Selective hydrogenation of o-chloronitrobenzene over palladium supported nanotubular titanium dioxide derived catalysts

Titania derived nanotubes were synthesized by treating P-25 Degussa TiO2 with a concentrated (18 M) KOH solution. Ageing the material in KOH solution for 2 days resulted in formation of tubular titania and Raman analysis revealed that the material has a titanate structure. The synthesized material was used as a catalyst support for the hydrogenation of ortho-chloronitrobenzene (o-CNB) with Pd as the active phase. The vapour-phase hydrogenation of o-CNB was carried out in ethanol at 523 K and atmospheric pressure over a Pd/TiO2 derived nanotube catalyst (Pd/TiO2-M). Pd/TiO2-M gave complete conversion (100%) of o-CNB with the selectivity to ortho-chloroaniline (o-CAN) of 86%. The stability of the Pd/TiO2-M catalyst was tested over 5 h during which time the conversion slowly dropped to 80% (selectivity 93%) due to catalyst poisoning. TPR analysis revealed the existence of a strong palladium-support interaction and this was found to be crucial to the overall activity of the catalyst.