Iridium(0) nanoparticles dispersed in zeolite framework: A highly active and long-lived green nanocatalyst for the hydrogenation of neat aromatics at room temperature

Abstract

The complete hydrogenation of aromatic molecules is one of the key transformation employed in the synthetic and petroleum chemistry. Described herein is a new catalytic nanomaterial for the hydrogenation of neat aromatics under mild conditions. A novel nanocatalyst, consisting of iridium(0) nanoparticles stabilized by zeolite with FAU framework could reproducibly been prepared from the reduction of iridium(III)-exchanged zeolite in an aqueous sodium borohydride solution at room temperature and characterized by ICP-MS, P-XRD, HRTEM, XPS, N2-Ads.-Des., and P(C6H11)3 poisoning. The results reveal the formation of iridium(0) nanoparticles of 5.8 ± 2.1 nm size dispersed on the external surface along with iridium(0) nanolclusters in cavities of zeolite-Y whereby the host matrix remains intact. The resulting iridium(0) nanoparticles were employed as heterogeneous catalyst in the hydrogenation of various aromatic substrates (benzene, toluene, o-xylene and mesitylene) in the solvent-free systems at room temperature and 3bar initial H2 pressure. They are highly active catalyst in the hydrogenation of neat aromatics, such as they can completely hydrogenate benzene to cyclohexane with an initial turnover frequency value of TOF=3215h−1. Moreover, they show high durability against to leaching and sintering throughout the catalytic runs, which make them reusable catalyst. More importantly, testing the catalytic lifetime of our iridium(0) nanoparticles showed that they provide previously unprecedented total turnover number of TTO=197,000 over 92h before deactivation in the hydrogenation of benzene at room temperature and 3bar initial H2 pressure.