Preparation Of Copper-nickel-based Nanocatalysts And Its Catalytic Performance For 4-nitrophenol

4-nitrophenol(4-NP), a major class of environmental contaminant, is toxicant, high stability and low efficiency of degradation under natural conditions. 4-NP hydrogenation reduction can be obtained for 4-aminophenol(4-AP), a kind of important organic intermediate. Although the reaction of conversion of 4-NP to 4-AP is thermodynamically feasible, it is kinetically restricted in the absence of a catalyst. Noble metal nanoparticles(NPs) have been studied for a long time as the catalyst in conversion of 4-NP to 4-AP. However, noble metal catalysts are expensive and scarce. It is essential to study a new kind of cheap catalyst to catalyze the hydrogenation reduction of 4-NP. In this work, we have designed several kinds of catalyst for the hydrogenation reduction of 4-NP. The main research contents and conclusions are as follows:(1) Preparation of Ni/C hybrid nanosheets and their catalytic properties: In this paper, the Ni/C nanosheets were prepared by decomposing nickel oleate(NiOA), with the template of sodium sulfate. Three catalysts(Ni/C-400, Ni/C-500 and Ni/C-600) were obtained under different calcination temperature. The average nickel sizes of Ni/C-400, Ni/C-500 and Ni/C-600 were of 2.63 nm, 2.78 nm and 2.84 nm, respectively. In the Ni/C hybrid nanosheets, carbon nanosheets can effectively inhibit the growth of the Ni NPs. At room temperature, the catalyst was used to catalyze the reaction of 4-NP. The apparent rate constants(kapp) of Ni/C-400, Ni/C-500, and Ni/C-600 are 0.019 min-1, 0.175 min-1 and 1.239 min-1, respectively. The catalytic activity of Ni/C-600 catalyst for the hydrogenation of 4-NP was higher than that of the noble metals reported in some literatures.(2) Preparation of carbon-encapsulated NiO and CuO hollow nanospheres(HNSs) and their catalytic properties: Ni/C and Cu/C nanosheets were prepared by decomposing nickel oleate(NiOA) and copper oleate(CuOA). Then the metal NPs/C hybrid nanosheets were heated in air for preparation of carbon-encapsulated metal oxide HNSs. The results of N2 adsorption-desorption noted that both metal oxides HNSs and the carbon shell had mesoporous pores. Therefore, small molecules can access the inner space of the whole HNSs@C, which facilitates their catalytic applications. In addition, the structural stability of metal oxide HNSs can be enhanced by the coated carbon. At room temperature, the catalyst was used to catalyze the reaction of 4-NP. The kapp of carbon-encapsulated NiO and CuO HNSs is 0.4118 min-1 and 0.5984 min-1, respectively.(3) Preparation of carbon-encapsulated NiO/CuO hybrid HNSs and their catalytic properties: It is reported that the NiO/CuO mixed oxide can display enhanced properties. Therefore, in this paper, carbon-encapsulated NiO/CuO mixed HNSs is prepared by the addition of nickel and copper sources in the preparation process. The results of TEM-mapping show that, in the HNSs nanostructure, the distributions of Cu, Ni and O elements are the very same. Similarly, the results of N2 adsorption-desorption noted that both metal oxides HNSs and the carbon shell had mesoporous pores. The kapp of carbon-encapsulated NiO/CuO HNSs for the reaction of 4-NP is 1.5032 min-1.