Minimizing Sinusoidal Channels of ZSM-5 for Propene Production From Molecular Traffic Controlled Cracking Reaction

The molecular traffic control (MTC) effect, a critical concept in porous materials catalysis, describes the diffusion behavior of reactant and product molecules through pore channels within zeolites, thereby establishing a relationship between the pore system and the catalytic performance. Herein, a series of a-oriented MFI-type ZSM-5 catalysts with modulated orientation length while maintaining comparable physicochemical properties are synthesized, and their performance in butene cracking reactions are evaluated. By precisely modulating the pore structure and crystal morphology of ZSM-5, it is demonstrated that minimizing the sinusoidal channel length along a-axis effectively optimizes the MTC effect, resulting in a superior propene selectivity (≈60%) and an enhanced propene-to-ethene ratio (≈12). Computational simulations coupled with experimental measurements reveal that reducing the length along a-axis facilitates preferential outward diffusion of propene molecules as terminal products. This work not only provides solid proof of molecular traffic control but also offers theoretical guidance for the rational design of other useful porous catalysts.