| Halogenated anilines are important intermediates for synthesis of organic fine chemicals, such as dyes, drugs, herbicides, and pesticides. The main synthesis routes to these chloroanilines involve reduction of the corresponding nitrocompounds through a metal-acid system or selectivity hydrogenation over metal catalysts. The hydrogenation routs is of great industrial interest in recent years, owing to lower impact on the environment since no acid effluents or metal oxides residue are produced. However, the hydrogenation process is difficult because of extensive dehalogenation during the catalytic reduction of the compound and increased the costs. The improvment of the the catalytic activity, selectivity and stability were the most important factors for the hydrogenation process.On base of catalytic hydrogenation system, the assemble catalyst with particle size controlled are selected as catalyst for the study of liquid phase hydrogenation of halogenated nitrobenzenes to produce halogenated anilines in the present thesis, expecting to solve the key problem of dehalogenation in catalytic hydrogenation reaction and improve the catalytic activity and stability. Assembled catalyst was obtained by capturing the "unprotected" Pt nanoclusters on the on the supports. Compared with traditional methods, this process is simple, easy to operate and with high reproducibility. The catalyst exhibited high selectivity, activity and catalyst life when used for the hydrogenation of o-CNB. Main points of this dissertation are listed as follows.1,The homogeneous platinum nanoclusters catalyst was produced by decomposing the organometallic Pt2(dba)3 while propylene carbonate used as solvent, hydrogen as reductant. Different from other soluble nanoclusters catalyst, this catalyst would not agglomerate for three months even without stabilizer. DLVO theory proved that the stability would be improved by using the solvent with high dielectric constant. Its catalytic performance was evaluated by liquid-phase hydrogenation of p-chloronitrobenzene. It was found that no dehalogenation was produced in the reaction. Besides, the reaction kinetic was studied using the homogeneous platinum nanoclusters catalyst. The result shows that the reaction rate is zero-order in p-chloronitrobenzene concentration and first-order with respect to hydrogen pressure, and the activation energy is 58.6kJ/mol.2,The assembled Pt catalyst was prepared using activated carbon as a support to capture "unprotected" Pt nanoparticles, obtained from the decomposition of Pt2(dba)3 (dba=dibenzene acetone). The size of the Pt nanoparticles depended on the decomposition pressure, smaller nanoparticles could be get when the Pt2(dba)3 was decomposed on high pressure. The catalytic activity was evaluated by the liquid-phase hydrogenation of o-chloronitrobenzene. It was found that the selectivity of o-chloroaniline was 99.9%, and the highest TOF was 40.4s-1 when the reaction was carried on 1.0MPa, 60℃, n(o-CNB:Pt)= 12000. This could be interpreted by size of nanoparticles, electronic effect and the geometric effect between the nanocluster and supports.3,The Pd-Pt/C bimetallic catalyst was prepared by this method. XPS results shown that the BE of Pd3d5/2 shift from 335.2eV to 336.8eV and the BE of Pt4f7/2 from 71.5eV to 72.2eV. This indicates that the electron transferd from Pd and Pt to the activated carbon, and Pd-Pt nanocluster displaying postivite-charged states. With the postivite-charged states the -NO2 was activated easilier, and the exhibited high cativity. It was found that when Pd: Pt=2:1, more electon was transfer to the supports, and higher catalytic activity was got.In conclusion, the obtained facts show that there are many advantages such as simple,green for this method. The catalyst prepared by this method show good catalytic activity and selectivity for the hydrogenation of o-chloronitrobenzene. Those might be provided new opportunities and alternatives of great interest for this kind of hydrogenation reduction reaction.
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