Breaking the inverse relationship between catalytic activity and selectivity in acetylene partial hydrogenation using dynamic metal–polymer interaction

Abstract

The partial hydrogenation of acetylene impurities in ethylene is industrially important because acetylene acts as a catalyst poison in downstream ethylene polymerization processes. In this reaction, simultaneously achieving high acetylene conversion and partial hydrogenation selectivity is challenging, and most known catalyst systems exhibit an inverse activity–selectivity relationship. Here, an amorphous polyphenylene sulfide (Am-PPS) was synthesized as a promoter for 0.1 wt% Pd/α-Al2O3. The catalyst modification using a trace amount of Am-PPS (0.15 wt%) enabled a remarkable enhancement of ethylene selectivity without an appreciable loss in acetylene hydrogenation activity. This could be attributed to the dynamic change of the Am-PPS–Pd interface, which selectively allows the cooperative adsorption of acetylene and H2, but not ethylene. Besides, the modified catalyst exhibited excellent long-term stability because of the high thermochemical stability of the polymer. These results demonstrate the unique possibility of using dynamic metal–polymer interaction to design partial hydrogenation catalysts that simultaneously exhibit high activity, selectivity, and stability.