In the present work, an alkoxide sol-gel method was applied to prepare Pd/MgO catalysts. The sol-gel procedure was followed by supercritical drying (aerogels) or conventional drying (xerogels) in a furnace. These materials were compared with the impregnated samples. The Pd loading was 1 wt% in all the cases. The as-prepared catalysts were characterized by a set of physicochemical methods. Both the type of the Pd precursor and the preparation route were found to affect the porous structure of the materials as well as the dispersion of the palladium particles and their localization over the MgO support. Both the xerogel and incipient wetness impregnation methods lead to a narrower pore size distribution in comparison to the aerogel technique. The most dispersed particles with an average size of ∼ 2.0–2.2 nm were observed for the samples prepared by xerogel and impregnation methods. In the case of aerogel-prepared samples, metallic palladium particles possess bimodal distribution with average diameters of 4.3 and 8.4 nm. The best catalytic performance in acetylene hydrogenation to ethylene (50 % acetylene conversion at 37 °C with selectivity ∼60 %) was observed for the Pd/MgO catalyst prepared via the aerogel route using [Pd(NH)](NO). Compared to other samples, this material is characterized by relatively weak metal-support interactions and the availability of active sites for reactants, which ensures the kinetic mode of the hydrogenation reaction (E = 74.9 kJ/mol).

中文翻译：

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纳米晶Pd/MgO催化剂制备条件对其乙炔选择加氢性能的影响

本工作采用醇盐溶胶-凝胶法制备Pd/MgO催化剂。溶胶-凝胶程序之后是在炉中进行超临界干燥（气凝胶）或常规干燥（干凝胶）。将这些材料与浸渍样品进行比较。在所有情况下，Pd 负载量均为 1 wt%。通过一系列物理化学方法对所制备的催化剂进行了表征。研究发现 Pd 前驱体的类型和制备路线都会影响材料的多孔结构以及钯颗粒的分散及其在 MgO 载体上的定位。与气凝胶技术相比，干凝胶和初湿浸渍方法都会导致更窄的孔径分布。对于通过干凝胶和浸渍方法制备的样品，观察到最分散的颗粒，平均尺寸为 ∼ 2.0–2.2 nm。对于气凝胶制备的样品，金属钯颗粒具有双峰分布，平均直径为 4.3 和 8.4 nm。使用[Pd(NH)](NO)通过气凝胶路线制备的Pd/MgO催化剂在乙炔加氢制乙烯中观察到最佳催化性能（37℃下乙炔转化率为50%，选择性~60%）。与其他样品相比，该材料的特点是相对较弱的金属-载体相互作用和反应物活性位点的可用性，这保证了加氢反应的动力学模式（E = 74.9 kJ/mol）。