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Silica microspheres are of much interest in several areas, such as liquid chromatography, medicine, biochemistry, colloidal chemistry and aerosol research. In this study, the sol−gel method was used to prepare these microparticles followed by three different drying processes. The first process involved intermittent supercritical fluid drying (SCF-I) using intermittent supercritical carbon dioxide (scCO 2 ) at a low temperature. The second approach involved continuous supercritical fluid drying (SCF-C) using continuous scCO 2 at low temperature, as well. The third approach involved vacuum drying (WO), which is a high temperature process. All of the experiments led to the successful precipitation of silica microparticles in the micrometre range. In all of the cases, a spherical morphology and no agglomeration were observed. The optimum preparation conditions were determined as follows: stirring speed is 200 r/min; continuous phase/dispersed phase is 2/1; Span® 80/ Tween® 20 is 5/2; the ratio of surfactant is 17%. In addition, the primary textural characteristics of these microspheres were investigated by nitrogen physisorption experiments. The results indicated that the size of the pore volume is as follows: V SCF-C > V SCF-I > V WO . The BET data indicate that the specific surface area of the porous silica microspheres is as follows: S SCF-C > S SCF-I > S WO .

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.