Depolymerization of lignin by catalytic oxidation with aqueous polyoxometalates

• Five lignins were tested in this work, among which pyrolytic lignin was show to be the best yield (65.21 wt%).
• Methanol and temperature plays an important role in the catalytic oxidation of lignin.
• The production of dimethyl succinate and aromatic compounds by catalytic oxidation of lignin used H5PMo10V2O40 as catalyst.
• The H5PMo10V2O40 catalyst was recycled for five times without significant deactivation.

In this work a method for the depolymerization of lignin by catalytic oxidation was studied. Using H5PMo10V2O40 as the catalyst, various lignin spices including pyrolytic lignin, hydrolytic lignin, alkali lignin, sodium lignosulfonate and calcium lignosulfonate were tested for the oxidative degradation. The influence of reaction conditions, i.e. reaction temperature, solvent, reaction time, initial O2 pressure and catalyst concentration were investigated. Under optimized conditions, the highest yield of 65.21% of the oxidative degradation products was achieved from pyrolytic lignin, and the main products were aromatic compounds and dimethyl succinate. Moreover, the H5PMo10V2O40 catalyst was recycled for five times without significant deactivation.

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