الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 169 |  |  |
| | | from | 169 | | |
Abstract
The catalytic activities of CaCO3-, TiO2-, Al2O3 - and SiO2- supported Ni catalysts in reduction of p-nitrophenol to p-aminophenol were investigated. Nickel nanoparticles with different sizes and different structures were prepared by impregnation method using a solution of appropriate concentrations of NiCl2 in order to obtain catalysts with 2.5,5 and 10% nanonickel and reduced by hydrazine hydrate in the presence of sodium hydroxide. The nanoparticles have been used as a solid phase catalyst for the reduction of p-nitrophenol in the presence of hydrazine hydrate as reducing agent under the same conditions. The catalytic activities of the nickel nanoparticles increased with decreasing the particle size in the hydrogenation of p-nitrophenol to p-aminophenol. The present study showed that nanoparticles are not poisoned after their repeated use in reduction of p-nitrophenol to p-aminophenol.
The supported Ni catalysts were characterized by Scanning Electronic Microscopy and X-ray diffraction techniques before and after conducting the reduction reaction of p-nitrophenol.
The results showed that all catalysts contain crystalline nano nickel. The catalysts were active in reduction of p-nitrophenol into p-aminophenol. Compared to unsupported catalyst (nickel without support), the catalytic activity of supported catalyst(Ni/ TiO2, Ni/ CaCO3, Ni/ SiO2 and Ni/ Al2O3 catalysts) is much superior, irrespective of the support used in the reduction process .
The catalytic activities of the supported Ni catalysts were in an order of: Ni/ TiO2 > Ni/ CaCO3 > Ni/ SiO2> Ni/ Al2O3 > unsupported nickel. The acidity of the supported Ni catalysts was in an order of unsupported nickel > Ni/ Al2O3> Ni/ SiO2 > Ni/ CaCO3> Ni/ TiO2 .The acidity of the supported Ni catalyst significantly affected the catalytic activity.
We found in our study that one-step reduction of p-nitrophenol is higher in catalytic activity than stepwise process for the same quantity of p- nitrophenol.
Keywords:
p-Nitrophenol, p-Aminophenol, Nickel, Catalytic Hydrogenation, Catalyst, Nano-sized nickel, Nickel nanoparticles, Catalysis, Ni/ TiO2, Ni/ Al2O3, Ni/ SiO2, Ni/ CaCO3, Hydrazine Hydrate.