Isolation of cellulose from steam-exploded rice straw with aniline catalyzing dimethyl formamide aqueous solution

An efficient and clean procedure was put forward for isolation of cellulose from rice straw, which included delignification of steam-exploded rice straw with recyclable mixed solvent system and bleaching with alkaline hydrogen peroxide. The condition of steam explosion was optimized through a series of experiments using statistical software (SPSS). The optimized conditions of steam explosion pretreatment was to keep the rice straw under 2.5 MPa for 25 min and then explode. A series of mixed solvent systems were designed and their delignification capabilities were analyzed. The most efficient mixed solvent consists of water, dimethyl formamide (DMF) and aniline in volume ratio of 20:10:1, and the delignified sample was analyzed to contain 0.87% lignin. After bleached with alkaline hydrogen peroxide, the bleached cellulose was analyzed to contain 95.58% cellulose, and the ratio of α-cellulose is 84.05%. The bleached cellulose possesses moderate degree of polymerization (549), and contains no detectable acid-insoluble lignin. The as-obtained cellulose was further characterized by FT-IR and 13C CP/MAS NMR spectroscopy. The recycled lignin and hemicelluloses were analyzed by FT-IR spectra.