Rapid conversion of cellulose to 5-hydroxymethylfurfural using single and combined metal chloride catalysts in ionic liquid

Direct conversion of cellulose into 5-hydroxymethylfurfural (HMF) was performed by using single or combined metal chloride catalysts in 1- ethyl-3-methylimidazolium chloride (Cl) ionic liquid. Our study demonstrated formation of 2-furyl hydroxymethyl ketone (FHMK), and furfural (FF) simultaneously with the formation of HMF. Various reaction parameters were addressed to optimize yields of furan derivatives produced from cellulose by varying reaction temperature, time, and the type of metal chloride catalyst. Catalytic reaction by using FeCl₃ resulted in 59.9% total yield of furan derivatives (HMF, FHMK, and FF) from cellulose. CrCl₃ was the most effective catalyst for selective conversion of cellulose into HMF (35.6%) with less concentrations of FHMK, and FF. Improving the yields of furans produced from cellulose could be achieved via reactions catalyzed by different combinations of two metal chlorides. Further optimization was carried out to produce total furans yield 75.9% by using FeCl₃/CuCl₂ combination. CrCl₃/CuCl₂ was the most selective combination to convert cellulose into HMF (39.9%) with total yield (63.8%) of furans produced from the reaction. The temperature and time of the catalytic reaction played an important role in cellulose conversion, and the yields of products. Increasing the reaction temperature could enhance the cellulose conversion and HMF yield for short reaction time intervals (5~20 min).