Surface Diffusion Barriers and Catalytic Activity Driven by Terminal Groups at Zeolite Catalysts

Defects that commonly exist on the surface of zeolites pose notable mass transport constraints and influence the catalytic performance. The mechanism underlying the surface defects inducing molecular transport limitations, however, is not fully understood. Herein, we use versatile spectroscopy, imaging techniques, and multiscale simulations to investigate the effect of surface defects on the molecular surface transport in zeolites, intending to establish the terminal structure–mass transport–performance relationship. Isolated silanol, which represents the foremost and eventual chemical defective accessible site at zeolite termination for guest molecules from the bulk fluid phase into zeolites or vice versa, is taken as a showcase. We demonstrate that isolated silanol at H-SAPO-34 zeolite termination not only enhances the adsorptive interaction between the polar molecules/alkenes and interface but also narrows the local 8-membered-ring pore at the external surface. The exterior surface with more isolated silanol could cause a higher diffusion barrier and hamper the accessibility of intracrystalline active sites. This work is expected to shed light on the mechanism underlying the zeolite catalyst upgrading via terminal surface modifications at zeolites

Surface Diffusion Barriers and Catalytic Activity Driven by Terminal Groups at Zeolite Catalysts

Defects that commonly exist on the surface of zeolites pose notable mass transport constraints and influence the catalytic performance. The mechanism underlying the surface defects inducing molecular transport limitations, however, is not fully understood. Herein, we use versatile spectroscopy, imaging techniques, and multiscale simulations to investigate the effect of surface defects on the molecular surface transport in zeolites, intending to establish the terminal structure–mass transport–performance relationship. Isolated silanol, which represents the foremost and eventual chemical defective accessible site at zeolite termination for guest molecules from the bulk fluid phase into zeolites or vice versa, is taken as a showcase. We demonstrate that isolated silanol at H-SAPO-34 zeolite termination not only enhances the adsorptive interaction between the polar molecules/alkenes and interface but also narrows the local 8-membered-ring pore at the external surface. The exterior surface with more isolated silanol could cause a higher diffusion barrier and hamper the accessibility of intracrystalline active sites. This work is expected to shed light on the mechanism underlying the zeolite catalyst upgrading via terminal surface modifications at zeolites

Spatiotemporal Heterogeneity of Temperature and Catalytic Activation within Individual Catalyst Particles

Temperature is a critical parameter in chemical conversion, significantly affecting the reaction kinetics and thermodynamics. Measuring temperature inside catalyst particles of industrial interest (∼micrometers to millimeters), which is crucial for understanding the evolution of chemical dynamics at catalytic active sites during reaction and advancing catalyst designs, however, remains a big challenge. Here, we propose an approach combining two-photon confocal microscopy and state-of-the-art upconversion luminescence (UL) imaging to measure the spatiotemporal-resolved temperature within individual catalyst particles in the industrially significant methanol-to-hydrocarbons reaction. Specifically, catalyst particles containing zeolites and functional nanothermometers were fabricated using microfluidic chips. Our experimental results directly demonstrate that the zeolite density and particle size can alter the temperature distribution within a single catalyst particle. Importantly, the observed temperature heterogeneity plays a decisive role in the activation of the reaction intermediate and the utilization of active sites. We expect that this work opens a venue for unveiling the reaction mechanism and kinetics within industrial catalyst particles by considering temperature heterogeneity

Surface Diffusion Barriers and Catalytic Activity Driven by Terminal Groups at Zeolite Catalysts

Defects that commonly exist on the surface of zeolites pose notable mass transport constraints and influence the catalytic performance. The mechanism underlying the surface defects inducing molecular transport limitations, however, is not fully understood. Herein, we use versatile spectroscopy, imaging techniques, and multiscale simulations to investigate the effect of surface defects on the molecular surface transport in zeolites, intending to establish the terminal structure–mass transport–performance relationship. Isolated silanol, which represents the foremost and eventual chemical defective accessible site at zeolite termination for guest molecules from the bulk fluid phase into zeolites or vice versa, is taken as a showcase. We demonstrate that isolated silanol at H-SAPO-34 zeolite termination not only enhances the adsorptive interaction between the polar molecules/alkenes and interface but also narrows the local 8-membered-ring pore at the external surface. The exterior surface with more isolated silanol could cause a higher diffusion barrier and hamper the accessibility of intracrystalline active sites. This work is expected to shed light on the mechanism underlying the zeolite catalyst upgrading via terminal surface modifications at zeolites