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Deactivation studies of bimetallic AuPd nanoparticles supported on MgO during selective aerobic oxidation of alcohols
Applied Catalysis A: General ( IF 5.5 ) Pub Date : 2017-08-05 , DOI: 10.1016/j.apcata.2017.07.045
Susana Guadix-Montero , Hamed Alshammari , Remco Dalebout , Ewa Nowicka , David J. Morgan , Greg Shaw , Qian He , Meenakshisundaram Sankar

Here we report the synthesis and characterisation of high surface area MgO prepared via the thermal decomposition of various magnesium precursors (MgCO3, Mg(OH)2 and MgC2O4). Bimetallic gold-palladium nanoalloy particles were supported on these MgO materials and were tested as catalysts for the solvent-free selective aerobic oxidation of benzyl alcohol to benzaldehyde. All these catalysts were found to be active and very selective (>97%) to the desired product (benzaldehyde). However, MgO prepared via the thermal decomposition of magnesium oxalate displayed the highest activity among all the magnesium oxide supports tested. Attempts were made to unravel the reasons for the deactivation of these catalysts using different characterisation techniques namely in situ XRD, XPS, ICP-MS, TEM, and TGA-MS. From the data obtained, it is clear that MgO undergoes phase changes from MgO to Mg(OH)2 and MgCO3 during catalyst preparation as well as during the catalytic reaction. Besides phase changes, strong adsorption of reactants and products on the catalyst surface, during the reaction, were also observed and washing the catalyst with organic solvents did not completely remove them. The phase change and catalyst poisoning were reversed through high temperature heat treatments. However, these processes led to the sintering of the metal nanoparticles. Moreover, substantial leaching of the support material (MgO) was also observed during the reaction. These latter two processes led to the irreversible deactivation of AuPd nanoparticles supported on MgO catalyst during the solvent-free selective aerobic oxidation of alcohols. Among the three different MgO supports studied in this article, an inverse correlation between the catalytic activity and Mg leaching has been observed. This article reports a deeper understanding of the mode of deactivation observed in metal nanoparticles supported on MgO during liquid phase reactions.



中文翻译:

乙醇选择性好氧氧化过程中负载在MgO上的双金属AuPd纳米颗粒的失活研究

在这里,我们报告了通过各种镁前体(MgCO 3,Mg(OH)2和MgC 2 O 4)的热分解制备的高表面积MgO的合成和表征。双金属金-钯纳米合金颗粒负载在这些MgO材料上,并被测试为无溶剂选择性好氧氧化苯甲醇为苯甲醛的催化剂。发现所有这些催化剂都具有活性,并且对所需产物(苯甲醛)具有很高的选择性(> 97%)。但是,MgO是通过草酸镁的热分解在所有测试的氧化镁载体中显示出最高的活性。尝试使用不同的表征技术(即原位XRD,XPS,ICP-MS,TEM和TGA-MS)阐明这些催化剂失活的原因。根据获得的数据,很明显MgO经历了从MgO到Mg(OH)2和MgCO 3的相变。在催化剂制备过程中以及在催化反应过程中。除了相变以外,在反应期间,还观察到反应物和产物在催化剂表面上的强吸附,并且用有机溶剂洗涤催化剂并不能完全除去它们。通过高温热处理可以逆转相变和催化剂中毒。然而,这些过程导致金属纳米颗粒的烧结。此外,在反应过程中还观察到载体材料(MgO)的大量浸出。后两种方法导致在无溶剂的醇选择性好氧氧化过程中,负载在MgO催化剂上的AuPd纳米颗粒不可逆地失活。在本文研究的三种不同的MgO支持中,已经观察到催化活性与Mg浸出之间呈负相关。本文报道了对液相反应过程中MgO上负载的金属纳米颗粒失活模式的更深入了解。

更新日期:2017-08-05
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