We focus on understanding selective reactions on natural materials to convert them into usable products, and how to make chemical transformations more sustainable in general. Entire new industries are developing which require new inventions in green chemistry and the use of renewable materials and a new generation of scientists and engineers must be trained. In particular, our work focuses on the design and synthesis of catalysts and adsorbents required by these processes. Our research on sustainable chemicals and fuels focuses on three aspects (see right) of sustainable chemical manufacture which are important technological problems and also long-standing challenges in catalyst and adsorbent design.
Utilizing renewable feedstocks.
Natural chemicals such as oils and sugars can be used as fuels and feedstocks for chemicals, but reactions using renewables are incompletely understood. Renewables can rarely be used directly in existing infrastructure (think sugar in a gas tank), and the challenge lies in taming the inherent complexity of these molecules. Thus, new chemical reactions, and specifically new catalysts, must be developed that are highly selective and can tolerate the unusual types and diverse array of chemical groups present in a typical natural molecule.
Renewables can be converted to chemicals or fuels via an indirect route (e.g. energy and capital intensive gasification, reforming, and Fischer-Tropsch synthesis) or direct routes using selective catalysts that we are investigating. Supported by the Department of Energy
“Institute for Catalysis in Energy Processes” and the American Chemical Society, we are developing shape-selective and atom-precise catalysts that selectively remove oxygen and nitrogen atoms from complex molecules such as sugars, glycols, lignin, natural oils, or tars to convert them into useful fuels or feedstocks compatible with existing infrastructure.
Novel catalysts include < 10 nm 'nanobowls’ carved into oxide surfaces for shape-selective reactions with sugars, (see right) and novel supported Ta and Fe catalysts. General development of the nanobowl methodology is being supported by an individual grant from the US Department of Energy. The National Science Foundation supports our research into adsorption into designed cavities (see left) for the shape-selective removal of butanol – a potential biofuel – from aqueous fermentation broths. The nanobowl concept is being extended to control selectivity and prevent deactivation of other catalysts.
Efficient chemical transformations (green chemistry).
In this area, we seek to develop catalysts that can perform selective oxidations that are atom-efficient, use Earth-abundant metals, operate at mild conditions, and use oxygen or hydrogen peroxide where required. We currently study epoxidation/hydroxylation and other reactions on novel solid catalysts that we have designed.These precisely-designed catalysts allow high reactivity and selectivity, but also shed light on the key features of classical catalysts that are often complex mixtures. We have developed several new catalysts based on supported Fe, Mn, Ti, and Ta that mimic biology, rather than classical catalysts that use precious metals. The image to the left shows a self-assembling manganese oxide catalyst and a site-isolated Ta catalyst developed in our laboratory to perform selective epoxidations or hydroxylations. Prior support for this work has come from the Camille and Henry Dreyfus Foundation and Dow Chemical via the Dow Methane Challenge and current work is primarily supported by a grant from Dow Chemical.
Man-made solar fuel from CO2 is a 'grand challenge’ that requires both fundamental research and technological development. Likewise, the conversion of combustion generated NOx is an increasing challenge as we push towards lower emissions limits and higher fuel efficiencies. A grant from Toyota Motor and Engineering and young investigator support from DuPont and 3M provide support into investigations of combined acid-base materials for CO2 capture and other important reactions, novel catalysts to replace precious metals in automotive exhaust catalysts, and develop well-controlled Ti-SiO2 materials to better understand photoreduction of CO2. We have also been supported by the Materials Research Science and Engineering Center (NSF) and the Initiative for Sustainability and Energy at Northwestern.
Check out our 2016 NRG research poster!