Welcome to Our Kinetics Group
Research Description
The efforts of our research team focus on the quantitative kinetic characterization of reaction systems that have the potential to lead to more efficient power generation (e.g., solid oxide fuel cells). For example, the gas-phase reactions in the fuel channel of a solid oxide fuel cell produce intermediates that can profoundly influence performance. We seek to understand the detailed chemical pathways that lead to production of the smaller hydrocarbons that might be catalytically converted within the anode before being electrochemically oxidized. We also seek to characterize the molecular weight growth processes that can lead to deposit formation within the anode channels (e.g., "Hydrocarbon Fuel Effects in SOFC Oxidation: An Experimental and Modeling Study of n-hexane Pyrolysis", Phys. Chem. Chem. Phys., 9, 4245-4258 (2007)). These reactions are strongly influenced by multiple transport processes including diffusion and reaction of the gaseous hydrocarbons as they migrate through the porous anode (e.g., "Methane reforming kinetics within a Ni-YSZ SOFC anode", Applied Catalysis A, 295, 40-51 (2005)). Once we characterize the gas-phase kinetics and the catalytic kinetics occurring within the porous anode, we can include these reactions into the combined transport-kinetic models needed for optimization of fuel cell performance (e.g., "The Influence of Heterogeneous Chemistry and Electrochemistry on Gas-Phase Molecular Weight Growth and Deposit Formation", Solid Oxide Fuel Cells IX, 679-688, (2005)).
Another area of interest is hydrocarbon oxidation (e.g., Detailed Kinetic Modeling of Ethane Oxidation", Comb. Flame 145, 16-37 (2006)) especially in the temperature regime of the "negative temperature coefficient", where the ignition delay increases as the temperature increases. Understanding the ignition kinetics is essential to be able to reliably characterize events such as ignition in a HCCI (homogeneous charge compression ignition) engine. To better characterize the kinetics, we are focusing on a detailed analysis of the reactions between alkyl radicals and molecular oxygen (e.g., "Detailed Kinetic Modeling of C2H5 + O2", J. Phys. Chem. A., 109, 2264-2281 (2005)). We incorporate the results from these detailed analyses into existing mechanisms to generate improved descriptions of the ignition process. These improved mechanisms can then be used to suggest combinations of fuel and engine conditions that should lead to more robust operation of the HCCI engine. Specific areas of current interest include the combustion kinetics of alternative fuels such as Fischer-Tropsch and biodiesel.
We continue to focus on the kinetics of elementary reactions, especially in the context of using electronic structure calcualtions to examine a series of similar reactions and then using these results to generate rate rules that are applicable to a wide range of such reactions (e.g., "Rate Constant Rules for the Automated Generation of Gas-Phase Reaction Mechanisms", J. Phys. Chem. A, 113, 367-380 (2009)). Predictions of the temperature and pressure dependence of the branching reactions of chemically-activated reactions continues to be an active research area for our group (e.g., "The Kinetics of Pressure-Dependent Reactions" in Comprehensive Chemical Kinetics, 42, 105-187 (2007)).
Our group is becoming heavily involved in the production of fuels and power from the thermal conversion of biomass. We are particularly interested in characterizing the elementary chemical reactions occurring during biomass pyrolysis and gasification. As part of this analysis, we are characterizing the gas-phase reactions that lead to tar formation during biomass gasification as well as exploring gas-phase pathways to selectively remove tars from biomass and coal derived syngas streams. Another thrust is the production of syngas from the gas-phase partial oxidation of bio-oil (the product of rapid biomass pyrolysis) (e.g., "Non-catalytic Partial Oxidation of Bio-Oil to Synthesis Gas for Distributed Hydrogen Production", Int. J. Hydrogen Energy, submitted).
Current Research Projects
• Modeling and Simulation Tools for Chemical and Electrochemical Systems: Bridging Between Atomistic Fundamentals and System Engineering (ONR)
• The Impact of Alternative Fuels on Combustion Kinetics (ONR)
• Development of Process Models of Low Temperature Oxidative Cracking of Oxygenates Relevant to the Conversion of Biomass Pyrolysis Products to Hydrogen (NREL)
• Solid Oxide Fuel Cells for Combined Tar Reforming and Electricity Production (NREL)
• Chemical Reaction Mechanisms and Kinetic Modeling of Biomass Thermochemical Conversion Processes (NREL)
• Experimental Validation of Kinetic Ignition Models for Alkanes and Methyl Esters (NREL)
• Renewable and Logistics Fuels for Fuel Cells (DOE)
• Coal/Biomass Gasification (DOE)
• Reactive 3D CFD Project (Delphi)