Spatiotemporal Coke Coupling Enhances para-Xylene Selectivity in Highly Stable MCM-22 Catalysts

Identifying zeolite catalysts that can simultaneously optimizep-xylene selectivity and feed utilization is critical to toluenealkylation with methanol (TAM). Here, we show that zeolite MCM-22(MWW) has an exceptional catalyst lifetime in the TAM reaction at highoperating pressure, conversion, and selectivity. We systematically probethe catalytic behavior of active sites in distinct topological features ofMCM-22, revealing that highp-xylene yield and catalyst stability arepredominantly attributed to sinusoidal channels and supercages,respectively. Using a combination of catalyst design and testing, densityfunctional theory, and molecular dynamics simulations, we propose aspatiotemporal coke coupling phenomenon to explain a multistagep-xylene selectivity profile wherein the formation of light coke in supercages initiates the deactivation of unselective external surfacesites. Ourfindings indicate that the specific nature of coke is critical to catalyst performance. Moreover, they provide unprecedentedinsight into the synchronous roles of distinct topological features giving rise to the exceptional stability and selectivity of MCM-22 in the TAM reaction