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We thank the NRSC-C (B.M.W.), the NWO-CW Top (B.M.W.), and the NWO-CW VICI (F.M.F.d.G.) for financial support and D. Cabaret (IMPMC, UniversitØ Pierre et Marie Curie) for providing the aluminum references. T. Tyliszczak (Lawrence Berkeley National Laboratory), J. Wang (Canadian Light Source), S. Svelle (University of Oslo), and A. M. J. van der Eerden (Utrecht University) are kindly thanked for their contributions.

The effect of a severe steaming treatment on the physicochemical properties and catalytic performance of H‐SAPO‐34 molecular sieves during the methanol‐to‐hydrocarbons (MTH) reaction has been investigated with a combination of scanning transmission X‐ray microscopy (STXM), catalytic testing, and bulk characterization techniques, including ammonia temperature programmed desorption and 27Al and 29Si magic angle spinning nuclear magnetic resonance. For this purpose, two samples, namely a calcined and a steamed H‐SAPO‐34 catalyst powder, have been compared. It has been found that calcined H‐SAPO‐34 displays a high selectivity towards light olefins, yet shows a poor stability as compared to a zeolite H‐ZSM‐5 catalyst. Moreover, in situ STXM at the carbon K‐edge during the MTH reaction allows construction of nanoscale chemical maps of the hydrocarbon species formed within the H‐SAPO‐34 aggregates as a function of reaction time and steam post‐treatment. It was found that there is an initial preferential formation of coke precursor species within the core of the H‐SAPO‐34 aggregates. For longer times on stream the formation of the coke precursor species is extended to the outer regions, progressively filling the entire H‐SAPO‐34 catalyst particle. In contrast, the hydrothermally treated H‐SAPO‐34 showed similar reaction selectivity, but decreased activity and catalyst stability with respect to its calcined counterpart. These variations in MTH performance are related to a faster and more homogeneous formation of coke precursor species filling up the entire steamed H‐SAPO‐34 catalyst particle. Finally, the chemical imaging capabilities of the STXM method at the Al and Si K‐edge are illustrated by visualizing the silicon islands at the nanoscale before and after steaming H‐SAPO‐34.

Zeolithe im Rampenlicht: Eine Kombination aus Rasterröntgenmikroskopie (siehe Bild) und Bulk‐Methoden liefert Einblicke in die nanoskopische Verteilung von Al und C in ZSM‐5‐Zeolithen während der Reformierung von Methanol zu Olefinen. Die verschiedenen Katalysatorleistungen konnten mit Unterschieden in der räumlichen Verteilung der Kohlenwasserstoffe in Verbindung gebracht werden.

Postsynthesis treatments are frequently used as a means of improving the performance of zeolitic catalysts. This study is concerned with the postsynthesis modification of zeolite H-SSZ-13 by neutron irradiation. An enhanced catalytic activity in the methanol to olefin (MTO) reaction is observed after neutron irradiation of the zeolite H-SSZ-13 catalyst. The magnitude of the neutron irradiation effect depends on the irradiation time and the Si/Al ratio of the parent material, as the highest increase in catalytic activity was observed for the irradiated high silica H-SSZ-13. FT-IR measurements with CO as a probe molecule revealed no significant change in the nature of the acid sites, and the acid strength of the catalytically important Brønsted acid sites was maintained after irradiation. Nitrogen physisorption measurements indicated a decrease in specific surface area and pore volume after neutron irradiation, whereas XRD confirmed that the crystallinity was maintained. The water content was found to be lower in the irradiated material, indicating an altered environment within the zeolite voids after irradiation. EPR measurements clearly showed the formation of radicals in consequence of the irradiation procedure. These radicals have been found to be stable in air, in daylight, and after heating to the MTO reaction temperature, and they were still detectable two years after irradiation. We suggest that the radical species consist of peroxy radicals (Si−O−O*) and nonbridging oxygen hole centers (NBOHC: ≡Si−O*) that are formed due to irradiation-induced bond rupture, and we further suggest that radiation-induced structural defects are responsible for the altered catalytic properties of zeolite H-SSZ-13.

Template decomposition followed by confocal fluorescence microscopy reveals a tetragonal-pyramidal intergrowth of subunits in micrometer-sized nearly cubic SSZ-13 zeolite crystals. In order to accentuate intergrowth boundaries and defect-rich areas within the individual large zeolite crystals, a treatment with an etching NaOH solution is applied. The defective areas are visualized by monitoring the spatial distribution of fluorescent tracer molecules within the individual SSZ-13 crystals by confocal fluorescence microscopy. These fluorescent tracer molecules are formed at the inner and outer crystal surfaces by utilizing the catalytic activity of the zeolite in the oligomerization reaction of styrene derivatives. This approach reveals various types of etching patterns that are an indication for the defectiveness of the studied crystals. We can show that specially one type of crystals, denoted as core-shell type, is highly accessible to the styrene molecules after etching. Despite the large crystal dimensions, the whole core-shell type SSZ-13 crystal is utilized for catalytic reaction. Furthermore, the confocal fluorescence microscopy measurements indicate a nonuniform distribution of the catalytically important Brønsted acid sites underlining the importance of space-resolved measurements.

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