- BSc, Virginia Polytechnic Institute and State University
- PhD, University of Florida
Our research group focuses on understanding and engineering the reaction process on and along a catalyst surface. This encompasses the preparation of novel catalyst materials, the fundamental characterization of catalyst surfaces, developing new analytic techniques, processes or devices, and preparing or manufacturing pilot-scale samples for testing and application. All of which results in our ability to obtain and translate in-depth fundamental catalyst knowledge to practical, industrially relevant application.
The list below contains areas that are currently being researched in our group.
Remediation of regulated emissions in lean-burn exhaust gasses
More widespread use of lean-burn engines would result in decreased fuel consumption. With lean-burn operation however, NOX emissions become significantly more difficult to control. Current after treatment systems for NOX control on gasoline-powered automobiles work only because the engine operates in a stoichiometric burn mode, and are inefficient when used in lean-burn exhaust gas. A novel catalyst technology, NOX Storage/Reduction (NSR), has been developed for this application.
We are currently focused on understanding the reaction chemistry that occurs on the surface of such catalysts and understanding how such chemistry changes as a function of axial position along the catalyst. With such results we engineer the reaction and catalyst, with the goal of reducing catalyst cost and fuel consumption associated with catalyst use.
Current predictions indicate that different fueling recipes in diesel engines will result in significantly less soot and NOX emissions in the future (Homogeneous Charge Compression Ignition (HCCI), for example). There will, however be a coincident and significant increase in hydrocarbon emissions. Although lean-burn operation would seemingly facilitate easier hydrocarbon oxidation, the exhaust gas temperatures associated with these new combustion recipes are very low. The challenge therefore becomes low-temperature hydrocarbon oxidation in a transient operating environment. Our current efforts focus on defining the operational boundaries of catalysts in this environment, evaluating optional (meaning cheaper) catalyst types, and monitoring catalytic changes as a function of time-on-stream.
Reaction characterization and engineering
Catalyst poisoning or other forms of catalyst degradation do not homogeneously affect industrial-scale systems. So, although most systems operate in a steady-state mode, the integral nature of catalyst systems needs to be modeled. We use and develop new tools, functionally-specific techniques and processes to monitor changes in catalyst reaction chemistry as a function of both catalyst life and position in the catalyst bed. These results are used as inputs for time-dependent control strategies and for designing and engineering better catalysts. Current applications include catalysts for aftertreatment systems and H2 generation for fuel cells.
An extension of this work includes pulsed/transient operation of catalyst systems. Via controlling the introduction of reactants, periodic temperature and concentration gradients within a catalyst system can be established which result in changed catalytic activity. This change can be associated with both selectivity and conversion to the desired products. Using experimental techniques designed to be functionally specific, we monitor the transient operation and optimize the strategy toward better performance.
- Shadab Mulla, Nan Chen, W. Nick Delgass, William S. Epling, Fabio H. Ribeiro, "NO2 inhibits the catalytic reaction of NO and O2 over Pt," Catalysis Letters 100(2005)267.
- William S. Epling, James E. Parks, Neal W. Currier and Aleksey Yezerets, "Evidence for Multiple NOx Sorption Sites or Mechanisms on NOx Storage/Reduction Catalysts," Catalysis Today 96(2004)21.
- William S. Epling, Larry E. Campbell, Aleksey Yezerets, Neal W. Currier, and James E. Parks II, "Overview of the Fundamental Reactions and Degradation Mechanisms of NOx Storage/Reduction Catalysts," Catalysis Reviews 46(2004)163.
- William S. Epling, Greg Campbell and James E. Parks, "The Effects of CO2 and H2O on the NOx Destruction Performance of a Model NOx Storage/Reduction Catalyst," Catalysis Letters 90(2003)45.
- Stuart Daw, Katey Lenox, Kalyana Chakravarthy, William Epling and Greg Campbell,"Phenomenology of NOx Adsorber Catalysts Part 1 : Lean-Phase Operation," International Journal of Chemical Reactor Engineering 1(2003)A24.
- Michael A. Henderson, William S. Epling, Charles H.F. Peden and Craig L Perkins, "Insights into Photoexcited Electron Scavenging Processes on TiO2 Obtained from Studies of the Reaction of O2 with OH Groups Adsorbed at Electronic Defects on TiO2 (110)," Journal of Physical Chemistry B 107(2003)534.
- William S. Epling, Praveen Cheekatamarla and Alan M. Lane , "Reaction and Surface Characterization Studies of Co- and Co/Pt-Based Catalysts for the Selective Oxidation of CO in H2 -Containing Streams," Chemical Engineering Journal 93(2003)61.
- Jim Parks, Aaron Watson, Greg Campbell and Bill Epling, "Durability of NOx Absorbers: Effects of Repetitive Sulfur Loading and Desulfation," SAE Technical Paper Series 2002-01-2880 .
- G.B. Hoflund, Z. Li, W.S. Epling, T. Gobel, P. Schneider and H. Hahn, "Catalytic Methane Oxidation Over Pd Supported on Nanocrystalline and Polycrystalline TiO2, Mn3O4, CeO2 and ZrO2 ," Reaction Kinetics and Catalysis Letters , 70(2000)97.
- William S. Epling, Gar B. Hoflund and David M. Minahan, "Reaction and Surface Characterization Study of Zn/Cr-Based Higher-Alcohol Synthesis Catalysts X: Effects of Excess Promoter Loading on Surface Chemistry," Reaction Kinetics and Catalysis Letters 67(1999)225.
- Gar B. Hoflund, William S. Epling and David M. Minahan, "Reaction and Surface Characterization Study Higher-Alcohol Synthesis Catalysts XII: K- and Pd-Promoted Zn/Cr/Mn Spinel," Catalysis Today 52(1999)99.
- Michael A. Henderson, William S. Epling, Craig L. Perkins, Charles H.F. Peden and Ulrike Diebold, "Interaction of Molecular Oxygen with the Vacuum-Annealed TiO2 (110) Surface: Molecular and Dissociative Channels," Journal of Physical Chemistry B 103(1999)5328.
- Gar B. Hoflund and William S. Epling, "Review of Research on Low-Temperature CO-Oxidation Catalysts," Recent Research Development in Catalysis 1(1996)31, Research Signpost, Trivandrum , India .
- William S. Epling, Gar B. Hoflund, Jason F. Weaver, Susumu Tsobota and Masatake Haruta, "Surface Characterization Study of Au/a-Fe2O3 and Au/Co3O4 Low-Temperature CO Oxidation Catalysts," Journal of Physical Chemistry 100(1996)179.