More than twenty years of my career has been spent in research and development with several industrial organizations. Consequently, my interests tend towards the applied side of the academic spectrum. The focus of our current research is on applying the principles of chemical reaction engineering to the solution of important problems in the areas of pollution prevention, pollution control, and alternate fuels.

The use of supercritical carbon dioxide as a medium for carrying out chemical reactions is an area of major emphasis. For example, many industrial polymerizations are conducted in organic solvents, resulting in large quantities of organic waste. Even when a polymerization is conducted in water, an aqueous stream containing significant concentrations of the monomer and/or polymer is produced and must be treated. Carrying out polymerizations in supercritical CO₂ is an exciting new way to avoid such waste streams. This requires a detailed conceptual and mathematical understanding of polymerization mechanisms and kinetics in supercritical CO₂. We are studying the polymerizations of vinylidene fluoride, acrylic acid, and poly (bisphenol A carbonate) in the laboratory and developing mathematical models to describe the important process parameters, e.g., monomer conversion and molecular weight distribution, as a function of the operating conditions of the reactor.

In a related project, the direct hydrogenation of polymers is being studied as a means to produce novel materials with unique properties.  The current focus is on polymers containing aromatic rings, such as polystyrene.  The hydrogenation reaction is being carried out in the presence of supercritical CO₂ in order to reduce the viscosity of the solution being hydrogenated, thereby improving the transport properties of the system, and facilitating separation of the catalyst from the viscous polymer solution.  The ultimate objective is to carry out the hydrogenation in a fixed bed of catalyst, e.g., in a trickle-bed reactor.

The depolymerization of step-growth polymers such as poly(ethylene terephthalate) is being investigated as a means to recycle plant and consumer waste plastic.  The polymer is reacted with compounds such as ethylene glycol or methanol to produce the component monomers, or low-molecular-weight oligimers. Supercritical CO₂ is employed to accelerate the reaction and reduce the viscosity of the polymer.  A twin-screw extruder is being used to carry out the reaction and to characterize the reaction kinetics.

A project is underway to study the selective oxidation of low concentrations of carbon monoxide in the presence of high concentrations of hydrogen.  This reaction is a critical step in the emerging technology for hydrogen-based fuel cells.  Novel monolithic metal foams are being used as catalyst supports. The intrinsic kinetics of both oxidation reactions are being studied as a function of catalyst composition and process conditions, as a precursor to constructing a kinetic model of the competing reactions.

Finally, we are conducting a fundamental study of heterogeneous catalysts for the reaction of carbon dioxide with methane to form acetic acid. This project also involves studying the formation of acetate groups on different surfaces by DRIFTS (diffuse reflectance infrared fourier transform spectroscopy). Chemical methods to drive the unfavorable equilibrium for this reaction also are being investigated.