Co-production of xylose, lignin, and ethanol from eucalyptus through a choline chloride-formic acid pretreatment

•A choline chloride-formic acid (ChCl-FA) pretreatment were developed in this work.•Pretreatment can significantly improve the hydrolysis and fermentation of eucalyptus.•The maximal ethanol yield 16.5 g/100 g feedstock, corresponding 74.5% theoretical yield.•A certain amount of xylose (61.4%) and lignin (80.7%) also can be obtained in this work.