Selected reactions of nitrogen dioxide over metals and metal oxides.

摘要

The catalyzed reactions between nitrogen oxides and reducing agents form the basis for a number of different detector technologies in use today. In this study, the interactions between nitrogen dioxide and {dollar}rm YBasb2Cusb3Osb{lcub}7-x{rcub}{dollar} and between nitrogen dioxide and different forms of gold were investigated. Nitrogen dioxide is desorbed from supported gold catalysts at temperatures as high as 375{dollar}spcirc{dollar}C. Over certain gold catalysts, the interaction between nitrogen dioxide and the metal surface was found to be highly dependent on the oxidized or reduced state of the catalyst. A two-step mechanism has been identified over catalysts consisting of gold or {dollar}rm YBasb2Cusb3Osb{lcub}7-x{rcub}{dollar} in which a reducing agent reacts with oxygen contained in the catalyst to form an oxygen vacancy. In a second step, nitrogen dioxide reacts with the oxygen vacancy to produce NO and an oxidized catalyst.; The selectivity of the catalysts was found to be dependent on the gold formulation used to prepare the catalyst. In addition, the glass supporting the gold was found to affect the reactivity of the catalyst towards oxidation of hydrocarbons by nitrogen dioxide.; Nitrogen dioxide was also employed in the oxidation of {dollar}rm YBasb2Cusb3Osb{lcub}7-x{rcub}{dollar} at lower temperatures than is possible with oxygen to form a material that superconducts below 90 K. A material with a stoichiometry of {dollar}rm YBasb2Cusb3Osb{lcub}7.4 pm 0.4{rcub}{dollar}(NO{dollar}sb2)sb{lcub}1.3 pm 0.2{rcub}{dollar} results from treatment of {dollar}rm YBasb2Cusb3Osb{lcub}6.0{rcub}{dollar} by nitrogen dioxide at 200{dollar}spcirc{dollar}C.