Patent ID: 8545633

Claim:
A method for pretreatment of cellulosic biomass feedstock comprising cellulose, hemicellulose, and lignin, the method comprising: contacting the cellulosic biomass feedstock with an acidic liquid medium to form an acid-impregnated biomass feedstock; contacting the acid-impregnated cellulosic biomass feedstock with H 2 O at elevated temperature and pressure within a contact zone under conditions effective for solubilizing hemicellulose and producing a steam treated feedstock, wherein the pressure in the contact zone is at least about 55 psig; subjecting the steam treated feedstock within a depressurization zone to conditions and for at time effective for solubilizing hemicellulose and producing a volatilized fraction of the steam treated feedstock; and releasing at least a portion of the volatilized fraction from the depressurization zone for control of temperature and pressure within the depressurization zone, wherein the pressure within the depressurization zone is controlled to from about 5 to about 50 psig.