In Situ Generation of Cu0 Supported on TiO2 Aerogel as a Catalyst for the Vapour Phase Hydrogenation of Nitrobenzene to Aniline

Abstract

This study is first to demonstrate a new strategy to synthesize Cu nanoparticles (NPs) supported on TiO2 (Cu@TiO2) catalyst towards the vapor phase hydrogenation of nitrobenzene. The experimental design involved the four different loadings (10, 15, 20 and 30 wt%) of Cu NPs onto the TiO2 aerogel to produce a complex with high surface area and increased pore volume. The developed catalysts were characterized using N2 physisorption analysis, powder-XRD studies, H2-temperature programmed reduction, field emission scanning electron microscopy–EDAX, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The characterisation results specified that the surface area, mesoporosity, the effective dispersion of Cu nanoparticles onto the TiO2 support exerted a significant influence on their catalytic activities. Further, it was found that the resulted process led to the complete in situ reduction of Cu2+ to Cu0, and fine dispersion of Cu0 NPs on the surface of TiO2. Thus, no further pre-reduction of the catalyst was required. The optimized 20 wt% Cu@TiO2 catalyst achieved about 94% nitrobenzene conversion with maximum aniline selectivity (> 98%), with enhanced stability where the catalyst was found to be active up to 15 h of continuous catalytic reactions. From the study, it is found that this approach is promising and provides insights into the fundamental understanding on the importance of aerogel materials as versatile catalysts.