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William EplingAssociate Professor Research WebSite: http://chemeng.uwaterloo.ca/wepling |
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.
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 aftertreatment 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
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.
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