Catalytic dehydration of fructose to 5-hydroxymethylfurfural over mesoporous Nb-W oxide solid acid catalyst

• Published in: Biomass & bioenergy 2023-07, Vol.174, p.106860, Article 106860
• Main Authors: Ren, Qiuhe, Ma, Hong, Wang, Wenbo, Chen, Chongchong, Xiao, Jinbin, Che, Penghua, Nie, Xin, Huang, Yizheng, Rao, Kasanneni Tirumala Venkateswara, Xu, Chunbao(Charles)
• Format: Article
• Language: English
• Subjects: 5-Hydroxymethylfurfural; bioenergy; biomass; catalysts; catalytic activity; Dehydration; Fructose; hydroxymethylfurfural; Mesoporous Nb-W oxide; porosity; porous media; Solid acid; solvents; surface area; temperature
• ISSN: 0961-9534; 1873-2909
• DOI: 10.1016/j.biombioe.2023.106860

In this study, a mesoporous Nb-W oxide solid acid catalyst was synthesized and characterized in detail by TEM, N2 physisorption, and Py-FTIR. Effects of the calcination temperature on the pore structure and acid properties were investigated. The results showed that increasing calcination temperature from 400 °C to 600 °C remarkably affected the characteristics of mesoporous Nb-W oxides, with a decrease in specific surface area, pore volume, and acid amount, but an increase in pore size from 5.1 nm to 10.4 nm. Furthermore, a notable decrease was found in both the fructose conversion and HMF yield in the dehydration of fructose to HMF over Nb-W oxides when increasing the calcination temperature, and the catalyst could keep high catalytic activity and selectivity after recycling 4 times. Solvents also played a key role in the fructose dehydration to HMF over the Nb-W oxides, and DMSO was the optimized solvent. 1H NMR and 13C NMR experiments revealed that the key intermediate, 4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde, could generate in DMSO but not in other solvents including NMP, DMF, DMAC, and EG. Over mesoporous niobium-tungsten oxide NbW-400 catalyst, dimethyl sulfoxide (DMSO) is favorable for the mutarotation of fructose from β-fructopyranose (Fβp) to α-fructofuranose (Fαf) and β-fructofuranose (Fβf), as well as the generation of the reaction intermediate which are conducive to transforming into HMF during the catalytic dehydration reaction. Although fructose exists in Fβp, Fαf, Fβf and α-fructopyranose (Fαp) forms of tautomers in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) and N-methyl pyrrolidone (NMP) solvents, while it is unable to form the reaction intermediate which make it is difficult to transform into HMF whereas only leads to little HMF or byproducts in other different solvents (DMF, DMAC, NMP and ethylene glycol (EG)). [Display omitted] •Mesoporous Nb-W oxides achieved 77% yield of HMF in the dehydration of fructose.•Calcination temperature dramatically affects the structure-activity of Nb-W oxides.•The formation of intermediate 4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde in DMSO facilitates HMF formation.