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/alpha-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 H-2, 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. (C) 2021 Elsevier Inc. All rights reserved.