Nickel-based xerogel catalysts: Synthesis via fast sol-gel method and application in catalytic hydrogenation of p-nitrophenol to p-aminophenol

In order to investigate the roles of three-dimensional network structure and calcium on Ni catalysts, the Ni, Ni-Al 2 O 3 , Ni-Ca-Al 2 O 3 xerogel catalysts were successfully synthesized via the fast sol-gel process and chemical reduction method. The crystal structure of three different catalysts was observed with X-ray powder diffraction (XRD). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption-desorption were employed to investigate the role of network structure of xerogel catalysts and the size distribution of Ni nanoparticles. The catalyst composition was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) measurement and energy-dispersive X-ray spectroscopy (EDS). Temperature-programmed reduction (TPR) experiments were carried out to investigate the reducibility of nickel species and the interaction between nickel species and alumina. The catalytic hydrogenation of p -nitrophenol to p -aminophenol was investigated over the prepared nickel-based xerogel catalysts. The conversion of p -nitrophenol was monitored by UV spectrophotometry and high performance liquid chromatography (HPLC). The results show that the catalysts are highly selective for the conversion of p -nitrophenol to p -aminophenol and the order of catalytic activities of the catalysts is Ni   <   Ni-Al 2 O 3   <   Ni-Ca-Al 2 O 3 . The catalysts were recycled and were used to evaluate the reutilization.