Toward Selective Lignin Liquefaction: Synergistic Effect of Hetero- and Homogeneous Catalysis in Sub- and Supercritical Fluids

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• 作者：Rudresh RajappagowdaAbu M. Numan-Al-Mobin ; Bin Yao ; Robert Daniel Cook ; Alevtina Smirnova
• 刊名：Energy & Fuels
• 出版年：2017
• 出版时间：January 19, 2017
• 年：2017
• 卷：31
• 期：1
• 页码：578-586
• 全文大小：534K
• ISSN：1520-5029

文摘

Selective liquefaction of lignin is important for synthesis of value-added phenolic monomers contributing to green chemistry and sustainable energy applications. In the present study, a synergistic effect of a supercritical carbon dioxide (scCO₂) acidic catalyst in combination with a heterogeneous metal oxide catalyst, specifically nickel oxide (NiO) or ceria-doped scandia-stabilized zirconia (CeScSZ), in sub- or supercritical water (sbcr/scH₂O) for selective liquefaction of alkali lignin is demonstrated for the first time. The scCO₂-assisted hydrothermal process in the temperature range of 100–400 °C resulted in highly selective synthesis of the phenolic monomers. On the basis of the total organic carbon (TOC) and gas chromatography–mass spectroscopy (GC–MS) analysis, it is evident that the scCO₂ catalyst is essential for enhancing the reaction selectivity in the presence of a heterogeneous catalyst. A combination of homogeneous scCO₂ and heterogeneous NiO catalysts resulted in the highest total relative yield of the phenolic monomers, reaching ∼97% at 200 °C. It is confirmed that the scCO₂-assisted hydrothermal depolymerization of the alkali lignin in the presence of both scCO₂ and a heterogeneous catalyst is superior to that of the each of these catalysts alone and in comparison of the systems where scCO₂ is replaced by inert nitrogen.