Lewis Acidic Zn/S-1 Zeolite Enables Direct Dehydrogenative Aromatization of Long-Chain Olefins

Abstract Aromatics, as essential chemical feedstocks, are predominantly derived from nonrenewable petroleum resources. With the rapid advancement of syngas–to–olefins (STO) technology, Fischer–Tropsch (F–T) olefin aromatization has emerged as a promising alternative route for aromatics production. Developing high-performance zeolite catalysts for the aromatization of long-chain olefins remains a significant challenge. In this study, a purely Lewis acidic catalyst, Zn/S-1, was synthesized by incorporating Zn into S-1 (Silicalite-1) zeolite via a dynamic gas-phase migration method. Under reaction conditions of 520 °C, 0.1 MPa, and a weight hourly space velocity (WHSV) of 0.2 h–1, the catalyst achieved complete conversion of 1-octene with an aromatic selectivity of up to 77.1%. Comprehensive characterization using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM) revealed that the incorporation of Zn species into the S-1 framework leads to the consumption of silanol groups and the formation of uniformly dispersed (Zn–Ox)2 dimeric active sites. Pyridine adsorption infrared spectroscopy further confirmed that these (Zn–Ox)2 dimeric species impart exclusively Lewis acidity to the S-1 zeolite. Compared with conventional Brønsted acid-catalyzed pathways, which typically involve multiple steps such as C–C bond cleavage, oligomerization, and hydrogen transfer, the Lewis acid sites enable a more direct aromatization pathway via dehydrogenation. This distinct mechanism not only enhances aromatic yield but also suppresses the formation of low-value alkanes.