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.
