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. 2023 May 11;13(1):7663.
doi: 10.1038/s41598-023-34876-4.

Tuning the acidity of halloysite by polyionic liquid to develop an efficient catalyst for the conversion of fructose to 5-hydroxymethylfurfural

Samahe Sadjadi  1 , Soheila Yaghoubi  2 , Xuemin Zhong  3 , Peng Yuan  4 , Majid M Heravi  5
Affiliations

Tuning the acidity of halloysite by polyionic liquid to develop an efficient catalyst for the conversion of fructose to 5-hydroxymethylfurfural

Samahe Sadjadi et al. Sci Rep. .

Abstract

In an attempt to prepare a low-cost and efficient acidic heterogeneous catalyst for the conversion of fructose to 5-hydroxymethylfurfural under mild reaction conditions, the acidity of halloysite was improved by covalent grafting of an acidic polyionic liquid. More precisely, halloysite was first vinyl functionalized and then polymerized with vinyl imidazole and 2-acrylamido-2-methylpropanesulfonic acid. The tangling imidazole rings were further converted to acidic ionic liquids by treating them with chlorosulfuric acid. UV-Vis spectroscopy and Hammett equation confirmed that conjugation of acid polyionic liquid resulted in the increase of the acidity of halloysite. Investigation of the efficiency of the catalyst for the synthesis of 5-hydroxymethylfurfural and optimization of reaction variables showed that 5-hydroxymethylfurfural was yielded in 97.8% after 30 min under the optimum conditions, i.e. catalyst loading of 20 wt% at 70 °C. Notably, the catalyst was highly reusable and it could be reused for at least seven reaction runs with insignificant loss of its activity. Furthermore, this catalyst could also promote the conversion of sucrose and maltose to give moderate yields of 5-hydroxymethylfurfural.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Synthetic procedure of the catalyst.
Figure 2
Figure 2
(A) XRD patterns of Hal and Hal-PIL, (B) FTIR spectra of Hal, Hal-PIL and reused Hal-PIL and (C) Thermograms of Hal and Hal-PIL.
Figure 3
Figure 3
SEM images of Hal-PIL.
Figure 4
Figure 4
(A) Investigation of the effect of the catalyst loading on the fructose conversion and yield of HMF in dehydration of fructose. Reaction conditions: temperature: 70 °C, t = 30 min, solvent: DMSO, (B) Investigation of the effect of the reaction time on the fructose conversion and yield of HMF in dehydration of fructose. Reaction conditions: temperature: 70 °C, catalyst loading 20 wt%, solvent: DMSO and (C) Investigation of the effect of the reaction temperature on the fructose conversion and yield of HMF in dehydration of fructose. Reaction conditions: catalyst loading 20 wt%, t = 30 min, solvent: DMSO.
Figure 5
Figure 5
(A) The results of recyclability of Hal-PIL for the synthesis of HMF from dehydration of fructose under the optimum conditions and (B) SEM image of the recycled catalyst after the last run of recycling.
Figure 6
Figure 6
Pictorial mechanism of conversion of fructose to HMF in the presence of Hal-PIL.
Figure 7
Figure 7
The catalytic activity of Hal-PIL for the synthesis of HMF using different substrates. Reaction conditions: temperature: 70 °C, catalyst loading 20 wt%, t = 30 min.
See this image and copyright information in PMC

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