ATMOCHEM - Reactivity of Oxygenated Volatile Organic Compounds (ROVOC): Esters

含氧挥发性有机化合物（OVOCs）在大气中无处不在。酯（烷酸烷基酯，例如RC（O）OR，R =烷基）是一类重要的OVOC，既有天然来源，也有人为来源。由长链羧酸组成的酯是动物和植物来源的蜡的主要成分，它们也天然存在于水果和花卉中。各种类型的酯在工业上广泛用作化学加工中的溶剂。对可再生燃料的追求已经看到生物柴油燃料的使用增加，生物柴油燃料通常由脂肪酸的甲酯和乙酯组成。酯也可以在大气中由例如醚的氧化原位产生。对大气中的酯类进行的测量很少，但已经进行的那些测量，迄今为止，对酯类大气化学的研究仅限于对一些直链和支链乙酸烷基酯的OH自由基动力学的温度依赖性研究以及对OH自由基或Cl-的产物的室温研究。原子引发氧化这些乙酸酯中的一些。对乙酸甲酯的研究表明，产物产率分布非常依赖于温度。尽管这组有限的数据已被用于改善298 K下烷基酯的结构-活性关系（SAR），但很明显，特别是在温度依赖性方面，确实需要进一步改进酯的SAR。在225 - 372 K范围内，OH自由基与各种酯反应的产物和机理数据库作为温度的函数，并将使用此信息进一步开发和完善酯的SAR。该项目将包括以下组成部分：一）使用绝对和相对方法确定作为温度函数的OH速率系数;二）确定作为温度和O2分压函数的反应产物;三）为模型构建明确和简化的反应机理; iv）开发适用于225 - 372 K温度范围的更广泛的酯类型的SAR。

Oxygenated volatile organic compounds (OVOCs) are omnipresent in the atmosphere. Esters (alkyl alkanoates, e.g. RC(O)OR, R = alkyl groups) are an important class of OVOC with both natural and anthropogenic sources. Esters made up of long chain carboxylic acids are the main constituents of animal- and plant-derived waxes and they also occur naturally in fruits and flowers. Various types of esters are used extensively by industry as solvents in chemical processing. The quest for renewable fuels has seen an increase in the use of biodiesel fuels, which typically consist of methyl and ethyl esters of fatty acids. Esters can also be produced in situ in the atmosphere from, for example, the oxidation of ethers. Few measurements of esters in the atmosphere have been made but those measurements, which have been made, confirm the presence of substantial levels of esters in the atmosphere.Investigations on the atmospheric chemistry of esters to date have been limited to temperature dependent studies of the OH radical kinetics of a number of linear and branched alkyl acetates and room temperature studies of the products from the OH radical or Cl-atom initiated oxidation of a few of these acetates. Studies on methylacetate have shown that the product yield distribution is very temperature dependent. Although this limited set of data has been used been used to improve the structure-activity relationship (SAR) for alkyl esters at 298 K it is clear that there is a definite need for further refine of the SAR for esters particularly with respect to temperature dependence.The project has the overall aim of improving the kinetic, product and mechanistic database for the reactions of OH radicals with a variety of esters as a function of temperature over the range 225-372 K and will use this information to further develop and refine the SAR for esters. The project will consist of the following components: i) determination of OH rate coefficients using absolute and relative methods as a function of temperature; ii) determination of the products of the reactions as a function of temperature and O2 partial pressure; iii) construction of explicit and simplified reaction mechanisms for models; iv) development of SAR for a wider range of ester types applicable over the temperature range 225-372 K.