The condensed structure of technical lignin presents significant challenges in converting it into valuable functionalized building blocks, such as single-ring aromatics. In this study, we explored how palladium-based catalysts influence the selectivity of monoaromatics during the fast pyrolysis depolymerization of lignin. A systematic study on the influence of the pyrolysis temperature (500 < T < 700 °C) and catalyst support nature (SiO2, Al2O3 and Carbon) was carried out by analytical pyrolysis. Creosol and guaiacol were the predominant species after non-catalytic and Pd/SiO2 catalyzed pyrolysis of Kraft lignin. However, when Pd/C and Pd/Al2O3 were applied, the selectivity to monoaromatics increased drastically, to 50.9 % and 34.4 %, respectively. The catalytic activity of Pd/C and Pd/Al2O3 was ascribed to the presence of medium and weak acid sites in the supports, which provides active sites for phenolics adsorption and deoxygenation. Additionally, metallic Pd sites activated the C-O and H2 bonds to further assist deoxygenation reactions, thus inducing a bifunctionality to these materials. This study offers valuable insights into the bifunctional effects of supported catalyst during the thermo-catalytic depolymerization of lignin.

中文翻译：

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木质素在 Pd 基催化剂上的热催化解聚：催化剂负载对单芳烃选择性的影响


工业木质素的缩合结构在将其转化为有价值的功能化结构单元（如单环芳烃）方面提出了重大挑战。在本研究中，我们探讨了钯基催化剂在木质素快速热解解聚过程中如何影响单芳烃的选择性。通过分析热解对热解温度 （500 < T < 700 °C） 和催化剂载体性质 （SiO2、Al2O3 和碳） 的影响进行了系统研究。Creosol 和 guaiacol 是非催化和 Pd/SiO2 催化热解 Kraft 木质素后的主要物种。然而，当施用 Pd/C 和 Pd/Al2O3 时，对单芳烃的选择性急剧提高，分别达到 50.9 % 和 34.4 %。Pd/C 和 Pd/Al2O3 的催化活性归因于载体中存在中弱酸位点，为酚类吸附和脱氧提供了活性位点。此外，金属 Pd 位点激活 C-O 和 H2 键以进一步协助脱氧反应，从而诱导这些材料具有双功能。本研究为负载型催化剂在木质素热催化解聚过程中的双功能效应提供了有价值的见解。