NMR imaging of gas phase hydrogenation in a packed bed flow reactor
Date Issued
2015-07-06
Abstract
In situ analysis of heterogeneously catalyzed gas phase reaction systems is becoming a valuable aid to their modeling and optimization. The commonly applied methods are either invasive, do not provide spatial information or are not applicable for optically inaccessible systems. This work investigates the possibility to use NMR imaging to study gas phase reaction processes in situ, spatially resolved and non-invasively.
A multislice NMR spectroscopic imaging pulse sequence, which was optimized to realize ultrashort echo time TE, was employed to study the ethylene hydrogenation reaction in an NMR-compatible packed bed flow reactor. The catalyst bed, containing inactive γ-Al2O3 pellets and Pt-Al2O3 pellets, was subdivided into several sections in order to identify reaction zones that depend on initial conditions. Spatial mapping of the chemical composition was demonstrated on the basis of two experiments with varying initial volume flow and ethylene conversion. The inlet and outlet temperature of the catalyst bed was simultaneously detected by analyzing the spectra of inserted glycol capsules.
The resulting spatial shift of the reactive zones in both experiments could be proven by the spatially resolved concentration measurements and the temperature measurements. The locations of single active catalyst pellets were also detectable by the same measure. The quantitative results of product gas composition of both experiments were in good agreement with accompanying mass spectrometric measurements.
The results demonstrate the applicability of NMR imaging methods to investigate gas phase reaction processes and can help to establish these methods as a standard tool to map chemical transformations in gas flow reactors.
A multislice NMR spectroscopic imaging pulse sequence, which was optimized to realize ultrashort echo time TE, was employed to study the ethylene hydrogenation reaction in an NMR-compatible packed bed flow reactor. The catalyst bed, containing inactive γ-Al2O3 pellets and Pt-Al2O3 pellets, was subdivided into several sections in order to identify reaction zones that depend on initial conditions. Spatial mapping of the chemical composition was demonstrated on the basis of two experiments with varying initial volume flow and ethylene conversion. The inlet and outlet temperature of the catalyst bed was simultaneously detected by analyzing the spectra of inserted glycol capsules.
The resulting spatial shift of the reactive zones in both experiments could be proven by the spatially resolved concentration measurements and the temperature measurements. The locations of single active catalyst pellets were also detectable by the same measure. The quantitative results of product gas composition of both experiments were in good agreement with accompanying mass spectrometric measurements.
The results demonstrate the applicability of NMR imaging methods to investigate gas phase reaction processes and can help to establish these methods as a standard tool to map chemical transformations in gas flow reactors.
Subjects
MRI gas measurements
;
Heterogeneously catalyzed gas phase reactions
;
Non invasive measurements of chemical composition
;
Fixed bed reactor
;
Ethylene hydrogenation
;
Multislice magnetic resonance spectroscopic imaging
;
Mimenima
Publisher
Elsevier
Institution
Type
journal article
Journal/Edited collection
Band
502
Start page
340
End page
349
Secondary publication
Yes
Document version
Postprint
Language
English
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J. Ulpts, W. Dreher, M. Klink, J. Thöming, NMR imaging of gas phase hydrogenation_2015_accepted version_Deckblatt_pdfa1.pdf
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2.4 MB
Format
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