Pd on imidazolium ionic liquid modified halloysite: A potent catalyst for the hydrogenation of nitro-compounds under mild reaction condition

Abstract

Cl-functionalized halloysite nanoclay was modified by multi imidazolium ionic liquids through successive reactions with imidazole, epichlorohydrin, tris(2-aminoethyl)amine and the as-prepared epoxide-functionalized imidazolium ionic liquid. The resultant compound was used as a support for the stabilization of Pd nanoparticles to furnish a heterogeneous catalyst for the hydrogenation of nitro-compounds in aqueous media. Investigation of the reaction variables confirmed that use of scant amount of the catalyst at ambient temperature and hydrogen pressure of 1 bar led to the formation of the hydrogenated products in high yields. Moreover, hydrogenation of the nitro compounds with carbonyl groups confirmed high selectivity of the catalyst towards hydrogenation of nitro group. Hot filtration test also demonstrated the true heterogeneous nature of the catalysis and recycling experiments indicated that the catalyst could be recovered and recycled for five successive reaction runs with slight Pd leaching and loss of the activity.