Transition Metal-catalysed Oxidation of Lignin Model Compounds for Oxygen Delignification of Pulp
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Polyoxometalate Oxidation of Phenolic Lignin Models Chapter 18
A new environmentally friendly technology for wood pulp delignification, based on the use of polyoxometalates (POMs) and oxygen, is being developed. Polyoxometalate solutions that selectively oxidize lignin under anaerobic conditions can be reoxidized by oxygen and also catalyze the aerobic mineralization ofthe lignin fragments to CO2 and H2O, making possible the closed-mill manufacture of pape...
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It has been found that polyoxometalates (POMs) can act as mediators in the electrochemical oxidation of lignin in pulps. An electrochemical cell, with a Nafion membrane separating the anode and cathode compartments, was used in the delignification experiments. A softwood kraft pulp was placed in the anode compartment with a buffered 0.01M solution of the polyoxometalate Na5[SiVW11O40]. During e...
متن کاملReactivities of various mediators and laccases with kraft pulp and lignin model compounds.
Laccase-catalyzed oxygen delignification of kraft pulp offers some potential as a replacement for conventional chemical bleaching and has the advantage of requiring much lower pressure and temperature. However, chemical mediators are required for effective delignification by laccase, and their price is currently too high at the dosages required. To date, most studies have employed laccase from ...
متن کاملInfluence of Nonprocess Elements on Lignin Structure During Oxygen Delignification
A series of kraft pulps were prepared in which the level of calcium was selectively enriched and depleted. These pulps were then oxygen delignified, and the pulps were characterized according to kappa number and viscosity. The residual lignin samples were isolated via acid-hydrolysis and characterized by NMR techniques. The results indicated that the presence of nonprocess elements could impact...
متن کاملPolyoxometalates in Oxidative Delignification of Chemical Pulps: Effect on Lignin
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove lignin from the pulp without a negative effect on the cellulose; for this reason, delignification should be performed in a ...
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