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A systematic study of microwave-assisted degradation of lignin model compounds such as benzyl phenyl ether (BPE) and guaiacol, in imidazolium-based ionic liquids, was performed by evaluating the catalytic activity of 29 types of ionic liquids as both solvent and catalyst. After measuring and comparing the acidity of each ionic liquid solution for BPE and guaiacol degradation under the microwave irradiation and conventional heating conditions, it was found that the ionic liquid 1-butyl-3methylimidazolium hydrogen sulfate ([BMIM]HSO 4 ) was the most effective for decomposing the lignin model compounds. The experimental results indicate that ionic liquid acidity is in favor of the catalytic activity for BPE and guaiacol degradation, microwave irradiation could accelerate the degradation rate by 650% for BPE and 1120% for guaiacol and significantly increase the reaction selectivity. It was also found in experiments that the ionic liquid [BMIM]HSO 4 could be used for 5 times without any loss of catalytic activity. The possible mechanisms for BPE and guaiacol degradation are proposed based on the product distributions.

A systematic study on microwave-assisted oxidative degradation of lignin model compounds, such as 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, was performed by evaluating the catalytic activity of 14 types of metal salts. The acidity of each metal salt solution for the oxidative degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol under the microwave irradiation and conventional heating conditions was measured and compared. The results showed that CrCl 3 and MnCl 2 were the most effective for the degradation of the lignin model compounds. The acidity of metal salt is in favor of the catalytic activity for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, and microwave irradiation is able to accelerate the degradation rate in a large scale. The possible mechanisms for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol are proposed on the basis of the product distributions.

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