One-pot depolymerization of lignin to well-defined chemicals and their further deoxygenation to arenes are extremely attractive. Based on our previous results that Nb₂O₅ species can promote the cleavage of C–O bonds and the synergistic effect between Ru and Nb₂O₅ species led to the direct transformation of lignin into arenes over a Ru/Nb₂O₅ catalyst [Nat. Commun., 2017, 8, 161041], the importance and influence of ruthenium particle size need to be further studied. Herein, we report the different performances of Ru/NbOPO₄ catalysts with various Ru particle sizes in the hydrogenolysis of a lignin model compound. This study shows that the catalytic activities and the product distributions strongly depend on the size of Ru nanoparticles (NPs): Ru NPs with smaller diameters (1.2 and 1.8 nm) have a higher activity for the cleavage of C_aliphatic–O and C_aromatic–O bonds, whereas Ru NPs with larger diameters (2.5 and 5.3 nm) show a much lower activity for C–O cleavage, especially for the C_aromatic–O bond, resulting in totally different product distributions. Density functional theory (DFT) calculations revealed that the presence of step and edge sites in smaller Ru particles can significantly lower the barriers for both C_aromatic–O and C_aliphatic–O bond cleavage. This study provides a new way for catalyst design towards highly efficient and selective hydrogenolysis of lignin to useful aromatic chemicals.

中文翻译：

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钌纳米粒子在β-O-4木质素模型化合物氢解中的尺寸依赖性催化性能†

木质素的一锅解聚为定义明确的化学物质以及它们进一步脱氧为芳烃的方法非常有吸引力。根据我们先前的结果，Nb ₂ O ₅物种可以促进C–O键的裂解，Ru和Nb ₂ O ₅物种之间的协同作用导致木质素在Ru / Nb ₂ O ₅催化剂上直接转化为芳烃。[ Nat。公社 ，2017，8，161041]，的重要性和钌粒径需要影响待进一步研究。在此，我们报告Ru / NbOPO ₄的不同性能木质素模型化合物的氢解中具有不同Ru粒径的催化剂。这项研究表明，催化活性和产物分布在很大程度上取决于Ru纳米颗粒（NPs）的尺寸：直径较小（1.2和1.8 nm）的Ru NPs对C_脂肪族-O和C_{芳族化合物}-的裂解具有更高的活性。O键，而直径较大（2.5和5.3 nm）的Ru NPs对C–O裂解的活性低得多，特别是对于C_芳香族–O键的裂解，导致产物分布完全不同。密度泛函理论（DFT）计算表明，较小的Ru颗粒中台阶和边缘部位的存在可以显着降低C_芳族-O和C的势垒_脂族–O键裂解。这项研究为木质素高效和选择性氢解为有用的芳香族化合物提供了一种新的催化剂设计方法。