Seed-Assisted Synthesis of Crystalline Mo3VOx Oxides and Their Crystal Formation Mechanism

Ishikawa, Satoshi; Tashiro, Masaya; Murayama, Toru; Ueda, Wataru

doi:10.1021/cg500661p

Cited by 12 publications

(9 citation statements)

References 31 publications

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“…The occurrence of trigonal (Mo,V)O x inclusions in an orthorhombic grain may be attributed to similar synthesis conditions of both phases, which are most commonly obtained by a hydrothermal treatment at different pH values, , and/or may originate from the condensation of individual (Mo,V)O x nanorods. In addition to the structural relaxation mechanism proposed above, which may originate from the differently connected {(Mo)Mo 5 O 27 } units, minute local chemical and/or surface potential fluctuations may cause the formation of trigonal phases.…”

Section: Resultsmentioning

confidence: 99%

Structural Complexity in Heterogeneous Catalysis: Cataloging Local Nanostructures

et al. 2017

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We present an analytical route toward a detailed and quantitative description of individual defects in heterogeneous catalysts. The investigation is based on a high resolution scanning transmission electron microscopy (STEM) study using complex (Mo,V)O_x mixed oxide as an example. Tiling the structural regions simplifies the identification of local modifications in the microstructure. Up to 19 different structures were observed that can be listed and classified into different structural motifs, intergrowth, channels, interstitial regions, and inclinations. The observed defects are expressed by the rearrangement of the {(Mo)Mo₅O₂₇} building blocks, exhibit different sizes, penetrate the bulk, and can form decoupled surface regions that partially cover the crystallographic bulk. The evaluation of 31 crystals yields an average defect concentration of 3.3% and indicates the absence of identical particles. We have, for example, observed 54 of these rearranged structures close to the surface of one (Mo,V)O_x particle (100 × 50 nm²). A detailed analysis of the atomic arrangement at the surface of this particle suggests a surface composition of (Mo₆₁₀V₂₃₀M₇₀)O_x (M = Mo and/or V). The resulting catalog of motifs reproduces individual fragments of the real structure of a catalyst and can reveal detailed defect−activity correlations that will contribute to a better understanding of heterogeneous catalysis

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Section: Resultsmentioning

confidence: 99%

Structural Complexity in Heterogeneous Catalysis: Cataloging Local Nanostructures

et al. 2017

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“…We have reported that Tri-MoVO is formed from a precursor solution containing Keplerate-type polyoxometalate, {Mo 72 V 30 }, in which twelve {Mo 6 O 21 } 6– pentagonal units are linked with thirty VO 2+ groups. ,, During the hydrothermal process under the appropriate conditions, {Mo 72 V 30 } provides building blocks such as pentagonal {Mo 6 O 21 } 6– units, which are assembled with appropriate countercations to form Tri-MoVO. Müller et al reported that Keplerate-type {W 72 V 30 }, in which twelve {W 6 O 21 } 6– pentagonal units are connected with thirty VO 2+ , can be formed in a manner similar to {Mo 72 V 30 }. , In consideration of the location of W in the Tri-MoVO structure and the molecular similarity of {Mo 72 V 30 } and {W 72 V 30 }, we speculate that {W 72 V 30 } was formed by the introduction of the W source into the precursor solution as in {Mo 72 V 30 }.…”

Section: Resultsmentioning

confidence: 99%

True Catalytically Active Structure in Mo–V-Based Mixed Oxide Catalysts for Selective Oxidation of Acrolein

et al. 2021

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Crystalline trigonal Mo3VO x (Tri-MoVO) catalyst is constructed of {Mo6O21}6– pentagonal units and octahedral {MO6} units that form hexagonal and heptagonal channels in the crystal structure. Tri-MoVO is an extremely active catalyst for selective oxidation of acrolein (ACR) to form acrylic acid (AA), with the local structure around the heptagonal channel responsible for the catalysis. Here, promoter elements that are widely used in industrial Mo–V-based mixed oxide catalysts (W and Cu) were introduced without altering the crystal structure of Tri-MoVO. W was located at the pentagonal unit sites by replacing Mo, and Cu was located in the interstitial spaces of lattice oxygens in the corner of the heptagonal channel micropore, forming a sophisticated crystal structure involving the four constituent elements. Introduction of W improved the ACR conversion without altering AA selectivity even when the water pressure in the reaction gas was decreased, owing to the promotion of the dissociative adsorption of water. The introduction of Cu resulted in improvement of the AA selectivity from ca. 93–94% to ca. 97%. Based on the structural and elemental similarities between Tri-MoVWCuO and industrially utilized Mo–V-based mixed oxide catalysts synthesized according to the patented procedure, we concluded that Tri-MoVWCuO is the true catalytically active structure for selective oxidation of ACR.

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“…Although the catalysts did not possess high quantities of total acid sites, medium and strong acid sites were present, notably in the samples calcined in oxygen (> 50%), which could be beneficial in the dehydration step. Several studies have shown that adequate strength of the acid sites is important because the adsorption of glycerol on relatively moderate strength acid sites favors the production of 3-hydroxypropa-nal, which consequently dehydrates to acrolein [41,42]. In the glycerol oxydehydration, the formation of CO and CO 2 is commonly associated with (Mo,V)O X species, the pure oxide phases, that promote complete oxidation of intermediates such as acetol, 3-hydroxypropane, and acrylic acid [16,45].…”

Section: Spent Catalystmentioning

confidence: 99%

Hydrothermal synthesis of Mo-V mixed oxides possessing several crystalline phases and their performance in the catalytic oxydehydration of glycerol to acrylic acid

et al. 2017

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The one-step oxydehydration of glycerol to acrylic acid over molybdenum and vanadium mixed oxides was investigated. The Mo-V oxide catalysts were prepared by a simple hydrothermal method under different synthesis and calcination atmospheres and were characterized by in situ XRD, TPD-NH 3 , N 2 adsorption/ desorption, X-ray absorption near vanadium K-edge spectroscopy and thermogravimetry. The catalytic performance of the samples at different temperatures (290, 320 and 350°C) and under different gas flow compositions (20% O 2 in N 2 , 100% O 2 , or 100% N 2) revealed that the arrangement of the crystallographic structures of the active phases directly influenced the catalytic performance. It was found that the catalysts heattreated in oxidizing atmosphere gave superior catalytic results comparing with the catalysts heat-treated in inert atmosphere due to the equilibrium between the crystalline phases MoVO 5 and Mo 4.65 V 0.35 O 14 that contains V +4 and V +5. Catalytic oxydehydration at 320°C under a flow of 100% O 2 gave the best performance, achieving selectivity of 33.5% towards acrylic acid and 100% conversion of glycerol.

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Seed-Assisted Synthesis of Crystalline Mo₃VO_x Oxides and Their Crystal Formation Mechanism

Cited by 12 publications

References 31 publications

Structural Complexity in Heterogeneous Catalysis: Cataloging Local Nanostructures

Structural Complexity in Heterogeneous Catalysis: Cataloging Local Nanostructures

True Catalytically Active Structure in Mo–V-Based Mixed Oxide Catalysts for Selective Oxidation of Acrolein

Hydrothermal synthesis of Mo-V mixed oxides possessing several crystalline phases and their performance in the catalytic oxydehydration of glycerol to acrylic acid

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