Raising the fuel heating value and recovering exhaust heat by on-board oxidative reforming of bioethanol

Abstract

Several reactions can contribute to the overall process of exhaust gas reforming, during which some of the engine fuel is catalytically converted mainly to H2 and CO. If the predominant reactions are endothermic, the process acts as a means of exhaust-heat recovery, and the fuel heating value is raised. When using conventional gasoline or diesel fuel, the reforming catalyst is required to promote steam- and dry-reforming, at the expense of the exothermic reactions—water gas shift, methanation, partial oxidation and combustion. In this study we show that a precious metal formulation is capable of catalysing most of the key reforming routes with the exception of the water gas shift reaction, under the set of conditions that we have used to simulate an exhaust from a bioethanol-fuelled spark ignition engine. Our results predict that the overall process of exhaust gas reforming of C2H5OH will be oxidative, and yet waste heat will be consumed. The expected increase in fuel heating value is 6%, but can rise towards 20% if there is less O2 available in the exhaust, allowing more of the bioethanol to react by steam- and dry-reforming in the catalyst bed. By feeding the reformate back to the engine, the intention is to improve the fuel economy and emission quality.