Martinez Jordan Santiago, Mazarío Jaime, Gutiérrez-Tarriño Silvia, Galdeano-Ruano Carmen, Gaona-Miguélez José, Domine Marcelo E, Oña-Burgos Pascual
Instituto de Tecnología Química (ITQ) Universitat Politécnica de Valencia-CSIC, Av. de los Naranjos - s/n, 46022 Valencia, Spain.
Department of Chemistry and Physics, Research Centre CIAIMBITAL, University of Almería, Ctra. Sacramento, s/n, 04120 Almería, Spain.
Dalton Trans. 2022 Nov 29;51(46):17567-17578. doi: 10.1039/d2dt02831j.
Alcohol oxidation is one of the most important industrial organic reactions. Traditionally, the best-suited catalysts are Pd, Pt and Au supported nanoparticles. The research community has recently started developing strategies for synthesizing carbon-supported Pd/Au bimetallic nanoparticles (NPs), leading to higher activities and selectivities. However, the metallic active species in these catalysts are usually generated using sodium borohydride (NaBH), which is not synthetically easy to reproduce. In fact, minor modifications in pH, concentration and/or other parameters have a prominent effect on the nature of the promoted material. In this work, a robust process involving dihydrogen flow (H) at 200 °C as a reducing agent for synthesizing Pd/Au supported bimetallic materials was considered an alternative to the common pathway. The physicochemical properties of the materials derived from different reducing reagents and of varying composition ranges were studied using HR-TEM, XRD, CO chemisorption, and XPS. Their stability and activity were also tested for benzyl alcohol oxidation to benzaldehyde under mild reaction conditions (60 °C, water as the solvent, and PO = 1.5 bar). Notably, a catalyst from the hydrogen reduction process with a metal composition of 0.8%Pd-0.2%Au/C consisting of bimetallic clusters (≈1.5 nm) proved to be the best material (C = 94%, S = 99%). Catalytic performances were strongly correlated with structural properties, such as nanoparticle size and distribution, which, in turn, were affected by the reduction step and the metal composition range. Finally, the influence of oxidants on benzyl alcohol oxidation has also been studied, along with the first approach for the tandem formation of HO coupled with alcohol oxidation.
酒精氧化是最重要的工业有机反应之一。传统上，最适合的催化剂是负载型钯、铂和金纳米颗粒。最近，研究界开始开发合成碳负载钯/金双金属纳米颗粒（NPs）的策略，以实现更高的活性和选择性。然而，这些催化剂中的金属活性物种通常使用硼氢化钠（NaBH）生成，其合成过程不易重现。事实上，pH值、浓度和/或其他参数的微小变化对促进材料的性质有显著影响。在这项工作中，一种在200℃下使用氢气流（H₂）作为还原剂合成负载钯/金双金属材料的稳健方法被认为是一种替代常规途径的方法。使用高分辨透射电子显微镜（HR-TEM）、X射线衍射（XRD）、一氧化碳化学吸附和X射线光电子能谱（XPS）研究了来自不同还原剂且组成范围不同的材料的物理化学性质。在温和的反应条件（60℃、水为溶剂、PO₂ = 1.5 bar）下，还测试了它们对苯甲醇氧化为苯甲醛的稳定性和活性。值得注意的是，由双金属簇（≈1.5 nm）组成的金属组成为0.8%Pd-0.2%Au/C的氢还原过程催化剂被证明是最佳材料（转化率C = 94%，选择性S = 99%）。催化性能与结构性质密切相关，如纳米颗粒尺寸和分布，而这些又受还原步骤和金属组成范围的影响。最后，还研究了氧化剂对苯甲醇氧化的影响，以及与醇氧化耦合的过氧化氢串联生成的初步方法。
