Early Transition Metal Doped Tungstite as an Effective Catalyst for Glucose Upgrading to 5-Hydroxymethylfurfural

Abstract

Glucose valorization to 5-hydroxymethylfurfural (HMF) remains challenging in the transition towards renewable chemistry. Lewis acidic tungstite is a viable, moderately active catalyst for glucose dehydration to HMF. Literature reports a multistep mechanism involving Lewis acid catalyzed isomerization to fructose, which is then dehydrated to HMF by Brønsted acid sites. Doping tungstite with titanium and niobium improves activity by optimizing the ratio between Lewis and Brønsted acid sites. Graphical AbstractKeywords Biomass · Glucose · 5-Hydroxymethylfurfural · Tungsten oxide · Doping

Mesoporous Doped Tungsten Oxide for Glucose Dehydration to 5-Hydroxymethylfurfural

“…Previous computational and experimental studies indicate that doping tungstite with cations such as titanium, vanadium, zirconium, and niobium increases the rate of isomerization and dehydration of glucose to 5-HMF. ,, As such, we prepared undoped and doped mesoporous tungsten oxide powders as described in the Experimental Methods section. Dissolution of WCl 6 in the cooled alcohol mixture provided an initially yellow solution, which turned dark blue and viscous after 10 min of stirring.…”

“…Cheap transition metal oxides such as TiO 2 and Nb 2 O 5 express water-tolerant Lewis acid sites and tunable acid–base properties, which are promising attributes for selective glucose conversion. , Recently, we have shown that doping Lewis acidic tungstite with niobium or titanium enhances its otherwise moderate selectivity toward 5-HMF by enhancing its Brønsted acidity . However, tungstite has a low surface area which negatively impacts its activity.…”

“…15,16 Recently, we have shown that doping Lewis acidic tungstite with niobium or titanium enhances its otherwise moderate selectivity toward 5-HMF by enhancing its Brønsted acidity. 17 However, tungstite has a low surface area which negatively impacts its activity. Strategies to enhance the surface area of metal oxides usually involve hard or soft templating agents.…”

Microporous and mesoporous structure catalysts for the production of 5‐hydroxymethylfurfural (5‐HMF)

“…Wiesfeld et al 52 investigated the metal‐doped tungstite with titanium and niobium by optimizing the Lewis and Brønsted acid ratio, which results in the enhancement of glucose dehydration due to the high density of Lewis and Brønsted acid active sites. Even tungstite exhibited water‐tolerant Lewis acid functionalities; it has relatively weak Brønsted acidity, restricting fructose dehydration.…”

“…The humin deposition on surface of the recycled catalyst was proved by the characteristic bands from the FTIR analysis, which are the carbonyl groups (C=O stretching), furan and/or aromatic compounds (C=C stretching), furan ring (C-O-C stretching), and ethers (C-O stretching). 44 Wiesfeld et al 52 investigated the metal-doped tungstite with titanium and niobium by optimizing the Lewis and Brønsted acid ratio, which results in the enhancement of glucose dehydration due to the high density of Lewis and Brønsted acid active sites. Even tungstite exhibited watertolerant Lewis acid functionalities; it has relatively weak Brønsted acidity, restricting fructose dehydration.…”