Degradation Of Lignin Model Compounds In Violuric Acid-mediatedelectrochemical Delignification System With Violuric Acid

Electrochemical bleaching technology is a promising approach for the development of environmentally friendly processes in pulp bleaching. Electrochemical bleaching process with violuric acid as a mediator is attractive not only due to its environmentally friendly but also based on its delignification selectivity. This technology is relative clean, compared with traditional pulp bleaching process. Guaiacol, veratryl alcohol and the β-O-4type model compound guaiacylglycerol-β-guaiacyl ether were respectively treated with a Violuric acid (VIO) mediated electrochemical delignification system, then concluded the reaction pathway of the model. This provides theoretical and technical basis for the application of this method in pulp industry.Guaiacol and sodium acetate anhydrous were used as basic materials, cupric bromide as catalyst alcohol as solvent during the synthesis of guaiacylglycerol-β-guaiacyl ether. The techniques of infrared spectra analysis and1H-NMR were used to investigate the structure of reaction intermediate and guaiacylglycerol-β-guaiacyl ether.Then it can confirm that the compound is guaiacylglycerol-β-guaiacyl ether.When the ratio of the amount of violuric acid free radical and lignin model was10:1,the lignin model was reacted completely; when the ratio of the amount of violuric acid free radical and lignin model was1:10,the violuric acid free radical was reacted completely. They were all multiple step reaction. The results indicated that the reaction intermediate such as phenoxy radical, catechol and benzoquinone were produced during the degradation of the guaiacol. The following reactions were caused by electrochemical oxidation:benzene ring cleavage and condensation reaction,then a series of furan compounds and aliphatic compounds with small molecule and dimmer were produced. The reaction intermediate C a free radical was produced during the degradation of the veratryl alcohol,then produced conjugated carbonyl. The following reactions were caused by electrochemical oxidation:benzene ring cleavage and demethylation,then ultimate products were produced.The amount of hydroxyl increased and the amount of methoxy reduced.After the treatment, it can be found that there are three kinds of main degradation products. They are aromatic compounds containing a single benzene ring, Cβ-C γ and the aromatic ring cleavage. The increase of carboxyl and carbonyl and hydroxyl indicates that this system is effective for the degradation of this phenolic P-O-4lignin model dimer.