ME Professor Angela Violi’s paper is titled “Formation and emission of large furans and oxygenated hydrocarbons from flames” and can be read on the Proceedings of the National Academy of Science’s site here. Violi is also a professor of Chemical Engineering, Biomedical Engineering, Macromolecular Science and Engineering, Applied Physics, and Biophysics. Below are the details of the paper.
Furans are highly toxic cyclic, dienic ethers, i.e., 5-member aromatic rings containing one oxygen atom. They are ubiquitous in the atmosphere and formed predominantly during combustion. They are found in cigarette smoke, roasted and brewed coffee, baked goods, baby food, and exhaust streams of biomass burning, waste incineration, and electronic waste recycling. However, not only have furan-formation pathways not been well understood, but the mechanism by which they are incorporated into combustion particulates has also been mysterious. This work employs a multifaceted experimental and theoretical approach and demonstrates that combustion generation of furans and large oxygenated hydrocarbons can be significant, even during the combustion of very simple fuels, such as ethylene. The results suggest that furans are present from the inception of soot and are actively incorporated into the growing particles. These results are used to develop and validate a description of furan chemistry in the gas and particulate phases of combustion.
Our approach uses ab initio electronic structure calculations to study chemical-reaction pathways of oxygen inclusion, which are incorporated into the Stochastic NanoParticle Simulator (SNAPS) to study the formation and growth of particles using atomistic simulations. SNAPS based on probabilistic follows the time evolution of molecular species as they transform from gas-phase to nanoparticles, providing insights into the relationships between reaction pathways and chemical compositions of the particles formed. Predictions were validated by extensive and detailed analysis of particulates from well- controlled and characterized test flames, employing VUV photoionization aerosol mass spectrometry, which allowed identification of oxygenated species by mass, and XPS measurements, which unambiguously identified the oxygen functional groups present in the particles. We report for the first time the presence of large furans and associated oxygenated species in flames. The results show a consistent behavior among combustion systems, supporting the generality of large-oxygenate formation. Cyclic ethers play an important role during carbon oxidation and require inclusion in kinetic mechanisms that describe the oxidation of hydrocarbons and in models aimed at predicting toxicity and hygroscopicity of soot particles and related organic carbon.
Team members: Olof Johansson (postdoc, Sandia), Tyler Dillstrom (grad student, Univ. Michigan), Matthew Campbell (postdoc, Sandia), Matteo Monti (postdoc, Stanford), Farid El Gabaly (PI, Sandia), Paul Schrader (technologist, Sandia), Denisia Popolan-Vaida (postdoc, LBNL), Nicole Richards-Henderson (postdoc, LBNL), Kevin Wilson (PI, LBNL), Angela Violi (PI, Univ of Michigan), Hope Michelsen (PI, Sandia)