A Study of Hydrogen Addition on Diesel Oxidation Catalyst Activities under the Real Diesel Engine

The impact of small hydrogen concentration (approximately 1000 ppm H2) on the performance of a commercial Diesel Oxidation Catalyst (DOC) in reducing carbonaceous components and oxidising NO into NO2 under actual diesel engine exhaust gas conditions has been investigated. The experimental work was carried out at steady-state engine conditions for the short time periods; hence the catalyst tolerance to sulphur was not investigated. Hydrogen addition enhances hydrocarbon (HC) and carbon monoxide (CO) oxidation at lower temperatures and promotes nitrogen oxide (NO) to nitrogen dioxide (NO2) oxidation in the diesel exhaust gas. Trends that are expected to enhance Diesel Particulate Filter (DPF) regeneration at low temperatures and improve the activity of other aftertreatment systems such as Lean NOx catalysts. The hydrogen benefit was found to be dependent on the engine operation (i.e. use of exhaust gas recirculation-EGR), space velocity, exhaust gas condition and composition.