Tuning the Spatial Distribution and Chemical Nature of Acid Sites in MCM-22 Zeolite by Atomically Dispersed Lanthanum Species for Alkylation of 2-Methylnaphthalene

Abstract

Rare-earth-promoted zeolites have broad applications in the petrochemical industry because modifying zeolites with rare-earth elements can remarkably improve hydrothermal stability and tune the physicochemical properties of the acid sites, resulting in substantial promotion in catalytic selectivity and long-term stability. However, for a specific reaction, it remains a challenge to elaborate the coordination environment of rare-earth elements within the zeolite structure and establish the structure–reactivity of rare-earth-promoted zeolite catalysts. In this work, we have employed multiple spectroscopy and electron microscopy techniques to elucidate the spatial location and coordination environment of atomically dispersed La species in MCM-22 concertedly. In particular, we have attempted to clarify the variation of the chemical nature of the acid sites in MCM-22 zeolite in response to the introduction of La promotor. By appropriately controlling the spatial distribution and chemical nature of the acid sites, we have obtained a La-modified MCM-22 catalyst with high activity, selectivity, and long-term stability (>800 h) for alkylation of 2-methylnaphthalene with methanol for the production of 2,6-dimethyl-naphthalene under industrially relevant conditions.