Effect of Ionic Liquid 1-Butyl-3-Methyl-Imidazolium Dihydrogen Phosphate Pretreatment on Pyrolysis of Lignin

Resumo

In order to improve the yield of liquid fraction and phenolics content during lignin pyrolysis, an effective method of lignin pyrolysis through the pretreatment of lignin by an acidic ionic liquid 1-butyl-3- methyl-imidazolium dihydrogen phosphate ([Bmim]H₂PO₄) at low temperature is investigated in this study. It is found that [Bmim]H₂PO₄ pretreatment increases the total yield of liquid products of lignin pyrolysis compared to that of original lignin. The [Bmim]H₂PO₄ pretreatment temperature significantly impacts the behaviors of the lignin pyrolysis. In the temperature range of 50 to 150°C, the yield of the overall liquid product obtained by pyrolysis of the sample pretreated at 50°C is the highest. After pretreatment, the [Bmim]H₂PO₄ can be efficiently recovered, but the structure and stability of the [Bmim]H₂PO₄ have been changed. The FTIR analysis shows that the ionic liquid [Bmim]H₂PO₄ pretreatment can break hydrogen bonds, ether linkages and ester bonds in lignin.