Pretreatment of sugarcane bagasse by acid-catalysed process in aqueous ionic liquid solutions

A biomass pretreatment process was developed using acidified ionic liquid (IL) solutions containing 10–30% water. Pretreatment of sugarcane bagasse at 130 °C for 30 min by aqueous 1-butyl-3-methylimidazolium chloride (BMIMCl) solution containing 1.2% HCl resulted in a glucan digestibility of 94–100% after 72 h of enzymatic hydrolysis. HCl was found to be a more effective catalyst than H2SO4 or FeCl3. Increasing acid concentration (from 0.4% to 1.2%) and reaction temperature (from 90 to 130 °C) increased glucan digestibility. The glucan digestibility of solid residue obtained with the acidified BMIMCl solution that was re-used for three times was >97%. The addition of water to ILs for pretreatment could significantly reduce IL solvent costs and allow for increased biomass loadings, making the pretreatment by ILs a more economic proposition.

► 10–30% water was used in an ionic liquid (IL) for pretreating sugarcane bagasse.
► Pretreatment required only 130 °C and 15–30 min with an acid catalyst.
► Glucan digestibility of the solid residues reached 93–100%.
► High glucan digestibility was attributed to delignification and removal of xylan.
► Recycling IL without replenishing acid catalyst didnt decrease the digestibility.