Dual functional Si-based multi-porous solid acid catalyst for 5-Hydroxymethylfurfural synthesis from glucose: Structural regulation and reaction kinetics

A high-performance Si-based solid acid catalyst, Al/Sp-SiO₂-13000-SO₃H, was successfully developed for the conversion of glucose to 5-hydroxymethylfurfural (HMF) in water. This catalyst had dual functional acid sites (Lewis and Brønsted sites) and adjustable microporous and mesoporous macropore structures which were customized by template agents. The multi-porous structure of catalyst was beneficial for glucose and derivative transfer, thus improved the accessibility of active sites and enhanced the synthesis of HMF. Achieved a 41.2 % HMF yield in water within 60 min under optimal reaction conditions predicted by response surface analysis. Also, a 71.2 % HMF yield was obtained in DMSO/H₂O under other identical conditions. Through selective poisoning experiments, the role of Lewis sites in promoting isomerization and Brønsted sites in promoting dehydration was determined. DFT calculations further confirmed that Sp-SiO₂-13000 has the strongest adsorption capacity for glucose, with an adsorption energy of up to −1.44 eV. Combined stronger adsorption performance with customized pore structure of Al/Sp-SiO₂-13000-SO₃H promotes the transfer of molecules in the pores, which plays the role of “killing two birds with one stone” in the synthesis of HMF. Additionally, the glucose isomerization process was the react-limiting step was verified by kinetic model, and a synergistic catalytic mechanism for HMF synthesis was proposed.