木质素氧化降解制备单酚类化合物

采用H2O2、CuO/Fe2(SO4)3复合氧化体系,在碱性条件、微波辅助作用下,对麦草碱木质素氧化降解制备单酚类化合物的工艺条件进行了研究。结果表明,在180℃相对温和的条件下,单酚类化合物的总收率可达11.86%,降解率为90.88%。单独H2O2作为氧化剂降解木质素导致了苯环的开裂,使得木质素的降解率虽高但单酚类收率偏低;Cu2+的参与促进了木质素侧链和醚键的断裂,有利于提高单酚类化合物的收率,而Fe3+的存在则提升了H2O2的氧化性能。适当提高氧化温度和延长降解反应时间有利于提高单酚类化合物收率。由于木质素的降解和聚合同时存在,防止降解产物的聚合成为提高单酚类化合物收率的关键。

Oxidative degradation of lignin for producing monophenolic compounds

Oxidative degradation of lignin for producing monophenolic compounds was carried out under microwave irradiation, with H₂O₂, CuO and Fe₂(SO₄)₃ as the oxidants. The results indicated that the yield of monophenolic compounds and degradation rate of lignin feed reach 11.86% and 90.88%, respectively, under the relatively benign conditions of 180 ℃. Oxidative degradation of lignin with H₂O₂ as a single oxidant gives a high degradation rate but a lower yield of monophenolic compounds, due to the aromatic ring opening reaction; however, Cu²⁺ present in the oxidant system is able to promote the cleavage of side chain and ether bond, whereas Fe³⁺ to enhance the oxidation ability of H₂O₂, which are then conducive to improving the yield of monophenolic compounds. A moderate increase of degradation temperature and reaction time are favorable for improving the yield of monophenolic compounds. Owing to the coexistence of lignin degradation and recondensation of degraded fragments, the prevention of degraded lignin from recondensation turns to be a key issue to achieve a high yield of monophenolic compounds.