Researchers efficiently produce hydrogen from biomass
Steenbock Professor James Dumesic and Research Scientist Randy Cortrightare leading graduate students Rupali Davda, John Shabaker and George Huber in developing a new process that efficiently produces hydrogen fuel from carbohydrates derived from plants. This source of hydrogen is non-toxic, non-flammable and safely transportable in the form of oxygenated hydrocarbons derived from carbohydrates otherwise known as sugars. The process uses low temperature, liquid-phase catalytic reforming of oxygenated hydrocarbons such as glucose, xylose, sorbitol, xylitol, glycerol and ethylene glycol. Currently, most hydrogen is produced from natural gas. But unlike conventional starting materials for hydrogen production, these oxygenated hydrocarbons come from renewable resources like corn and sugar beets, or waste biomass streams like paper mill sludge and cheese whey.
"The process should be greenhouse gas neutral," says Cortright. "Carbon dioxide is produced as a byproduct, but the plant biomass grown for hydrogen production will fix and store the carbon dioxide released the previous year."
Low reaction temperatures mean the process generates hydrogen without the need to vaporize water. That represents a major energy savings compared with vapor-phase, steam-reforming processes. In addition, the low reaction temperatures result in very low carbon monoxide concentrations, making it possible to generate fuel cell-grade hydrogen using a single chemical reactor. (Carbon monoxide poisons the electrode surfaces of low-temperature hydrogen fuel cells.) Like ethanol production, the process can utilize carbohydrates extracted from corn. The new process extracts hydrogen fuel from the same carbohydrate source at significantly higher energy yields when compared with ethanol production by fermentation and distillation.
Finding better catalysts for fuel cells
Assistant Professor Manos Mavrikakis is searching for more suitable catalysts for fuel-cell electrodes. Government and industry are shifting focus from gasoline engines to fuel cell technology to efficiently power cars and reduce the nation's reliance on foreign oil. Direct methanol fuel cells (DMFC) hold the promise of direct conversion of methanol to electricity, a process that can be as much as four times more efficient than combustion in internal combustion engines. However, before DMFCs can be made commercially viable, technological problems must be solved, such as the development of an electrooxidation catalyst that will both produce a high power density and be impervious to carbon monoxide (CO) poisoning over time. Poisoning occurs as the catalyst absorbs small amounts of CO.
Using theoretical tools, Mavrikakis seeks fundamental understanding of methanol behavior on existing catalysts and new alloys that may lead to improved catalyst performance. In addition, his group is developing low-temperature catalytic routes to hydrogen production from renewable alcohols, such as glycol and glycerol. (See "Researchers efficiently produce hydrogen fom biomass," above.)
His research team is looking at CO adsorption on various alloys to determine which give the lowest binding energy, and thus has the greatest potential for CO tolerance. On the cathode side he is looking at cathode catalytic bond breaking of oxygen-oxygen bonds. Subsequent investigations will include the total cathode reaction, which typically involves water formation.
Understanding the effects of host physiology on virus growth
Professor John Yin and graduate students Lingchong You and Patrick Suthers are using methods of chemical engineering, molecular and cell biology, and systems science to study how viruses grow and evolve. Viruses are useful as model genomic systems because their intracellular developmental processes are relatively simple, their molecular functions have been well characterized, and they can be readily cultured in the laboratory. Moreover, viruses are important because they can cause a variety of diseases such as AIDS, cancer and the common cold.
Using the growth of bacteriophage T7 as a model system, the team is developing a better understanding of how the physiology and resources of the host relate to the productivity of a phage infection (a virus that attacks bacterial cells). Yin says the studies may suggest means to alleviate bottlenecks and improve yields in the bioprocessing of viral vaccines and gene therapy vectors.
The team's latest simulation, as reported in the journal Science, shows the primary limitation on T7 growth is the number of ribosomes. The simulation also was used to follow how bottlenecks to phage growth shift in response to variations in host or phage functions.
Chemical sensors from liquid crystals
The behavior of liquid crystals provides the foundation for highly sensitive, very small, real-time and potentially wearable chemical sensors. John T. and Magdalen L. Sobota Professor of Chemical Engineering Nicholas Abbott developed the device with Rahul R. Shah (PhD '00), now at 3M Corporation. The sensors could be used to measure personal exposure to chemicals in a variety of environments including pesticides and chemical warfare agents.
In flat panel displays, electric fields change the orientation of liquid crystals to produce different optical appearances. Abbott's sensors also take advantage of this shift in orientation but do not require electrical input. Abbott's group engineered surfaces that change the orientation and appearance of liquid crystals when different chemicals bind to the surface. The research team has demonstrated the device's sensitivity to both amine and organophosphorus compounds. The process is being commercialized by Platypus Technologies LLC, in the UW-Madison Research Park.