Interfacial Impregnation Chemistry in the Synthesis of Chromium Catalysts Supported on Titania

Petsi, Theano; Panagiotou, George D.; Bourikas, Kyriakos; Kordulis, Christos; Voyiatzis, George A.; Lycourghiotis, Alexis

doi:10.1002/cctc.201000446

Cited by 11 publications

(16 citation statements)

References 74 publications

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“…8a). One has to note that most of the examples given below are referring to the deposition of cations (Ni 2+ and Co 2+ ) but a similar approach was pursued by the Patras group with anionic precursors (tungstates, molybdates and chromates) [108][109][110].…”

Section: Chemistry Of Impregnationmentioning

confidence: 99%

Interfacial coordination chemistry for catalyst preparation

Marceau¹,

Bonneviot

Dźwigaj

et al. 2021

Journal of Catalysis

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The concept of interfacial coordination chemistry was one of the innovation for which Michel Che became internationally known during his tenure as full professor at the Université Pierre et Marie Curie. Isolated metal ions on oxide surfaces behave like coordination compounds to which the surface contributes not only via neutral oxo bridges but also via hydroxyl groups. The latter being pH sensitive, the surface can be charged either positively or negatively, allowing selective adsorption of transition metal ions of opposite charge. In the early eighties, examples exploiting these properties for the preparation of oxide/metal supported catalysts were still rare. This review presents Michel Che's early studies, mostly on molybdenum and nickel ions, on which he built, developed and promoted the concept of interfacial coordination chemistry, now widely used in the field of heterogeneous catalysis. This allowed him and his close collaborators to achieve a molecular-scale understanding of several catalyst preparation procedures, such as impregnation, selective adsorption, grafting, depositionprecipitation, and zeolite functionalization. The impact and legacy of the concept of Interfacial Coordination Chemistry on the current design of improved catalytic formulations is also reviewed.

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Section: Chemistry Of Impregnationmentioning

confidence: 99%

Interfacial coordination chemistry for catalyst preparation

Marceau¹,

Bonneviot

Dźwigaj

et al. 2021

Journal of Catalysis

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“…Specifically, we follow the evolution of the various Co(II) species formed at the interface as the surface concentration of the Co(II) increases. The study is part of the entire efforts of our group to rationalize the method of preparation of supported catalysts and shift catalyst preparation from the art to the science [24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition

Vakros¹,

Bourikas²,

Kordulis³

et al. 2014

TOCATJ

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Abstract:The mode of retention of Co(H 2 O) 6 2+ species at the "γ-alumina/aquatic solution" interface is refined using simulations, adsorption isotherm, potentiometric mass titrations and mainly proton -ion titrations jointly with diffuse reflectance spectroscopy. It was found that the increase in the Co(II) surface concentration affects considerably the kind of the Co(II) species deposited. Mononuclear/mono-substituted inner sphere Co(II) complexes are formed at extremely low Co(II) surface concentration. A mixed surface state involving mononuclear/mono-substituted and binuclear/bi-substituted Co(II) complexes is formed at relatively low Co(II) surface concentration. Only binuclear/bi-substituted Co(II) complexes are formed at intermediate Co(II) surface concentration. Finally, oligo-nuclear inner sphere Co(II) species are formed at relatively high Co(II) surface concentration, in addition to the bi-nuclear ones. The above species concern a range of surface Co(II) concentration extending from zero to 2.7 theoretical surface layers of [Co(H 2 O) 6 ] 2+. The formation of Co(II) surface precipitate starts above these theoretical surface layers. The above indicates that one may control the surface Co(II) concentration, by adjusting the Co(II) concentration in the impregnating solution, and thus the Co(II) surface species formed. This control allows tailoring the preparation of cobalt catalysts supported on γ-alumina and thus the development of effective Co/γ-alumina catalysts.

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“…The absence of decamers at the interface (although predominant in the solution) will be further examined and verified by laser Raman Spectroscopy. It should be mentioned that the preferential adsorption of monomeric species on titania in a wide pH range has also been observed in the deposition of other oxoanions of transition metals, such as tungstates [53], molybdates [49], and chromates [50]. .…”

Section: Solution Speciation Of Vanadatesmentioning

confidence: 97%

“…The last can be achieved by working at too low V concentrations and a very high solid/solution ratio [41,49,64]. A successful fitting of these curves is only possible if the right deposition mechanism is adopted in the simulation [49][50][51][52][53]. This is the case in Figure 4.…”

Section: Modeling the Deposition Of Vanadates On Titania Surfacementioning

confidence: 99%

“…Moreover, excellent reviews and book chapters have been published on this subject, showing how the more sophisticated synthesis methods of supported catalysts can help us rationalize their synthesis, improve their efficiency, and control the formation of their active sites [41][42][43][44][45][46][47][48]. In this context, in the last years, we have developed supported transition metal catalysts through a molecular approach, using the equilibrium deposition filtration method (EDF), in order to fully control the impregnation step and specify the transition metal ionic species deposited on the support surface [49][50][51][52][53]. The present study is concerned with an effort to follow the formation of the vanadia site from the first to the final step of the catalyst synthesis procedure using the EDF method.…”

Section: Introductionmentioning

confidence: 99%

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Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

et al. 2021

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Vanadia/titania catalysts were synthesized by the equilibrium deposition filtration (EDF) method, which is a synthesis route that follows a molecular-level approach. The type of interfacial deposition as well as the interfacial speciation of the deposited oxo-V(V) species were determined by means of a model that takes into account experimental “proton-ion” curves and “adsorption edges”. It is shown that at pH ≥ 9.5, the deposition proceeds exclusively through the formation of mono-substituted inner sphere monomeric species in an “umbrella”-like Ti–OV(OH)2O configuration, whilst with lowering of the pH, a second species, namely the disubstituted inner sphere quadrameric species in a (Ti-O)2V4O10 configuration possessing two mono-oxo V=O and two di-oxo V(=O)2 terminations gradually prevails, which is in co-existence with the monomeric species. Raman spectroscopy is used for verifying the solution speciation, which is different compared to the interfacial speciation of the deposited oxo-V(V) species. Furthermore, in situ Raman spectroscopy was used to verify the model-predicted interfacial speciation of the deposited oxo-V(V) species and to monitor the temperature-dependent evolution up to 430 °C. Hence, a controlled formation of a specific vanadia species on a titania surface is enabled, which, depending on the synthesis conditions, can result in specific catalyst characteristics and thus possibly different catalytic behavior for a specific reaction.

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Interfacial Impregnation Chemistry in the Synthesis of Chromium Catalysts Supported on Titania

Cited by 11 publications

References 74 publications

Interfacial coordination chemistry for catalyst preparation

Interfacial coordination chemistry for catalyst preparation

Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition

Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

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