Modeling and optimization of the dilute-sulfuric-acid pretreatment of corn stover, poplar and switchgrass

Lignocellulosic biomass may be used as a potential renewable feedstock for biochemical production of ethanol as an alternative transportation fuel. However, cellulose, which is the major source of fermentable sugars in these materials, is protected by a network of lignin and hemicellulose. The dilute-sulfuric-acid pretreatment removes this protecting shield and makes the cellulose more susceptible to enzymatic digestion. In this study, three lignocellulosic feedstocks (i.e. corn stover, poplar and switchgrass) were pretreated with dilute sulfuric acid (0.6, 0.9 and 1.2% w/w) at relatively high temperatures (140, 160 and 180°C) in a Parr batch reactor. The hydrolysis of hemicellulose to its monomeric constituents and possible degradation of these monomers were modeled by a series of first-order reactions. The kinetic parameters of two mathematical models for predicting the percentage of xylan remaining in the substrate after pretreatment and the net xylose yield in the liquid stream were determined using the actual acid concentration in the reactor after accounting for the neutralization effect of the substrates.