Sulfur dioxide and/or sulfurous acid pretreatment with sulfur dioxide recovery

摘要

A process for producing ethanol from lignocellulosic biomass includes adding at least one of sulfur dioxide and sulfurous acid to the lignocellulosic biomass to provide an equivalent sulfur dioxide loading of at least 10 wt % sulfur dioxide to dry lignocellulosic biomass. The acidified lignocellulosic biomass is pretreated at a temperature above about 185° C. and for a pretreatment time less than about 10 minutes, to provide a pretreated biomass composition wherein the biomass is readily hydrolyzed by enzymes. Advantageously, sulfur dioxide from at least one of the flash stream and a stream derived from the flash is recovered and recycled back into the process.