Catalytic Conversion of Glucose into 5-Hydroxymethylfurfural by Hf(OTf)4 Lewis Acid in Water

Abstract

A series of Lewis acidic metal salts were used for glucose dehydration to 5-hydroymethylfurfural (HMF) in water. Effect of valence state, ionic radii of Lewis acidic cation, and the type of anions on the catalytic performance have been studied systematically. The experimental results showed that the valence state played an important role in determining catalytic activity and selectivity. It was found that a higher glucose conversion rate and HMF selectivity could be obtained over high valent Lewis acid salts, where the ionic radii of these Lewis acidic metal salts are usually relatively small. Analysis on the effect of the anions of Lewis acid salts on the catalytic activity and the selectivity suggested that a higher glucose conversion and HMF selectivity could be readily obtained with Cl´. Furthermore, the recyclability of high valence state Lewis acid salt was also studied, however, inferior catalytic performance was observed. The deactivation mechanism was speculated to be the fact that high valence state Lewis acid salt was comparatively easier to undergo hydrolysis to yield complicated metal aqua ions with less catalytic activity. The Lewis acidic activity could be recovered by introducing a stoichiometric amount of hydrochloric acid (HCl) to the catalytic before the reaction.

Acid‐Catalyzed Conversion of Carbohydrates into Value‐Added Small Molecules in Aqueous Media and Ionic Liquids

“…ChemSusChem 2018, 11,642 -660 www.chemsuschem.org acids. [84] This discoveryr elies on the ability of triflatest oi nduce both Lewis and Brønsted acidity,a sp reviously shown by Williams and Lawton. [3] The conversion of glucose into HMFw ith metal triflates follows the same pattern as that of metal chlorides, in accordance with the ionic radius of the metal cations in the series Al 3 + > Sc 3 + > La 3 + > Yb 3 + .O nt he other hand, the use of higher valence-state metal triflates,s uch as Hf(OTf) 4 , and the addition of hydrochloric acids ignificantly improves the yields of HMF (Table 1).…”

“…These resultss how promise for the application of metal triflates to the conversion of cellulose, with the additional benefit that it is, in principle,possible to recycle the metal triflate catalyst. [84] Despite the promise of this chemistry,t here is an absence of information on the metal triflate catalyzed synthesis of HMF from polymers of glucose (e.g.,cellulose).…”

“…[85] This is also reflected in al arge number of reports dedicated to the catalytic conversion of carbohydrates into HMF by using typical acidic resins, functionalized silica, zeolites, heteropolyacids, and other solids. [86][87][88] Notwithstanding the ability to recover heterogeneous catalysts by filtration, homogeneous catalysts can often be efficiently recovered by the simple removal of the organic phase, which containsp roducts, [84,89] leaving the acid catalyst in the aqueous phase. On the other hand, solid acids are frequently disposedofdue to their irreversible deactivation by the formation of byproduct polymer humins on their surface.…”

Catalytic Conversion of Biomass

“…Along similar lines, two additional contributions for the Special Issue from Li et al [2] and Fachri et al [3] disclosed the catalytic aqueous conversion of glucose and inulin into HMF using Lewis acid and metal salts catalysts, respectively, providing also interesting modelling insights into the proposed chemistries.…”

Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts

“…In the meantime, alkyl carbamates could be used as feedstocks for the synthesis of corresponding organic carbonates such as dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and so on. Significantly, the alkyl carbamate could be used as carbonyl source to replace phosgene for the synthesis of isocyanates [13][14][15][16]. Since more than 85% phosgene was consumed in isocyanate industry, this could be the promising usage of carbamates in the future [17].…”