Browsing by Author "Gilkey, Matthew J."
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Item Insights into ring opening of biomass-derived furanics over Ru/C(Wiley Online, 2016-10-14) Gilkey, Matthew J.; Mironenko, Alexander V.; Yang, Leerang; Vlachos, Dionisios G.; Xu, Bingjun; Matthew J. Gilkey, Alexander V. Mironenko, Leerang Yang, Dionisios G. Vlachos, Bingjun Xu; Gilkey, Matthew J.; Mironenko, Alexander V.; Vlachos, Dionisios G.; Yang, Leerang; Xu, BingjunSelective ring opening of cellulose-derived furanic molecules is a promising pathway for the production of industrially relevant linear oxygenates, such as 1,6-hexanediol. 2,5-dimethylfuran (DMF) is employed as a model compound in combined experimental and computational investigations to provide insights into metal-catalyzed ring opening. Ring opening to 2-hexanol and 2-hexanone and ring saturation to 2,5-dimethyltetrahydrofuran (DMTHF) are identified as two main parallel pathways. Density functional theory calculations and microkinetic modeling indicate DMF adsorbs on Ru in an open-ring configuration, which is potentially a common surface intermediate leading to both ring opening and ring saturation products. While the activation barriers for the two pathways are comparable, formation of DMTHF is more thermodynamically favorable. In addition, steric interactions with co-adsorbed 2-propoxyl, derived from the solvent, and the oxophilic nature of Ru play key roles in determining the product distribution: the former favors less bulky, i.e., ring-closed, intermediates, and the latter retards O-H bond formation. Finally, we show that hydrodeoxygenation of oxygenated furanics, such as 5-methylfurfural and (5-methyl-2-furyl)methanol, on Ru preferentially occurs at oxygen-containing side groups to form DMF, followed by either ring opening or ring saturation.Item Mechanistic insights into hydrodeoxygenation of biomass-derived furans to value-added products(University of Delaware, 2018) Gilkey, Matthew J.Biomass upgrading technology to value-added fuels and chemicals has been intensely studied in recent years, owing to concerns over the sourcing, availability, and environmental impacts of conventional fossil resources with ~50 gigatons CO2 emitted annually. Although recent advances in hydraulic fracturing have introduced shale gas as an inexpensive source of natural gas andItem Poisoning of Ru/C by Homogeneous Brønsted Acids in Hydrodeoxygenation of 2,5-Dimethylfuran via Catalytic Transfer Hydrogenation(Elsevier, 2017) Gilkey, Matthew J.; Vlachos, Dionisios G.; Xu, Bingjun; Matthew J. Gilkey, Dionisios G. Vlachos, Bingjun Xu; Gilkey, Matthew J.; Vlachos, Dionisios G; Xu, BingjunIt has been proposed that the combination of metal and acid sites is critical for effective ring opening of biomass-derived furans to linear molecules, a reaction that holds promise for the production of renewable polymer precursors and alkanes. In this work, we use 2,5-dimethylfuran (DMF) as a model compound to investigate hydrogenolysis and hydrogenation pathways using a combination of H2SO4 and Ru-mediated catalytic transfer hydrogenation in 2-propanol. Acid-catalyzed hydrolytic ring opening of DMF to 2,5-hexanedione (HDN) occurs readily at 80 °C with a selectivity of 89% in 2-propanol. Over Ru/C, HDN is fully converted after only 2 h at 80 °C, forming a mixture of both ring-closed products (~68% total yield), i.e., 2,5-dimethyltetrahydrofuran (DMTHF) and 2,5-dimethyl-2,3-dihydrofuran (DMDHF), as well as ring opened products (~28% total yield), i.e., 2,5-hexanediol (2,5-HDL) and 2-hexanol (HOL). Rather than observing sequential hydrolysis/hydrogenation reactions, we observe severe suppression of metal chemistry when having both Ru/C and H2SO4 in the reaction system. While minor leaching of Ru occurs in the presence of mineral acids, X-ray photoelectron spectroscopy coupled with CO chemisorption studies suggest that the primary cause of the lack of Ru-mediated chemistry is poisoning by strongly adsorbed sulfate species. This hypothesis is supported by the observation of Ru-catalyzed chemistry when replacing H2SO4 with Nafion, a solid Brønsted acid, as sulfonic acid groups tethered to the polymer backbone cannot adsorb on the metal sites.