低共熔离子液体中氯化钯催化改性木质素的结构特征

在氯化胆碱和尿素形成的低共熔离子液体中,加入不同质量的氯化钯催化剂,探讨其对木质素化学结构催化降解的影响。采用UV、FT-IR和1H-NMR等仪器分析手段,对比处理前后木质素酚羟基浓度以及木质素化学结构变化。结果表明:离子液体与木质素质量比为10:1,处理时间2 h,温度为90 ℃时,当加入氯化钯催化剂质量占木质素质量的10%时改性效果较好。与未改性的木质素相比,总酚羟基浓度提高了152%,部分醚键断裂,甲氧基被还原成羟基,从而引起大分子木质素的降解,提高了木质素的化学活性。
In this study, different dosages of palladium chloride were added in the eutectic ionic liquid formed by choline chloride and urea. The catalytic effects of palladium chloride on lignin degradation were analyzed. Ultraviolet spectroscopy(UV), Fourier transform infrared spectroscopy(FTIR)and 1H Nuclear Magnetic Resonance(NMR)were used to analyze the change of the chemical structure of lignin and free phenolic hydroxyl content. The results showed that higher chemical activity of lignin could be achieved when it was treated at 90 ℃ for 2 h, and the mass ratio of both ionic liquid to lignin and lignin to palladium chloride was 10:1. The total phenolic hydroxyl content of the treated lignin increased about 152% compared with that of the untreated lignin. Some ether bonds were broken, while methoxyl groups were reduced to hydroxyl groups which caused the degradation of lignin macromolecules and improved lignin chemical activity