Probing the Transport of Paramagnetic Complexes inside Catalyst Bodies in a Quantitative Manner by Magnetic Resonance Imaging

Bergwerff, Jaap A.; Lysova, Anna A.; Alonso, Leticia Espinosa; Koptyug, Igor V.; Weckhuysen, Bert M.

doi:10.1002/anie.200701399

Cited by 51 publications

(25 citation statements)

References 22 publications

(9 reference statements)

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“…Adversely, such differences in the distribution of metal complexes inside a catalyst body can also be used to obtain information on their interaction with the support surface. Recently, for instance, we were able to demonstrate from UVvis-NIR and MRI measurements, that the affinity of [Co(H 2 O) 6 ] 2+ complexes for an Al 2 O 3 surface is rather limited [23,24]. It was shown that a homogeneous distribution of Cocomplexes was obtained relatively short after impregnation with a 0.2 M Co(NO 3 ) 2 solution.…”

Section: The Role Of Interactions In the Impregnation Processmentioning

confidence: 99%

On the interaction between Co- and Mo-complexes in impregnation solutions used for the preparation of Al2O3-supported HDS catalysts: A combined Raman/UV–vis–NIR spectroscopy study

2008

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Research has been carried out on the formation of cobalt (Co) and molybdenum (Mo) complexes in CoMo-solutions, which are used for the preparation of Al 2 O 3 -supported hydrodesulphurization (HDS) catalysts. Aim of this study was to obtain more insight into possible Co-Mo interactions and their implications for the impregnation process. For this purpose, Raman and UV-vis-NIR spectroscopy has been carried out on different impregnation solutions at various pH. In addition, multivariate curve resolution (MCR) of the Raman spectra has been applied to obtain information on the molecular structure and speciation of the different complexes present in solution. Furthermore, Raman microscopy and SEM-EDX were applied on Al 2 O 3 extrudates after impregnation, to obtain information on the distribution of the different metal-ions into the catalyst body as a function of time. It is demonstrated that an interaction between Co(II)-cations and different molybdate anions is indeed present in CoMosolutions. Two different CoMo-complexes are proposed in which Co 2+ -cations are bound to the outside of H x Mo 7 O 24 (6Àx)À complexes, resulting in a simultaneous transport of the Co and Mo metal-precursor complexes. Since Co acts as a promotor, a close interaction between Co and Mo in the final catalyst is of major importance for the catalytic activity. As such, the interaction should also be taken into account in the preparation of supported CoMo-HDS catalysts. #

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Section: The Role Of Interactions In the Impregnation Processmentioning

confidence: 99%

On the interaction between Co- and Mo-complexes in impregnation solutions used for the preparation of Al2O3-supported HDS catalysts: A combined Raman/UV–vis–NIR spectroscopy study

2008

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“…MRI has also been applied by Bergwerff et al 15b. 22 to determine Co distributions in Co/γ‐Al 2 O 3 Fischer–Tropsch catalysts that had previously been studied using UV/Vis microspectroscopy 23. Quantitative distributions of paramagnetic metal‐ion complexes could be deduced from 1 H‐MRI images of water protons because paramagnetic ions such as Co 2+ , Ni 2+ and Cu 2+ have a detrimental effect on the 1 H‐nuclear magnetic resonance (NMR) signal.…”

Section: Imaging Catalytic Reactors and Catalyst Bodies: Catalyst mentioning

confidence: 99%

Imaging Catalysts at Work: A Hierarchical Approach from the Macro‐ to the Meso‐ and Nano‐scale

2012

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This review highlights the importance of developing multi‐scale characterisation techniques for analysing operating catalysts in their working environment. We emphasise that a hierarchy of in situ techniques that provides macro‐, meso‐ and nano‐scale information is required to elucidate and optimise catalyst performance fully. This combined methodology should ideally embrace spatially resolved and spatio‐temporal monitoring of a) the structure, catalytic activity, temperature and heat/mass transfer pattern in axial and radial directions in real reactors, b) the structure and temperature/heat/mass transport gradients in shaped catalysts and catalyst grains and c) meso‐ and nano‐scale information about particles and clusters, whose physical and electronic properties are linked directly to the micro‐kinetic behaviour of the catalysts. Techniques such as X‐ray diffraction (XRD), infrared (IR), Raman, X‐ray photoelectron spectroscopy (XPS), UV/Vis, and X‐ray absorption spectroscopy (XAS), which have mainly provided global atomic scale information, are being developed to provide the same information on a more local scale, often with sub‐second time resolution. X‐ray microscopy, both in the soft and more recently in the hard X‐ray regime, allows two‐ and three‐dimensional information to be collected down to 10 nm spatial resolution in a gas atmosphere or liquid, although this improvement is at the expense of temporal resolution. Electron microscopy, which provides excellent local atomic scale structural and spectroscopic information, is being developed towards tomographic imaging and realistic conditions, allowing gaps to be bridged in pressure, reaction conditions and length scales, up to the meso‐ and macro‐scale. In addition, new techniques such as single molecule fluorescence spectroscopy and non‐linear spectroscopic techniques are emerging. In this review, we discuss prospects for the development and combined application of both existing and new techniques for in situ catalyst characterisation.

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“…[17] Recently, we briefly reported how the distribution of paramagnetic [CoA C H T U N G T R E N N U N G (H 2 O) 6 ] 2 + complexes after impregnation of support bodies can be monitored quantitatively in a noninvasive manner via their destructive effect on the 1 H NMR signal of the water solvent in MRI measurements. [18] Here we present a full account and show that this novel MRI method in the field of heterogeneous catalysis is generally applicable to monitoring the macrodistribution of different types of Co 2 + complexes inside Co/Al 2 O 3 catalyst bodies. By adding citric acid to the impregnation solution and varying its pH, the macrodistribution of the Co 2 + complexes in the impregnated extrudates could be varied from eggshell, through egg white and egg yolk, to uniform.…”

Section: Introductionmentioning

confidence: 95%

Monitoring Transport Phenomena of Paramagnetic Metal‐Ion Complexes Inside Catalyst Bodies with Magnetic Resonance Imaging

Bergwerff

Lysova

Espinosa-Alonso

et al. 2008

Chemistry A European J

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An indirect magnetic resonance imaging (MRI) method has been developed to determine in a noninvasive manner the distribution of paramagnetic Co2+ complexes inside Co/Al2O3 catalyst extrudates after impregnation with Co2+/citrate solutions of different pH and citrate concentrations. UV/Vis/NIR microspectroscopic measurements were carried out simultaneously to obtain complementary information on the nature of the Co2+ complexes. In this way, it could be confirmed that the actual distribution of Co2+ inside the extrudates could be derived from the MRI images. By combining these space‐ and time‐resolved techniques, information was obtained on both the strength and the mode of interaction between [Co(H2O)6]2+ and different Co2+ citrate complexes with the Al2O3 support. Complexation of Co2+ by citrate was found to lead to a stronger interaction of Co with the support surface and formation of an eggshell distribution of Co2+ complexes after impregnation. By addition of free citrate and by changing the pH of the impregnation solution, it was possible to obtain the rather uncommon egg‐yolk and egg‐white distributions of Co2+ inside the extrudates after impregnation. In other words, by carefully altering the chemical composition and pH of the impregnation solution, the macrodistribution of Co2+ complexes inside catalyst extrudates could be fine‐tuned from eggshell over egg white and egg yolk to uniform.

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Probing the Transport of Paramagnetic Complexes inside Catalyst Bodies in a Quantitative Manner by Magnetic Resonance Imaging

Cited by 51 publications

References 22 publications

On the interaction between Co- and Mo-complexes in impregnation solutions used for the preparation of Al2O3-supported HDS catalysts: A combined Raman/UV–vis–NIR spectroscopy study

On the interaction between Co- and Mo-complexes in impregnation solutions used for the preparation of Al2O3-supported HDS catalysts: A combined Raman/UV–vis–NIR spectroscopy study

Imaging Catalysts at Work: A Hierarchical Approach from the Macro‐ to the Meso‐ and Nano‐scale

Monitoring Transport Phenomena of Paramagnetic Metal‐Ion Complexes Inside Catalyst Bodies with Magnetic Resonance Imaging

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