Characterization of metal-incorporated molecular sieves

Chao, Kuei‐Hsiang; Wei, A.C.; Wu, Han Chieh; Lee, J.F.

doi:10.1016/s0920-5861(98)00434-9

Cited by 28 publications

(15 citation statements)

References 35 publications

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“…tert-Butanol, a useful high-octane oxygenate, is formed as the byproduct when tert-butyl hydroperoxide is used as the oxidant. Metal-substituted aluminophosphates [23,24] catalyze oxidation [25,26] and oxidative hydrogenation [27] of alkanes, but they have not been reported to catalyze oxidation reactions of organosulfur compounds. Crystalline molecular sieves with relatively large channels [Co/H-Y (FAU, 0.74 0.74 nm, three-dimensional) and CoAPO-5 (AFI, 0.73 0.73 nm, one-dimensional)] were chosen to avoid diffusional constraints that would corrupt kinetic measurements.…”

Section: Introductionmentioning

confidence: 99%

Selective Catalytic Oxidation of Organosulfur Compounds with tert‐Butyl Hydroperoxide

Chica¹,

Gatti²,

Modén³

et al. 2006

Chemistry A European J

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Rates and selectivities for the oxidation of various organosulfur compounds with tert-butyl hydroperoxide were measured on CoAPO-5 (APO = aluminophosphate; Co/P = 0.05), Co/H-Y (Co/Al = 0.15), and MoO(x)/Al2O3 (15 % wt MoO3). Rates increased with increasing electron density at the sulfur atom (methyl phenyl sulfide>diphenyl sulfide>4-methyldibenzothiophene>2,5-dimethyl thiophene). Rates (per metal atom) were significantly higher on CoAPO-5 than on Co/H-Y, MoO(x)/Al2O3, or homogeneous Co acetate catalysts. Small amounts of sulfoxides (1-oxide) were detected on all catalysts at low reactant conversions, together with their corresponding sulfones; at higher conversions, only sulfones (1,1-dioxide) were detected, indicating that the oxidation of sulfoxides is much faster than for organosulfur reactants in the sequential oxidation pathways prevalent on these catalysts. Framework Co cations were not leached from CoAPO-5 during the oxidation of 4-methyldibenzothiophene, but most exchanged Co cations in H-Y and >20 % of Mo cations in MoO(x)/Al2O3 were extracted during these reactions. The fraction of redox-active Co cations in CoAPO-5 and Co/H-Y was measured by reduction-oxidation cycles using H2 and O2 and by UV-visible spectroscopy. This fraction was much larger in CoAPO-5 (0.35) than in Co/H-Y (0.01), consistent with the higher oxidation rates measured on CoAPO-5 and with the involvement of redox-active species in kinetically-relevant steps in catalytic oxidation sequences. Redox-active Co cations at framework positions within accessible channels are required for catalytic activity and structural stability during oxidative desulfurization, whether hydroperoxides are used as reactants or as intermediates (when O2 is used as the oxidant).

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Section: Introductionmentioning

confidence: 99%

Selective Catalytic Oxidation of Organosulfur Compounds with tert‐Butyl Hydroperoxide

Chica¹,

Gatti²,

Modén³

et al. 2006

Chemistry A European J

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“…5a, the best fit bond distance Co-O obtained for the first shell is 2.05 for the sample synthesized at pH 8.5. This value is much larger than those usually reported for CoAlPO4-n materials [1,[13][14][15][16], ˚ which are generally between 1.92-1.95 A. This may indicate the presence of the Co 2?…”

Section: Effect Of the Synthetic Condition On The Redox Chemistry Of mentioning

confidence: 54%

Effects of the synthetic condition on the stability, particle size and redox chemistry of nanoporous CoAlPO-34

2016

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This study focuses on the effect of the synthetic conditions on the stability, particle size, redox chemistry of cobalt into the framework of CoAlPO-34. It seems that the most sufficient pH for the substitution of Co into the framework of CoAlPO-34 was pH around 7.5 when the assynthesized bifunctional catalyst has the best redox property. The pH of the initial gel has strong effect on the particle size of CoAlPO-34. The substitution of cobalt and redox chemistry were determined by: EXAFS combined with XRD, XANES, IR. Stability of the nanoporous catalyst studied by in situ XRD were also reported.

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“…56 The coordination and the oxidation number of vanadium sites in VAPO-5 following a redox treatment were investigated by XANES/EXAFS. 57 On the basis of the spectroscopic and catalytic results, the presence of a framework V 4+ /V 5+ redox center is assumed. The following scheme for the oxidation and reduction of vanadium sites has been proposed.…”

Section: Vanadiummentioning

confidence: 99%

“…The following scheme for the oxidation and reduction of vanadium sites has been proposed. 57 Vanadium incorporation in VAPO-5, -11, -17 and -31 was investigated by UV-Vis, XPS, NMR and ESR techniques. 58,59 It has been suggested that in calcined VAPOs, isolated tetrahedral V 5+ is present in the framework positions, substituting for phosphorus.…”

Section: Vanadiummentioning

confidence: 99%

Open‐Framework Aluminophosphates: Synthesis, Characterization and Transition Metal Modifications

Rajić

2005

ChemInform

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Characterization of metal-incorporated molecular sieves

Cited by 28 publications

References 35 publications

Selective Catalytic Oxidation of Organosulfur Compounds with tert‐Butyl Hydroperoxide

Selective Catalytic Oxidation of Organosulfur Compounds with tert‐Butyl Hydroperoxide

Effects of the synthetic condition on the stability, particle size and redox chemistry of nanoporous CoAlPO-34

Open‐Framework Aluminophosphates: Synthesis, Characterization and Transition Metal Modifications

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