Efficient one-pot synthesis of ethyl levulinate from carbohydrates catalyzed by Wells-Dawson heteropolyacid supported on Ce-Si pillared montmorillonite

Efficient conversion of biomass-derived carbohydrates to alkyl levulinates is an important goal of biorefinery process, but is still challenging on applicable catalyst. Ce-Si pillared montmorillonite (CeSiM) clay heterostructures, incorporated with Wells-Dawson tungstophosphoric acid (H6P2W18O64, DPW), were prepared for the first time and used as the multifunctional catalyst for direct production of ethyl levulinate (EL) from various biomass-derived sugars. The DPW introduced by sol-gel method (DPW-CeSiM) has been effectively incorporated into the framework of porous CeSiM, while part of DPW was just absorbed on the surface of CeSiM by impregnation method (DPW-CeSiM-I). The DPW-CeSiM catalyst has large specific surface area owing to the insertion of Ce-Si pillars, and possesses strong Bronsted acidity and moderate Lewis acidity originated from the incorporated DPW and the Ce-doping, respectively. Due to the well synergistic effect of porous structure and dual acid, the DPW-CeSiM catalyst efficiently catalyzed the conversion of glucose into EL with 56.2% yield and nearly 100% conversion at 170 degrees C for 4 h. The recyclability studies certified that DPW-CeSiM catalyst showed higher stability than DPW-CeSiM-I over cycles and could be easily recovered from consecutive alcoholysis of biomass-derived sugars. The DPW-CeSiM catalyst also displayed high activity toward the conversion of other biomass-derived carbohydrates (fructose, sucrose, cellobiose and cellulose) into EL. Therefore, this work provides an instructive strategy for the design of efficient and stable DPW-based catalysts with dual acid sites uniformly distributed over the porous structure, which is obviously potential for industrial production of alkyl levulinates from carbohydrates and biomass.