Palladium decorated nickel and zinc ferrite spinel nanoparticles applied in aniline synthesis – development of magnetic catalysts

Abstract

Aniline is one of the most important chemical in the polyurethane industry and it is produced by the catalytic hydrogenation of nitrobenzene. The development of novel, multifunctional catalysts, which are easily recoverable from the reaction mixture is therefore of paramount importance. Transition metal-containing ferrites decorated with palladium were prepared by using a combination of sonochemical and combustion steps. First of all, magnetic ferrites were produced to be used in catalyst preparation as supports for palladium nanoparticles. On the surface of the ferrite particles palladium nanoparticles were deposited by applying ultrahigh sonication in an alcoholic phase. All in all, three magnetic catalysts, Pd/NiFe2O4, Pd/ZnFe2O4, and Pd/NiZnFeO4 have been created. The catalysts have been tested and their activity have been compared in nitrobenzene hydrogenation to synthesize aniline at four different temperatures, and 20 bar pressure. The most active catalysts were the Pd/ZnFe2O4 and Pd/NiZnFeO4 systems with which aniline yields of 99.2 and 92.8 n/n% were achieved after 3 h of hydrogenation, respectively. In contrast, by applying the Pd/NiFe2O4 catalyst, a significantly lower aniline yield was achieved. It was proved that, due to their magnetic properties, the prepared catalysts are easily removable from the reaction medium by using a magnetic field. Thus, catalysts with excellent properties have been successfully developed and tested in nitrobenzene hydrogenation.