Substrate-Support Interactions Mediate Hydrogenation of Phenolic Compounds by Pd/CeO2 Nanorods
Substrate-Support Interactions Mediate Hydrogenation of Phenolic Compounds by Pd/CeO2 Nanorods
复制标题
DOI：
10.1021/acsanm.0c02381
复制
发表时间：
2020-11-25
影响因子：
5.9
通讯作者：
Venditti, Vincenzo
中科院分区：
文献类型：
--
作者：
An, Yeongseo;Naik, Pranjali;Venditti, Vincenzo
二氧化铈负载的钯(Pd/CeO2)催化剂能够在温和的温度和压力下催化酚类化合物选择性加氢生成环己酮和环己醇，近年来引起了人们的极大关注。然而，CeO_2促进催化转化的机理仍不清楚。用溶液核磁共振方法研究了酚类化合物在Pd/CeO2催化剂表面的吸附。结果表明，羟基苯酚比未衍生化的苯酚和甲氧基苯酚更有效地吸附在载体上，并且2位含氧的苯酚衍生物(即2-羟基苯酚和2-甲氧基苯酚)与Pd/CeO2的Pd位形成非常稳定的相互作用。加氢动力学分析表明，催化转化与底物与CeO2载体形成相互作用的能力呈线性关系，并被稳定的底物-钯加合物的形成所抑制。我们的数据表明CeO2-底物相互作用比Pd-底物相互作用更有效地催化苯酚加氢，并解释了Pd/CeO2优异的催化性能。
Ceria-supported palladium (Pd/CeO2) has spawned significant attention in recent years due to its ability to catalyze selective hydrogenation of phenolic compounds to cyclohexanones and cyclohexanols at a mild temperature and pressure. However, the mechanistic basis by which ceria enhances catalytic conversion is still unclear. Here, we use the increase in the C-13 transverse relaxation rate upon the addition of nanoparticles (NPs) (C-13 Delta R-2) to investigate the adsorption of phenolic compounds on the surface of the Pd/CeO2 catalyst by solution NMR We show that hydroxyphenols adsorb on the support more efficiently than underivatized phenol and methoxyphenols and that phenol derivatives with an oxygen atom at position 2 (i.e., 2-hydroxyphenol and 2-methoxyphenol) form very stable interactions with the Pd site of Pd/CeO2. An analysis of the kinetics of hydrogenation revealed that catalytic conversion is linearly correlated with the ability of the substrate to form interactions with the CeO2 support and is inhibited by the formation of stable substrate-Pd adducts. Our data suggest that CeO2-substrate interactions mediate phenol hydrogenation more efficiently than Pd-substrate interactions and explain the exceptional catalytic performance reported for Pd/CeO2.