Synergy effects in the catalytic properties of bismuth molybdates

Carson, Douglas; Coudurier, G.; Forissier, M.; Védrine, J.C.; Laarif, Ahmed; Théobald, F.

doi:10.1039/f19837901921

Cited by 73 publications

(51 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our initial experiments were conducted using Bi 2 MoO 6 a material that is known to be an active oxidation catalyst [27] and in a separate study we confirmed that our material was active for the oxidation of isobutene with similar activity/selectivity to that reported previously. In our initial studies we have investigated using five cycles of TPO/TPR or TPR/TPO using dilute H 2 (10% H 2 in Ar) or dilute isobutene (4% isobutene in He) as the reducing agents and dilute O 2 (10% O 2 in He) as the oxidant.…”

Section: Resultssupporting

confidence: 69%

Comments on the characterisation of oxidation catalysts using TPR/TPO

et al. 2005

View full text Add to dashboard Cite

Temperature programmed reduction (TPR) and oxidation (TPO) are used extensively in catalyst characterisation. In this paper, we examine the use of TPR/TPO cycles for the characterisation of a range of molybdates and single oxides. In particular we observe that the first cycle differs from that of subsequent analyses, even when the maximum temperature is limited to that used in the catalytic reaction. The effect is independent of heating rates and cooling atmospheres and has been demonstrated using different bed configurations. This observation has significance when these oxides are used in periodic flow reactors that involve many cyclical reduction/oxidation.

show abstract

Section: Resultssupporting

confidence: 69%

Comments on the characterisation of oxidation catalysts using TPR/TPO

et al. 2005

View full text Add to dashboard Cite

show abstract

“…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%

“…Since the development of bismuth molybdate catalysts for the oxidation and ammoxidation of propylene to acrolein or acrylonitrile by Sohio in 1959 [1,2], these mixed oxides have received strong attention and their catalytic properties have been studied in considerable detail [3][4][5][6][7][8][9][10][11][12]. Addition of further elements such as iron, cobalt or vanadium increased the acrolein and acrylonitrile yields and stabilized the catalyst during the reaction.…”

Section: Introductionmentioning

confidence: 99%

“…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%

See 1 more Smart Citation

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

et al. 2015

View full text Add to dashboard Cite

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.

show abstract

“…One of the most striking examples came from the bismuth molybdate-type catalysts developed at SOHIO in the 1960s for propene oxidation/ammoxidation in acrolein/acrylonitrile [2]. It was further shown that the different phases α, β and γ are active for propene oxidation to acrolein, the α-phase being the best [70]. Moreover, industrial catalysts, designated as multicomponent catalysts, contain also other molybdates, in particular Co(Fe)MoO 4 .…”

Section: Importance Of Electron Transfer Propertiesmentioning

confidence: 99%

Heterogeneous Partial (amm)Oxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

Védrine

2016

Catalysts

View full text Add to dashboard Cite

This paper presents an overview of heterogeneous partial (amm)oxidation and oxidative dehydrogenation (ODH) of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the "seven pillars", and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms), Me-O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C 1 -C 4 ) oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(Sb)Nb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (amm)oxidation to (acrylonitrile) acrylic acid on MoVTe(Sb)Nb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO) 2 P 2 O 7 -based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features) and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until reaching steady state, which makes characterisation of active and selective surface sites quite difficult. The use of oxidants other than O 2 , such as H 2 O 2 , N 2 O or CO 2 , is also briefly discussed. Based on such analysis and recent discoveries and process developments, our perspective is given.

show abstract

Synergy effects in the catalytic properties of bismuth molybdates

Cited by 73 publications

References 0 publications

Comments on the characterisation of oxidation catalysts using TPR/TPO

Comments on the characterisation of oxidation catalysts using TPR/TPO

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

Heterogeneous Partial (amm)Oxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

Contact Info

Product

Resources

About