de Abreu Wiury C, Garcia Marco A S, Nicolodi Sabrina, de Moura Carla V R, de Moura Edmilson M
Departamento de Química, Universidade Federal do Piauí Teresina 64049-550 PI Brazil
Instituto Federal do Maranhão Buriticupu 65393-000 MA Brazil.
RSC Adv. 2018 Jan 22;8(7):3903-3909. doi: 10.1039/c7ra13590d. eCollection 2018 Jan 16.
Gold nanoparticles have shown excellent activity for selective oxidation of alcohols; such catalytic systems are highly dependent on the initial activation of the substrates, which must occur on the catalyst surface in heterogeneous catalysts. In many cases, an extra base addition is required, although the basicity of the support may also be of significant importance. Here, we explored the intrinsic basicity of magnesium-based enrichments on CoFeO magnetic nanoparticles for the oxidation of benzyl alcohol using molecular oxygen as oxidant. The MgO and Mg(OH) enrichments enabled gold impregnation, which was not possible on the bare CoFeO nanoparticles. The Au/MgO/CoFeO and Au/Mg(OH)/CoFeO catalysts reached 42% and 18% conversion, respectively without base promotion, in 2.5 hour and 2 bar of O. When the catalysts were tested with sub-stoichiometric amounts of base, they became more active (>70% of conversion) and stable in successive recycling experiments without metal leaching, under the same reaction conditions. We also showed the oxide phases of the enrichments performed using Rietveld refinements and how the Mg(OH) phase interferes with the activity of MgO-based materials.
金纳米颗粒在醇的选择性氧化中表现出优异的活性；此类催化体系高度依赖于底物的初始活化，而异相催化剂中这一过程必须在催化剂表面发生。在许多情况下，尽管载体的碱性可能也很重要，但仍需要额外添加碱。在此，我们利用分子氧作为氧化剂，探索了钴铁氧体磁性纳米颗粒上基于镁的富集物对苯甲醇氧化的固有碱性。氧化镁和氢氧化镁富集物能够实现金的浸渍，而在裸露的钴铁氧体纳米颗粒上则无法实现。在2.5小时和2巴氧气条件下，金/氧化镁/钴铁氧体和金/氢氧化镁/钴铁氧体催化剂在无碱促进的情况下分别达到了42%和18%的转化率。当使用亚化学计量的碱对催化剂进行测试时，在相同反应条件下，它们在连续循环实验中变得更具活性（转化率>70%）且稳定，无金属浸出。我们还通过Rietveld精修展示了富集物的氧化物相，以及氢氧化镁相如何影响氧化镁基材料的活性。
