Catalytic reduction of 4-nitrophenol to 4-aminophenol over Ni/SiO2 catalyst made from reduced SiO2@NiPhy

NiO/SiO2 derived from the reduction of SiO2@NiPhy was investigated as a catalyst for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent. The various properties of the Ni catalysts were characterized by classical procedures that included XRD, SEM, FTIR, TPR, DSC/TGA, XRF and nitrogen adsorption–desorption procedures. The XRD results clearly showed that the nickel nanoparticles reacted with the silica support to give a nickel-phyllosilicate structure, SiO2@NiPhy. After a reduction step, the Ni in the SiO2@NiPhy was converted completely to a NiO face-centered cubic structure with a particle size of 8.9 nm. Both the SiO2@NiPhy and the Ni/SiO2 were examined for 4-nitrophenol reduction and the data indicated that the catalytic activity was related to the formation of NiO particles. The effects of catalyst dosage, the 4-NP/catalyst molar ratio, NaBH4 concentration, and temperature on the reaction were evaluated and a conversion yield of > 98% was obtained after optimization. The rate constant K1 and the activation energy obtained had values of 0.109 min−1 and 15.84 kJ mol−1 respectively.