoats is based on the results from these experiments. One of the catalysts with the advanced washcoat Z exhibits lower light-off temperatures (T(sub 50)) for ethanol oxidation than the corresponding catalysts with washcoat X. The by-product formation shows a more complex picture. A number of parallel and consecutive reactions occur simultaneously in the reactor, where formation of acetaldehyde is by far the most common. Generally, the formation of acetaldehyde follows the conversion of ethanol, so that the catalysts with the lowest light-off temperature also form most acetaldehyde. If the peak for acetaldehyde formation can be shifted towards 150 deg C or temperatures below, this means that the acetaldehyde formation will not occur in practical fleet operation, since this is outside the normal exhaust temperature of the engine 26 figs, 4 tabs