Research Interests

• Fabrication of Selective Oxygen Permeable Membrane Reactors
• Production of Biodiesel
• Production of Synthesis Gas (Autothermal Reforming)
• Production of Hydrogen (CO oxidation / LTWGS)

Fabrication of Selective Oxygen Permeable Membrane Reactors

In recent years, the investigation of membrane materials for both reactant and effluent separation has experienced significant growth.  Of particular interest is the use of selective oxygen permeable membranes as catalytic reactors.  These materials are 100% selective to oxygen allowing form complete separation of oxygen from air without a costly cryogenic separation system. One class of unique materials are mixed ionic-electronic conductors which have the ability to conduct both electrons and ions. Mixed ionic-electronic conducting membranes have significant applications in fuel processors, oxygen sensors, and oxygen generation systems. However, commercialization of the technology continues to be plagued by low oxygen flux, high membrane fabrication costs, and high temperatures required for operation. Minor modifications to the membrane chemical composition will not be sufficient to overcome the technological and economic barriers. Thus, our group is investigating novel ideas to increase oxygen permeation and reduce the fabrication cost.

In our laboratory we are studying the enhancement of the oxygen flux through the membranes by modifying the surface of the membranes. We have recently shown that the oxygen ion flux can be more than doubled by placing a platinum catalyst on the air side of the membrane. We are currently using surface science techniques to understand the role of the catalyst in facilitating oxygen dissociation and increasing oxygen ion flux. We are also fabricating and studying thin films of dense dual conducting materials deposited on porous substrates as a means of further increasing the flux and the commercial viability of the membranes. Decreasing the thickness of the membranes will result in increased flux while depositing the membranes on strong, inexpensive supports will decrease the fabrication costs while making the membranes more robust. The projects associated with the research are aimed at gained a fundamental understanding of the membranes and the mechanism of oxygen ion flux, both of which are vital to the commercialization of these membranes in medical, environmental, and energy applications. The work is being done in collaboration with Dr. Karen Nordheden's Plasma Research Laboratory.

Production of Biodiesel

A significant fraction of the chemicals and fuels consumed around the world are produced from petrochemical based processes. In recent years there has been a significant growth in the interest of renewable feedstocks and the concepts of green chemistry. One can envision the ultimate goal as the ability to use domestic, renewable resources in efficient, economical processes to produce value added products and more environmentally benign fuels. Alkyl esters have potential applications as intermediates for chemicals and as a renewable, biodegradable, and nontoxic biodiesel fuel. The production of alkyl esters typically occurs via the transesterification of vegetable oils with alcohol using alkaline catalysts in a batch process. Large scale production of alkyl esters from vegetable oil is currently prohibitively expensive due to costs associated with purifying the feedstock. The high free fatty acid and water content in cheaper feedstocks lead to increased separation costs and decreased catalyst efficiency. Our research investigates alternative solid acid and base catalysts for the esterification of free fatty acids in a fatty acid-methanol-oil system to make inexpensive feedstocks viable without pretreatments via corrosive liquid acids or high pressures. In addition we are investigating ways to exploit CO2 to increase the viability of smaller pore solid acids by reducing mass transfer limitations typically present with such large chain, branched higher hydrocarbons. This work is being performed as part of the Center for Environmentally Beneficial Catalysis.

Production of Synthesis Gas

Significant global efforts are currently being dedicated to the investigation of partial oxidation, steam and carbon dioxide (dry) reforming of methane and other feedstocks for the production of synthesis gas. The synthesis gas can be further processed to form higher value commodities such as ammonia, methanol, polycarbonates, and oxygenated alcohols or be used as a fuel feedstock. When performed independently, the reactions have limitations, which reduce the feasibility or desirability of the process. For example, current partial oxidation technology requires oxygen separation plants which can account for a large fraction of the overall cost of the system. Likewise, dry reforming catalysts capable of carbon free operation have yet to be discovered, inhibiting the commercialization of this technology. Our goal is to find an efficient and economical technology for production of synthesis gas from methane, and biorenewable feedstocks such as ethanol, soybean oil, and sunflower oil.

One method is to investigate novel support materials which have a high capacity to store and release oxygen, resulting in increase catalyst stability. Recent results indicate that increasing the oxygen storage and transfer capacity of the support can enhance the activity and stability of supported Pt catalysts for the carbon dioxide reforming of methane. The support material acts as an active participant in the reaction rather than simply functioning as a material to anchor small particles of active metal. We are currently studying the mechanism of reaction in the presence of various feed conditions to better understand the role of the support material. This work is being performed in collaboration with the Instituto Nacional de Tecnologia Laboratorio de Catalise in Rio de Janeiro, Brazil.

Production of Hydrogen for use as a Fuel Cell Feedstock

Production of H₂ from hydrocarbons is currently achieved in the chemical industry for ammonia and alcohol production using carefully controlled catalytic processes. However, each process unit has limitations that prevent their application in fuel cell technology for mobile and stationary sources. These limitations include high pressures, expensive oxygen separation units, and pyrophoric or self-heating catalysts.

We are currently studying alternate catalytic systems that overcome these technological barriers by developing new catalysts for the low temperature water gas shift (WGS) and selective CO oxidation reactions. Specific emphasis is being placed on the fundamental understanding of the reaction mechanism and the role of the catalysts components in the activity and selectivity of the catalyst. Fundamental studies on the WGS and CO oxidation reactions are critical to the development of more efficient and cost effective fuel cell technology and will benefit other industrial processes where these reactions appear, such as steam reforming, coal gasification and ammonia synthesis.

Limited Peer Reviewed Publications

• Venkatesh Phadnavis, Bakul Pant, and Susan M. Stagg-Williams, "Promoted Pt catalysts for the dry reforming of methane in the presence of oxygen", accepted in Fuel Chemistry Division Preprints, Vol. 41 (1), (2002).

Non-Reviewed PublicationS

• Susan Williams, "Using Learning Styles to Enhance Education," Teaching Matters, A publication by the University of Kansas Center for Teaching Excellence, Vol 3(4), (2000).