Structure–Activity Relationships in the Ammoxidation of Ethylene in the Absence of Molecular Oxygen over γ-Al2O3-Supported Molybdenum Oxide Catalysts

Peeters, I Imre; Gon, A. W. Denier van der; Reijme, M.A.; Kooyman, Patricia J.; Jong, A.M. de; Grondelle, J. van; Brongersma, H.H.; Santen, Rutger A. van

doi:10.1006/jcat.1997.1879

Cited by 18 publications

(10 citation statements)

References 20 publications

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“…A fundamental understanding of the structure-activity relationships observed in heterogeneous catalytic oxidation is of basic importance for the development of new catalytic materials and for improving the performance of existing catalysts. 35 To this end, methods such as oxygen chemisorption have been studied extensively in recent years to find active phase dispersion in supported metal oxide systems.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Reactivity of Molybdenum Oxide Catalysts Supported on Niobia

et al. 2001

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A series of MoO3/Nb2O5 catalysts with Mo loadings varying from 2.5 to 15 wt % were prepared and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of ammonia, electron spin resonance (ESR), oxygen chemisorption, and pore size distribution measurements. X-ray diffraction patterns indicate the presence of a crystalline molybdenum phase at higher Mo loadings on niobia. Dispersion of molybdenum was determined by the oxygen chemisorption at 623 K by a static method on the samples prereduced at the same temperature. At low Mo loadings, i.e., <10.0%, molybdenum oxide is found to be present in a highly dispersed state. Pore size distribution studies indicate a decrease in average pore diameter and pore volume with increased Mo loading. ESR results suggest the presence of Mo5+ in the reduced catalysts. TPR results suggest that the reducibility of MoO3 increases with increased Mo loading. The reduction peaks due to niobia in TPR appeared at high temperatures (>1173 K) and their intensity decreases with Mo loading. TPD of ammonia results suggest that acidity of the catalysts was found to increase with increased molybdenum loading. The catalytic properties were evaluated for the vapor-phase ammoxidation of 3-picoline to nicotinonitrile and related to oxygen chemisorption sites.

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Section: Introductionmentioning

confidence: 99%

Characterization and Reactivity of Molybdenum Oxide Catalysts Supported on Niobia

et al. 2001

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“…The experimental details are comparable to those on silica except for the fact that the samples were cleaned by calcination (heating overnight in 0.5 bar of oxygen at 550 K). More details on sample preparation and measurement are given in Peeters et al 4 If LEIS spectra of non-compacted and compacted (300 MPa) -Al 2 O 3 are compared, a doubling (factor 2.0 š 0.2) of the absolute LEIS yields is observed for the compacted samples. The Al/O ratio is not affected by compaction.…”

Section: Results On Powdersmentioning

confidence: 99%

“…with low dose and thus negligible damage. All measurements on the silica (supported) samples were, unless stated otherwise, carried out with 3 keV 4 19 During a measurement a 200-fold lower dose is used, therefore we do not expect a significant change due to preferential sputtering. To prevent charging of the insulating samples, low-energy electrons (10 eV) were flooded from all azimuths over the sample during measurements.…”

Section: Low-energy Ion Scatteringmentioning

confidence: 99%

Influence of compaction and surface roughness on low‐energy ion scattering signals

Jansen

Knoester²,

Maas³

et al. 2004

Surface & Interface Analysis

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“…This catalyst has previously been extensively studied by several techniques, including low-energy ion scattering. 10 The sample studied here was pretreated in 0.5 bar O 2 at 300°C for 90 min. The sample preparation method used was the same as described previously.…”

Section: Resultsmentioning

confidence: 99%

“…The sample preparation method used was the same as described previously. 10 The open circles in Fig. 5 show a conventional LEIS spectrum, obtained with a continuous 2 keV 4 He ϩ ionbeam current of 0.8 nA.…”

Section: Resultsmentioning

confidence: 99%

A combined time-of-flight and electrostatic analyzer for low-energy ion scattering

Gon¹,

Reijme²,

Rumphorst³

et al. 1999

Review of Scientific Instruments

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A new instrument for low-energy ion scattering ͑LEIS͒ is presented which employs a combination of electrostatic and time-of-flight analysis. In this instrument, electrostatic analysis is used to determine the kinetic energy of the ions, and flight-time analysis is used to select the mass of the ions. The combination allows us to discriminate the signals resulting from particles with a different mass than the primary ions, resulting in a very efficient suppression of signals caused by sputtered particles. The suppression of signals from sputtered particles enables more accurate determination of LEIS signals, especially for light elements. This technique is especially suited for the study of polymers and oxides, but can also be valuable for determination of low concentration of heavier elements. In this article the design of the instrument is presented and the method is demonstrated by some examples of LEIS spectra.

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Structure–Activity Relationships in the Ammoxidation of Ethylene in the Absence of Molecular Oxygen over γ-Al2O3-Supported Molybdenum Oxide Catalysts

Cited by 18 publications

References 20 publications

Characterization and Reactivity of Molybdenum Oxide Catalysts Supported on Niobia

Characterization and Reactivity of Molybdenum Oxide Catalysts Supported on Niobia

Influence of compaction and surface roughness on low‐energy ion scattering signals

A combined time-of-flight and electrostatic analyzer for low-energy ion scattering

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