Bismuth molybdate catalysts synthesized using spray drying for the selective oxidation of propylene

Le, Minh-Tuan; Craenenbroeck, Jeroen Van; Driessche, Isabel Van; Hoste, Serge

doi:10.1016/s0926-860x(03)00222-9

Cited by 67 publications

(68 citation statements)

References 25 publications

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“…At pH = 4-7, the Bi/Mo ratio on the surface was not the same as the ratio in the bulk (Bi/Mo ≈ 1 for pH = 4 and 5, Bi/Mo ≈ 2 for pH = 6 and 7), whereas at pH = 8 a surface enrichment of bismuth (Bi/Mo = 2.5) was observed by XPS. High Bi/Mo surface ratios were also reported in the literature for γ-Bi2MoO6 prepared by different methods (spray drying: 2.4 [29], co-precipitation: 2.6 [10,58]), but the existence of surface Bi2O3 could neither be confirmed in literature nor in the present work. The sample synthesized at pH = 5 featured the highest specific surface area (32 m 2 /g), whereas with increasing and decreasing pH value the surface area of the resulting product was reduced (Table 1) to 4 m 2 /g and 3 m 2 /g for pH = 9 and pH = 1, respectively.…”

Section: Characterization Of the Samples Synthesized With Bi/mo = 1/1contrasting

confidence: 60%

“…The most common method to prepare bismuth molybdate catalysts is co-precipitation [9,10,18,19,[24][25][26], but also solid-state routes [27], sol-gel synthesis [28], and spray drying of aqueous solutions [11,29] have been used. All of these methods require heating or calcination at temperatures >400 °C to yield crystalline materials, which may result in a decrease of the catalytic performance of the resulting phase due to bismuth enrichment of the catalyst surface [30].…”

Section: Introductionmentioning

confidence: 99%

“…other unsupported bismuth molybdate catalysts (1-4 m 2 /g) [9,10,29,42] by variation of the pH between 1 and 9. Hydrothermally synthesized bismuth molybdates were mostly applied in photocatalysis under visible light irradiation [36,40,43], where, especially, γ-Bi2MoO6 is attractive due to its layered structure.…”

Section: Introductionmentioning

confidence: 99%

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Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene

et al. 2015

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A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and Raman spectroscopy. The pH value during synthesis had a strong influence on the catalytic performance. Synthesis using a Bi/Mo ratio of 1/1 at pH ≥ 6 resulted in γ-Bi2MoO6, which exhibited a better catalytic performance than phase mixtures obtained at lower pH values. However, a significantly lower catalytic activity was observed at pH = 9 due to the low specific surface area. γ-Bi2MoO6 synthesized with Bi/Mo = 1/1 at pH = 6 and 7 exhibited relatively high surface areas and the best catalytic performance. All OPEN ACCESSCatalysts 2015, 5 1555 samples prepared with Bi/Mo = 1/1, except samples synthesized at pH = 1 and 9, showed better catalytic performance than samples synthesized with Bi/Mo = 2/3 at pH = 4 and 9 and γ-Bi2MoO6 synthesized by co-precipitation at pH = 7. At temperatures above 440 °C, the catalytic activity of the hydrothermally synthesized bismuth molybdates started to decrease due to sintering and loss of surface area. These results support that a combination of the required bismuth molybdate phase and a high specific surface area is crucial for a good performance in the selective oxidation of propylene.

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Section: Characterization Of the Samples Synthesized With Bi/mo = 1/1contrasting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

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Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene

et al. 2015

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“…Bismuth molybdates, the properties of which have been investigated in the literature [7][8][9][10][11] up to now, were prepared essentially by the solid state reaction and precipitation. In the present study, we have studied the charge transport in three pure bismuth molybdate phases α -, β -and γ prepared by the spray HARTMANOVÁ et al . drying technique [12]. The present investigation could be useful for our future study of the synergy effect in the catalytic activities of bismuth molybdate mixtures as well as for the application of bismuth molybdates in the gas sensors.…”

Section: Introductionmentioning

confidence: 83%

Phase Composition and Charge Transport in Bismuth Molybdates

Hartmanová

Driessche

et al. 2005

Russ J Electrochem

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The study of structural and electrical properties of three pure bismuth molybdate phases, α -Bi 2 Mo 3 O 12 , β -Bi 2 Mo 2 O 9 and γ -Bi 2 MoO 6 , prepared by the spray drying technique, is described and discussed. The structure of polycrystalline, layered samples investigated by means of XRD and Raman spectroscopy was found to be monoclinic for the α -and β -phases and orthorhombic for the γ -phase. The microstructure of the asprepared samples was not sufficiently developed under the given conditions of preparation, however, the thermal treatment can improve it. The high polarizability of Bi 3+ cations with their lone-pair electrons influences the stability of the disordered oxygen sublattice. All as-prepared phases undergo a slight structural change in the temperature region of 280-430°ë resulting in a decrease of the electrical conductivity probably due to an order disorder transition in the oxygen arrangement during the sample heating. The change of electrical conductivity observed was found to be reversible in the high-temperature region and irreversible in the lowtemperature one. The blocking of oxygen transport by the bismuth lone-pair electrons results in an increase of the activation energy and a decrease of the electrical conductivity in the high-temperature region. Relatively high relative dielectric permittivities ε r , 36-52, were observed in dependence on the investigated phase.

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“…Researchers have thoroughly studied the mixtures of aforementioned three phases as a single catalyst system to study the synergy effects [2,3]. Most of the authors credit γ phase for the oxygen transport [4,5], whereas α and β phases are credited for their possession of more number of active sites for propylene chemisorption [6,7]. Recently Grunwaldt et al [8] have prepared Bi-Mo oxides by flame pyrolysis with enhanced surface area.…”

Section: Introductionmentioning

confidence: 99%

Partial Oxidation of Propylene over as Prepared and Acid Enriched Bi2Mo1-xWxO6 System

Parab

Naik

Salker

2017

Bull. Chem. React. Eng. Catal.

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The compounds Bi2Mo1-xWxO6 (x = 0.0, 0.2, and 0.4) were obtained through a Citrate sol-gel process. Thermogravimetric differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were used for characterization. Reitveld refinement of the XRD data confirmed the crystal structure of all the compositions to be orthorhombic, having Pca21 space group. XPS studies indicated the presence of +6 as well as +4 oxidation state for Mo. Surface acid enrichment of all the catalysts was done and monitored by NH3-TPD studies. Partial oxidation of propylene was studied over all the compounds. The W doping was found to increase the catalytic activity. Moreover, as-prepared catalysts and acid enriched catalysts were compared for their catalytic activity wherein, acid-enriched catalysts showed the improved conversion of propylene without hampering the product selectivity profile.

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Bismuth molybdate catalysts synthesized using spray drying for the selective oxidation of propylene

Cited by 67 publications

References 25 publications

Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene

Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene

Phase Composition and Charge Transport in Bismuth Molybdates

Partial Oxidation of Propylene over as Prepared and Acid Enriched Bi2Mo1-xWxO6 System

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