Nitrobenzene hydrogenation over Ni/TiO2 catalyst in vapour phase at atmospheric pressure: influence of preparation method

Highly dispersed nickel nanoparticles on supports such as ZrO2 and TiO2 were prepared by reductive deposition method using hydrazine as reducing agent and applied to nitrobenzene hydrogenation. The highlight of this work is to compare the characteristics and activity of these catalysts with the catalysts of the same composition prepared by impregnation method. All the catalysts were characterized by various techniques such as BET, H2 pulse chemisorption, TEM, XRD (crystalline nature), reduction behaviour (TPR) and state of nickel species (XPS). Ni/TiO2 catalyst prepared by reductive deposition method shows excellent conversion of nitrobenzene (99 %) to aniline. This is due to the presence of higher number of surface Ni species than other catalysts as evidenced by H2-chemisorption. TPR results reveal the formation of metallic Ni species in the reductive deposition method. XRD results suggest that the all catalytic systems show peaks corresponding to the supports only and not due to the metallic Ni because of its presence in highly dispersed form. The decrease in catalytic performance is observed during the time on stream might be due to coking of the catalyst by the reaction intermediate.