Rb-promoted Fe/CeO2 nanocatalyst for aniline conversion into azoxybenzene, DFT calculations and mechanism

IF 2.7 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY
Afsar Khan, Sa Xiao, Yu Xie, Savaş Kaya, Shah Zareen, Nisar Muhammad, Kousar Parveen and Dayong Xu
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Abstract

Selectivity control of aniline oxidation and low reactant conversion in traditional synthesis methods are great challenges, and it is desirable to develop a green, low-cost and highly efficient catalytic route toward value-added products. Herein, an Rb-promoted Fe/CeO2 nanocatalyst was prepared to understand the effects of Rb-promoter on the catalytic performance for the selective oxidation of aniline to azoxybenzene using H2O2 as an oxidant. The 0.1 M Rb-4% Fe/CeO2 (Rb–Fe/CeO2) catalyst showed a high aniline conversion of 100% with 91% selectivity of azoxybenzene. This is because the existence of Rb contributes to the electron transportation property, decreases activation energy and leads to lattice distortion of Fe/CeO2 and further formation of oxygen vacancies and Ce3+, which contributes to improving the activity of Fe/CeO2 nanocatalysts for aniline conversion reaction. The Rb used to modify Fe/CeO2 nanocatalysts can not only passivate the strong Brønsted acid sites and stability of Fe/CeO2 but also enhance the Fe dispersion and induce an electron-rich chemical environment for the supported Fe species and promote the activation of the substrate. All these effects lead to the desirable catalytic performance. The increased basic strength of the cation-promoted catalyst improves the electron density of the active Fe species, resulting in a higher yield of the desired aromatic azo compounds. This compensates for electronic deficiencies in the Fe, enhancing its catalytic activity without interference. Experiments were conducted as a function of catalyst loading (20–100 mg), time (2–24 h), temperature (25–100 °C), types of solvent and solvent amount (0.5–2 ml) in 50 ml round bottom flask with reflux condenser. Our work proposes a facile approach to develop and promote non-noble metal catalysts for the effective conversion of aniline into azoxybenzene under mild reaction conditions.

Abstract Image

rb催化苯胺转化为偶氮氧苯的Fe/CeO2纳米催化剂,DFT计算及机理
传统合成方法对苯胺氧化的选择性控制和低反应物转化率存在很大挑战,开发绿色、低成本、高效的高附加值产品催化途径是迫切需要的。本文制备了一种rb促进的Fe/CeO2纳米催化剂,以H2O2为氧化剂,了解rb促进剂对苯胺选择性氧化制偶氮氧苯催化性能的影响。0.1 M Rb-4% Fe/CeO2 (Rb-Fe /CeO2)催化剂的苯胺转化率为100%,偶氮氧苯的选择性为91%。这是因为Rb的存在提高了Fe/CeO2的电子传递性能,降低了活化能,导致Fe/CeO2的晶格畸变,进一步形成氧空位和Ce3+,从而提高了Fe/CeO2纳米催化剂在苯胺转化反应中的活性。用Rb修饰Fe/CeO2纳米催化剂,不仅钝化了Fe/CeO2的强Brønsted酸位,提高了Fe/CeO2的稳定性,而且增强了Fe的分散性,为负载的Fe物种诱导了富电子的化学环境,促进了底物的活化。所有这些影响导致了理想的催化性能。阳离子促进催化剂碱性强度的提高提高了活性Fe的电子密度,从而提高了所需芳香偶氮化合物的收率。这弥补了Fe中的电子缺陷,增强了其催化活性而不受干扰。在带回流冷凝器的50 ml圆底烧瓶中,对催化剂负载(20-100 mg)、时间(2-24 h)、温度(25-100℃)、溶剂类型和溶剂量(0.5-2 ml)进行了实验。我们的工作为开发和推广非贵金属催化剂在温和的反应条件下将苯胺有效转化为偶氮氧苯提供了一种简便的方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
New Journal of Chemistry
New Journal of Chemistry 化学-化学综合
CiteScore
5.30
自引率
6.10%
发文量
1832
审稿时长
2 months
期刊介绍: A journal for new directions in chemistry
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