Mechanistic Understanding of Ring-Opening of Tetrahydrofurfuryl Alcohol over WO_x-Modified Pt Model Surfaces and Powder Catalysts

Abstract

The upgrading of heterocyclic biomass-derived oxygenates such as tetrahydrofurfuryl alcohol (THFA) via ringopening is a promising pathway to produce value-added diol molecules using renewable carbon sources. This study combines model surface experiments, first-principles calculations, and powder catalyst characterization and activity evaluation to unravel the nature of the Pt and WO x active sites and the reaction mechanism of the THFA ring-opening reaction on a WO x /Pt inverse oxide catalyst. Temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) measurements on model surfaces demonstrated that THFA ring opened on Pt(111) but underwent further decomposition due to its strong bonding with the surface. However, WO x deposited on Pt(111) altered the interaction strength between the ring-opened intermediate and the surface to a proper extent to facilitate the facile desorption of the desired 1,5-pentanediol (1,5-PeD) product. Density functional theory (DFT) calculations showed that WO x /Pt(111) could promote ring opening of THFA via an oxocarbenium ion-like transition state, which was stabilized by hydrogen bonding with the hydroxyl groups of WO x . The hydrogenation of the ring-opened 5-hydroxyvaleraldehyde intermediate to 1,5-PeD was then feasible via Brønsted acid sites present on WO x . Steady-state activity studies on the corresponding powder catalysts showed that the 1,5-PeD selectivity increased from 20% on Pt/SiO 2 to 65% on WO x /Pt/SiO 2 with 1 wt % WO x loading, consistent with model surface experiments and DFT calculations. This study demonstrates the feasibility of using model surface experiments and first-principles calculations to guide practical catalyst design, and provides a design strategy that can be applied to the selective ring-opening of relevant heterocyclic biomass-derived oxygenates.

Controlling Bond Scission Pathways of Isopropanol on Fe- and Pt-Modified Mo2N Model Surfaces and Powder Catalysts

“…Due to the presence of multiple functionalities in biomass molecules, upgrading them requires breaking certain bonds while retaining the functional groups of interest . Many processes of converting lignocellulosic biomass into useful fuels and chemicals involve selective bond scission steps: from C–O cleavage during hydrodeoxygenation of bio-oil to selectively breaking C–C or C–O bonds of biomass-derived oxygenates. − Thus, one of the fundamental challenges of commercializing these processes is effectively controlling these pathways. Among the various upgrading reactions, which include dehydrogenation, , hydrodeoxygenation, hydrolysis, and dehydration, the dehydrogenation of alcohols to carbonyl compounds has recently gained interest as a method of producing biomass-derived alcohols and H 2 .…”

Effect of Dynamic and Preferential Decoration of Pt Catalyst Surfaces by WOx on Hydrodeoxygenation Reactions

“…Two different step models, Pt(221) and Pt(553), were chosen to understand the effect of terrace width on WO x stability. Based on a recent phase diagram analysis of WO x domains on Pt(111), W 3 O 7 is considered a representative model structure for reduced WO x growth on metal surfaces. , Additional WO x models, including domains containing Brønsted acid sites ( e.g. , W 3 O x H), higher W-oxidation states, and select W 4 O x structures, were considered.…”

“…Inverse catalysts can exhibit significantly altered reaction kinetics as compared to the bare metal catalysts, ,− with an important application being hydrodeoxygenation (HDO) of lignin-derived monomers toward biomass valorization. − For example, inverse catalysts such as WO x /Pt/C and NbO x /Pt/MgAl 2 O 4 achieve >98% selectivity to desirable deoxygenated aromatics, in stark contrast to their unmodified analogues that exhibit considerable aromatic hydrogenation activity to produce undesired products with saturated rings. Recently, we reported on the structure sensitivity of Pt catalysts for HDO of model lignin-derived phenolic monomers, identifying that low-index terraces, consisting of well-coordinated Pt atoms (Pt WC , ≥8 nearest Pt neighbors), are responsible for the undesired aromatic hydrogenation reaction .…”

A Data and DFT-Driven Framework for Predicting the Microstructure of Submonolayer Inverse Metal Oxide on Metal Catalysts

“…For example, recent DFT studies have successfully elucidated the factors driving key reactions, including the strength of Brønsted acid sites in selectively promoting biomass upgrade, the role of the oxidation state of the metal oxide phase in the hydrogen evolution reaction, and the synergy of metal sites and metal oxide in electrochemical alcohol oxidation, among others. 2,7,16,17 However, a substantial gap exists in understanding the actual active site under experimental conditions for complex catalysts. 18−20 This gap can be bridged by systematically modeling geometric and stoichiometric features of potential active sites and determining their stability.…”

“…First-principles simulation techniques, such as Density Functional Theory (DFT), can uncover important geometric and electronic features that dictate the stability and reactivity of active sites. For example, recent DFT studies have successfully elucidated the factors driving key reactions, including the strength of Brønsted acid sites in selectively promoting biomass upgrade, the role of the oxidation state of the metal oxide phase in the hydrogen evolution reaction, and the synergy of metal sites and metal oxide in electrochemical alcohol oxidation, among others. ,,, However, a substantial gap exists in understanding the actual active site under experimental conditions for complex catalysts. − This gap can be bridged by systematically modeling geometric and stoichiometric features of potential active sites and determining their stability. This requires generating a large pool of possible atomic configurations, sampling stable configurations, and mapping structures onto experimentally observed quantities, such as those based on X-ray adsorption (XAS) spectroscopies. − …”