(461c) Pretreatment and Fractionation of Corn Stover Using Zinc Chloride and Ammonium Hydroxide

A novel pretreatment and fractionation method of corn stover using zinc chloride (ZnCl2) and ammonium hydroxide (NH4OH) was developed to achieve the complete utilization of biomass and improve the economics of the biorefinery process. Zinc chloride, one of the strongest swelling chemicals, is effective reagent for hemicellulose hydrolysis while ammonium hydroxide was proven to be effective for lignin removal. In this study, two different modes of reactions were investigated: (1) single-stage treatment using zinc chloride and (2) two-stage treatment using zinc chloride in the first stage and ammonium hydroxide in the second stage. We found that zinc chloride is highly selective for hemicellulose hydrolysis (70-80% of xylan), but it retained most of lignin and cellulose with the solids. In the optional second stage, ammonia was added to solubilize lignins and remaining cellulose after treatment was highly digestible by commercial cellulase enzymes. Both processes enhanced enzyme digestibility of remaining cellulose (80-90%) and effectively fractionated biomass into glucan-rich solid, xylooligomer-rich stream, and soluble lignin stream. Zinc chloride and ammonia can be recovered and reused in this process. The optimal process conditions for effective pretreatment and fractionation were explored. Various effects on the compositional changes, enzyme digestibility, fermentability, and other technical aspects related to development of process will be presented.