Jiao-Xuan Bai , Cong Xu , Jie-Ping Wang , Rui Guo , Wei-Ze Wu , Ting Lu , Guang-Yue Li , Ying-Hua Liang
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引用次数: 0
Abstract
The oxygen-oxidation of lignite to carboxylic acids (CAs) using environmentally friendly iron catalyst represents an efficient and clean technology for lignite utilization. However, the mechanism remains unclear due to the difficulty in observing the cleavage of chemical bonds and the challenge in capturing transient intermediates and radicals. In this work, the microscopic reaction mechanism of iron-catalytic oxidation of lignite was investigated by combining experimental and theoretical methods. Catalytic oxidation experiments revealed that water-soluble intermediates generated by solid-state lignite decomposition underwent a continuous carbon–carbon bond cleavage oxidation (including oxidative cleavage of aliphatic moieties and oxidative ring-opening of aromatic moieties) to form CAs with aldehyde moieties as the direct precursor. Based on molecular dynamics simulations and density functional theory, a reaction network from lignite to CAs was proposed. The iron catalyst was present in the form of iron-aqua complexes in the liquid phase and iron-phenyl complexes in the solid phase. These iron-aqua/iron-phenyl complexes could reduce the energies of oxidation reactions, promoting the cleavage of bridge bonds, the formation of o-quinones and the oxidation of aromatic moieties, thus accelerating elementary reactions for the formation of CAs. These findings provide a theoretical support for the oxidation of lignite and an in-depth insight into iron-catalytic mechanism.
使用环境友好型铁催化剂将褐煤氧氧化成羧酸(CAs)是一种高效、清洁的褐煤利用技术。然而,由于难以观察化学键的裂解以及捕捉瞬时中间产物和自由基的挑战,其机理仍不清楚。本研究结合实验和理论方法,研究了铁催化氧化褐煤的微观反应机理。催化氧化实验发现,固态褐煤分解产生的水溶性中间产物经过连续的碳碳键裂解氧化(包括脂肪族分子的氧化裂解和芳香族分子的氧化开环),形成以醛分子为直接前体的 CAs。根据分子动力学模拟和密度泛函理论,提出了从褐煤到 CAs 的反应网络。铁催化剂在液相中以铁-水络合物的形式存在,在固相中以铁-苯基络合物的形式存在。这些铁-水/铁-苯基络合物可以降低氧化反应的能量,促进桥键的裂解、-醌的形成和芳香分子的氧化,从而加速形成 CAs 的基本反应。这些发现为褐煤的氧化提供了理论支持,并深入揭示了铁催化机理。
期刊介绍:
The exploration of energy sources remains a critical matter of study. For the past nine decades, fuel has consistently held the forefront in primary research efforts within the field of energy science. This area of investigation encompasses a wide range of subjects, with a particular emphasis on emerging concerns like environmental factors and pollution.