An effective method for the cleavage of the C–O bonds in lignin α-O-4 dimers and various alkaline lignins including the lignin from pulp industry was developed over a heterogeneous ReO_x/AC catalyst. High yield of aromatic monomers (up to 98.0%) from α-O-4 model compounds and up to 80.1% lignin oil with 24.5% yield of monomers from realistic lignin were obtained under optimized conditions. Alkaline poplar lignin provided syringylpropane and 4-propenylsyringol with the highest yield of 6.6% and 7.4%, respectively. The active sites of ReO_x/AC could be assigned to Re^IV–VI according to XPS and EXAFS characterization. The lignin structures of different botanical species (hardwood, softwood and herbaceous crop) were compared and the activity of ReO_x/AC on these lignins was investigated in detail. GPC and 2D HSQC NMR analysis of isolated lignin and lignin oil showed that hardwood lignin was more liable to be deconstructed than softwood and grass lignins due to the less amounts of β-5 linkages, lower molecular weight and richer syringyl (S) units in hardwood lignin.

中文翻译：

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ReO _x / AC催化的木质素模型化合物和碱性木质素中C–O键的裂解

在异质ReO _x / AC催化剂上开发了一种有效的裂解木质素α-O-4二聚体和各种碱性木质素（包括来自制浆工业的木质素）中的C-O键的方法。在优化的条件下，可以从α-O-4模型化合物中获得高收率的芳族单体（最高98.0％）和从实际的木质素中获得最高80.1％的木质素油，以及来自实际木质素的24.5％的单体。碱性杨木木质素提供的丁香基丙烷和4-丙烯基丁香酚的最高产率分别为6.6％和7.4％。根据XPS和EXAFS的特征，可以将ReO _x / AC的活性位点分配给Re ^IV-VI。比较了不同植物种类（硬木，软木和草本作物）的木质素结构，并测定了ReO _x的活性。/ AC对这些木质素进行了详细研究。分离的木质素和木质素油的GPC和2D HSQC NMR分析表明，硬木木质素比软木和草木素更易于分解，这是因为硬木中β-5键的数量较少，分子量较低且丁香烯基（S）单元更丰富木质素。