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Selective cleavage of aryl ether bonds in dimeric lignin model compounds

机译：二聚体木质素模型化合物中芳基醚键的选择性切割

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Lignin is an abundant renewable feedstock with a complicated and ill-defined structure. As β- O -4 aryl ether bonds are dominant among all the linkages in lignin, it is important to explore lignin depolymerization targeting the cleavage of the β- O -4 aryl ether bond for efficiently utilizing this biomass. Selective cleavage of chemical bonds in β- O -4 lignin model compounds was investigated by using Fe _(2) (SO _(4) ) _(3) , HZSM-5 and Pd/C as catalysts under microwave irradiation. When Fe _(2) (SO _(4) ) _(3) or HZSM-5 was used as a catalyst, the C _(α) –C _(β) bond of the C3 side chain in the model compound was broken to form aldehyde, secondary alcohol or ketone compounds. When Pd/C and formate were used as the catalyst, the β- O -4 aryl bond of the non-phenolic model compound was selectively cleaved and hydrogenation of CC on the side chain occurred at the same time. However, the hydrogenation reaction of CC on the side chain was faster than that of cleavage of the ether bond. Increasing Pd content favored the selective cleavage of the β- O -4 bond, and microwave irradiation accelerated the cleavage of the β- O -4 bond dramatically. At a high dosage of formate or high temperature, the condensation reaction among phenolic products was promoted due to the presence of an active phenolic hydroxyl group. The β- O -4 bond of the phenolic model compound was also selectively cleaved with Pd/C as the catalyst, and the reaction temperatures of cleaving about one half β- O -4 bonds of the non-phenolic and phenolic model compounds were 120 and 100 °C, respectively.
机译：木质素是一种丰富的可再生原料，结构很复杂，结构不明显。由于β-O -4芳基醚键在木质素中的所有键中显着，重要的是探讨靶向β-O -4芳基醚键的切割以有效利用这种生物质的裂解。通过使用Fe _（2）（SO _（4））_（3），HZSM-5和Pd / C作为微波辐射的催化剂，研究了β-O -4木质素模型化合物中的化学键的选择性切割。当Fe _（2）（SO _（4））_（3）或HZSM-5用作催化剂时，模型化合物中C3侧链的C _（α）-C _（β）键是破碎以形成醛，仲醇或酮化合物。当使用Pd / C和甲酸盐作为催化剂时，选择性地切割非酚类模型化合物的β-O -4芳基键，并在侧链上氢化CC的同时发生。然而，Cc在侧链上的氢化反应比醚键的切割更快。增加PD含量赞成β-O -4键的选择性切割，微波辐射急剧加速了β-O -4键的切割。在高剂量的甲酸盐或高温下，由于存在活性酚羟基的存在，促进酚类产物之间的缩合反应。酚类模型化合物的β-O -4键也用Pd / c选择性地切割为催化剂，并且裂解约一半β-O -4键的反应温度为非酚类和酚醛化合物的键是120和100°C分别。

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