3-60: Comparison of Kinetics of Xylose and Lignin Removal During Hot Water and Dilute-Acid Pretreatment of Corn Stover using a Continuous Flow-Through Reactor

A flow through reactor (FTR) was used to determine the kinetics of xylose and lignin removal during hot water and dilute-acid pretreatment for bioethanol production. The removal rates of xylan and lignin during hot water (HW) and dilute-acid flow-through (DA) experiments with corn stover were studied between 170°C and 230°C for HW and 150°C and 210°C for DA. During all FTR pretreatments, insoluble dark precipitates were observed in the effluent and were characterized as lignin-carbohydrate complexes (LCC). Oligomeric and monomeric xylan was measured in the effluent during all of the FTR experiments. At temperatures beyond 200 °C significant xylan degradation to unknown products was observed.  Total xylan removed was proportional to lignin and acetate release over the reaction time.  Increases in pretreatment temperatures from 200°C to 230 °C did not significantly enhance the kinetics of xylan, lignin or acetate removal. Melting and mobilization of lignin also likely contribute to the process of xylan release.  The results show that a flow through reactor is suitable for kinetics studies because the products are removed from the reaction zone, therefore less sugar degradation and lignin condensation reactions occur as compared to a batch reactor system.