THE DEVELOPMENT OF A NEW PRETREATMENT METHOD (RAPID STEAM HYDROLYSIS) AND THE COMPARISON OF RAPID STEAMING, STEAM EXPLOSION, AUTOHYDROLYSIS, AND WET OXIDATION AS PRETREATMENT PROCESSES FOR BIOMASS CONVERSION OF SOUTHERN HARDWOODS.

摘要

Southern hardwoods offer a plantiful source of lignocellulosic material for biomass conversion. It is advantageous to pretreat wood for biomass conversion in order to separate the wood into its components and to increase the reactivity of the individual components. In this study, southern hardwood chips (predominantly oak and gum species) were pretreated by a new process of rapid steaming with continuous extraction of volatile and soluble products. Steam was introduced at the top of a pressurized reactor containing wood chips, while steam condensate and partible products were removed at the bottom of the reactor. Reaction temperatures ranged from 160 to 280(DEGREES)C, with a reaction time of 1.0 minute. Fractionation of wood occurred at temperatures above 200(DEGREES)C as hemicellulose and lignin began to appear in the steam condensate fraction, leaving a cellulose-rich fraction in the steaming reactor. At high temperatures, hemicellulose and cellulose were not degraded as much as in other pretreatments, presumably due to short reaction times and continuous removal of acetic acid. Lignin extracted from the solid residue appeared particularly reactive as determined by nitrobenzene oxidation and pyrolysis/gas chromatography. Lignin collected in the steam condensate was also very reactive, presumably due to its rapid cooling after being removed from the reactor. Steam explosion, autohydrolysis, and wet oxidation pretreatments of southern hardwoods were also carried out and compared to rapid steaming by investigating the separation of the wood components, the change in enzymatic hydrolysis rates, and the change in morphology of the pretreated material.