Catalytic hydrogenation of aromatic nitro-compounds to corresponding aromatic amines is an environmental-friendly transformation for the production of dyes and pigments in industrial. Herein, an efficient low-coordinated Pt derived from Ni-Pt alloy archored on silica has been fabricated via dealloying process. Transmission electron microscopy (TEM) analysis confirmed an equivalent metal particle size to the reference dense Pt. Additionally, the characterizations revealed that the generation of unsaturated coordination in the resultant material leads to enhanced active surface area, increased fraction of low-coordinated and electron-enriched Pt. The as-prepared low-coordinated Pt catalyst was applied for liquid-phase m-dinitrobenzene (m-DNB) hydrogenation. Under the reaction conditions of ambient temperature, atmospheric pressure and m-DNB/Pt molar ratio of 140, both the m-DNB conversion and the selectivity to m-phenylenediamine (m-PDA) reached 99% within 2 h, superior to those observed over the reference dense Pt and the reported Pt-based catalysts. The enhanced catalytic properties were attributed to the promotional effect of unsaturated coordinated structure, which provided more Pt active sites with low coordination number and high electron density. This study demonstrates the importance of unsaturated coordination in metallic catalysts and establishes a powerful protocol for the design of an effective metal catalyst for the hydrogenation of a range of nitroaromatic compounds.
The hydrogenation of m -dinitrobenzene to m -phenylenediamine is a significant transformation for the synthesis of dyes and pigments in the fine chemical industry. Owing to the complexity of this reaction mechanism and negative effect of the first amino group on the reduction of the second nitro group, it is difficult to inhibit eminently the generation of side products and obtain m -phenylenediamine efficiently. Hence it is imperative to establish kinetic network and investigate the intrinsic kinetic parameters of this reaction for further optimization. In this study, a continuous flow system based on micro-packed bed reactor was developed and a kinetic model of the hydrogenation of m -dinitrobenzene was established successfully. The activation energies and pre-exponential factors were acquired using the kinetic network and the kinetic model exhibited reasonable fit for the transformation of each substance. Moreover, the influence of pressure was investigated, and the accuracy of kinetic model was validated by the comparison with the values in literature. This kinetic model enabled the accurate determination of kinetic parameters with Pt/C and Ni/SiO 2 catalysts, and provided the rate determining steps and characteristics of different catalysts for the process optimization.
危险品化学品经营许可证（带存储）