Dynamic metal-polymer interaction: new catalytic phenomena enabling the design of selective and stable hydrogenation catalysts

Abstract

Metal catalysts have been generally supported on hard inorganic materials. Here we support Pd particles on a thermochemically stable but soft engineering plastic, polyphenylene sulfide (PPS), for the acetylene partial hydrogenation. Near the glass transition temperature of PPS (~353 K), the polymer chains completely cover the entire surface of Pd particles via strong metal-polymer interaction. The Pd-PPS enables H2 activation only in the presence of acetylene that has a strong binding affinity to Pd and thus can disturb the Pd-PPS interface. When acetylene is hydrogenated to weakly binding ethylene, it is repelled from the Pd surface by re-adsorption of the PPS chain before over-hydrogenation. As a result, the catalyst enables selective partial hydrogenation of acetylene to ethylene even in an ethylene-rich stream. In addition, the strong Pd-PPS interaction repels coke precursors from the Pd surface, significantly suppressing catalytic deactivation. This result shows the unique possibility of using dynamic metal-polymer interactions in the design of chemoselective and long-lived catalysts.