Compounds of chromium(VI) as ligands

Gili, Pedro; Lorenzo‐Luis, Pablo

doi:10.1016/s0010-8545(98)00256-2

Cited by 29 publications

(13 citation statements)

References 63 publications

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“…As shown in Figures 5 (Cr 1.0 SiBEA as prepared and calcined) and 6 (Cr 3.4 SiBEA as prepared and calcined), the peaks at about 578 and 587 eV corresponding to Cr 2p 3/2 and Cr 2p 1/2 , respectively, can be deconvoluted into three components, hereafter referred to as low, intermediate, and high BE components. Following earlier reports on CrO x /SiO 2 , 56 Cr/clinoptilolite, 57 and Cr(VI) compounds, 58 the low BE component of Cr 2p 3/2 at ∼ 576 eV and of Cr 2p 1/2 at ∼ 586 eV (Figures 5 and 6) may correspond to tetrahedral Cr(III) ions, while the high BE component of Cr 2p 3/2 at ∼ 580 eV and of Cr 2p 1/2 at ∼ 589 eV may be attributed to octahedral Cr(VI).…”

Section: Resultsmentioning

confidence: 77%

Influence of the Content and Environment of Chromium in CrSiBEA Zeolites on the Oxidative Dehydrogenation of Propane

et al. 2009

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Cr x SiBEA catalysts (x ) 0.2, 1.0, and 3.4 Cr wt %) are prepared by a two-step postsynthesis method. The introduction of Cr ions in the framework of dealuminated SiBEA zeolite evidenced by XRD generates Brønsted acidic sites as shown by FTIR of pyridine used as molecular probe. In Cr x SiBEA as prepared, chromium is mainly present as octahedral Cr(III) and in calcined Cr x SiBEA (773 K, 3 h, flowing air) as distorted tetrahedral Cr(VI), as evidenced by DR UV-vis, TPR, and XPS. Upon outgassing of calcined Cr x SiBEA at 773 K for 1 h (10 -3 Pa), part of Cr(VI) is reduced to distorted tetrahedral Cr(V), as shown by EPR. Isolated distorted tetrahedral Cr sites present in activated Cr x SiBEA are responsible for their catalytic activity in the oxidative dehydrogenation (ODH) of propane, performed in the presence of air or N 2 O. The propane conversion increases with Cr content in the presence of air or N 2 O, while the selectivity toward propene depends on the reaction temperature and oxidant. In the presence of air, the selectivity toward propene is highest for 1.0 Cr wt %. The lower selectivity for the content of 3.4 Cr wt % may be the result of the presence of some amount of extra-framework octahedral Cr sites. The lower propane conversion and the higher selectivity toward propene in the presence of N 2 O probably depend on the oxidation state of Cr under reaction conditions and on the nature of surface oxygen. The presence of isolated tetrahedral chromium sites with oxidation state lower than (VI) on activated Cr x SiBEA is essential for maintaining a high selectivity.

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Section: Resultsmentioning

confidence: 77%

Influence of the Content and Environment of Chromium in CrSiBEA Zeolites on the Oxidative Dehydrogenation of Propane

et al. 2009

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“…In the liquid phase Cr (VI) co-ordination is more flexible; up to 7-coordinate in solution [9]. In the species distribution diagram of chromate (VI) in aqueous solution [10], at 2 6 pH P 6, dichromate (Cr 2 O 7 2À ) is the most abundant species [11]. In some cases the dichromate dianion may form a trimer, as found, e.g.…”

Section: Introductionmentioning

confidence: 82%

Adsorption kinetic study: Effect of adsorbent pore size distribution on the rate of Cr (VI) uptake

Idris

Alotaibi

Peshkur

et al. 2013

Microporous and Mesoporous Materials

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“…12,32,33 The coordination chemistry of Cr(VI) as a ligand is mainly the chemistry of anions as chromates, dichromates and polychromates with T d symmetry. 34 RL-Cr(VI) interaction could be based on binding of CrO 4 2-as a ligand for protonated carboxylate groups of fatty acids residues of RL in complexes (RL-COOH 2 + ) 2 CrO 4 2-. RL preparations obtained by P. aeruginosa NCAIM(P), B001380 without (control) and with Cr(VI) (II) were analyzed by FT-IR, EI-MS and NMR spectroscopy to find and elucidate the structural relationship between RL and Cr(VI).…”

Section: Structural Elucidation Of Rl-cr(vi) Adduct/complexmentioning

confidence: 99%

Influence of rhamnolipids, produced by Pseudomonas aeruginosa NCAIM(P), B001380 on Cr(VI) removal capacity in liquid medium

Avramovic

Nikolic-Mandic

Karadzic

2013

JSCS

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Pseudomonas aeruginosa NCAIM(P), B001380, a propitious bacterial strain isolated from mineral cutting oil was identified to be chromium tolerant and a producer of biosurfactant rhamnolipid (RL) with potential application in heavy metal bioremediation. Culture growth, RL production and Cr(VI) removal capacity of the strain in the presence of 50 mg L-1 (I) and 100 mg L-1 of Cr(VI) (II) were studied. Maximum of RL production were found in the late-stationary phase at 72 h for both Cr(VI)-amended cultures: I (236 mg L-1) and II (160 mg L-1), as well as the maximum of Cr(VI) removal capacity: 70 % (I) and 57 % (II). The amount of Cr in RL preparation II was 22 mg mg-1 determined by flame atomic absorption spectroscopy (FAAS). Appearance of a new band at 914 cm-1 in infrared (IR) spectrum of RL (II) indicated a significant proof for possible coordination of CrO42-ion with RL. The effect of Cr(VI) on monorhamnolipids (RL1) and dirhamnolipids (RL2) distribution and its ratio were studied by electrospray ionization mass spectrometry (ESI-MS). An increase was observed in a RL2/RL1 ratio for II compared to control

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Compounds of chromium(VI) as ligands

Cited by 29 publications

References 63 publications

Influence of the Content and Environment of Chromium in CrSiBEA Zeolites on the Oxidative Dehydrogenation of Propane

Influence of the Content and Environment of Chromium in CrSiBEA Zeolites on the Oxidative Dehydrogenation of Propane

Adsorption kinetic study: Effect of adsorbent pore size distribution on the rate of Cr (VI) uptake

Influence of rhamnolipids, produced by Pseudomonas aeruginosa NCAIM(P), B001380 on Cr(VI) removal capacity in liquid medium

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