The Suitability of the Three-way Catalyst for Hydrogen Fuelled Engines

This experimental study investigates the palladium/rhodium based three-way catalytic converter (TWC) in a H2 - gasoline dual-fuel spark ignition (SI) engine under stoichiometric and lean conditions. The work focused on lean-burn engine operating conditions with the aim of reducing NOX emissions during the combustion process, where the TWC is not effective, while improving the thermal efficiency of the engine. Under these lean-burn engine conditions, the combustion promoting properties of H2 allowed for maintained engine combustion stability as determined by the COVimep values even up to ultra lean conditions (λ=2.0). It was found that by reducing the combustion temperature through the application of lean conditions, engine out NOX emissions could be reduced or even eliminated, while under these conditions the TWC was effective in reducing engine-out carbon-based gaseous emissions

An investigation on the redox kinetics of NH3-SCR over a V/Mo/Ti catalyst: Evidence of a direct role of NO in the re-oxidation step

This study addresses a kinetic investigation of NH3-SCR on commercial SCR catalysts with composition V2O5/MoO3/TiO2. Objective of the study is an improved kinetic description of the reaction, based on the recognition of the redox nature of the V-site; which calls for an understanding of the effect of O2. At this scope, an extensive experimental investigation over a powdered catalyst was performed at largely varying concentrations of O2 (from 0.06 to 8%) both at high and at low NO and NH3 concentration. It was found that the increase of the O2 feed content promoted NO conversion with asymptotic trend: the promotion was important in the range 0.06–3%, but became moderate in the range 3–8%. Unexpectedly, the effect of O2 was equally important at high NO and NH3 concentration as well as at low NO and NH3 concentration (where a kinetic control from the reduction step and thus a negligible role of the oxidation step were expected). The kinetic analysis revealed that the observed experimental trends can be described by a Mars-van Krevelen rate expression assuming that the rate of re-oxidation depends on NO concentration as well as the rate of reduction does. A molecular rate equation which incorporates a simple linear dependence on NO concentration in the re-oxidation kinetics fully describes the whole bulk of data and is suitable to engineering purposes. The existence of an NH3 inhibiting effect was also included. The global rate expression was successfully validated against independent pilot-scale experiments on slabs