Upgrading of furfural to C10 furoin catalyzed by diimidazole ionic liquids

Biomass-based platform compound furfural can be upgraded to C-10 furoin, which is significant to the development and utilization of biomass energy. In this work, a series of diimidazole ILs were applied to explore a feasible way for upgrading of furfural to furoin. The results showed that the catalytic performance of diimidazole ILs were affected by the solvent and the structure of the anion and cation. Furoin yield could increase from 14.8% to 45.0% with the extension of the side chain, and it could be greatly enhanced by the transformation of ethyl group into unsaturated vinyl group. Theoretical calculations revealed it was due to the higher absorption energy and shorter distance between the di (vinylimidazole) ILs and furfural. Furthermore, the anion of diimidazole ILs also displayed influence by affecting the acidity and the electron distribution on the imidazole ring. Finally, the optimized yields of 84.4%, 82.0% and 84.8% were obtained by optimizing the BV4, FV4 and SV4 catalytic sys-tems, respectively. Mechanistic studies suggested that C-2 deprotonation was the key to the reaction, and both the sigma hyperconjugation and 7C-7C conjugation with the imidazole ring could facilitated the reaction. This work may provide some reference in upgrading biomass energy

Automated summary

By using a series of diimidazole ILs, furfural can be upgraded to furoin effectively. Factors affecting the yield include the solvent composition, the structure of the cation and anion of the ILs. The study suggests that extending the side chain and transforming ethyl group into unsaturated vinyl group can greatly enhance the production yield.