Pt-Zn nanoparticles supported on porous polymeric matrix for selective 3-nitrostyrene hydrogenation

We report the promoting effect of Zn on performance of Pt-based catalyst in liquid-phase hydrogenation of 3-nitrostyrene (3-NS) to 3-vinylaniline (3-VA). Bimetallic Pt-Zn nanoparticles (NPs) were prepared within the hypercross-linked polystyrene (HPS) support. The nanoporous structure of HPS allows a size control of Pt-Zn NPs by confining them in the cavities (ca. 4-5 nm) of the polymeric matrix. The TEM analysis showed that the mean size of the resulted metal particles (4.7 nm) corresponds to the HPS pore size. The properties of the bimetallic catalyst were assessed by IR spectroscopy of chemisorbed CO that suggested the modification of Pt surface and electronic structure invoked by Zn incorporation. The catalytic results demonstrated an increased yield of 3-VA over Pt-Zn/HPS catalyst (97%) relative to monometallic Pt/HPS (16%). This is the highest result reported over Pt catalysts for NS hydrogenation without any additional reaction modifiers. Furthermore, stability of Pt-Zn/HPS under reaction conditions was confirmed over repeated reaction runs. Our results demonstrate the Pt modification with Zn as efficient means to control 3-VA selectivity, whereas HPS serves as a suitable support to control NP size and avoid metal leaching.