David W. Flaherty: Pursuing new approaches and tools in catalysis, surface science and materials synthesis
This profile originally appeared in the Spring/Summer 2018 issue of Mass Transfer, the magazine for alumni and friends of Chemical and Biomolecular Engineering at Illinois. For a listing of all our faculty members, please visit our directory or explore the department’s research pages for overviews of our groundbreaking research programs.
In David Flaherty’s lab for catalysis, spectroscopy, and materials chemistry research, Flaherty and his team of students and postdoctoral fellows are committed to solving some of the most formidable and longstanding challenges in the chemicals industry. Those challenges include developing methods to make fuels and chemicals from renewable sources and generating insight to decrease waste and environmental impact of oxidation chemistry.
A dedicated scientist and teacher, Flaherty joined the Department of Chemical and Biomolecular Engineering at the University of Illinois in January 2013. Since then, he has become a rising star in heterogeneous catalysis and has received a number of notable awards, including the National Science Foundation CAREER Award and honors for research, teaching, and advising.
He and members of his group have performed pioneering research into the direct synthesis of hydrogen peroxide and established principles for its use in clean oxidations and replacing toxic chlorine. They aim to improve production of value-added fuels and chemicals from small alcohols derived from biomass fermentation. They have been researching ways to create new sources for key platform chemicals needed for specialty polymers, lubricants and surfactants. And the group is developing spectroscopic methods to investigate catalysis at complex interfaces.
Born in the San Francisco Bay area, Flaherty grew up in California, Utah, Wyoming, and Louisiana. His father worked for Chevron for 30 years and his mother taught at elementary schools. When it came time to choose a college, he headed to the University of California, Berkeley. He would become the third generation of his family to graduate from the school.
Being the son of a chemical engineer and a teacher, perhaps it was inevitable that Flaherty would become a chemical engineering professor. But the path wasn’t always clear to him and when he meets with undergraduates who are questioning if the program is right for them, he’ll tell them he can identify with those feelings.
It wasn’t until later in his college years that he was certain chemical engineering was the field for him. That’s when he began taking classes such as thermodynamics and mass transfer, when he learned about reactors and separation processes, and he clearly saw the connections between classroom concepts and practical engineering challenges. This coincided with Flaherty’s initial involvement in research.
His first project, led by Professors Clay Radke and John Prausnitz, entailed characterizing water absorption and diffusion rates into new polymer composites for contact lenses. For the second project, done in collaboration with Professor David Graves and retired IBM scientist Harold Winters, Flaherty measured the dissociation cross sections of gases used in plasma processing for semiconductors. With help from his mentors, he designed experiments, built instrumentation, took measurements, and eventually published results.
“I realized I enjoyed the research process and it would be rewarding to work with students and train them to develop their own scientific skills. I valued the time and energy my advisors invested in me and wanted to give back. I also appreciated the freedom we had to choose problems and develop innovative methods to study them,” Flaherty said.
With a newly-discovered passion for research, he chose to pursue graduate school in chemical engineering at the University of Texas at Austin. Under the guidance of his advisor, C. Buddie Mullins, Flaherty pursued a number of projects under the umbrella of surface chemistry, such as clean production of hydrogen and selective oxidation chemistry on gold surfaces. For his postdoctoral research, Flaherty returned to UC-Berkeley, where he worked alongside chemical engineering professor Enrique Iglesia, the same faculty member who had first piqued his interest in reactor design and engineering as an undergrad. Flaherty’s mentors led by example and he learned not only how to conduct research, but also how to advise and teach students.
Illinois research portfolio
Flaherty joined the Illinois faculty in early 2013.
“I was really impressed by the large number of young faculty, how collegial they were, and the amount of collaborative work performed at Illinois. I liked the idea of working with them. And overall, it’s a welcoming campus,” he said.
Because Flaherty and his group members are engaged in intensive, experimental research and they require infrastructure and resources, he appreciates the advantages of being housed in the School of Chemical Sciences. This connection provides access to machine, glass, and electronics shops as well as to interdisciplinary labs and staff members who work with students to build unique instruments and new skills.
Since 2013, the group has grown to include 13 graduate and undergraduate students and one postdoctoral fellow as of Spring 2018.
“Our challenge is to reduce the amounts of energy consumed and harmful waste created when we create the functional molecules needed for consumer products like plastics, resins, and building materials. Most companies recognize these problems and would prefer to adopt new, more efficient catalytic methods,” Flaherty said.
But many of the alternatives are not currently economical. He said there needs to be a better understanding of how to control the chemistry, as well as how to create new and more effective catalysts and processes that require lower capital expenses and less energy.
“As one example, our group is developing materials and strategies to directly activate molecular oxygen from air and to create hydrogen peroxide inexpensively, because these reactions would enable selective oxidations in industrial chemistry.” Both approaches avoid the environmental risks and drawbacks of current processes, he said.
About two-thirds of the research in the Flaherty lab centers around this area. Their work entails trying to understand how reactions proceed and how to use their understanding of the mechanism to engineer new materials. From there, Flaherty said the goal is to develop design rules for next generation catalysts.
“We need to build concepts that provide specific hypotheses related to surface and materials chemistry and then test these ideas to expand our understanding. Doing so involves classical reaction engineering and also detailed kinetic and spectroscopic experiments,” he said.
The group uses these methods to identify crucial reactive species in these complex networks, to characterize their structure, their coordination structure, and to figure out how they can design materials that modify their stabilities to encourage the right reaction pathway.
The group has also been active in trying to convert alcohols, lipids, and furanic molecules (all derived from biomass) into chemicals. Because petroleum is inexpensive now, biomass conversion is more economically appealing if it produces valuable chemicals in addition to fuels.
“One of the challenges we first tackled was how hydrodeoxygenation chemistry occurred in these cyclic oxygenated molecules from biomass,” he said.
In collaboration with researchers from the University of Florida, the group figured out the mechanism for this chemistry on related metal and ceramic catalysts.
“We used insight from classical kinetic experiments and computational catalysis to hypothesize that differences in the types of products formed were caused by how the surfaces of nanoparticles binds reactive species.”
But there was no way to directly prove that because of the limits of spectroscopic techniques. The lab had to come up with a new methodology.
“We are working on a series of papers that shows how the binding configurations of small molecules relate to the chemical selectivity of these reactions at surfaces. We can see direct changes in the structure of reactive intermediates and relate kinetics of surface and fluid phase processes. We wouldn’t be able to do this without this powerful method for interrogating surface chemistry, particularly in liquids or at high pressures,” Flaherty said.
On the horizon
Lab members have begun using this methodology to understand the dynamic changes of metal containing zeolites, a nanoporous material, for reactions that convert to alcohols, which are important platform chemicals that can be used to produce many other products.
“If we could convert methane into methanol directly, we could turn abundant natural gas into valuable chemicals. And if we can do it in one step, it will cost less and reduce carbon emissions,” Flaherty said.
“The longstanding challenge has been trying to understand how these particular catalysts perform this chemistry selectively. The spectroscopic techniques we have developed will allow us to watch how metal atoms come together, activate oxygen molecules (which is a difficult part of this process), and then use that oxygen to form methanol. There are many things that are not understood about this system, and exploring this area will be exciting.”
In other areas, the group has figured out how to manipulate and control complex reaction networks that couple ethanol from biomass fermentation into mixtures of fuels and valuable chemicals. This can be done by controlling a number of different attributes of the catalysts, including the strength of surface acid sites and hydrogen bonding interactions near the catalytic center. They’re now looking to understand how to control this chemistry by incorporating different transition metals into the structure of zeolites.
Since the lab was first established, Flaherty and his students have participated in a number of research collaborations on campus and across the country. They are involved with the U of I’s Energy Biosciences Institute (leading to collaborations with BP and Shell) and now the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI), a new Department of Energy research center on campus. These collaborations on the production of chemicals from biomass and the direct synthesis of hydrogen peroxide from its elements have been helpful for not only supporting impactful research but also for educating students, he said. More recently, they are initiating a collaboration with Dow Chemical through its University Partnership Initiative on a project to develop catalysts and processes to selectively convert biomass-derived chemicals into monomers for functional materials with improved properties.
Looking ahead, Flaherty said the lab will continue to tackle the chemistry of complex systems that are relevant for industrial chemical production.
A lot of catalysis research looks at model systems because they are relatively simple and researchers can glean fundamental information through simple measurements, he said. But for Flaherty it has been rewarding to study complicated systems and to figure out how all the different components fit together.
“Combining our relatively powerful and unique spectroscopic capabilities together with the more traditional kinetic approaches has been a rewarding strategy. We can investigate systems that were previously considered intractable,” he said.
“Decades of previous work in this field have led to important discoveries in heterogeneous catalysis. Now, the questions that remain will require increasingly sophisticated tools and approaches to understand what’s happening at the surface.”