Experiments and theory are combined in our group to better understand and control homogeneous and heterogeneous chemical reaction processes. Using experimental and computational facilities, we are developing insights on the detailed chemical kinetic mechanisms (DCKM) associated with catalysis, combustion and other industrially important reaction processes. In addition, we are contributing to the development of Combinatorial Catalysis as a new sub-field of Catalysis. Furthermore, our laboratories are also developing highly sensitive detectors to monitor process emissions in real time using lasers and time-of-flight mass spectrometry. Our current research interests are summarized below. You can also check out the papers published by our group by clicking on the Papers button on the left.
Combinatorial catalysis is a methodology or set of tools where large diversities of chemically and/or physically different materials libraries are prepared, processed and tested for desired performance in a highly parallel fashion. Combinatorial catalysis also embodies microfabrication, robotics, automation, instrumentation, computational chemistry and large-scale information management (informatics), and as such carry the promise of a renaissance in catalytic reaction engineering. Our laboratories pioneered the use of resonance enhanced multiphoton ionization (REMPI) for the high-throughput testing of catalysts libraries as well as array microreactors as library structures. In our research program we are preparing catalyst libraries using solution based techniques such as computerized microdrop/microjet dispensers and aerosol synthesis. Channel/Array microreactor libraries are screened either using REMPI or mass spectrometry. In a parallel program, we are developing new catalysts for NOx reduction, the oxidative coupling of methane using quantum chemistry where novel catalyst formulations are theoretically tested (screened) first before undertaking laboratory experiments. We model the catalysts as clusters and study the energetics of adsorption, surface diffusion, reaction and desorption processes.
Combustion is the major source of energy production today as well as the primary source of air pollution. Polycyclic Aromatic Carbons (PAC) are the largest single class of chemical carcinogens produced by combustion at trace levels. We are generating fundamental new information on the levels of PAC, soot and other toxic by-products formed in premixed and diffusion flames, and these studies have already led to discovery that methane, contrary to what is generally believed, is not the cleanest burning hydrocarbon fuel. Related research is also underway on the flame chemistries of halogenated hydrocarbons, which our laboratories pioneered.
In this program we use quantum chemistry, both ab initio and semi- empirical, to determine the thermochemistry of molecules, free radicals, clusters, surfaces and bulk materials related to combustion, catalysis and the synthesis of new materials. Reaction rate parameters that are needed for the development DCKMs are then determined via the use of the transition state theory. The kinetics of energy transfer limited reactions are determined using various forms of the RRKM theory. DCKMs are then coupled with models describing the transport phenomena and integrated for the simulation of chemical reaction behavior of processes. Sensitivity analysis is also undertaken to asses the influence of uncertainties in thermochemical, kinetic and transport parameters on model predictions.
Our group is leading the development of highly sensitive experimental techniques to monitor process emissions in real time using Resonance Enhance Multi- Photon Ionization (REMPI) coupled to Time-of-Flight Mass Spectrometry (TOF/MS). We have already demonstrated the feasibility of real time detection of naphthalene at parts per trillion (ppt) using KrF excimer laser. With the use of multi-color lasers further increases in selectivity and sensitivity appear to be possible. Other possible applications of this technology include the monitoring of indoor and outdoor air pollution.The REMPI-TOF/MS promises to be a universal detector because of its sensitivity, versatility and broad mass range. In addition to volatile species, it can be used to detect fullerenes, metals and even large biomolecules.
For further information on the topics discussed above, or other material about our laboratory,
please send your e-mail to
senkan@seas.ucla.edu
or call (310) 825-6303. Thank you.