Rational Design of Ultrasmall PtZn Nanoparticles Supported on Zeolite Composites as Bifunctional Catalysts for n-Butane Dehydroisomerization

The development of efficient technologies for light olefin production is crucial to the petrochemical industry. In particular, isobutene synthesis via n-butane dehydroisomerization, catalyzed by a bifunctional catalyst containing Pt nanoparticles supported on acidic zeolites, is one of the most significant catalytic pathways. However, it often suffers from low catalyst stability due to sintering and coke deposition, eventually hindering their catalytic performance. In this contribution, we report the rational design of ultrasmall PtZn nanoparticles supported on diverse zeolite composites containing different parent zeolites [e.g., ferrierite (FER), mordenite, and Zeolite Socony Mobil-5] as cores and hierarchical silicalite-1 (SN1) as shells via a two-step hydrothermal process. The synthesized composites revealed that the SN1 nanocrystals were fully covered on the outermost surfaces of core zeolites with highly dispersed PtZn nanoparticles on the SN1 phase. The synergistic effect of the additional zinc species in Pt, preventing sintering and altering electronic properties of metals, along with weakened Br & oslash;nsted acidity at the outermost surface of a parent zeolite due to covered SN1 shells, enhanced the catalytic performance and stability in n-butane dehydroisomerization. Among several designer composites, FER/SN1 achieved the highest isobutene yield (16.2%) by suppressing side reactions through modified acid and shape-selective properties. These findings demonstrate the feasibility of the rational design of alloy nanoparticles supported on zeolite composites with modified acid and shape-selective properties for isobutene production.