The current production of aromatic hydrocarbons, crucial in fuel and polymer production, relies heavily on fossil resources. Finding carbon-neutral alternatives is necessary to address the current environmental challenges. Lignin emerges as a promising source for bio-based aromatics. However, existing catalytic hydrodeoxygenation processes often yield mixtures of cycloalkanes and aromatics. In our study, we investigated a selective route to obtain aromatics from phenols using the keto-tautomer reaction mechanism. According to this mechanism, the initial hydrogenation of the carbonyl group while a phenol compound is in its keto form leads to the removal of the hydroxyl group while preserving the aromatic structure. Our experiments focused on -cresol, guaiacol, and mequinol, employing Pd/C and Ru/C catalysts. Experimental results revealed that aromatic hydrocarbons were favored during the hydrodeoxygenation of -cresol and mequinol, while steric effects from the methoxy group hindered guaiacol's conversion. Furthermore, we observed significantly higher conversion rates when using hydrocarbon solvents compared to water, with toluene yields of up to 13.5 % by mass achieved on Pd/C. Our computational simulations confirmed the feasibility of the keto-tautomer mechanism on Pd cluster surfaces, similar to those found in Pd/C catalysts.

中文翻译：

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溶剂在单体酚选择性加氢脱氧中的作用


目前对燃料和聚合物生产至关重要的芳香烃生产严重依赖化石资源。寻找碳中和替代品对于应对当前的环境挑战是必要的。木质素成为生物基芳烃的有前景的来源。然而，现有的催化加氢脱氧工艺常常产生环烷烃和芳烃的混合物。在我们的研究中，我们研究了利用酮互变异构体反应机制从苯酚中获取芳族化合物的选择性路线。根据该机理，当苯酚化合物处于酮形式时，羰基的初始氢化导致羟基的去除，同时保留芳香结构。我们的实验主要针对甲酚、愈创木酚和对甲酚，采用 Pd/C 和 Ru/C 催化剂。实验结果表明，在对甲酚和对甲酚的加氢脱氧过程中，有利于芳香烃的生成，而甲氧基的空间效应阻碍了愈创木酚的转化。此外，我们观察到，与水相比，使用烃溶剂时的转化率明显更高，在 Pd/C 上甲苯的产率高达 13.5%（按质量计）。我们的计算模拟证实了 Pd 簇表面酮互变异构体机制的可行性，类似于 Pd/C 催化剂中发现的机制。