René Verel

Last Name

Verel

First Name

René

ORCID

0000-0003-1575-2232

Organisational unit

02513 - Laboratorium für Anorganische Chemie / Laboratory of Inorganic Chemistry

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Publications 1 - 10 of 79

A supplementary coil for H 2 decoupling with commercial HCN MAS probes
Huber, Matthias; With, Oliver; Schanda, Paul; et al. (2012)
Journal of Magnetic Resonance
Direct evidence of the effect of synthesis conditions on aluminum siting in zeolite ferrierite: A 27Al MQ MAS NMR study
Pinar, Ana B.; Verel, René; Peréz-Pariente, Joaquín; et al. (2014)
Microporous and Mesoporous Materials
The tailoring of the aluminum distribution over the various T sites in zeolites remains a major challenge. By using differing combinations of templating molecules, we managed to control the aluminum siting over the T sites as identified by 27Al MQ MAS NMR in samples of the same Si/Al ratio. This is unique evidence of a modified aluminum distribution in samples prepared following a strategy to tailor the location of aluminum in the zeolite ferrierite framework.
Selective Oxidative Dehydrogenation of Ethane and Propane over Copper-Containing Mordenite: Insights into Reaction Mechanism and Product Protection
Artsiusheuski, Mikalai; Verel, René; van Bokhoven, Jeroen A.; et al. (2023)
Angewandte Chemie. International Edition
Copper(II)-containing mordenite (CuMOR) is capable of activation of C−H bonds in C1-C3 alkanes, albeit there are remarkable differences between the functionalization of ethane and propane compared to methane. The reaction of ethane and propane with CuMOR results in the formation of ethylene and propylene, while the reaction of methane predominantly yields methanol and dimethyl ether. By combining in situ FTIR and MAS NMR spectroscopies as well as time-resolved Cu K-edge X-ray absorption spectroscopy, the reaction mechanism was derived, which differs significantly for each alkane. The formation of ethylene and propylene proceeds via oxidative dehydrogenation of the corresponding alkanes with selectivity above 95 % for ethane and above 85 % for propane. The formation of stable π-complexes of olefins with CuI sites, formed upon reduction of CuII-oxo species, protects olefins from further oxidation and/or oligomerization. This is different from methane, the activation of which proceeds via oxidative hydroxylation leading to the formation of surface methoxy species bonded to the zeolite framework. Our findings constitute one of the major steps in the direct conversion of alkanes to important commodities and open a novel research direction aiming at the selective synthesis of olefins.
Structure and Framework Association of Lewis Acid Sites in MOR Zeolite
Yakimov, Alexander V.; Ravi, Manoj; Verel, René; et al. (2022)
Journal of the American Chemical Society
Zeolites, although key materials used in industrial processes, remain poorly understood on a molecular level despite their well-defined crystal lattices. In fact, obtaining a direct spectroscopic signatures and resolving the structure of Lewis acid sites (LAS) has remained a challenge. In this work, thanks to 1D and 2D 1H, 15N, and 27Al MAS NMR spectroscopy, carried out at different temperatures (from 298 down to 107 K), we were able to obtain the NMR spectroscopic signatures of LAS and Brønsted acid sites (BAS) in mordenite zeolite in the presence and the absence of adsorbed pyridine (Py). Combined with DFT modeling, this information enabled the structure of LAS to be revealed, namely (≡SiO)3Al sites interacting with pyridine, thus indicating that the corresponding base-free framework-associated sites are pseudo tricoordinated Al sites, namely tricoordinated Al sites interacting with an additional coordinated adjacent siloxane bridge. With this information in hand, we propose a molecular-level understanding on how the AlIV and AlVI framework and framework-associated sites evolve upon dehydration and exposure to Py into BAS and LAS, and their associated Py adducts. By measuring and analyzing the changes in quadrupolar coupling constants (CQ) that reflect electrical charge distribution around the nuclei, we further show that the lower CQ values observed at 298 K are due to residual dynamics that makes the electric field around aluminum nuclei more symmetric. Thus, NMR spectroscopic signatures of 27Al greatly vary with temperature; this information illustrates the importance of accounting for the temperature effect when confronting experimental and calculated CQ values of the corresponding aluminum sites in zeolites in order to obtain accurate structural assessment.
Identification of lower-order inositol phosphates (IP5 and IP4) in soil extracts as determined by hypobromite oxidation and solution 31P NMR spectroscopy
Reusser, Jolanda E.; Verel, René; Zindel, Daniel; et al. (2020)
Biogeosciences
Inositol phosphates (IPs) are a major pool of identifiable organic phosphorus (P) in soil. However, insight into their distribution and cycling in soil remains limited, particularly of lower-order IP (IP5 and IP4). This is because the quantification of lower-order IP typically requires a series of chemical extractions, including hypobromite oxidation to isolate IP, followed by chromatographic separation. Here, for the first time, we identify the chemical nature of organic P in four soil extracts following hypobromite oxidation using solution 31P NMR spectroscopy and transverse relaxation (T2) experiments. Soil samples analysed include A horizons from a Ferralsol (Colombia), a Cambisol and a Gleysol from Switzerland, and a Cambisol from Germany. Solution 31P nuclear magnetic resonance (NMR) spectra of the phosphomonoester region in soil extracts following hypobromite oxidation revealed an increase in the number of sharp signals (up to 70) and an on average 2-fold decrease in the concentration of the broad signal compared to the untreated soil extracts. We identified the presence of four stereoisomers of IP6, four stereoisomers of IP5, and scyllo-IP4. We also identified for the first time two isomers of myo-IP5 in soil extracts: myo-(1,2,4,5,6)-IP5 and myo-(1,3,4,5,6)-IP5. Concentrations of total IP ranged from 1.4 to 159.3 mg P per kg soil across all soils, of which between 9 % and 50 % were comprised of lower-order IP. Furthermore, we found that the T2 times, which are considered to be inversely related to the tumbling of a molecule in solution and hence its molecular size, were significantly shorter for the underlying broad signal compared to for the sharp signals (IP6) in soil extracts following hypobromite oxidation. In summary, we demonstrate the presence of a plethora of organic P compounds in soil extracts, largely attributed to IPs of various orders, and provide new insight into the chemical stability of complex forms of organic P associated with soil organic matter.
Selective Production of Carbon Monoxide via Methane Oxychlorination over Vanadyl Pyrophosphate
Paunović, Vladimir; Zichittella, Guido; Verel, René; et al. (2016)
Angewandte Chemie. International Edition
Crystal and Electronic Structure of the Lithium-Rich Silver Silicide Li12Ag1−xSi4 (x=0.15)
Slabon, Adam; Budnyk, Serhiy; Cuervo-Reyes, Eduardo; et al. (2013)
Chemistry - A European Journal
Structural control on bulk melt properties
Malfait, Wim J.; Halter, Werner E.; Morizet, Yann; et al. (2007)
Geochimica et Cosmochimica Acta
Characterization of different water pools in solid-state NMR protein samples
Boeckmann, Anja; Gardiennet, Carole; Verel, René; et al. (2009)
Journal of Biomolecular NMR
Polarization-transfer methods in solid-state magic-angle-spinning NMR: Adiabatic CN pulse sequences
Verel, René; Meier, Beat H. (2004)
ChemPhysChem

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René Verel

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