The Fischer–Tropsch-to-olefins (FTO) process, which typically uses iron‑ and cobalt‑based catalysts, has been widely explored for the direct conversion of syngas to light olefins. A major constraint, however, is the broad distribution of hydrocarbon products, often described by the Anderson–Schulz–Flory (ASF) distribution, which limits the maximum selectivity for light olefins to below 60%. This limitation arises from the intrinsic mechanism of FTO synthesis, in which both carbon monoxide activation and C–C bond formation occur on the same iron or cobalt carbide surfaces, without spatial confinement to regulate chain growth.
While progress toward addressing this challenge continues today, this retrospective piece highlights the work by Xinhe Bao, Xiulian Pan and co-workers, reported in Science in 2016, on the development of an oxide–zeolite (OX–ZEO) FTO process, which separates carbon monoxide activation on ZnCr binary oxide (ZnCrOx) from C–C bond formation within a mesoporous SAPO zeolite (MSAPO) (Science 351, 1065–1068; 2016). The bifunctional OX–ZEO catalytic system achieves C2=–C4= selectivity of up to 80% and C2–C4 selectivity of 94% at a carbon monoxide conversion of 17% during 110 hours of testing without observable deactivation — far exceeding the ASF selectivity limitation. Impressively, the selectivity of both C1 and C5+ products is below 5%, whereas simultaneous suppression of these fractions is difficult in conventional FTO processes.
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