Palladium Supported Catalysts for Nitrocyclohexane Hydrogenation to Cyclohexanone Oxime with High Selectivity



Different kinds of activated carbon- and carbon nanotube-supported palladium catalysts were investigated in the selective hydrogenation of nitrocyclohexane to cyclohexanone oxime under mild conditions. Carbon nanotube-supported palladium catalysts demonstrate better catalytic performance than activated carbon-supported palladium catalysts in general because of their mesoporous structures, which are favorable supports for the accessibility of the reactants to the active sites and the product desorption from the catalyst. Hydrogen chemisorption, transmission electron microscopy and X-ray photoelectron spectroscopy indicate that higher composition of Pd+ on the catalyst surface, larger palladium surface area, and better palladium dispersion contribute to an increase in the activity and selectivity toward cyclohexanone oxime. In addition, single-wall carbon nanotube-supported palladium catalysts give the best result of 97.7 % conversion of nitrocyclohexane and 97.4 % selectivity toward cyclohexanone oxime. On the basis of the results of GC–MS and the designed experiments, a possible reaction scheme was proposed.