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Abstract:
The synthesis pathway to the biofuel 2,5-dimethylfuran (DMF) from cellulose involves acidcatalyzed, mechanocatalytic depolymerization of cellulose to glucose, Lewis acid catalyzed isomerization of glucose to fructose, Brønsted acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF), and finally the hydrodeoxygenation of HMF over a noble metal alloy catalyst deposited on carbonaceous support.
A one-pot reaction system to produce HMF directly from glucose avoiding the isolation of fructose is developed using solely Sn-incorporated zeolite of the beta structure as catalyst under an elevated temperature of 180°C in a mixture of water and ethanol in the ratio of 80 to 20. The best-obtained yield of HMF is 36 %.
In the second part of the study, purified HMF is used to produce DMF over a PtCo alloy catalyst supported on graphitic carbon. A major aim is to avoid separation and purification by choosing a solvent, which might be used as a fuel blended with DMF. Among a variety of solvents studied, commercial gasoline is found to be well suited for this reaction. The reaction in gasoline is conducted in a sequential manner up to three times with an optimized initial loading of 10 wt% HMF per step, resulting in a concentration increase of up to 7 wt% DMF for each conversion step, by which a concentration range between 7 and 20 wt% DMF in the final blend is covered. Best results are obtained with gasoline:ethanol mixtures in the ratio 9:1, commonly known as E10, as ethanol is found to act as a solvent mediator for the dissolution of HMF in the reaction system. The fuel properties of the resulting fuel blend are accessed by measuring the derived cetane number (DCN) and the distillation profile and found to be comparable with reference blends. This makes final purification obsolete and leads to a biofuel blend potentially usable in current internal combustion engines.
