title: Large zeolite H-ZSM-5 crystals as models for the methanol-to-hydrocarbons process: bridging the gap between single-particle examination and bulk catalyst analysis.
abstract: The catalytic, deactivation, and regeneration characteristics of large coffin-shaped H-ZSM-5 crystals were investigated during the methanol-to-hydrocarbons (MTH) reaction at 350 and 500 °C. Online gas-phase effluent analysis and examination of retained material thereof were used to explore the bulk properties of large coffin-shaped zeolite H-ZSM-5 crystals in a fixed-bed reactor to introduce them as model catalysts for the MTH reaction. These findings were related to observations made at the individual particle level by using polarization-dependent UV-visible microspectroscopy and mass spectrometric techniques after reaction in an in situ microspectroscopy reaction cell. Excellent agreement between the spectroscopic measurements and the analysis of hydrocarbon deposits by means of retained hydrocarbon analysis and time-of-flight secondary-ion mass spectrometry of spent catalyst materials was observed. The obtained data reveal a shift towards more condensed coke deposits on the outer zeolite surface at higher reaction temperatures. Zeolites in the fixed-bed reactor setup underwent more coke deposition than those reacted in the in situ microspectroscopy reaction cell. Regeneration studies of the large zeolite crystals were performed by oxidation in O2 /inert gas mixtures at 550 °C. UV-visible microspectroscopic measurements using the oligomerization of styrene derivatives as probe reaction indicated that the fraction of strong acid sites decreased during regeneration. This change was accompanied by a slight decrease in the initial conversion obtained after regeneration. H-ZSM-5 deactivated more rapidly at higher reaction temperature.
authors: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
authors: Jan P
authors: JP
authors: Hofmann
authors: Davide
authors: D
authors: Mores
authors: Luis R
authors: LR
authors: Aramburo
authors: Shewangizaw
authors: S
authors: Teketel
authors: Marcus
authors: M
authors: Rohnke
authors: Jürgen
authors: J
authors: Janek
authors: Unni
authors: U
authors: Olsbye
authors: Bert M
authors: BM
authors: Weckhuysen