RUI: Sulfur Chemistry: Molecular Mechanisms

美国国家科学基金会化学部化学结构、动力学和机理项目支持米德尔伯里学院化学系AnGayle Vasiliou教授的研究。Vasiliou教授和她的学生们正在努力了解含硫碳化合物在加热时的分解。含硫污染物通常存在于燃料来源中，如煤、石油和生物质。为了减少腐蚀性酸雨的形成，从潜在的燃料源中去除硫是很重要的。瓦西里乌博士研究了利用热量将大分子的化学键断裂成更容易挥发的小分子，以及去除硫的方法。人们对石油和生物燃料中硫化合物的高温化学性质知之甚少。这种知识差距阻碍了炼油厂清理工艺发展的进展。本课题研究了八种重要含硫分子的高温反应。这项研究是在以本科生为主的米德尔伯里学院进行的，只有本科生作为合作者。这种类型的研究经验鼓励本科生追求科学事业。本研究重点研究了与石油和生物质相关的八种分子的单分子分解：二甲基硫化物、二乙基硫化物、二甲基二硫化物、乙硫醇、叔丁基硫醇、甲基噻吩、3-乙基噻吩和半胱氨酸。这项研究首次建立了热分解过程中形成自由基中间体的直接证据。反应研究是使用一个过热喷嘴进行的，该喷嘴配置便于基质分离，红外吸收和真空紫外光电离质谱。这些技术允许热可调性（298-1700 K）和敏感的检测中间物质，如自由基。在实验研究的基础上，利用密度函数和从头算量子化学技术对8种硫的热分解机理进行了理论研究。由于该项目具有实验和计算两个方面，它使本科生接触到物理化学。

The Chemical Structure, Dynamics and Mechanism Program of the NSF Chemistry Division supports the research of Professor AnGayle Vasiliou in the Department of Chemistry at Middlebury College. Professor Vasiliou and her students are working to understand the decomposition of carbon compounds containing sulfur when heated. Sulfur-containing contaminants are often present in fuel sources such as coal, petroleum and biomass. It is important to remove the sulfur from potential fuel sources to reduce the formation of corrosive acid rain. Dr. Vasiliou investigate the use of heat to break the chemical bonds of larger molecules into smaller more volatile species and removal of sulfur. The high-temperature chemistry of sulfur compounds in petroleum and biofuels is poorly understood. This knowledge gap hinders progress in the development of refinery clean-up processes. This project studies the high-temperature reactions of eight important sulfur-containing molecules. The research is conducted at a predominantly undergraduate institution, Middlebury College, with only undergraduate students as collaborators. This type of research experience encourages undergraduates to pursue careers in science.This study focuses on the unimolecular decomposition of eight petroleum and biomass relevant molecules: dimethyl sulfide, diethyl sulfide, dimethyl disulfide, ethanethiol, tert-butylthiol, methylthiophene, 3-ethylthiophene and cysteine. This research is the first to establish direct evidence for radical intermediates formed during thermal decomposition. The reaction studies are conducted using a hyperthermal nozzle configured to facilitate matrix isolation infrared absorption and vacuum ultraviolet photoionization mass spectroscopies. These techniques allow for thermal tuneablity (298-1700 K) and sensitive detection of intermediate species such as radicals. In addition to experimental studies, the thermal decomposition mechanisms of the eight sulfur species are investigated theoretically using density function and ab initio quantum chemical techniques. As the project has both experimental and computational aspects it exposes the undergraduate students to physical chemistry.