A phenolic β-O-4 type lignin model compound, guaiacylglycerol-β-guaiacyl ether (GG) was treated with 70 wt% aq 1,3-butanediol solution at 160-200°C to investigate the delignification mechanism under HBS (high-boiling solvent) pulping conditions. Recovery of GG was determined by GC. The disappearance of GG exhibited a pseudo first-order rate behavior. The pseudo first-order rate constants were as follows: k = 1.20 x 10~(-2) min~(-1) at 160°C; k = 2.31 x 10~(-2) min~(-1) at 170°C; k = 3.65 x 10~(-2) min~(-1) at 180°C; k = 10.4 x 10~(-2) min~(-1) at 200°C. The activation energy was 90.8 kJmol~(-1). The following compounds were identified from the reaction products by use of GC-MS: guaiacol (2), coniferyl alcohol (3), γ-etherified coniferyl alcohols (4) and α-etherified guaiacylglycerol-β-guaiacyl ethers (5), but acidolysis products, such as Hibbert's ketones were not detected. These results indicate that phenolic β-O-4 linkage was cleaved homoliticaly under HBS pulping conditions. The formation of higher molecular-weight compounds was confirmed by GPC. It is highly probable that polymeric products were derived from the recombination of radicals formed by homolysis of the β-aryl ether.
展开▼
机译：酚醛β-O-4型木质素模型化合物，在160-200℃下用70wt％aq 1,3-丁二醇溶液处理Guaiacylg甘油-β-愈桂基醚（gg），以研究HBS下的脱磷油机制（高 - 沸腾溶剂）制浆条件。 GG的回收率由GC确定。 GG的消失表现出伪一阶率行为。伪一阶率常数如下：k = 1.20×10〜（-2）min〜（-1），160°C; k = 2.31 x 10〜（-2）min〜（-1）在170°C; k = 3.65×10〜（-2）min〜（-1）180°C; k = 10.4 x 10〜（-2）min〜（-1）在200°C。活化能量为90.8 kJmol〜（-1）。通过使用GC-MS：Guaiacol（2），Coniferyl（3），γ-醚化果糖醇（4）和α-醚化愈菌甘氨酸（5）从反应产物中鉴定了以下化合物。但是未检测到酸溶解产物，例如柠檬酸酮。这些结果表明，在HBS制浆条件下，酚醛β-O-4连杆在HBS制浆条件下裂解同核。通过GPC确认更高分子量化合物的形成。高度可能的是，聚合物产物源自通过α-芳基醚的均解形成的自由基的重组。
展开▼
