Electron paramagnetic resonance studies on labile intermediates in a free-burning methanol-air flame. Effects of water and hydrogen bromide additions

Abstract

Labile intermediates in a premixed methanol-air flame burning freely at atmospheric pressure have been studied by probe sampling and EPR detection. H, 0, and OH have been detected at a pressure of 0.45 torr in the EPR cavity. It was found that H and 0 atoms have their maximum concentrations in the inner flame region within 1 mm from the burner mouth, while the OH concentration slowly increases in the outer flame region to reach a maximum at about 8 mm from the burner mouth. The slow increase in OH concentration is attributed to the reaction H + O2 -OH + 0 effectuated by diffusion of O2 from the surrounding air into the flame. Addition of H 2 0 reduced the 0 atom concentration and increased the OH radical concentration in the inner flame region. The reaction 0 + H 2 0 -20H is suggested as an explanation. Addition of HBr gave additional signals from Br and was found to reduce the H, 0, and OH concentrations in the flame. It also caused the flame to shrink probably as a result of H atom deficiency in the inner flame region leading to insufficient generation of 0 and OH in the outer flame region. About 70% of the bromine was found to exist in the atomic form.

Role of OH Radical in Fuel-NOx Formation during Cocombustion of Ammonia with Hydrogen, Methane, Coal, and Biomass

“…Methanol was used as a main fuel (Fuel1) for the flat flame burners' experiments. 10,11,15,16 The added impurities were CH 3 NH 2 , CS 2 , HBr, and H 2 S. The mole fraction distributions of O atoms, H atoms, and OH radicals in the flames were measured. Methane was used as a main fuel (Fuel1) for the partial premixed burner's experiments.…”

“…Representative O, H, and OH radicals govern the overall combustion reaction rates and burning velocities. 9,10 The mole fractions of these radicals in the flame had been measured and compared with the results of detailed calculations. 11−14 The radical mole fractions have also been measured in the flames produced from fuels containing impurities such as halogens, fuel nitrogen (Fuel-N), and fuel sulfur.…”

“…11−14 The radical mole fractions have also been measured in the flames produced from fuels containing impurities such as halogens, fuel nitrogen (Fuel-N), and fuel sulfur. 9,10,15,16 In addition, the H atom radicals in the ammonia−methane flame have been measured. 17 Usually, O, H, and OH radicals are captured by the impurities in the flames.…”

“…Combustion reactions are composed of numerous radical reactions. Representative O, H, and OH radicals govern the overall combustion reaction rates and burning velocities. , The mole fractions of these radicals in the flame had been measured and compared with the results of detailed calculations. − The radical mole fractions have also been measured in the flames produced from fuels containing impurities such as halogens, fuel nitrogen (Fuel-N), and fuel sulfur. ,,, In addition, the H atom radicals in the ammonia–methane flame have been measured . Usually, O, H, and OH radicals are captured by the impurities in the flames.…”

Time-dependent Quantum Scattering Calculation of the O(³P)+HBr(DBr) Reaction

“…Thereaction O( 3 P)+HBr寅HO+Br 驻H(0K)=-62.4kJ•mol -1 isoneoftheprototypicalhydrogen鄄atom鄄transferreactionsand belongstotheheavy鄄light鄄heavyreactionclass.Thereactionis characterizedby a verysmallskewingangle (茁=15.6毅) [1] , which promotesapproximateconservationofkineticenergy,andthe preferentialreleaseofthereactionexothermintoproductOHvi鄄 brationalandrotationaldegreesoffreedom.Itisexpectedto manifestimportantquantummechanical(QM)effects,suchas tunnelingandresonancesatthetransitionstate [2鄄4] . TheO( 3 P)+ HBrreactionisalsoimportantasonepossiblesourceofretarda鄄 tioninHBrinhibitedflames [5] .…”