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c Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading, RG4 9NH, UKThe novel monolithic-type electrochemical promoted reactor (MEPR), filled with thick Rh and Pt coated films on thin yttriastabilized zirconia (YSZ) plates, has been tested in simulated and real automotive exhaust gas. Ethylene oxidation and NO reduction by C 2 H 4 in presence of oxygen were investigated in laboratory scale while the automotive bench testing was performed in the exhaust of a diesel engine. In all cases electropromotion was achieved, an advance which in addition to their compact and simple design, makes electropromoted units quite promising for automotive exhaust pollution control.

Relatively small amounts of H 2 (500-3000 ppm) have been added to a real diesel exhaust gas during passive hydrocarbon-selective catalytic reduction (SCR) over a silver catalyst. The added H 2 is very effective at promoting low-temperature activity and at sustaining it by removing carbon-rich poisoning species from the catalyst surface. NO 2 production by the catalyst appears to be a key step in the self-cleaning process, but it is highly dependent upon the gas-phase concentrations of H 2 , total NO x , and hydrocarbons and the exhaust-gas temperature. Careful control of H 2 addition is therefore required in response to changes in conditions, to maintain suppression of the carbon-rich species without releasing NO 2 from the tailpipe. The highest overall NO x reduction can be achieved by operating the engine with exhaust gas recirculation in combination with H 2 -promoted passive hydrocarbon-SCR as an aftertreatment.