Direct Conversion of Carbohydrates into Ethyl Levulinate with Potassium Phosphotungstate as an Efficient Catalyst

Abstract

A series of metal-modified phosphotungstates were prepared and performed for direct synthesis of ethyl levulinate from fructose in ethanol. Considering the cost of catalysts, catalytic activity of catalysts, and easy separation of catalysts together, K-HPW-1 was chosen as the most suitable catalyst for synthesis of ethyl levulinate from fructose. A high ethyl levulinate yield of 64.6 mol% was obtained at 150 °C within 2 h in ethanol. The introduction of low polar toluene as a co-solvent improved the yield of ethyl levulinate to 68.7 mol%. The recovered catalyst remained high activity with the yield of ethyl levulinate converted from fructose above 50 mol% after being used five times. Moreover, the generality of the catalyst was further demonstrated by glucose, sucrose, inulin, and cellulose with ethyl levulinate yielding 14.5, 35.4, 52.3, and 14.8 mol%, respectively.

Catalytic and mechanistic insights into the production of ethyl levulinate from biorenewable feedstocks

“…EDGP isomerization to EDFF is a Lewis acid catalyzed reaction 87 as shown in Figure-6. Similar to the results obtained on ILs, several research groups have experimented with metal doped K-HPA (H3PW12O40) and measured a low EL yield (14.5%, Table-4, entry 12) on glucose ethanolysis 146 . A combination of both Brønsted and Lewis acidity is therefore essential for glucose conversion to EL.…”

“…A combination of both Brønsted and Lewis acidity is therefore essential for glucose conversion to EL. The Lewis acidity of HPAs is expected to be enhanced by introducing metal dopants which needs to be further explored for glucose ethanolysis reaction 146 . Interestingly, compared to IL, on HPA, the time (120 min) required to obtain this yield was shorter 140,145 , which can be attributed to the presence of appreciable amount (0.03 mmol/g) of Lewis acid sites (Brønsted to Lewis site ratio, B/L > 58) 150 .…”

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…The first step for cellulose valorization is based on its depolymerisation into oligomers and glucose followed by catalytic reactions (hydrogenation, oxidations, esterification, etc.) for the manufacture of a pool of chemicals such as C6-C2 polyols, levulinic acid, hydroxymethylfurfural (HMF), among others ( [25][26][27][28][29] and "references within"). Polyols, owing to their peculiar chemical properties, could represent an important resource for production of several building-block chemicals.…”

“…Therefore, its utilization for chemicals production has not a negative impact on the food supply. For this reason, its conversion into added-value chemicals and/or fuel components is one of the core technologies in the modern bio-refinery [25][26][27][28]. The first step for cellulose valorization is based on its depolymerisation into oligomers and glucose followed by catalytic reactions (hydrogenation, oxidations, esterification, etc.)…”

Catalytic Conversion of Biomass

“…Along these lines, Wang et al proposed the utilization of cheap and environmentally friendly Nb/Al oxide catalysts for the conversion of kiwifruit waste to levulinic acid [7]. Additionally, the direct conversion of carbohydrates into ethyl levulinate using potassium phosphotungstate as efficient catalyst was reported by Zhao et al [8]. Further conversion of levulinic acid to gamma-valerolactone (GVL) could also take place efficiently on nickel/alumina catalysts [9].…”