NOx

About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.

Studies on kinetics and reactions mechanism of La2−xKxCu1−yVyO4 layered perovskites for the combined removal of diesel particulate and NOx

Abstract: Layered-type perovskite catalysts (A2−xA′xB1−yB′yO4±δ, where A, A′=La, K and B, B′=Cu, V), prepared by the citrates method and characterized by BET, XRD, and catalytic activity analysis, proved to be effective in the simultaneous removal of soot and NOx, the two prevalent pollutants in diesel exhaust gases, but only at temperatures as high as 450–500 °C, seldom reached at the exhaust line location unless next to the engine exit (close-coupled system). Furthermore, stability at high temperature (800 °C) was only poor for the most promising of the studied catalysts (La1.8K0.2Cu0.9V0.1O4). A detailed kinetic study was carried out on this last perovskite by FT-IR analysis as well as by temperature-programmed and isothermal oxidation tests, by assessing the effect of the prevalent affecting parameters. Some of the reaction intermediates were singled out and several different and rather complex reaction schemes were finally hypothesized, involving reaction intermediates either present on the catalyst surface or on that of the carbon particulate itself. The role of the various elements on the perovskite composition was also defined. The effect of vanadium in particular seemed to be dominant in assuring a peculiar activity towards NOx reduction.

Environmental applications of low-temperature plasmas

Abstract: Treatment of NOx in diesel engine exhaust represents a big opportunity for the environmental application of low-temperature plasmas. This paper discusses the effect of gas composition on the NOx conversion chemistry in a plasma. It is shown that the plasma by itself cannot chemically reduce NOx to N2 in the highly oxidizing environment of a diesel engine exhaust. To implement the reduction of NOx to N2, it is necessary to combine the plasma with a heterogeneous process that can chemically reduce NO2 to N2. Data is presented that demonstrates how the selective partial oxidation of NO to NO2 in a plasma can be utilized to enhance the selective reduction of NOx to N2 by a catalyst.

Measurements of oxides of nitrogen and nitric acid in clean air

Abstract: We have measured oxides of nitrogen, nitric acid, and ozone in air at a remote site in the Rocky Mountains west of Boulder, Colorado. The site is infrequently polluted by upslope air movements from the Denver-Boulder metropolitan area and most often experiences flows of clean air from the west and north. We find NOx (NO + NO2) levels commonly ≈0.2 ppb, with considerable diurnal variation around this mean value, and occasional excursions well below it. Nitric acid (HNO3) levels were <0.03 to 0.1 ppb, and were always smaller than the NOx level. We find the photostationary state equation does not hold in clean air, and we suggest that the deviation from theory may arise from the presence of peroxy radicals.