NOx

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

Studying the effect of compression ratio on an engine fueled with waste oil produced biodiesel/diesel fuel

Abstract: Wasted cooking oil from restaurants was used to produce neat (pure) biodiesel through transesterification, and then used to prepare biodiesel/diesel blends. The effect of blending ratio and compression ratio on a diesel engine performance has been investigated. Emission and combustion characteristics was studded when the engine operated using the different blends (B10, B20, B30, and B50) and normal diesel fuel (B0) as well as when varying the compression ratio from 14 to 16 to 18. The result shows that the engine torque for all blends increases as the compression ratio increases. The bsfc for all blends decreases as the compression ratio increases and at all compression ratios bsfc remains higher for the higher blends as the biodiesel percent increase. The change of compression ratio from 14 to 18 resulted in, 18.39%, 27.48%, 18.5%, and 19.82% increase in brake thermal efficiency in case of B10, B20, B30, and B50 respectively. On an average, the CO 2 emission increased by 14.28%, the HC emission reduced by 52%, CO emission reduced by 37.5% and NOx emission increased by 36.84% when compression ratio was increased from 14 to 18. In spite of the slightly higher viscosity and lower volatility of biodiesel, the ignition delay seems to be lower for biodiesel than for diesel. On average, the delay period decreased by 13.95% when compression ratio was increased from 14 to 18. From this study, increasing the compression ratio had more benefits with biodiesel than that with pure diesel.

OH-initiated oxidation of benzene

Abstract: The present work represents a continuation of part I of this series of papers, in which we investigated the phenol yields in the OH-initiated oxidation of benzene under conditions of low to moderate concentrations of NOx, to elevated NOx levels. The products of the OH-initiated oxidation of benzene in 700–760 Torr of N2/O2 diluent at 297 ± 4 K were investigated in 3 different photochemical reaction chambers. In situ spectroscopic techniques were employed for the detection of products, and the initial concentrations of benzene, NOx, and O2 were widely varied (by factors of 6300, 1500, and 13, respectively). In contrast to results from previous studies, a pronounced dependence of the product distribution on the NOx concentration was observed. The phenol yield decreases from approximately 50–60% in the presence of low concentrations ( 10 000 ppb) NOx concentrations. In the presence of high concentrations of NOx, the phenol yield increases with increasing O2 partial pressure. The rate constant of the reaction of hydroxycyclohexadienyl peroxyl radicals with NO was determined to be (1.7 ± 0.6) × 10−11 cm3 molecule−1 s−1. This reaction leads to the formation of E,E-2,4-hexadienedial as the main identifiable product (29 ± 16%). The reaction of the hydroxycyclohexadienyl radical with NO2 gave phenol (5.9 ± 3.4%) and E,E-2,4-hexadienedial (3.4 ± 1.9%), no other products could be identified. The residual FTIR product spectra indicate the formation of unknown nitrates or other nitrogen-containing species in high yield. The results from the present work also show that experimental studies aimed at establishing/verifying chemical mechanisms for aromatic hydrocarbons must be performed using NOx levels which are representative of those found in the atmosphere.

On the interaction of isotopic exchange processes with photochemical reactions in atmospheric oxides of nitrogen

Abstract: Gas-phase isotopic exchange between NO and NO2 enriches the heavier 15N isotope in the more oxidized form. In the atmosphere the concentration of both gases, NO and NO2, is controlled during daytime by the Leighton relationship through the oxidation of NO with O3 and the photolytic reaction of NO2 to NO. For atmospheric concentrations (e.g., NOx, ∼10 ppb), isotopic exchange and photolytic reaction are very fast with characteristic time constants of a few minutes compared to other removing reactions of atmospheric NOx via OH radicals (daytime reaction) and O3 (nighttime reaction) with time constants of some hours and more. We have found from 15N/14N measurements of atmospheric NO2 and NOx at Julich that both processes, isotopic exchange and photolytic reaction, interact and have an influence on the 15N/14N isotopic ratio. This interaction, together with seasonal variations of the NOx/O3 ratio at daytime and either complete oxidation of NO to NO2 or isotopic exchange between NO and NO2 at nighttime, explains the seasonal variation of the 15N/14N ratio of atmospheric NO2, which agrees with results from a simple model.

NO and NO2 Adsorption on Barium Oxide: Model Study of the Trapping Stage of NOx Conversion via Lean NOx Traps

Abstract: The use of NOx traps is one strategy being pursed to enable the implementation of more fuel-efficient lean-burn gasoline engines. Materials development to enhance NOx storage capacity and sulfur tolerance will be necessary for performance improvement. Progress in these areas will benefit from a more detailed understanding of the base metal oxide−precious metal surface chemistry involved in the trapping, release, and reduction of NOx. In this work, we have focused on the adsorption of NO and NO2 on in-situ evaporated thin films of barium oxide, the primary storage material in lean NOx traps, to accentuate the details of the trapping stage of NOx conversion using these systems. X-ray photoelectron spectroscopy has been used to identify the species formed and their relative abundance following room-temperature adsorption. Annealing experiments were performed to follow changes in adsorbed species with temperature. For NO, our results are consistent with nitrites forming as a result of molecular adsorption. In...