Oxovanadium complexes catalyzed oxidation of lignin and lignin dimers in acetonitrile/water under O2,Biomass Conversion and Biorefinery

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Oxovanadium complexes catalyzed oxidation of lignin and lignin dimers in acetonitrile/water under O2
Biomass Conversion and Biorefinery ( IF 3.5 ) Pub Date : 2022-01-15 , DOI: 10.1007/s13399-021-02175-5
Chao Liu ₁ , Fei Lin ₁ , Xiangchen Kong ₁ , Yuyang Fan ₁ , Weicong Xu ₁ , Rui Xiao ₁

Affiliation

Selective oxidation of lignin is increasingly investigated due to its advantage of retaining the aromatic rings to produce value-added platform chemicals. In this paper, oxovanadium complexes catalyzed oxidation of lignin and lignin dimers in acetonitrile/water system under O₂ was reported. Under optimal conditions of VO(acac)₂ catalyzed oxidation, 95 mol% of lignin dimer 2-phenoxy acetophenone was converted, producing 43 mol% of phenol and 83 mol% of benzoic acid. The catalytic ability of V(acac)₃ was higher than that of VO(acac)₂, but it caused heavier repolymerization and lower product yields. VO(acac)₂ catalyzed oxidation system also cleaved various β-O-4 lignin dimers, achieving > 95 mol% conversion. Whereas, yields of phenols from these dimers were lower than 5 mol%. These phenolics were shown to polymerize under reaction conditions. Furthermore, this oxidation system depolymerized poplar organosolv lignin. After oxidation, aromatic and C-O aliphatic functionalities in the heavy fractionation largely disappeared, and the weight-average molecular weight decreased from 5720 to 1140 Da.

Graphical abstract

Oxovanadium complexes show the good ability for the catalytic oxidation of lignin and lignin dimers in MeCN/H₂O co-solvent in the presence of O₂, achieving higher than 95 mol% conversion of β-O-4 lignin dimers and lowering the molecular weight of poplar organosolv lignin from 5720 to 1140 Da.

中文翻译：

O2氧钒配合物在乙腈/水中催化木质素和木质素二聚体的氧化

木质素的选择性氧化由于其保留芳环以生产增值平台化学品的优势而受到越来越多的研究。本文报道了氧钒配合物在O ₂下催化乙腈/水体系中木质素和木质素二聚体的氧化。在VO(acac) ₂催化氧化的最佳条件下，95 mol%的木质素二聚体2-苯氧基苯乙酮被转化，产生43 mol%的苯酚和83 mol%的苯甲酸。_{V(acac) 3}的催化能力高于VO(acac) ₂，但导致重聚较重，产物收率较低。VO(acac) ₂催化的氧化系统也裂解了各种β-O-4 木质素二聚体，转化率 > 95 mol%。然而，来自这些二聚体的酚类产率低于 5 mol%。这些酚醛树脂显示在反应条件下聚合。此外，该氧化系统解聚了杨树有机溶剂木质素。氧化后，重分馏中的芳香族和CO脂肪族官能团基本消失，重均分子量从5720 Da下降到1140 Da。