A Spectroscopic Study of Gaseous Products of Soot-Oxides of Nitrogen/Water Reactions

Abstract

The simultaneous evolution of CO, CO2, N2O, and NO, detected and estimated by both infrared spectroscopy and chemiluminescence during the reaction of soot and NO2/N2O4 over a range of temperatures, suggests that, in addition to the previously described chemisorption reaction, there also is a redox process occurring in the initial stages of the reaction. Estimations of these gases suggest that the redox reaction also includes reactive components other than the olefinic segment of soot, and occurs under all conditions examined. Infrared studies show that gaseous NO, produced immediately on the introduction of NO2/N2O4 into a reactor containing soot and water vapor, subsequently decreases with the accompanying formation of N2O.

Heterogeneous production of nitrous acid on soot in polluted air masses

“…19) predicts the formation of equal amounts of HNO 2 and HNO 3 , but we were not able to detect the latter as a product of the NO 2 /soot interaction. Although it is conceivable that HNO 3 remains adsorbed to the particle surface, or that it decomposes into NO (ref.…”

“…O 3 at the same time, indicating that ozone will not significantly influence HNO 2 formation on soot in the atmosphere in the short term. Whereas reaction (1) was found to be very sensitive to the water concentration 19 , in our experiments, at 0.5% relative humidity the formation of HNO 2 was (within the experimental uncertainty) the same as at 60%. Even at these low humidities, the gas-phase concentration of H 2 O is large enough to allow some soot functionalities (such as carboxyl groups) to be hydrated or to lead to the presence of physisorbed H 2 O (ref.…”

“…These observations imply that, instead of the disproportionation of N(IV) into equal amounts of N(V) and N(III) species, a net reduction of N(IV) to N(III) is taking place at low NO 2 concentrations. Although previous studies 8, 9,19 have already indicated that NO 2 may be reduced on soot to form NO or N 2 O, our observations suggest the existence of an additional reaction channel (reaction (2)) that results in HNO 2 formation. Fig.…”

The chemical kinetics of HONO formation resulting from heterogeneous interaction of NO2 with flame soot

“…However, due care must be exercized when extrapolating the present kinetic results to atmospheric conditions because only a limited set of fuels has been used to generate soot whose properties may depend in a complex way on both the type of fuel as well as the manner in which it was generated. No N20 formation has been observed in this study in contrast to recent results [Chughtai et al, 1990]. As far as atmospheric applications are concerned the HONO source described in this work may affect the chemistry both in the tropospheric boundary layer of heavily polluted urban environments as well as air traffic corridors in the upper troposphere and lower stratosphere [Calvert et al, 1994;Fabian and Kiircher, 1997].…”

The reactivity of NO2 and HONO on flame soot at ambient temperature: The influence of combustion conditions

“…Because of its simplicity this technique has been applied in several studies. 10,11,27,28,31,35 In order to establish a link with the studies cited above, a series of experiments were performed using hexane as a fuel. In the present work, however, the same co-Ñow system used for decane was applied in order to produce soot originating from a rich and a lean Ñame.…”