Carboxyl groups in wood fibers. 2. The fate of carboxyl groups during alkaline delignification and its application for fiber yield prediction in alkaline pulping

Detailed characterizations of the content of carboxyl groups in wood fibers derived from alkaline delignification of loblolly pine using various processes were conducted in this study (part 2) using the method presented in the preceding paper, part 1. It was demonstrated that the content of hexenuronic acid (HexA) groups can be used to account for the carboxyl groups associated with hemicelluloses in wood fibers. The difference between the measured contents of carboxyl and HexA groups can be used to account for the carboxyl groups associated with wood lignin. As a result, the calculated content of carboxyl groups associated with lignin correlated very well to the pulp number. An empirical correlation for predicting fiber yield with the measured contents of carboxyl and HexA groups was developed on the basis of mass conservation. Good agreement between measured and predicted fiber yield for the two wood species studied was obtained.