Conversion of sunflower stalk based cellulose to the valuable products using choline chloride based deep eutectic solvents

The direct conversion of cellulose into valuable products such as 5- hydroxymethyl furfural (5-HMF), levulinic acid, furfural and formic acid was studied using deep eutectic solvents in conventional and microwave reactors. Starting from sunflower stalk based cellulose, the mechanism of degradation was highlighted and applicability of deep eutectic solvents as solvent and catalyst was searched. Three different deep eutectic solvents (DES) were synthesized using choline chloride as hydrogen bond acceptor and oxalic acid/citric acid/tartaric acid as hydrogen bond donor. The most effective DES was found as DESO formed by choline chloride and oxalic acid. Using DESO as catalyst and solvent, 99.07% of carbon efficiency was achieved at 180 °C in microwave reactor within only 1 min. At these conditions, 76.2% of levulinic acid, 4.07% of 5-HMF, 5.57% of furfural and 15.24% of formic acid were obtained. We described simple, cheap, catalytically effective and environmentally friendly process for the conversion of cellulose into valuable products. DESs showed superior properties for the solvation of cellulose and catalyzed the reactions of cellulose.