Analysing and understanding the active site by IR spectroscopy

Vimont, Alexandré; Thibault-Starzyk, Frédéric; Daturi, Marco

doi:10.1039/b919543m

Cited by 196 publications

(178 citation statements)

References 131 publications

(157 reference statements)

Supporting

Mentioning

173

Contrasting

Order By: Relevance

“…It was observed that this activation treatment does not influence the performance of MIL-101(Cr), while the activity for MIL-101(Fe) increases upon activation. It has been reported that under these activation conditions Fe 3+ becomes reduced to Fe 2+ in MIL-101(Fe), [51][52][53] while this reduction process has not been observed for the case of MIL-101(Cr). 12 Also, coordinated water is easier desorbed from MIL-101(Fe) than in MIL-101(Cr).…”

Section: Resultsmentioning

confidence: 99%

“…It has been frequently observed that, in order to be used as catalyst, MOFs have to be submitted to an activation process to remove co-adsorbed water and solvent molecules and to generate coordinatively unsaturated sites around the metal centers. 13,22,49,50 In the present case, MIL-101 solids were activated at 150 ○ C under vacuum for 6 h and the performance of the materials submitted to activation compared with that of untreated materials. In all cases it was observed that the only reaction product was the corresponding DBT sulfone (DBTsulfone) and the process is accompanied by some oxidation of the solvent (~ 1 %).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

et al. 2016

View full text Add to dashboard Cite

MIL-101 promotes the aerobic oxidation in n-dodecane of dibenzothiophene (DBT) and its methyl-substituted derivatives to their corresponding sulfone with complete selectivity, without observation of the sulfoxide. DBT sulfones can be completely separated from n-dodecane by water extraction. MIL-101(Cr) without the need of pre-activation was found more convenient than the also-active MIL-101(Fe) analog. The reaction exhibits an induction period due to the diffusion inside the pore system of the solvent or oxygen and it is not observed if the MIL-101 sample is first contacted with the solvent at the reaction temperature for sufficiently long times. MIL-101 is reusable for at least five times without any sign of deactivation according to the time-conversion plots. Evidence by electron paramagnetic resonance spectroscopy detecting the hydroperoxide radical adduct with a spin trapping agent and Raman spectroscopy detection of superoxide supports that the process is an autooxidation reaction initiated by MIL-101 following the expected radical chain mechanism inside the MIL-101 cages.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

et al. 2016

View full text Add to dashboard Cite

show abstract

“…[9][10][11][12][13][14][15][16][17][18][19] The experimental tools have progressed enormously in the last years, allowing to investigate catalysts in action, even in extreme conditions (high temperature, high pressure, etc.) and with increasing time-and space-resolution.…”

Section: Introductionmentioning

confidence: 99%

Activation and In Situ Ethylene Polymerization on Silica-Supported Ziegler–Natta Catalysts

et al. 2015

View full text Add to dashboard Cite

The structural, vibrational and electronic properties of silica-supported Ziegler-Natta catalysts industrially relevant for polyethylene production were investigated in details by means of a multi-technical approach, at each step of catalyst preparation -including pre-catalyst activation. In the pre-catalyst, the TiCl x phase is mainly grafted to the silica surface, and almost independent of the supported MgCl x phase. However, the subsequent activation by means of an aluminum-alkyl compound causes important changes to both, the supported MgCl x phase and the TiCl x phase. The resulting catalyst is entirely reconstructed, so that most of the titanium sites are detached from the silica surface and in interaction with a highly dispersed MgCl 2 phase, thus mimicking the most famous and highly investigated Ziegler-Natta catalysts (not silica-supported). For the first time, the catalyst performances were monitored by means of in situ FT-IR spectroscopy in transmission mode, simulating industrially significant polymerization conditions (i.e. ethylene is fed onto the catalyst in the presence of the activator and of the solvent). These results demonstrate that it is now possible to achieve a complete description at a molecular level of all the constituents of Ziegler-Natta catalysts, at each step of the catalyst preparation.

show abstract

“…A realistic catalyst for practical purposes would need larger pores. Modifying the dimensions of the linkers without truly altering the active site, is actively explored within the MOF community [86][87][88][89], [90] .…”

Section: Theoretical and Experimental Investigation Of The Catalyst Smentioning

confidence: 99%

Insight in the activity and diastereoselectivity of various Lewis acid catalysts for the citronellal cyclization

Vandichel

Vermoortele

Cottenie

et al. 2013

Journal of Catalysis

View full text Add to dashboard Cite

RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) TITLE RUNNING HEAD Kinetics of the Lewis acid catalyzed citronellal cyclization 2 ABSTRACT Industrial (-)-menthol production generally relies on the hydrogenation of (-)-isopulegol, which is in turn produced with high selectivity by cyclization of (+)-citronellal. This paper uses a combined theoretical and experimental approach to study the activity and selectivity of three Lewis acid catalysts for this reaction, namely ZnBr 2 , aluminum tris(2,6-diphenylphenoxide) (ATPH) and the heterogeneous metal-organic framework Cu 3 BTC 2 (BTC = benzene-1,3,5-tricarboxylate). ATPH is a strong Lewis acid homogeneous catalyst with bulky ligands which provides very high selectivities for the desired stereoisomer (> 99 %). The performance of the catalysts was evaluated as a function of temperature, which revealed that higher catalyst activity allows working at lower temperatures and improves the selectivity for isopulegol. The selectivity distribution is kinetically driven for ZnBr 2 and ATPH. The theoretical selectivity distributions rely on the determination of an extensive set of diastereomeric transition states, for which the differences in free energy have been calculated using a complementary set of ab initio techniques. Given the sensitivity of the selectivity to small Gibbs free energy differences, the agreement between experimental and theoretical selectivities is satisfactory. On basis of the obtained insights rational design of new catalysts may be obtained. As proof of concept, the hypothetical Cu 3 (BTC-(NO 2 ) 3 ) 2 Lewis catalyst -in which each phenyl hydrogen of the BTC ligand is replaced by a nitro group -is predicted to be very selective.

show abstract

Analysing and understanding the active site by IR spectroscopy

Cited by 196 publications

References 131 publications

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

Activation and In Situ Ethylene Polymerization on Silica-Supported Ziegler–Natta Catalysts

Insight in the activity and diastereoselectivity of various Lewis acid catalysts for the citronellal cyclization

Contact Info

Product

Resources

About