The Influence of Sulfur on NOx Formation in Combustion

该项目的目标是分离与燃烧系统中硫/氮相互作用相关的单个基本反应，并表征其在广泛温度范围内的反应动力学。脉冲紫外准分子激光或闪光灯光解前体分子可产生短寿命的反应物质，包括氮、氧、氢、硫原子和双原子自由基，如NH、NH2、CN、SO、CS和SH。用时间分辨荧光光谱法（激光诱导荧光法测定分子自由基，真空紫外共振荧光法测定原子自由基）监测瞬态自由基的浓度，得到速率常数和产物鉴定随温度和压力的函数。研究了在稳定反应物大量过剩的伪一阶条件下的反应。实验包括自由基与稳定分子的反应，如硫化氢、二氧化硫和一氧化氮，以及涉及SO的自由基-自由基反应。火焰和废气中氮和硫化学的相互作用影响燃烧产生的氮氧化物，从而影响酸雨、光化学烟雾和对流层臭氧。根据条件的不同，硫可以增加或减少氮氧化物的排放量。这项研究调查了这种相互作用的潜在化学作用。该项目通过德克萨斯州数学与科学学院和上界数学与科学项目为本科生和中学生的参与提供了一个工具。

The goal of this project is the isolation of individual elementary reactions relevant to the sulfur/nitrogen interaction in combustion systems and the characterization of their reaction kinetics over a wide range of temperature. Short-lived reactive species including atoms of nitrogen, oxygen, hydrogen, and sulfur and diatomic radicals such as NH, NH2, CN, SO, CS, and SH are generated by pulsed ultraviolet excimer-laser or flash-lamp photolysis of precursor molecules. The concentration of transient radical species are monitored with time-resolved fluorescence spectroscopy - laser-induced fluorescence for molecular radicals and vacuum-ultraviolet resonance fluorescence for atomic species - to obtain rate constants and product identification as functions of temperature and pressure. Reactions are studied under pseudo-first-order conditions with a large excess of the stable reactant. Experiments include reactions of radicals with stable molecules such as hydrogen sulfide, sulfur dioxide, and nitric oxide and also radical-radical reactions involving SO.The interaction of nitrogen and sulfur chemistry within flames and exhaust gases influences the generation of nitrogen oxides from combustion and thusly impacts acid rain, photochemical smog, and tropospheric ozone. Depending on conditions, sulfur may augment or reduce the amounts of nitrogen oxides emitted. This study investigates the underlying chemistry of this interaction.This project provides a vehicle for the participation of undergraduate and secondary-school students through the Texas Academy of Math and Science and the Upward Bound Math and Science Program.