Preparation Of Novel Nickel-based Catalyst For P-Chloronitrobenzene Hydrogenation

p-Chloroaniline (p-CA) is an important intermediate in the chemical industry. Normally,p-Chloroaniline is prepared by hydrogenation of p-chloronitrobenzene (p-CNB), which is enviromentally friendly and p-Chloroaniline was given with high selectivity and high yield. Thus, the selective catalytic hydrogenation of p-chloronitrobenzene to p-Chloroaniline is of great important because of some merits, such as enviromentally friendly, purer product, high output etc. p-CA can be obtained through the continuous hydrogenation of p-CNB by Raney Ni. However, it is difficult to conserve and transport because of high activity of Raney Ni which can easily lead to burnt. Therefore, how to obtain a novel effective, economic, environment beginning catalyst is a research focus during a long period of investigation.The objective of the dissertation work was exploring a novel method to prepare highly dispersed nickel catalysts with enhanced catalytic activity, which was studied from two main aspects:choice for support and organic modification of nickel active component. The samples were prepared by different methods and characterized using powder X-ray diffraction (XRD), high-resolution transmission electron micrography (TEM), scanning electron micrography (SEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), scanning force microscopy (SFM) and fourier transform infrared spectroscopy (FTIR). The prepared catalysts were evaluated in the hydrogenation reaction of p-CNB.In the study of choice for support, denoted as EG, with special structural and textural properties was used as support for novel NiB catalysts. EG and the catalysts were measured by BET,SEM,TEM,SAED,ICP. The results show that EG is a macroporous and inert material and the NiB clusters of the catalysts are well dispersed on EG with the homogeneous size. The effect of pretreatment of EG on the catalytic performance of NiB/EG catalyst was researched, and an optimal preparation procedure adjusting for industrial manufacture was developed. The as-prepared catalyst showed high catalytic activity in the hydrogenation of p-CNB, which could be attributed to the unique properties of EG, higher specific surface area and wide pore size, which could not only promote a higher NiB dispersion but also favor diffusion of product molecular in the catalyst.Amorphous NiB supported on microcapsule with extremely small size was synthesized by chemical reduction. The morphology and structure of the samples were characterized by high resolution transmission electron microscopy, select area electron diffraction. The grain size of amorphous Ni was below 10 nm, and the distribution of the components was regular. NiB/capsule exhibited a higher hydrogenation activity than commercial Raney Ni. This was ascribed to the high surface area of the microcapsule and available groups of PVP to anchor the active catalyst. The active Ni was highly dispersed on the support, and the surface effects of the small nanoparticles played a key role in hydrogenation.Both the porous Al2O3 layer and epoxy resin were used as support for a new composite catalysts. The surface of supports were pretreated and modified by previous treatment processes. Then, the silane coupling agent self-assembled monolayers were introduced on the support surface to improve the microscopic surface state of support effectively, which made the polypyrrle films deposited on the surface of support. The porous structure of polypyrrole can provide the higer surface area for the amorphous NiB catalysts loading. The new NiB supported on film composites have been pursued with the hope of delivering polypyrrle properties to a synergistic host, used as catalyst material for the hydrogenation ofp-CNB.Chemical reduction is one of the feasible and convenient methods for preparing nano-scale metal clusters. Nano-scale metal clusters could be obtained through dispersal in a liquid medium using surfactant-stabilized methods. In theroy, NiCoB-PEG catalyst was prepared by the mixing of Ni2+ with Co2+salt solution containing PEG and a sequential reduction with KBH4. The catalyst had been investigated by XRD, HRTEM and SAED. The results revealed that NiCoB-PEG catalyst exhibited better performance than Raney Ni in the hydrogenation of p-CNB. This was because that NiCoB-PEG had small particles and high dispersion. Ni species could disperse on the surface of the support to a higher extent due to the separative effect of the surfactant.