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[Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(XCN)2][OTf]2 (X = Me, Ph) and [Ru(2,9-di(pyrid-2'-yl)-1,10-phenanthroline)(MeCN)2][OTf]2 as Catalysts for the Hydrodeoxygenation of Biomass-Derived Substrates in Aqueous Acidic Media

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Title: [Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(XCN)2][OTf]2 (X = Me, Ph) and [Ru(2,9-di(pyrid-2'-yl)-1,10-phenanthroline)(MeCN)2][OTf]2 as Catalysts for the Hydrodeoxygenation of Biomass-Derived Substrates in Aqueous Acidic Media
Author: Stones, Maryanne
Department: Department of Chemistry
Program: Chemistry
Advisor: Schlaf, Marcel
Abstract: Classically, the biomass conversion field has focused heavily on both process engineering and the design of effective heterogeneous catalysts for the purpose of obtaining high-value compounds from sugar-derived furanic platform chemicals. One variable that is missing from this equation is the intrinsic reactivity of the substrates that process engineers have chosen to work with. To create a catalytic biomass conversion process that is competitive with current industrial processes, both catalyst design and substrate choice must be considered. This work outlines the synthesis of two molecular ruthenium pre-catalysts featuring tetradentate nitrogen-based ligands, [Ru(BPOPD)(XCN)2][OTf]2 (X = Me, Ph) and [Ru(DPP)(MeCN)2][OTf]2. The catalytic activity of [Ru(DPP)(MeCN)2][OTf]2 was evaluated for the conversion of biomass-derived furfuryl alcohol, and furfuryl acetate to the value-added compounds 1,4-pentanediol – being the primary target compound – and cyclopentanol in aqueous, acidic reaction medium at elevated temperature and pressure. Catalytic reactions using furfuryl alcohol as a substrate were severely limited by the formation of solid resins (the product yields showing a strong negative correlation with increasing substrate concentration), with maximum yields of 1,4-pentanediol and cyclopentanol being 23% and 41% respectively. A 2-level full factorial design of experiments study with four independent variables and a centre point was carried out in two replicate sets for the conversion of furfuryl acetate by [Ru(DPP)(MeCN)2][OTf]2, showing good reproducibility between replicates, and no solid humin formation. This enabled a full statistical analysis of variable impact on product distribution and yield. The maximum yields of 1,4-pentanediol and cyclopentanol using furfuryl acetate as a substrate are 68% and 35% respectively. The decreased self-reactivity of furfuryl acetate with respect to furfuryl alcohol dramatically increases the yields of target products, but there is still a strong negative correlation of product yield to increasing substrate concentration which is highlighted by the design of experiments study. This negative correlation between target product yield and increasing substrate concentration – brought about by the intrinsic self-reactivity of the highly oxygenated compounds present in carbohydrates and their derivatives – continues to be a primary challenge towards realizing an effective transformation of biomass-derived compounds to useful chemicals or fuels.
Date: 2020-05
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