Our research is focused on the areas shown below. Find out more regarding each topic by clicking on them or in the sub tabs to the left.
Metals supported on reducible oxides have shown promise for a variety of important reactions. Some examples include higher rates of selective deoxygenation and C-O activation when compared to metals supported on inert supports. A great challenge is understanding the underlying cause of the promising activity. Unique catalytic activity can arise due to highly active sites at the perimeter of the metal particle, electronic interaction with the support, new sites that arise on the support that are promoted by the metal, or even decoration or covering of the nanoparticle by the support. Unique sites involving exposed support cations as well as reduced metal particles are capable of carrying out several promising transformations. We focus on combining reaction kinetics with careful catalyst synthesis to determine the root cause of the underlying activity, and we collaborate with excellent theoretical groups of Bin Wang and Lars Grabow to help explain our experimental observations.
The unique ability to tune the confining environment around an active site, as well as the distance between active sites in zeolites leads to very promising catlaytic activity. While many industrial applications such as catalytic cracking and hydrocracking are well established, zeolites offer the unique potential to facilitate the production of several specialty chemicals as well. Our group has focused on understanding the mechanism of carboxylic acid coupling to make higher value products through ketonization and very promising acylation reactions over acidic zeolite catalysts. More recently, we have also begun to investigate the interesting role that water plays through interaction of various transition states relevant to hydrocarbon activation within a zeolite pore.
Particles that lie at the water-oil interface are capable of exhibiting many interesting catalytic features that are not possible in a single phase system. Tuning the location of an active site with respect to an oil-water interface can modify the transition state stabilization, transport rates of reactants and products, as well as catalyst deactivation rates in some cases. We have previously shown the promising ability to carry out cascade reactions in such systems, and now our group is focusing on tuning local reaction environments to carry out selective photocatalytic partial oxidation reactions. We also aim to better understand the interesting behavior of carbon nanotubes in these biphasic systems, as the nanotube-nanotube attractive forces allow for remarkable Pickering emulsion stability and stacking of particles at the oil-water interface. More recently, we have begun to focus on responsive catalytic particles as well, such that reaction selectivity as well as catalyst regeneration can be tuned by the introduction of external stimuli.
Carbon nanotubes are interesting materials with promise for a wide range of applications. Our group has been focused on syhtesizing nanotubes with unique functionality along the length. This opens up useful applications as catalyst supports, emulsion stabilizers, and as anchors for immiscible polymers (in collaboration with Brian Grady's group). We have focused on both manipulating forests to introduce functionality at different ends of the nanotubes, as well as tuning growth conditions to introduce blocks of functionality in well defined regions. In addition to anisotropically functionalized nanotubes, we also grow nanotubes on waste refinery catalysts to make unique hydrophobic materials.
Biomass can be converted to a stream of oxygenates through thermal decomposition in the absence of air. Selective conversion and separation of this complex stream to high value fuels and chemicals is a great challenge. By using a series of torrefaction steps, biomass-derived streams can result that are highly concentrated in a few compounds such that targeted catalytic strategies can be developed that substantially improve the amount of useful products that arise from the biomass. Evaluating and optimizing the tradeoff between increased process complexity and improved yields is a large group effort. Experimentally we use both blends of model compounds as well as real torrefaction vapors to demonstrate the effectiveness of our proposed strategies for producing high value products and specialty chemicals. We collaborate with several groups at OU as well as Vikas Khanna's group and Christos Maravelias' group to determine the technoeconomic and life cycle impacts of the promising strategies that are proposed.
Plastic production has been growing exponentially throughout the last decades. Huge amounts of plastic waste are generated every day, and only a tiny fraction of it is currently recycled. We are studying apporaches to chemically upcycle plastic, that is, to turn waste into valuable streams via catalytic reactions.
We explore catalyst designs that selectively target specific polymers, in order to effectively recycle mixed plastic streams. Our key goals involve developing unique catalysts that facilitate the selective separation of contaminant layers from polyolefin films and the sequential conversion of blends of polyolefins. Also, our group is working to understand the effect that common impurities may play in the depolymerization reactions, as well as their long-term effect on the catalyst used.
