evolution of palladium and ruthenium species
Yuan, Ning
(2019).
Unveiling catalytic species in suspension/solution-based reactions by in situ X-ray absorption spectroscopy.
Diss. (sammanfattning/summary)
Uppsala :
Sveriges lantbruksuniv.,
Acta Universitatis Agriculturae Sueciae, 1652-6880
; 2019:33
ISBN 978-91-7760-384-9
eISBN 978-91-7760-385-6
[Doctoral thesis]
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Abstract
The palladium (Pd) and ruthenium (Ru) species in several attractive catalysts have been probed using X-ray absorption spectroscopy (XAS). The study of catalyst evolution in suspension- and solution-based reactions was the primary aim. It was achieved by performing in situ XAS experiments on Pd and Ru over the course of the reactions. A custom-made reactor was employed which allowed the catalysts to be mixed with other reaction components under desired conditions.
The first system investigated was the Heck coupling reaction catalyzed by Pd(II) complexes embedded on metal-organic frameworks. Mononuclear Pd complexes are the active species at the first stage of the measurement which then gradually transform into Pd nanoclusters. At a later stage of the measurement, chloride ligands start to bind to surface atoms of the Pd nanoclusters, leading to a deactivation of the catalyst. Pd(II) carbene complexes catalyzing undirected C–H acetoxylation of benzene in the presence of an oxidant were then explored. A gradual ligand substitution occurs, and the mean oxidation state of Pd increases at the same time. At a later stage, Pd nanoclusters form, while the mean oxidation state of Pd returns to the start value. Deactivation of a heterogeneous Pd(II) catalyst during cycloisomerization of acetylenic acids was also investigated using in situ XAS. The choice of substrates showed to significantly influence the nature of Pd species, and the formation of Pd(0) aggregates causes the deactivation. Moreover, strategies of reactivating the catalyst and prevention of the deactivation were developed and examined. In the end, the activation process of a Ru catalyst was studied and the structure of the intermediate was determined by in situ XAS. It was demonstrated that an electron-donating substituent on the cyclopentadiene ligand exhibits a promoting effect on the activation, while an electron-withdrawing substituent inhibits the activation.
Authors/Creators: | Yuan, Ning | ||||||||||||||
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Title: | Unveiling catalytic species in suspension/solution-based reactions by in situ X-ray absorption spectroscopy | ||||||||||||||
Subtitle: | evolution of palladium and ruthenium species | ||||||||||||||
Series Name/Journal: | Acta Universitatis Agriculturae Sueciae | ||||||||||||||
Year of publishing : | 2019 | ||||||||||||||
Number: | 2019:33 | ||||||||||||||
Number of Pages: | 133 | ||||||||||||||
Papers/manuscripts: |
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Place of Publication: | Uppsala | ||||||||||||||
Publisher: | Swedish University of Agricultural Sciences, Department of Molecular Sciences, | ||||||||||||||
ISBN for printed version: | 978-91-7760-384-9 | ||||||||||||||
ISBN for electronic version: | 978-91-7760-385-6 | ||||||||||||||
ISSN: | 1652-6880 | ||||||||||||||
Language: | English | ||||||||||||||
Additional Information: | The thesis has also been published by Stockholm University and in the repository of DIVa | ||||||||||||||
Publication Type: | Doctoral thesis | ||||||||||||||
Article category: | Other scientific | ||||||||||||||
Full Text Status: | Public | ||||||||||||||
Agris subject categories.: | X Agricola extesions > X50 Chemistry | ||||||||||||||
Subjects: | (A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Analytical Chemistry (A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Inorganic Chemistry | ||||||||||||||
Keywords: | palladiu uthenium species, catalysts, suspension and solution, in situ X-ray absorption spectroscopy, activation, deactivation | ||||||||||||||
URN:NBN: | urn:nbn:se:slu:epsilon-p-99640 | ||||||||||||||
Permanent URL: | http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-99640 | ||||||||||||||
ID Code: | 16080 | ||||||||||||||
Faculty: | NJ - Fakulteten för naturresurser och jordbruksvetenskap | ||||||||||||||
Department: | (NL, NJ) > Department of Molecular Sciences | ||||||||||||||
Deposited By: | SLUpub Connector | ||||||||||||||
Deposited On: | 24 Apr 2019 06:50 | ||||||||||||||
Metadata Last Modified: | 07 Nov 2019 12:02 |
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