FER-type ZSM-35 catalyst for selective C4–C6 olefin oligomerization
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FER-type ZSM-35 Catalyst for Selective C₄–C₆ Olefin Oligomerization
FER-type ZSM-35 (framework type FER) is a medium-pore zeolite that has attracted significant interest as a catalyst for the selective oligomerization of light olefins, particularly C₄–C₆ hydrocarbons. Its unique pore architecture and tunable acidity enable high selectivity toward desired oligomeric products while suppressing side reactions such as cracking, isomerization, or excessive coking.
Key Features of FER-Type ZSM-35 in Olefin Oligomerization:
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Pore Structure:
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The FER framework contains two intersecting channel systems:
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8-membered ring (8-MR) pores (～0.35 × 0.48 nm) along the [010] direction.
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10-membered ring (10-MR) pores (～0.42 × 0.54 nm) along the [001] direction.
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This constrained pore geometry enhances shape selectivity, favoring linear or slightly branched C₈–C₁₂ oligomers from C₄–C₆ feedstocks while limiting the formation of bulky byproducts.
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Acidity Control:
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Brønsted acid sites (from framework Al) are crucial for protonating olefins to initiate carbocationic chain growth.
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The density and strength of acid sites can be tuned via Si/Al ratio, ion exchange, or post-synthetic modifications (e.g., steaming, acid leaching).
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Moderate acidity helps balance activity and stability—high acidity may accelerate coking, while low acidity reduces conversion.
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Selectivity & Product Distribution:
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ZSM-35 favors dimerization and trimerization over higher oligomerization, yielding valuable gasoline-range hydrocarbons (C₈–C₁₈) with high octane numbers.
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Compared to large-pore zeolites (e.g., BEA, FAU), FER-type catalysts exhibit superior selectivity to dimers and trimers due to spatial constraints.
