Infrared and Raman spectra of MoO3 molybdenum trioxides and MoO3 · xH2O molybdenum trioxide hydrates

Seguin, L.; Figlarz, M.; Cavagnat, R.; Lassègues, J.C.

doi:10.1016/0584-8539(94)00247-9

Cited by 521 publications

(356 citation statements)

References 31 publications

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“…350 nm in the UV-Vis and Raman bands at 992 (nMoLO), 820 and 664 (nMo-O-Mo), 335 (dMo-O-Mo) and 281 (dMoLO) cm 21 respectively. 10 All are consistent with previous observations for supported molybdenum catalysts in which Mo 6+ species are present as a mixture of distorted tetrahedral and octahedral environments (MoO 3 aggregates form due to a poor interaction with the silica support). 11,12 These features however were observed to quickly diminish during the subsequent propane dehydrogenation step.…”

supporting

confidence: 92%

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

et al. 2005

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The potential of combined operando UV-Vis/Raman/XAFS has been explored by studying the active site and deactivation mechanism of silica-and alumina-supported molybdenum oxide catalysts under propane dehydrogenation conditions.Ideally scientists would like to take real-time spectra inside a catalytic reactor when a catalytic process is operating, giving them detailed insight into the working principles of the catalytic material. 1 On this basis, it would then be possible to improve upon existing catalyst formulations or design completely new ones, which are more active and/or selective. Such rational catalyst design is still a dream since the experimental tools available to study the active catalyst do not yet provide sufficient insight. In this respect, it is advantageous to look on catalytic systems from different perspectives by making use of multiple characterisation techniques. In recent years, many attempts have been made to combine multiple spectroscopic techniques into one experimental set-up. The following combinations of two spectroscopic techniques have been recently reported for studying heterogeneous catalysts in action: EPR/UV-Vis, NMR/UV-Vis, XAFS/IR, UV-Vis/Raman and IR/UV-Vis. [2][3][4][5][6][7] Here, we describe a newly developed and powerful operando set-up to measure combined energy-dispersive (ED)-XAFS, UVVis and Raman to study a working catalytic solid. To our best knowledge, this is the first device which couples three spectroscopic techniques in one reactor, focuses on the same spot of a metal oxide catalyst under true reaction conditions and is capable of delivering sub second time resolution. A scheme of the set-up is given in Fig. 1. Further details are given in the ESI.{The operando device developed is widely applicable in the field of heterogeneous catalysis and its potential has been explored for the dehydrogenation of propane (5% in He) over supported Mo catalysts which have shown potential for alkane activation. 8,9 We have studied 13 wt% Mo/Al 2 O 3 and Mo/SiO 2 catalysts during successive propane dehydrogenation cycles at 550 uC. The three techniques are sensitive to changes in the oxidation/coordination states of Mo allowing us to obtain complementary information on the catalysts behaviour during dehydrogenation and regeneration. The set-up allows us to discriminate between the dynamics of both catalysts under reaction conditions and to identify the possible active site and deactivation pathways. Also the complementary aspects of this setup are demonstrated by showing how the catalyst undergoes changes which cannot be followed using one of the techniques alone and how it is possible to obtain quantitative Raman information without the use of an internal standard. Fig. 2 shows data collected using the three techniques during the first propane dehydrogenation cycle (PC1) for Mo/SiO 2 . The initial features observed in the spectra included a distinct 1s-4d pre-edge feature at 20002 eV in the ED-XANES, a strong LMCT band at ca. 350 nm in the UV-Vis and Raman bands at 992 (nMoLO), 82...

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confidence: 92%

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

et al. 2005

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“…It became sharper as the annealing duration increased. This peak corresponded to the Mo = O unresolved stretching vibrations of a-MoO 3 (Seguin et al, 1995). Thus, it confirmed the existence of a-MoO 3 , even in sample after a very short sintering.…”

Section: Thermal Propertiessupporting

confidence: 64%

Catalytic Activity of Biomorphic α-MoO₃ in the Degradation of Methyl Violet Dye

Diao

Kwong²,

Li³

et al. 2012

Environmental Engineering Science

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A network of fibers comprising orthorhombic molybdenum trioxide (a-MoO 3 ) crystals were synthesized using paper as template via a biomorphic approach. The template was completely removed by annealing the sample at 600°C for 5 min. Monoclinic MoO 3 was formed and consequently converted into orthorhombic a-MoO 3 after prolonged annealing. Three milligrams of the biomorphic a-MoO 3 could degrade up to 90% of a methyl violet aqueous solution with a concentration of 20 mg/L under normal visible light. The size of the a-MoO 3 grains and the porosity of the biomorphic sample affected catalytic performance.

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“…5(a) it can be seen that the film deposited at 250 C shows two peaks, at 777 and 849 cm À1 , corresponding to the metastable monoclinic b-crystal phase. 32,33 For 300 and 350 C a clear peak is visible at 818 cm…”

Section: Crystallinity and Surface Morphologymentioning

confidence: 99%

Atomic layer deposition of molybdenum oxide from (NtBu)2(NMe2)2Mo and O2 plasma

Vos

Macco

Thissen

et al. 2015

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

120

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Molybdenum oxide (MoOx) films have been deposited by atomic layer deposition using bis(tert-butylimido)-bis(dimethylamido)molybdenum and oxygen plasma, within a temperature range of 50–350 °C. Amorphous film growth was observed between 50 and 200 °C at a growth per cycle (GPC) around 0.80 Å. For deposition temperatures of 250 °C and higher, a transition to polycrystalline growth was observed, accompanied by an increase in GPC up to 1.88 Å. For all deposition temperatures the O/Mo ratio was found to be just below three, indicating the films were slightly substoichiometric with respect to MoO3 and contained oxygen vacancies. The high purity of the films was demonstrated in the absence of detectable C and N contamination in Rutherford backscattering measurements, and a H content varying between 3 and 11 at. % measured with elastic recoil detection. In addition to the chemical composition, the optical properties are reported as well.

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Infrared and Raman spectra of MoO3 molybdenum trioxides and MoO3 · xH2O molybdenum trioxide hydrates

Cited by 521 publications

References 31 publications

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

Catalytic Activity of Biomorphic α-MoO₃ in the Degradation of Methyl Violet Dye

Atomic layer deposition of molybdenum oxide from (NtBu)2(NMe2)2Mo and O2 plasma

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Infrared and Raman spectra of MoO3 molybdenum trioxides and MoO3 · xH2O molybdenum trioxide hydrates

Cited by 521 publications

References 31 publications

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

Adding a third dimension to operando spectroscopy: a combined UV-Vis, Raman and XAFS setup to study heterogeneous catalysts under working conditions

Catalytic Activity of Biomorphic α-MoO3 in the Degradation of Methyl Violet Dye

Atomic layer deposition of molybdenum oxide from (NtBu)2(NMe2)2Mo and O2 plasma

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Catalytic Activity of Biomorphic α-MoO₃ in the Degradation of Methyl Violet Dye