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The process of delignification during the pretreatment of corn stover in supercritical CO2 with ethanol-water as co-solvent was investigated. After pretreatment, many lignin droplets were found deposited on the fiber surface which hinder cellulose digestibility. These lignin droplets were removed by ethanol-water and after washing the optimal glucose yield increased significantly. Lignin degradation reactions competed with condensation reactions during pretreatment. The cleavage of ether bonds and the high solubility of lignin fragments in ethanol-water co-solvent were the key factors for lignin removal and degradation behavior during pretreatment.

The amount of trace organic acids must be controlled in the fuel ethanol product in order to reduce the chance to corrode automotive cylinder. Ion-exchange resin was investigated to remove acids from fuel ethanol in this paper. Industrial resins, D301R, 330, 201×7, and D201, were selected as candidates, and a series of experiments were carried out to determine which one is the best. Acetic acid was employed as a simulated compound in these experiments for it is the main residual acid in fuel ethanol product. The results showed that the 330 resin was the most effective one to remove acid from fuel ethanol, and then, both static and dynamic experiments were carried out to evaluate the performance of the 330 resin. It was found that equilibrium data can be well described by Langmuir isotherm during the temperature range from 25 to 35 °C. The kinetic data fitted well with the pseudo-second-order kinetic model. Furthermore, a bench scale fixed bed was set up to determine the optimal adsorption and regeneration...