Hydrogenation of citral over nitrogen-doped carbon nanofibre-supported nickel catalyst

Herringbone carbon nanofibres (hCNFs) and nitrogen-doped carbon nanofibres with 0.115g/g (11.5%) of N (N-hCNFs) were used as the supports of nickel catalysts in the liquid phase hydrogenation of citral using toluene as a solvent. Over 96% selectivity to citronellal was obtained at 150 degrees C for both catalysts. At the reaction temperature of 200 degrees C, reasonable amounts of isopulegol were formed additionally as a result of citronellal cyclization. The catalytic activity of Ni nanoparticles was significantly improved when supported on CNFs doped with nitrogen. The hydrogenation of cis-citral was remarkably favoured over the trans-citral isomer regardless of the reaction temperature. The hydrogenation of citronellal under the same process conditions was also studied. The sequential-parallel reactions network for the hydrogenation of citral under the applied conditions was proposed and the kinetic constants were evaluated, assuming pseudo-first order kinetics of the hydrogenation process.