Catalysis
Reaction Kinetics
Conversion of Syngas to Chemicals and Fuels
Catalytic Reduction and Decomposition of NO
Green Chemistry and Engineering
My major research interests are in the areas of catalysis, reaction engineering, and environmental engineering. The current themes in my research groups are basic research in heterogeneous catalysis, environmental catalysis, and environmentally benign synthesis processes.
Transient Infrared Study of Adsorbates in Heterogeneous Catalysis (Funded by National Science Foundation) Determination of the reactivity of adsorbates under reaction conditions has been a major challenge in the fundamental research of heterogeneous catalysis. An experimental technique which couples in situ infrared spectroscopy with isotopic transient method has been developed to study the reactivity and dynamic behavior of adsorbates during NO-CO, CO-H2, and CO-H2-C2H4 reactions over Rh-based catalysts. The transient responses of isotope-labeled adsorbates and gaseous products obtained from this approach allow distinction between spectator and reactive adsorbates and determination of their surface concentration during reaction. The overall goal of this program is to develop the relationships among the surface states and the composition of catalysts, the dynamics of elementary steps, the structure and coverage of adsorbates and reaction intermediates, and the macroscopic reaction kinetics, thus significantly increasing the fundamental understanding of heterogeneous catalysis.
In Situ Infrared Study of Catalytic Decomposition of Nitric Oxide (Funded by Department of Energy) Catalytic decomposition of NO to N2 and O2 is an attractive approach for the control of NO emission for its simplicity. In spite of extensive studies, effective catalysts for the direct NO decomposition in an oxidizing atmosphere remain to be developed. Mechanistic studies have shown that low activity of supported metal catalysts is due to their inability to desorb oxygen from NO dissociation sites. Promotion of oxygen spillover and desorption from the NO dissociation site should provide free sites needed for NO dissociation and complete the catalytic cycle for NO decomposition. Preliminary studies have demonstrated that Terbium oxide can serve as a promoter to enhance the rate of oxygen desorption. This program is focused on investigation of mechanism of oxygen spillover from Pt, Pd, and Rh sites to Lanthanide series oxide. This study could provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.
Catalytic Reduction of Nitric Oxide (Funded by Environmental Protection Agency) This research project addresses two critical technical issues, catalyst durability and catalyst activity, in control of NO emission. Catalyst durability is a major problem in all catalytic converter systems. The Rh/Pt- and Pd- based catalysts used in the current catalytic converters and the Cu- and Co-ZSM-5 catalysts being explored for NO reduction have suffered from hydrothermal degradation and sintering, resulting in loss of catalyst activity. Silanation offers an opportunity to impart hydrophobicity to the oxide surface and to provide impurities which may trap mobile metal species, inhibiting hydrothermal degradation and sintering during the reaction process. Interaction of silane with the catalyst surface and the mechanism of NO reduction on the silane-treated catalysts are now being studied by a series of spectroscopic techniques including in situ infrared spectroscopy, mass spectroscopy, and X-ray photoelectron spectroscopy. Improvement of catalyst activity is addressed by investigation of the reactivity of adsorbed CO, NO, and hydrocarbons on the catalyst surface. The goal is to identify the most active forms of adsorbed CO and NO for the reaction and the sites to which these species adsorb. This knowledge is required for the design of catalyst preparation methods to populate the most active form of the sites on the catalyst surface.
In Situ Infrared Study of Carbonylation of Nitrocompounds (Funded by National Science Foundation) The carbonylation reaction has been recognized as the most promising environmentally benign process to replace the conventional method of isocynate synthesis from the reaction of phosgene with amines. However, lack of mechanistic understanding of the reaction has greatly hindered industry's capability to develop efficient catalysts for the carbonylation of nitrocompounds. We have designed and constructed an infrared cell capable of operating up to 523 K and 10 MPa in a corrosive environment for investigation of infrared-observable intermediate for the homogeneous and heterogeneous carbonylation processes in liquid phase. Fundamental understanding of mechanisms obtained from this study will be used to guide catalyst design and development.
Heterogeneous Hydroformylation on Rh/Carbon Molecular Sieve Hydroformylation is the largest homogeneously catalyzed process employed in chemical industry. The present industrial process is catalyzed by Co or Rh complexes which exhibit high activity and selectivity. However, the process involves a costly catalyst separation step and the use of toxic solvents. Our goal is to encapsulate the Co or Rh complexes in the cage of carbon molecule sieves which provide solvent-like environment to maintain the catalyst activity and offer the advantages of heterogeneous catalysis. Preliminary work has demonstrated the feasibility of using carbon molecular sieve to immobilize the homogeneous catalysts. The present work involves the synthesis of carbon molecular sieves and determination of the nature of active site for the reaction.
Catalytic Decomposition of Polymers (Ohio Board of Regents) Catalytic decomposition of polymers provides a promising route for the selective production of hydrocarbons from waste plastics. Control of product selectivity requires fundamental understanding of the bond-breaking and bond-formation steps on the catalyst surface. The initial work is aimed at investigation of the mechanism of polypropylene decomposition in the presence and absence of hydrogen over solid acid-metal catalysts with dual functions of cracking and hydrogenation.
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Dr. Steven Chuang's email: schuang@uakron.edu
Webpage updated on 12/30/1998 by RWS