Preparation of 5-hydroxymethylfurfural from cellulose catalyzed by mixed acid: optimization and kinetics

5-Hydroxymethylfurfural (HMF) is an important platform compound that can be used to synthesize drugs, fine chemicals, fuels, and biodegradable plastics. Synthesis of HMF from cellulose is a key step in the production of high-value-added chemicals and fuels from renewable cellulosic biomass. Herein, a cheap way to produce HMF from cellulose was found in this study. Combination of inexpensive metal salts and inorganic acids shows exciting catalytic efficiency in tetrahydrofuran (THF)/H 2 O system. In this article, the effects of key factors such as water/organic solvent ratio, metal salt type, and concentration on the synthesis of HMF from cellulose were investigated. A maximum HMF yield of 46.5% was obtained with high substrate loading (50 g/L) when H 2 SO 4 and Al 2 (SO 4 ) 3 was used as mixed acid catalysts. Reaction kinetics experiments revealed that combination of H 2 SO 4 and Al 2 (SO 4 ) 3 could effectively reduce the activation energy of cellulose hydrolysis, glucose isomerization, and fructose dehydration compared to the single H 2 SO 4 and single Al 2 (SO 4 ) 3 system. Fortunately, the purity of HMF after separation and purification was up to 98.3%, and both the solvent and the extractant can be recycled. A promising strategy is provided for HMF production from cellulose over simple catalysts.