Preparation Of Pt/C Catalysts And Catalytic Properties

Chlorinated organic compounds are harmful to the environment and human life because of their acute toxicity and thermal stablility. Currently, catalytic hydrogenation has been considered as a green and convenient approach to clear these chlorinated organic compounds. It can not only convert toxic substances into safer compounds, but also produce useful products from the chlorinated wastes. In the field of liquid phase heterogeneous reactions, actived cabrons have been used for a long time as an excellent support for catalytic nanoparticles, due to its various valuable properties:high surface area, robustness and chemical inertness, possibility to fine-tune the porosity and availability with different surface properties, such as hydrophilicity and interaction with the supported metal particles. In this thesis, the preparation and properties of actived cabrons supported platinum catalysts (Pt/C) has been studied.Firstly, colloidal platinum nanoparticles were prepared and then adsorpted to actived cabrons. The reuse stability of the Pt/C catalyst was investigated in the liquid-phase hydrodechlorination (HDC) of chlorobenzene. The surface oxygen groups and external surface area in actived cabrons impact on the catalytic HDC performance, (?) When the external surface area decrease, the activity of Pt/C catalysts become lower, (?) The oxygen surface groups (specially carboxylic) inhibit HDC, possibly through stabilizing interactions with the reactant(s) where the presence of an additional Cl substituent (in chlorobenzene) appears to strengthen the interaction with an oxidized active cabron surface leading to a more severe HDC inhibition. The deactivation was mainly due to the loss of the active metal, significantly reduce surface area and the adsorption of the HC1 on the catalyst.Secondly, a polyol process activated by microwave irradiation was implemented to prepare efficient Pt/C for hydrodechlorination of chlorobenzene. The particle size of Pt nanoparticles on the carbon support greatly depended on the irradiation time, the types of reductant, the amount of reducing agent, the molar ratio of NaOH and Pt, and the loading percentage of Pt. Small particle size and narrow size distribution of the catalysts were prepared. The catalysts could be reused for several times without losing their activities.Finally, Pt/C catalysts were prepared by microwave irradiation and treated at 473 K in Ar for 10 hours. The stability of Pt/C catalysts was studied, and the catalysts could be sustainable for more than two hundred circles under mild condition. The overall catalytic activity increased after heat treatment, which is tentatively related to the decreasing amount of oxygen of the actived cabrons and strengthen the interaction between cabrons and Pt particles. In addition, Pt/C catalysts exhibit a better performance in the hydrogenation of polychlorobenzenes, nitrobenzene, chloronitrobenzene, olefin and ?,?-unsaturated.