Production of 5-hydroxymethylfurfural from cellulose in a fully component-recoverable catalytic system containing modified montmorillonite solid acid

The catalytic conversion of cellulose into 5-hydroxymethylfurfural (HMF) is a viable way to achieve high-value utilization of renewable biomass energy. Herein, cheap, non-synthetic natural layered montmorillonite (MMT) was employed as a porous catalytic carrier. Through saturated hafnium ion exchange and subsequent sulfonation treatment, a bifunctional modified Hf/MMT-S solid acid catalyst was obtained, and its morphology, crystal, texture, acidity, elemental state and thermal stability were studied in detail. In a water(NaCl)/tetrahydrofuran biphasic system, Hf/MMT-S catalyzed the cellulose to achieve a 50 % HMF yield. The specific catalytic pathway was also depicted by the captured intermediates, namely the ring-opening isomerization of glucose into fructose, followed by the ring-closing dehydration of fructose, accompanied by C3-C24 by-product molecules. Furthermore, the modified solid acid Hf/MMT-S catalyst still exhibited certain catalytic performance after being consecutively recycled for five times. More importantly, the entire catalytic system was capable of achieving full recovery of all components (catalyst, solvent, additive, product) through simple filtration, distillation and extraction methods without reagent waste. This study provided a reference for the active site regulation strategy of clay-based catalysts and also contributed to the high-value utilization prospects of renewable cellulosic energy.