(610f) Fractionating Pretreatment of Lignocellulosic Biomass As An Entry Into Biomass Refining
Pretreatment is an important step to enzymatic saccharification of lignocellulose for its further conversion. To integratedly utilize the main chemical compositions of lignocellulose, we have developed several processes to pretreat lignocellulosic biomass with organic acids to obtain cellulosic pulp, hemicellulosic syrup and lignin products, which is termed as “fractionating pretreatment”. The cellulosic pulp showed excellent enzymatic digestibility and fermentability for ethanol production via simultaneous saccharification and fermentation (SSF). Ethanol concentration could reach 80g/L via multi-step fed-batch SSF process. Based on the multilayered structure of plant cell wall and the inhibitive effect of dissolved lignin on delignification rate, a novel pseudo-homogeneous kinetic model was proposed for organic acid pretreatment by introducing the concepts of “potential degree of delignification (d D)” into the model for delignification and “potential degree of hydrolysis (hD)” for xylan solubilizaiton. These models could well describe the experimental data of acetic acid pretreatment of sugarcane bagasse, and explain why the cell wall xylan shows as fast-hydrolyzing and slow-hydrolyzing fractions. The obtained hemicellulosic syrup mainly contained xylose, which can be further converted to furfural under the catalysis of residual organic acid without addition of mineral acids. The lignin product can be well converted to solid acids by sulfonation, which can be used as a catalyst to catalyze transesterification of oil feedstocks for biodiesel production. The spent liquor obtained by pretreatment could be directly reused for delignification process for several times. Simulation of the process with Aspen Plus indicates that the energy consumption for solvent recovery accounts for a considerable part of the total energy consumption. Therefore, direct recycling of spent liquor for pretreatment can significantly decrease the energy consumption.
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