Probing the Influence of SSZ-13 Zeolite Pore Hierarchy in Methanol-to-Olefins Catalysis by Using Nanometer Accuracy by Stochastic Chemical Reactions Fluorescence Microscopy and Positron Emission Profiling

Understanding the role of the hierarchical pore architecture of SSZ-13 zeolites on catalytic performance in the Methanol-to-Olefins (MTO) reaction is crucial for guide the design of better catalysts. We investigated the influence of the space velocity on the perfor-mance of a microporous SSZ-13 zeolite, and several hierarchically structured SSZ-13 zeolites. Single catalytic turnovers, as recorded with fluorescence microscopy verified that the hierarchical zeolites contain pores larger than the 0.38 nm apertures native to SSZ-13 zeolite. The amount of fluorescent events correlated well with the additional pore volume available due to hierarchical structuring of the zeolite. Positron Emission Tomography (PET) using 11C-labelled methanol was used to map the 2D spatial distribution of the deposits formed during the MTO reaction in the catalyst bed. PET imaging demonstrates that hierarchical structuring not only improves the utilization of the available microporous cages of SSZ-13 but also that the aromatic hydrocarbon pool species are involved in more turnovers before they condense into larger multi-ring structures that deactivate the catalyst.