Catalytic Decomposition of Nitric Oxide in an Oxygen Rich Environment 2001-01-3280
An initial study to search out a catalytic method of removing oxides of nitrogen in an oxygen rich gas effluent has been performed. The system demonstrates the capability to mount a two stage reactor system to decompose nitric oxide in dioxygen, where stage 1 converts nitric oxide to oxidising NOx molecules, and stage 2 performs the catalytic decomposition of the NOx species to dinitrogen and dioxygen. The study has confirmed that a palladium-zinc catalyst supported on a gadolinium stabilised zirconia system has the capability to oxidise nitrogen(II) oxide to oxides of nitrogen (N>+2). The results show that the catalytic strategy for oxidising the relatively unreactive nitrogen(II) oxide to the strong oxidant nitrogen(>II) oxides, with the subsequent decomposition of reactive NOx species using a sacrificial metal substrate is feasible. The study confirms that there is competitive adsorption between nitrogen(II) oxide and dioxygen for the adsorption sites available at the catalyst surface. Modification of the activity of the catalyst to generate higher oxides of nitrogen can be induced by the application of a negative bias to the catalyst bed. The study also investigates the ability of a solid state electrolytic cell coated with a tin or rhodium-tin couple to decompose a feed of nitrogen oxides of nitrogen oxidation states > 2. The results confirm that the application of a negative bias to a sacrificial electrode can stabilise the electrode against oxidation and hence insure its continuing ability to convert NOx eluent to dinitrogen and dioxygen. The study shows that the applied polarity to the electrode is critical, such that deactivation of the electrode occurs if it is placed under a positive bias.