Relative reactivities of black liquors and sulfate process spent liquor toward formaldehyde

Four black liquors and one sulfite process spent liquor were obtained from pulping mills located in the northwestern and southeastern United States. The reactivities of the black liquors and the sulfite process spent liquor toward formaldehyde were investigated by reaction at 60? and 85?C. The unreacted formaldehyde was determined during the course of reaction and plotted as the function of reaction time to indicate the reactivities of lignin materials toward formaldehyde. The free formaldehyde was measured by hydroxylamine hydrochloride titration to the end point of pH4 and gas chromatograph (GC) analysis. Cannizzaro reaction was detected by GC analysis and the extent of Cannizzaro reaction was determined by measuring the quantity of methanol produced in reaction mixture. The reaction temperature significantly influenced the reactivities of lignin materials toward formaldehyde. The reactivity also differed significantly among the materials examined. The formaldehyde absorbed by one lignin material at the end of 180 minutes was approximately 0.6 mole per 100 g crude lignin at reaction temperature of 60?C, and 0.9 mole at 85?C; for a second material the amounts were approximately 0.7 mole at 60?C and 1.0 mole at 85?C. The unreacted formaldehyde in reaction mixtures decreased rapidly during the first 60 to 120 minutes and slowly after that. These results provide important information about the use of lignin materials for resin formulation and synthesis.

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