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

9711923霍夫曼硫化物是平流层中硫酸的主要还原硫源，也是大气中含量最丰富的硫化物。从羰基硫化物生产硫酸气溶胶的过程包括COS的光解和氧气的氧化生成二氧化硫，而二氧化硫又被羟基自由基氧化成硫酸。硫酸冷凝会导致气溶胶的形成。平流层硫酸盐气溶胶层影响地球的辐射收支。认为连接全球硫氮循环的某些反应途径(通过COS的氧化和硝酸的还原)可能在对流层上层和平流层下层的非均相化学中起重要作用，并可能影响对流层上层NOY/NOx的比值。在这个项目中，将在广泛的温度和溶质条件下研究涉及浓硫酸溶液中COS的选定反应和过程的体相动力学、机理和热力学。将研究COS与水(酸催化水解)、质子化双氧水、硝酸根离子、硫酸根阴离子和硝酸根的反应。次要研究目标包括：确定二元硫酸/水体系和三元硫酸/硝酸/水体系的形态随温度、组成和热历史的变化，测定过氢离子和质子化COS的酸性强度，以及测定过氧化氢和羰基硫化物的有效亨利定律常数。将采用的实验技术包括多波长快速扫描停流分光光度法、液体低温控制白池构型中的长光程激光吸收光谱、拉曼光谱、时间分辨拉曼光谱和衰减全反射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.