Engineering Mordenite zeolite surface defect by secondary growth strategy to improve diffusion and carbonylation performance

Zeolites are widely used in acid-catalyzed reactions, where molecular transport is often limited by surface diffusion barriers from external defects. The issue is especially critical for Mordenite (MOR), which serves as the catalyst of choice for the dimethyl ether (DME) carbonylation reaction——a key step in the synthetic ethanol process. Here, a seed-assisted secondary growth strategy regulated the density of surface Si–OH defects in MOR zeolites. By tuning secondary crystallization time, we obtained MOR samples with controlled defect density, morphology, and framework composition. Multiple characterization techniques quantified the evolution of surface defects and Brønsted acid sites, especially in 8-MR channels. Diffusion kinetics and catalytic tests linked defect regulation, diffusion behavior, and catalytic performance. Reducing surface Si–OH-related adsorption and diffusion resistance enhanced apparent activity. This study demonstrates secondary growth as an effective approach to engineer zeolite surfaces and clarifies how surface defects control diffusion in acid catalysis.