Author:

Keywords:

Science & Technology, Physical Sciences, Chemistry, Physical, Chemistry, mesoporous materials, methanol-to-olefins, fluorescence microscopy, positron emission tomography, zeolites, PRODUCT SELECTIVITY, BED REACTOR, CONVERSION, HYDROCARBONS, SAPO-34, PERFORMANCE, REACTIVITY, DEACTIVATION, ARCHITECTURE, TEMPERATURE, hierarchical zeolite, SSZ-13, single molecule fluorescence, PET, 0302 Inorganic Chemistry, 0306 Physical Chemistry (incl. Structural), 0904 Chemical Engineering, Organic Chemistry, 4004 Chemical engineering

Abstract:

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An understanding of the role of the hierarchical pore architecture of SSZ-13 zeolites on the catalytic performance in the methanol-to-olefins (MTO) reaction is crucial to guide the design of better catalysts. We investigated the influence of the space velocity on the performance of a microporous SSZ-13 zeolite and several hierarchically structured SSZ-13 zeolites. Single catalytic turnovers, as recorded by nanometer accuracy by using stochastic chemical reactions (NASCA) 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 because of the hierarchical structuring of the zeolite. Positron emission tomography (PET) using 11 C-labeled methanol was used to map the 2 D spatial distribution of the deposits formed during the MTO reaction in the catalyst bed. We used PET imaging to demonstrate 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 multiring structures that deactivate the catalyst.