Hydrodeoxygenation
(HDO)
Research goal: Selectively upgrade furans to fuel-grade compounds and to (partially) deoxygenated chemicals.
Approach: Develop design principles of efficient hydrodeoxygenation catalysts and for ring opening of furanics and hydrodeoxygenation by combining multiscale modeling and experiments. Synthesize multisite/multifunctional materials with nearly atomic scale control to carry out these processes selectively. Perform kinetic and spectroscopic studies for upgrading of furan-based compounds.
Learn more about HDO
The HDO Thrust has aimed to develop science and catalysts for the upgrade of furan-based compounds.
Furans, obtained from dehydration of sugars or pyrolysis of lignocellulose and oxygenated fuel precursors obtained from chain growth chemistry of furans are important intermediate platforms of lignocellulosic biomass.
However, owing to their oxygen-rich content, their transformation to fuels and chemicals requires selective oxygen removal. Upgrade of furans requires transformative technology to improve product yields and introduce new chemicals and to reduce catalyst cost.
Research highlights
We discovered that moderately reducible metal oxides, such as RuOx, can contain multifunctional sites that can selectively hydrogenate carbonyl groups, compared to the ring, via the MPV mechanism over Lewis acidic sites, and then hydrodeoxygenate the side OH groups on vacancies. The latter behave like redox centers, where a single concerted mechanism occurs, entailing radical formation and ring conjugation to facilitate the C-OH bond scission. While RuOx is an effective and selective catalyst, it is being reduced during catalysis. In order to improve catalyst stability, this concept was extended further. Computational studies allowed for the first time to establish catalyst design principles, which can ultimately lead to the discovery of the next-generation of C-O activation catalysts. First, we have explored the activity and stability tradeoff of single metal oxides and demonstrated a volcano curve where the activity/stability is correlated with the bulk Gibbs free energy as well as surface properties of the oxides. RuOx and IrOx are the best single metal oxide catalysts. Second, we used colloidal synthesis and atomic layer deposition (ALD) of bimetallics to create metal core/oxide monolayer thick shell, e.g., cobalt-oxide-overcoated Pt nanoparticles and Cu/Ni catalysts. These catalysts activate hydrogen and importantly do not get reduced; they can excitingly provide nearly quantitative yield in converting HMF to dimethyl furan (DMF).
In a parallel effort, we developed efficient and highly selective catalysts for (1) ring-opening catalytic pathways to convert biomass-derived furans and tetrahydrofurans into adipic acid, an essential monomer in 6,6-nylon; (2) deoxydehydration of vicinal diols to olefins, a class of compounds with a multitude of uses. A first generation of catalysts was obtained by adopting transition metals and structural motifs from homogeneous catalysts, e.g., oxide-supported oxo-rhenium; (3) non-precious metal oxide catalysts for the ring-opening of furanics. We have demonstrated that the use of reduced Cu-Co-Al mixed metal oxides achieves the formation of 1,5-pentanediol with upward yields of 45% and 1,2-pentanediol with upward yields of 17%. This is the highest reported yield for 1,5-pentanediol when compared with other catalysts with a similar mechanism; (4) production of mono and di-ethers of furans suitable for detergents and fuels via the MVP reaction over Lewis acid centers, e.g., Sn-containing zeolites, and etherification over acid sites.
