Precise regulation of acid centers in different cavities of FER-zeolite via selective passivation to identify pentene monomolecular cracking reaction position

Precisely controlling acid center position in zeolites is still challenging. Pentene monomolecular cracking offers an ideal route to maximize ethylene and propylene yields simultaneously. To reveal the relationship between acid site distribution in FER-zeolite and pentene monomolecular cracking activity, this study proposes a novel strategy integrating pyridine pre-adsorption with K⁺ exchange modification to selectively shield acid sites within FER cages, while phosphorus modification is employed to selectively passivate acid sites in 10-MR channels and on the external surface. Adsorption infrared (IR) spectroscopy (CD₃CN-IR, Py-IR, and 2,6-DMPy-IR), and OH-IR characterization verified the selectivity and efficiency of these modification process. FER zeolites with distinct acid site distributions exhibit typical monomolecular cracking characteristics in pentene cracking, where the pentene cracking activity is linearly related to the acid density in the 10-MR channel and independent of the FER cage acidity. This result identifies 10-MR channel as primary pentene monomolecular cracking reaction position for the first time, providing a theoretical basis for designing zeolite catalysts that maximize ethylene and propylene production. The synergistic application of the pre-adsorption-K⁺ exchange modification strategy using different size basic molecules and phosphorus modification will provide an effective approach for precise control of acid site locations in zeolites with diverse pore/cavities architectures.