Lignin Depolymerization into Aromatic Monomers over Solid Acid Catalysts
Lignin Depolymerization into Aromatic Monomers over Solid Acid Catalysts
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DOI：
10.1021/cs501371q
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发表时间：
2015-01-01
期刊：
影响因子：
12.9
通讯作者：
Dhepe, Paresh L.
中科院分区：
文献类型：
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作者：
Deepa, Ayillath K.;Dhepe, Paresh L.
当务之急是开发一种高效且环境友好的途径，将大量可用的木质素（非食用木质纤维素材料的组成部分）转化为增值芳香族单体，可用作燃料添加剂和平台化学品。为了转化木质素，早期的研究使用矿物碱（NaOH、CsOH）或负载型金属催化剂（Pt、Ru、Pd、C上的Ni、SiO2、Al2O3等）在氢气气氛下进行转化，但这些方法面临着一些缺点，如腐蚀、催化剂回收困难、金属烧结、活性损失等。这里我们表明，在惰性气氛下，各种固体酸催化剂可以有效地将六种不同类型的木质素转化为增值的芳香族单体。特别是，SiO2Al2O3 催化剂产生了异常高的产率。脱碱木质素、甘蔗渣木质素以及 ORG 和 EORG 木质素在 250 摄氏度下 30 分钟内解聚时，有机溶剂可溶性提取产物的质量平衡为 60%，质量平衡为 95 +/- 10%。对有机溶剂可溶性萃取产物的 GC、GC-MS、HPLC、LC-MS 和 GPC 分析证实了芳香族单体的形成。 90% 选择性。在产品中，通过 FT-IR 以及 H-1 和 C-13 NMR 研究确认了木质素中存在的芳香性质的保留以及多个官能团的出现。此外，通过柱色谱法分离主要产物以获得纯净形式的芳香族单体，并通过NMR对其进行表征。对从不同来源获得的六种不同类型木质素的详细表征有助于证实这些反应中获得的催化结果。对新鲜催化剂和废催化剂的细致研究表明，为了获得可重复的催化结果，优选使用无定形催化剂。
It is imperative to develop an efficient and environmentally benign pathway to valorize profusely available lignin, a component of nonedible lignocellulosic materials, into value-added aromatic monomers, which can be used as fuel additives and platform chemicals. To convert lignin, earlier studies used mineral bases (NaOH, CsOH) or supported metal catalysts (Pt, Ru, Pd, Ni on C, SiO2, Al2O3, etc.) under a hydrogen atmosphere, but these methods face several drawbacks such as corrosion, difficulty in catalyst recovery, sintering of metals, loss of activity, etc. Here we show that under an inert atmosphere various solid acid catalysts can efficiently convert six different types of lignins into value-added aromatic monomers. In particular, the SiO2Al2O3 catalyst gave exceptionally high yields of ca. 60% for organic solvent soluble extracted products with 95 +/- 10% mass balance in the depolymerization of dealkaline lignin, bagasse lignin, and ORG and EORG lignins at 250 degrees C within 30 min. GC, GC-MS, HPLC, LC-MS, and GPC analysis of organic solvent soluble extracted products confirmed the formation of aromatic monomers with ca. 90% selectivity. In the products, confirmation of retention of aromatic nature as present in lignin and the appearance of several functional groups has been carried out by FT-IR and H-1 and C-13 NMR studies. Further, isolation of major products by column chromatography was carried out to obtain aromatic monomers in pure form and their characterization by NMR is presented. A detailed characterization of six different types of lignins obtained from various sources helped in substantiating the catalytic results obtained in these reactions. A meticulous study on fresh and spent catalysts revealed that the amorphous catalysts are preferred to obtain reproducible catalytic results.