Kinetics and Mechanisms of Heterogeneous Reactions Involving Carbonyl Sulfide in Sulfuric Acid Media

小行星9711923 羰基硫（COS）是平流层中硫酸的主要还原硫源，也是大气中最丰富的含硫化合物。由硫化羰产生硫酸气溶胶涉及COS的光解离和被氧气氧化以产生二氧化硫，二氧化硫继而被羟基自由基氧化成硫酸。硫酸冷凝导致气溶胶的形成。平流层硫酸盐气溶胶层影响地球的辐射收支。 有人提出，某些反应途径，连接全球硫和氮循环（通过氧化COS和还原硝酸）可能在对流层上部和平流层下部的非均相化学中发挥重要作用，并可能影响对流层上部的NOy到NOx的比例。在这个项目中，体相动力学，机制和选定的反应和过程中涉及COS在浓硫酸溶液的热力学将在广泛的温度和溶质条件下进行研究。将研究COS与水（酸催化水解）、质子化过氧化氢、硝离子、硫酸根阴离子和硝酸根的反应。次要的研究目标包括：确定二元硫酸/水系统和三元硫酸/硝酸/水系统的形态，作为温度、组成和热历史的函数，确定过氧化氢离子和质子化COS的酸性强度，以及确定过氧化氢和硫化羰的有效亨利定律常数。 采用的实验技术包括多波长快速扫描停流分光光度法、液相低温控制白色池配置中的长光程激光吸收光谱法、拉曼光谱法、时间分辨拉曼光谱法和衰减全反射FTIR。

9711923 Hoffmann Carbonyl sulfide (COS) is the primary reduced-sulfur source of sulfuric acid in the stratosphere, and is the most abundant sulfur compound in the atmosphere. The production of sulfuric acid aerosol from carbonyl sulfide involves the photodissociation of COS and oxidation by oxygen to yield sulfur dioxide, which, in turn, is oxidized by hydroxyl radicals to sulfuric acid. Sulfuric acid condensation leads to the formation of aerosols. The stratospheric sulfate aerosol layer influences the earth's radiation budget. It is proposed that certain reaction pathways that link the global sulfur and nitrogen cycles (via the oxidation of COS and reduction of nitric acid) may play an important role in the heterogeneous chemistry of the upper troposphere and lower stratosphere, and may affect the ratios of NOy to NOx in the upper troposphere. In this project, the bulk-phase kinetics, mechanisms, and thermodynamics of selected reactions and processes involving COS in concentrated sulfuric acid solutions will be investigated over a broad range of temperature and solute conditions. Reactions of COS with water (acid-catalyzed hydrolysis), protonated hydrogen peroxide, nitronium ion, sulfate radical anion, and nitrate radical will be studied. Secondary research objectives include: the determination of the speciation of binary sulfuric acid/water systems and ternary sulfuric/nitric acid/water systems as a function of temperature, composition, and thermal history, the determination of the acidic strength of the perhydroxonium ion and protonated COS, and the determination of the effective Henry's Law constants for hydrogen peroxide and carbonyl sulfide. Experimental techniques to be employed include multi-wavelength rapid-scan stopped-flow spectrophotometry, long path-length laser absorption spectroscopy in a liquid-phase cryogenically-controlled White cell configuration, Raman spectroscopy, time-resolved Raman spectroscopy, and attenuated total reflectance FTIR.