Abstract
There is a demand for renewable resources, such as biomass, to produce compounds considered as platform molecules. This study deals with dehydration of fructose for the formation of 5-hydroxymethylfurfural (HMF), a feedstock molecule. Different catalysts (aluminosilicates, niobic acid, 12-tungstophosphoric acid—HPW, and supported HPW/Niobia) were studied for this reaction in an aqueous medium. The catalysts were characterized by XRD, FT-IR, N2 sorption at −196 °C and pyridine adsorption. It was evident that the nature of the sites (Brønsted and Lewis), strength, quantity and accessibility to the acidic sites are critical to the conversion and yield results. A synergic effect of acidity and mesoporous area are key factors affecting the activity and selectivity of the solid acids. Niobic acid (Nb2O5·nH2O) revealed the best efficiency (highest TON, yield, selectivity and conversion). It was determined that the optimum acidity strength of catalysts should be between 80 to 100 kJ mol−1, with about 0.20 to 0.30 mmol g−1 of acid sites, density about 1 site nm−2 and mesoporous area about 100 m2 g−1. These values fit well within the general order of the observed selectivity (i.e., Nb2O5 > HZSM-5 > 20%HPW/Nb2O5 > SiO2-Al2O3 > HY > HBEA).
Highlights
Human society’s current energy dependence on fossil and non-renewable sources is indisputable and is growing [1,2,3,4]
A quantitative method for fructose and HMF determination was developed by High-Performance Liquid Chromatography (HPLC) using the analytical curves for each substrate (Supplementary Materials Figure S1)
Several catalysts were tested in the reaction of fructose dehydration for HMF, providing a complete examination of its behavior in an aqueous medium, which grants a green and sustainable protocol for such transformation
Summary
Human society’s current energy dependence on fossil and non-renewable sources (predominantly oil and natural gas) is indisputable and is growing [1,2,3,4]. In this scenario, several environmental and social complications have arisen, such as air pollution and global warming [2,5]. An alternative that has gained prominence in recent decades is biomass, which is basically any and all natural organic matter that can be used to produce energy It is constantly generated in nature, starting with the fixation of the carbon present in the air in carbohydrates, through the process carried out by plants and known as photosynthesis [6]. An intermediary deserves to be highlighted: 5-hydroxymethylfurfural (HMF), which is considered a platform molecule [9,10,11]
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