Dehydration of Fructose to 5-Hydroxymethylfurfural: Effects of Acidity and Porosity of Different Catalysts in the Conversion, Selectivity, and Yield

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).

Unraveling Structural and Acidic Properties of Al‐SBA‐15‐supported Metal Phosphates: Assessment for Glucose Dehydration

“…Moreover, the Brønsted acid peak of CrPO(2)/Al‐SBA‐15 had a lower wavenumber than other samples (see Figure 9B), suggesting a stronger site, leading to a higher 5‐HMF yield. The hypothesis is possible because the stronger Brønsted acid could accelerate the dehydration of fructose intermediate to 5‐HMF [53] . This observation agrees well with the presence of P−O−Cr covalent bonds in Cr(III) phosphate property, which is dominant in CrPO(2)/Al‐SBA‐15 suggested by XANES of P K‐edge.…”

“…The hypothesis is possible because the stronger Brønsted acid could accelerate the dehydration of fructose intermediate to 5-HMF. [53] This observation agrees well with the presence of PÀ OÀ Cr covalent bonds in Cr(III) phosphate property, which is dominant in CrPO(2)/Al-SBA-15 suggested by XANES of P K-edge. This explanation is consistent with Ramis et al [54] that the Brønsted acid strength of the surface PÀ OH groups increases with increasing covalency of the (PO)À M bond.…”

“…This result could imply the presence of different acid strengths due to the different interactions between P−OH and the lone pair electrons of N in pyridine. The stronger interactions generate the stronger Brønsted acid due to the decrease in the bond order of aromatic pyridine [53] …”

“…The stronger interactions generate the stronger Brønsted acid due to the decrease in the bond order of aromatic pyridine. [53]…”

Elaboration of Nanostructured Levan-Based Colloid System as a Biological Alternative with Antimicrobial Activity for Applications in the Management of Pathogenic Microorganisms

“…The highest yield of fructose was reached after 3 h of hydrolysis with 0.1 M HCl at 90 • C in the case of BL from S. salivarius K12. In comparison, a higher degree of hydrolysis for L. mesenteroides DSM 20343 was found after 6 h. It was observed that with increasing molarity of the HCl solution, there was a noticeable decrease in the fructose content, possibly due to fructose dehydration to hydroxymethylfurfural [80]. Moreover, the non-selectivity of HCl as a catalyst in cleavage of glycosidic linkages and weak fructose release from BL produced by Zymomonas mobilis was highlighted by Bekers et al [81] and Kennedy et al [82] as a high amount of fructooligosaccharides was observed in the final products.…”