Selective hydrogenation of nitrocyclohexane to cyclohexanone oxime by alumina-supported gold cluster catalysts

Abstract Metal oxides (Al 2 O 3 , SiO 2 , MgO)-supported Au cluster catalysts prepared by colloid deposition method and well established Au/TiO 2 prepared by deposition–precipitation method were tested for the selective reduction of nitrocyclohexane into cyclohexanone oxime. The activity and selectivity depended strongly on the size of Au and support material. Au/Al 2 O 3 with smaller Au particle size (2.5 nm) was the most effective catalyst, exhibiting a high cyclohexanone oxime yield (86%) under mild condition (0.6 MPa H 2 , 100 °C). To study the origin of support and size effects, in situ FTIR experiments for OH/D 2 exchange reaction and nitrobenzene adsorption combined with poisoning experiments using pyridine and acetic acid were carried out. It is suggested that cooperation of coordinatively unsaturated Au atoms and the acid–base pair site (Al δ+ –O δ− site) plays an important role in H 2 dissociation step. Al δ+ –O δ− site also acts as the adsorption site of the nitro group.