Elemental analysis of catalysts in a fixed-bed reactor by laser-induced breakdown spectroscopy

In situ and operando characterization techniques provide molecular, surface, electronic, and structural information about catalysts in reactors. Accessing changes in the “Elemental Composition” of catalysts under reaction conditions remains yet an unsolved challenge. This work takes a first step in this direction by investigating the potential and limitations of Laser-Induced Breakdown Spectroscopy (LIBS) for monitoring catalyst deactivation, specifically during Dry Reforming of Methane over Ni/γ-Al2O3 and Propane Dehydrogenation over VOX/γ-Al2O3. The study increases complexity stepwise, starting from spatially resolved ex situ LIBS analysis of catalyst particles removed from the reactor after reaction, to the development of a fiber-optic LIBS system and time-resolved intra-reactor measurements. Spectroscopic measurements are complemented by monitoring catalyst activity and temperature at each stage. For the dry reforming of methane, a correlation was found between catalyst performance, temperature, and the spatial distribution of coke, with distinct zoning along the catalyst bed. A cost-effective fiber-optic LIBS probe was developed, allowing for intra-reactor measurements under harsh conditions. The LIBS probe was used to study catalyst deactivation and regeneration during propane dehydrogenation by measuring time-resolved carbon and vanadium profiles. A Partial Least Squares regression model was developed to correlate the amount of carbon deposits with the LIBS spectra, allowing the derivation of quantitative statements. Despite its limitations, such as invasiveness and gas sensitivity, the study highlights the potential of LIBS as an in situ/operando elemental analysis technique.

Subjects

Catalyst deactivation

Chemometrics

Heterogeneous catalysis

In situ LIBS

Laser spectroscopy

Profile reactor

DDC Class

541: Physical; Theoretical

660: Chemistry; Chemical Engineering

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publishedVersion

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https://creativecommons.org/licenses/by/4.0/

Name

ChemCatChem - 2025 - Espinoza - Elemental Analysis of Catalysts in a Fixed‐Bed Reactor by Laser‐Induced Breakdown.pdf

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3.16 MB

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Adobe PDF

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Elemental analysis of catalysts in a fixed-bed reactor by laser-induced breakdown spectroscopy