Li Weijie, Deng Xin, Ma Yujie, Qin Bin, Dang Jian, Wu Guangjun, Yang Sihai, Li Landong
Key Laboratory of Advanced Energy Materials Chemistry of Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, P. R. China.
Department of Chemistry, The University of Manchester, Manchester, M13 9PL, U.K.
J Am Chem Soc. 2024 Oct 9;146(40):27600-27609. doi: 10.1021/jacs.4c08813. Epub 2024 Sep 26.
The selective oxidation of olefins by molecular oxygen holds great importance in the chemical industry due to its remarkable adaptability in constructing carbonyl compounds. Classical homogeneous Wacker oxidation with a complex system of PdCl-CuCl-HO is currently employed in the industrial production of acetaldehyde, which suffers from several key drawbacks. The development of alternative heterogeneous catalytic systems for Wacker-type oxidations has been hotly pursued for decades. Herein, we report a novel heterogeneous catalyst, namely Pd@FAU containing exclusive singular Pd sites confined in zeolite, showing remarkable performance in the Wacker-type oxidation of light olefins to the corresponding carbonyl compounds. Typically, stable propylene conversion rates of 2.3-3.5 mol/mol/min and an acetone selectivity of 75-89% can be achieved simultaneously, surpassing the state-of-the-art homogeneous Wacker oxidation systems. spectroscopic investigations disclose the spontaneous redox cycle of Pd-Pd-Pd in Pd@FAU during the reaction, in significant contrast to the known Pd-Pd-Pd redox cycle. Theoretical calculations reveal the unique reaction pathway and mechanism of Wacker-type oxidation over Pd@FAU, without the participation of water as the nucleophile. Overall, a novel heterogeneous catalyst of Pd@FAU has been developed for Wacker-type oxidations with the unique reaction mechanism fully interpreted. This study will contribute to more sustainable Wacker-type oxidations and further improve the current understanding of Pd redox catalysis.
由于分子氧对烯烃的选择性氧化在构建羰基化合物方面具有显著的适应性，因此在化学工业中具有重要意义。经典的均相Wacker氧化反应体系（PdCl-CuCl-HO）目前用于乙醛的工业生产，但存在几个关键缺点。几十年来，人们一直在积极开发用于Wacker型氧化反应的替代多相催化体系。在此，我们报道了一种新型多相催化剂，即Pd@FAU，其在沸石中含有独特的单原子钯位点，在将轻质烯烃Wacker型氧化为相应羰基化合物方面表现出卓越的性能。通常，可以同时实现2.3-3.5 mol/mol/min的稳定丙烯转化率和75-89%的丙酮选择性，超过了目前最先进的均相Wacker氧化体系。光谱研究揭示了反应过程中Pd@FAU中Pd-Pd-Pd的自发氧化还原循环，这与已知的Pd-Pd-Pd氧化还原循环形成了显著对比。理论计算揭示了Pd@FAU上Wacker型氧化反应的独特反应途径和机理，且反应过程中没有水作为亲核试剂参与。总的来说，我们开发了一种新型的Pd@FAU多相催化剂用于Wacker型氧化反应，并对其独特的反应机理进行了充分解释。这项研究将有助于实现更可持续的Wacker型氧化反应，并进一步加深我们目前对钯氧化还原催化的理解。
