Studies on Kinetics and Reuse of Spent Liquor in the TEMPO-Mediated Selective Oxidation of Mechanical Pulp

Abstract

The kinetics and reuse of spent liquor in the TEMPO-mediated oxidation of mechanical pulp have been studied. It was found that the oxidation reaction of the mechanical pulp by the 2,2,6,6-tetramethyl piperidine-1-oxyl radical (TEMPO)−NaBr−NaOCl system can be approximately described by first-order kinetics with respect to TEMPO and NaBr. In the concentration range used, the rate constant k is directly proportional to the concentration of TEMPO and NaBr, whereas the concentration of NaOCl determines the end of conversion of the primary alcohol groups on the mechanical pulp into carboxylic acid groups. It was also found that the spent reaction liquor can be recycled and reused with reinforced addition of NaOCl without additional TEMPO and NaBr and remains effective in generating carboxylic acid groups on mechanical pulp.