Single-particle spectroscopy on large SAPO-34 crystals at work: methanol-to-olefin versus ethanol-to-olefin processes.

The formation of hydrocarbon pool (HCP) species during methanol-to-olefin (MTO) and ethanol-to-olefin (ETO) processes have been studied on individual micron-sized SAPO-34 crystals with a combination of in situ UV/Vis, confocal fluorescence, and synchrotron-based IR microspectroscopic techniques. With in situ UV/Vis microspectroscopy, the intensity changes of the λ=400 nm absorption band, ascribed to polyalkylated benzene (PAB) carbocations, have been monitored and fitted with a first-order kinetics at low reaction temperatures. The calculated activation energy (Ea ) for MTO, approximately 98 kJ mol(-1) , shows a strong correlation with the theoretical values for the methylation of aromatics.

Coke formation during the methanol-to-olefin conversion: in situ microspectroscopy on individual H-ZSM-5 crystals with different Brønsted acidity.

Coke formation during the methanol-to-olefin (MTO) conversion has been studied at the single-particle level with in situ UV/Vis and confocal fluorescence microscopy. For this purpose, large H-ZSM-5 crystals differing in their Si/Al molar ratio have been investigated. During MTO, performed at 623 and 773 K, three major UV/Vis bands assigned to different carbonaceous deposits and their precursors are observed.

Morphology-dependent zeolite intergrowth structures leading to distinct internal and outer-surface molecular diffusion barriers.

Zeolites play a crucial part in acid-base heterogeneous catalysis. Fundamental insight into their internal architecture is of great importance for understanding their structure-function relationships. Here, we report on a new approach correlating confocal fluorescence microscopy with focused ion beam-electron backscatter diffraction, transmission electron microscopy lamelling and diffraction, atomic force microscopy and X-ray photoelectron spectroscopy to study a wide range of coffin-shaped MFI-type zeolite crystals differing in their morphology and chemical composition.

Space- and time-resolved in-situ spectroscopy on the coke formation in molecular sieves: methanol-to-olefin conversion over H-ZSM-5 and H-SAPO-34.

Formation of coke in large H-ZSM-5 and H-SAPO-34 crystals during the methanol-to-olefin (MTO) reaction has been studied in a space- and time-resolved manner. This has been made possible by applying a high-temperature in-situ cell in combination with micro-spectroscopic techniques. The buildup of optically active carbonaceous species allows detection with UV/Vis microscopy, while a confocal fluorescence microscope in an upright configuration visualises the formation of coke molecules and their precursors inside the catalyst grains.