Pretreatment of miscanthus is essential for enzymatic production of sugars to yield bioethanol. A two-step process using 10 wt % aqueous ammonia in the first step is followed by 1 wt % sodium hydroxide (with or without oxygen or 1 wt % hydrogen peroxide) in the second step. The first step retains about 90% of the cellulose and about 67% of the hemicellulose in the solid while removing about 62% of the lignin. Both steps together achieve 83–90% delignification. Subsequent enzymatic conversion to fermentable sugars is close to 90% after 96 h. While an oxidant does not significantly increase delignification, it has a favorable effect on saccharification of the recovered solid. Infrared spectroscopy, X-ray diffraction, and two-dimensional nuclear magnetic resonance spectroscopy provide data concerning the chemical composition of the recovered solid. Inclusion of an oxidant to the pretreatment breaks β-O-4′-linked aryl ether bonds of the remaining lignin in the recovered solid.
Liu, Z., Padmanabhan, S., Cheng, K., Xie, H., Gokhale, A. A., Afzal, W., Na, H., Pauly, M., Bell, A. T., & Prausnitz, J. M. (2014). Two-step delignification of miscanthus to enhance enzymatic hydrolysis: aqueous ammonia followed by sodium hydroxide and oxidants. Energy & Fuels, 28(1), 542-548. https://doi.org/10.1021/ef401317z