Pulping of rice straw with high-boiling point organosolv solvents

Rice straw was used as an alternative raw material to obtain paper pulp. Pulping was done by using high-boiling point organic solvents of decreased polluting power relative to classical (Kraft, sulphite) solvents but affording operation at similar pressure levels.The holocellulose, α-cellulose and lignin contents of rice straw (viz. 60.7, 41.2 and 21.9%, respectively) are similar to those of some woody raw materials such as pine and eucalyptus, and various non-wood materials including olive tree prunings, wheat straw and sunflower stalks.Pulping tests were conducted by using ethyleneglycol, diethyleneglycol, ethanolamine and diethanolamine under next operating conditions: 80% solvent, 180 °C and 150 min. The solid/liquid ratio was 6. The amine solvents were found to provide pulp with better properties than did the glycol solvents. Diethanolamine pulp exhibited the best viscosity, Kappa index, drainage index and burst index (viz. 956 mL/g, 17.0, 21°SR and 1.23 kN/g, respectively). Paper made from ethanolamine pulp exhibited the best stretch (1.99%), tear index (0.44 mNm2/g) and brightness (41.7%).