Abstract Three lignin fractions with different molecular size (Fraction 3 > Fraction 2 > Fraction 1) were prepared by sequential solvent fractionation of soda lignin. These were structurally investigated by several analytical techniques, such as GPC, 31P-NMR, 2D-HSQC-NMR, and TGA. They revealed that F1 was the smallest and the most thermally labile lignin fraction. Pyrolyzing lignin fractions at 600 °C with zeolite Y produced aromatic hydrocarbons (benzene, toluene, xylenes, and naphthalenes) with several types of monomeric phenols. Total pyrolysis product yields were the highest for F1, followed by F2 and F3. Additionally, aromatic hydrocarbons formation was inversely proportional to molecular size and abundantly produced with F1 (35.0 mg/g). They gradually increased in all fractions as the pyrolysis temperature increased (up to 800 °C). The transformation behaviors of functional groups were also investigated by using lignin model compounds. Lignin fractions prepared in this study had not only molecular size but also different phenolic hydroxyl (Phe-OH) content which would play a deleterious role in aromatic hydrocarbon formation during zeolite-catalyzed pyrolysis. Therefore, we prepared methylated lignin from each fraction (Methylated fraction 1, 2, and 3) and these were also pyrolyzed under same condition to investigate the independent effect of molecular size.

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木质素分子大小对沸石催化热解芳烃生成的影响

摘要 通过对苏打木质素进行连续溶剂分级，制备了三种不同分子大小的木质素组分（组分 3 > 组分 2 > 组分 1）。通过多种分析技术对这些进行了结构研究，例如 GPC、31P-NMR、2D-HSQC-NMR 和 TGA。他们发现 F1 是最小和最热不稳定的木质素部分。在 600 °C 下用沸石 Y 热解木质素馏分，产生芳香烃（苯、甲苯、二甲苯和萘）和几种类型的单体酚。F1 的总热解产物产率最高，其次是 F2 和 F3。此外，芳烃的形成与分子大小成反比，并且大量生成 F1 (35.0 mg/g)。随着热解温度的升高（高达 800 °C），它们在所有馏分中逐渐增加。还通过使用木质素模型化合物研究了官能团的转化行为。本研究中制备的木质素馏分不仅具有分子大小，而且具有不同的酚羟基 (Phe-OH) 含量，这将对沸石催化热解过程中芳烃的形成起到有害作用。因此，我们从每个馏分（甲基化馏分 1、2 和 3）制备甲基化木质素，这些也在相同条件下热解以研究分子大小的独立影响。本研究中制备的木质素馏分不仅具有分子大小，而且具有不同的酚羟基 (Phe-OH) 含量，这将对沸石催化热解过程中芳烃的形成起到有害作用。因此，我们从每个馏分（甲基化馏分 1、2 和 3）制备甲基化木质素，这些也在相同条件下热解以研究分子大小的独立影响。本研究中制备的木质素馏分不仅具有分子大小，而且具有不同的酚羟基 (Phe-OH) 含量，这将对沸石催化热解过程中芳烃的形成起到有害作用。因此，我们从每个馏分（甲基化馏分 1、2 和 3）制备甲基化木质素，这些也在相同条件下热解以研究分子大小的独立影响。