Probing coke formation during the methanol-to-hydrocarbon reaction on zeolite ZSM-5 catalyst at the nanoscale using tip-enhanced fluorescence microscopy†‡ † The original data used in this publication are made available in a curated data archive at ETH Zurich (https://www.researchcollection.ethz.ch) at https://doi.org/10.3929/ethz-b-000567250.‡ Electronic supplementary information (ESI) available: Experimental details, scheme of the optical set-up, scheme of zeolite ZSM-5 crystal, Raman measurements of pristine ZSM-5 crystal, optical and UV-vis characterisation of MTH reaction, CFM measurements of typical coke compounds, comparison of average CFM spectra from zeolite 10-ZSM-5 and 90-ZSM-5 catalysts. See DOI: https://doi.org/10.1039/d2cy01348g

ABSTRACT: The deactivation mechanism of the widely used zeolite ZSM-5 catalysts remains unclear to date due to the lack of analytical techniques with sufficient sensitivity and/or spatial resolution. Herein, a combination of hyperspectral confocal fluorescence microscopy (CFM) and tip-enhanced fluorescence (TEFL) microscopy is used to study the formation of different coke (precursor) species involved in the deactivation of zeolite ZSM-5 during the methanol-to-hydrocarbon (MTH) reaction. CFM submicron-scale imaging shows a preferential formation of graphite-like coke species at the edges of zeolite ZSM-5 crystals within 10 min of the MTH reaction (i.e., working catalyst), whilst the amount of graphite-like coke species uniformly increased over the entire zeolite ZSM-5 surface after 90 min (i.e., deactivated catalyst). Furthermore, TEFL nanoscale imaging with ∼35 nm spatial resolution revealed that formation of coke species on the zeolite ZSM-5 surface is non-uniform and a relatively larger amount of coke is formed at the crystal steps, indicating a higher initial catalytic activity. Inhomogeneities in coke formation during methanol-to-hydrocarbon reaction on the zeolite ZSM-5 catalyst are imaged with ∼35 nm spatial resolution using tip-enhanced fluorescence microscopy.

SUBMITTER: Bienz S 

PROVIDER: S-EPMC9528927 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature