Use of formaldehyde for making wheat straw cellulose pulp

A central composite design was used to investigate the influence of the coo king conditions (time, temperature and formaldehyde concentration) for whea t straw with formaldehyde-water mixtures on the properties of the pulp obta ined (yield and holocellulose, alpha-cellulose, lignin and ethanol-benzene extractives contents) and the pH of the resulting wastewater. A second-orde r polynomial model consisting of three independent process variables was fo und to accurately describe the organosolv pulping of wheat straw The equati ons derived predicted the yield, the holocellulose, alpha-cellulose, lignin and ethanol-benzene extractives contents of the pulp, and the pH of the wa stewater with multiple-R, R-2, adjusted-R-2 and Snedecor F values of 0.99, 0.99, 0.99 and 321.33, 0.98, 0.95, 0.92 and 35.01; 0.92, 0.86, 0.78 and 10. 68, 0.99, 0.97, 0.96 and 68.19; 0.91, 0.83, 0.80 and 29.68 and 0.97, 0.95, 0.93 and 46.10, respectively. While ensuring a high holocellulose content a nd low lignin and ethanol-benzene-extractive contents entails using high le vels of the process variables involved, a compromise can be made in order t o achieve both the previous objectives and a high alpha-cellulose content p rovided a long cooking time, a high temperature and a low formaldehyde conc entration are used - alternatively, a long time, a high formaldehyde concen tration and a low temperature can be equally effective and save energy. The yield, pH and holocellulose, alpha-cellulose, lignin and alcohol/benzene e xtractive contents are more sensitive to changes in the cooking time than t hey are to modifications of the formaldehyde concentration. (C) 1999 Elsevi er Science Ltd. All rights reserved.