Delignification of wheat straw by use of low-molecular-weight organic acids

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and acid concentration) for wheat straw with organic acid-water mixtures on the properties of the pulp obtained (yield and holocellulose, alpha-cellulose and lignin contents). A second-order polynomial model, consisting of three independent process variables, was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, alpha-cellulose and lignin contents of the pulp with multiple-R, R-2 and adjusted-R-2 high values. The process variables must be set low in order to ensure a high yield. Conversely if high holocellulose and alpha-cellulose contents and low lignin contents are desired, then a long cooking time (120 min), an intermedia temperature (100 degrees C), and a low formic acid concentration (50%) must be used.