Preparation Of The Supported AUPD Catalysts And Their Catalytic Properties In4-Nitrophenol Reduction

The preparation reaction of aromatic amine substance from aromatic nitro compounds becomes more and more important in many domains such as fine chemicals, fuel and medicine. Catalytic synthesis of the aromatic amine materials over catalysts is one of the most common methods. Meanwhile, this catalytic reduction method is the focus of recent research because of its advantages such as easy operation and low environmental pollution. Among these, the preparation of4-aminphenol (4-AP) reducted from4-nitrophenol (4-NP) is an representative reaction. So in this thesis, we synthesized two supported precious metal catalysts and studied them in the reduction of4-NP to4-AP. Main researches are included as follows:(1) Through the screening process of AuPd bimetallic colloid and carriers, the AuPd/MgO supported catalyst is prepared and studied its catalytic reduction of4-NP. The experimental results show as follows:the AuPd/MgO catalyst has an average particle size of4.91nm with a bimetallic loading of1.22%. AuPd/MgO catalyst has a good catalytic activity and has a high reaction rate constant6.41×10-2s-1in the reduction of4-NP, which is higher than that of most catalysts reported in literatures. What is more, reaction temperature, the quantity of reducing agent and the amount of catalysts have obvious effects on the catalytic reduction of4-NP. Taking the comprehensive factors of both economic and reaction rate in accoount, an optimal reaction condition is choosed. Finally, through the recycling experiments, good stability of the AuPd/MgO catalyst is confirmed.(2) Graphene is choosed as the carrier and the bimetallic catalyst AuPd/graphene is obtained. The reduction reaction of4-NP is investigated over the AuPd/graphene catalyst. The results show as follows:the AuPd/graphene catalyst has a best molar ratio of1:3and the graphene has a most suitable volume of3ml. And the AuPd/graphene catalyst has an average particle size3.03nm with a metal loading of9.1%. Due to the existance of graphene, AuPd/graphene shows better catalytic property than AuPd/MgO, which gives a larger TOF value of26.67min-1(AuPd/MgO:TOF9.76min-1). Reaction temperature and the amount of catalyst also have impact on the reduction reaction. Moreover, the reduction of4-NP has a lower reaction activation energy over AuPd/graphene. So the catalyst activity is not very sensitive to the changes in temperature. The present catalyst shows good activity in a wide temperature range. And it is expected to exhibit good activity in other reaction systems.