Dilute-Sulfuric Acid Pretreatment of Corn Stover in Pilot-Scale Reactor

Abstract

Hydrolysis of α-cellulose by H2 SO4 is a heterogeneous reaction. As such the reaction is influenced by physical factors. The hydrolysis reaction is there- fore controlled not only by the reaction conditions (acid concentration and temperature) but also by the physical state of the cellulose. As evidence of Mid Sweden University, 891 18 Örnsköldsvik, Sweden; and 230 Ross Hall, Auburn University, Auburn, AL 36849, National Renewable Energy Laboratory, this, the reaction rates measured at the high-temperature region (above 1617 Cole Blvd., Golden, CO 80401 200°C) exhibited a sudden change in apparent activation energy at a certain temperature, deviating from Arrhenius law. Furthermore, α-cellulose, once it was dissolved into concentrated H2 SO4 and reprecipitated, showed a reac- tion rate two orders of magnitude higher than that of untreated cellulose, about the same magnitude as cornstarch. The α-cellulose when treated with a varying level of H2 SO4 underwent an abrupt change in physical structure (fibrous form to gelatinous form) at about 65% H2 SO4 . The sudden shift of physical structure and reaction pattern in response to acid concentration and temperature indicates that the main factor causing the change in cellulose structure is disruption of hydrogen bonding . Finding effective means of disrupting hydrogen bonding before or during the hydrolysis reaction may lead to a novel biomass saccharification process. Index Entries: Acid hydrolysis; cellulose; hydrogen bonding; kinetics; crystallinity.