Some selectivity criteria in mild oxidation catalysis V$z.sbnd;P$z.sbnd;O phases in butene oxidation to maleic anhydride

Bordes, E.; Courtine, P.

doi:10.1016/0021-9517(79)90028-9

Cited by 245 publications

(65 citation statements)

References 14 publications

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“…This more layered structure is claimed to possess better catalytic performance than the VPP characterized by a lower exposure of the (100) crystallographic plane. [29][30][31][32] X-ray photoelectron spectroscopy (XPS) of equilibrated samples yielded P/V surface ratios that are not very different for the two samples: 1.76 AE 0.05 and 1.84 AE 0.05 for P/ V1.0 and P/V1.2, respectively; this difference did correspond to that found by bulk analytical methods (Table 1). This means that in the latter sample, the excess P with respect to the stoichiometric value is not located on the VPP surface in the form of polyphosphates, a phenomenon that would lead to an XPS P/V atomic ratio considerably higher than the bulk value.…”

Section: Resultssupporting

confidence: 55%

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

Cavani

Luciani

Esposti

et al. 2010

Chemistry A European J

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This work focused on investigating the effect of the P/V atomic ratio in vanadyl pyrophosphate, catalyst for n-butane oxidation to maleic anhydride, on the nature of the catalytically active phase. Structural transformations occurring on the catalyst surface were investigated by means of in situ Raman spectroscopy in a non-reactive atmosphere, as well as by means of steady-state and non-steady-state reactivity tests, in response to changes in the reaction temperature. It was found that the nature of the catalyst surface is affected by the P/V atomic ratio even in the case of small changes in this parameter. With the catalyst having P/V equal to the stoichiometric value, a surface layer made of alpha(Iota)-VOPO(4) developed in the temperature interval 340-400 degrees C in the presence of air; this catalyst gave a very low selectivity to maleic anhydride in the intermediate T range (340-400 degrees C). However, at 400-440 degrees C delta-VOPO(4) overlayers formed; at these conditions, the catalyst was moderately active but selective to maleic anhydride. With the catalyst containing a slight excess of P, the ratio offering the optimal catalytic performance, delta-VOPO(4) was the prevailing species over the entire temperature range investigated (340-440 degrees C). Analogies and differences between the two samples were also confirmed by reactivity tests carried out after in situ removal and reintegration of P. These facts explain why the industrial catalyst for n-butane oxidation holds a slight excess of P; they also explain discrepancies registered in the literature about the nature of the active layer in vanadyl pyrophosphate.

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Section: Resultssupporting

confidence: 55%

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

Cavani

Luciani

Esposti

et al. 2010

Chemistry A European J

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“…Note that these compounds are already used in the chemical industry as catalysts for the synthesis of maleic anhydride from n-butane or n-butene. 8 Hence many 31 P NMR studies of these materials have been performed. In particular, the spin-echo mapping technique has been shown to be a powerful tool to quantify the amounts of V IV and V V species.…”

Section: Introductionmentioning

confidence: 99%

⁵¹V magic angle spinning NMR in VOPO₄ phases

Siegel

Dupré

Quarton

et al. 2004

Magnetic Reson in Chemistry

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51V magic angle spinning NMR was applied to the alpha(II), beta and gamma phases of VOPO4 at three magnetic field strengths (4.7, 7.1, and 11.7 T). The 51V quadrupole and chemical shift tensors were determined by iterative fitting of the NMR lineshapes at the three magnetic field strengths. The applicability of the method is illustrated by comparison with literature data. Although determined chemical shift tensors are completely axially symmetric and of the same magnitude, all studied phases can clearly be distinguished by their quadrupole coupling tensor. Relationships between the 51V NMR data and structural characteristics such as crystal symmetries are discussed.

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“…This difference might possibly be only a surface effect, the fraction of the catalyst surface available to the reagents being (25), among other authors, as being the active phase, while no quantitative correlation between catalytic activity and selectivity and the content of vanadium pyrophosphate could be found by Van Geem et al (6) and Hodnett et al (7,28). To other authors, it turns out rather that the best catalysts appear to be poorly crystallized or even amorphous VPO phases (25), while for Bordes and Courtine (29) and Morselli et a1. (30) activity and selectivity are associated with the simultaneous presence of p-VOPO, and (VO),P207.…”

Section: Discussionmentioning

confidence: 89%

Catalytic activity of vanadyl phosphate supported on TiO₂ (anatase) and SiO₂ (silica)

Martı́nez-Lara¹,

Moreno-Real²,

Pozas-Tormo³

et al. 1992

Can. J. Chem.

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M. MARTINEZ-LARA, L. MORENO-REAL, R. POZAS-TORMO, A. JIMENEZ-LOPEZ, S. BRUQUE, P. RUE, and G. PONCELET. Can. J. Chem. 70, 5 (1992).Oxidation of n-butane was investigated on vanadyl phosphate (VP) prepared in the presence of titania (anatase) and silica as supports. In the case of silica, a-VOPO, was synthesized with no sign of interaction between the silica surface and vanadium phosphate. On the contrary, titania was coated with amorphous VP (P/V = l), preventing the crystallization of VOPO, at least up to the VP content of 21%. rz-Butane was completely converted into C 0 2 for the VP/Ti02 catalytic system. Upon impregnation with metal sulfates, maleic anhydride (MA) was produced with selectivities depending on the nature of the added metallic species, the best effect being observed with Fez+ (V/Fe = 3). Selectivities to MA were influenced by the P/V ratio, with a maximum at P/V = 1.2.Key words: vanadyl phosphate, maleic anhydride, butane oxidation, anatase, rutile. On a ktudi6 l'oxydation du butane sur de phosphate de vanadyle (PV) prkpare en prksence de titania (anatase) et de silica comme supports. Dans le cas de la silice, on a synthktise du a-VOPO, sans signes d'interactions entre la surface de la silice et le phosphate de vanadium. Au contraire, le titania etait couvert de PV (P/V = 1) et cette situation emp&che la cristallisation du VOP04, au moins jusqu'a un contenu en PV de 21%. Avec le systirme catalytique PV/Ti02, le butane est completement transform6 en COz. Apres imprkgnation sur des sulfates mktalliques, il y a formation d'anhydride malkique (AM) avec des s6lectivitCs qui d6pendent de la nature des especes mktalliques ajoutkes; les meilleurs resultzits sont obtenus avec le Fe" (V/Fe = 3). Les s6lectivitks en AM sont influenckes par le rapport P/V; le maximum se situe a P/V = l , 2 .Mors clbs : phosphate de vanadyle, anhydride malkique, oxydation du butane, anastase, rutile.[Traduit par la rkdaction]

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Some selectivity criteria in mild oxidation catalysis V$z.sbnd;P$z.sbnd;O phases in butene oxidation to maleic anhydride

Cited by 245 publications

References 14 publications

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

⁵¹V magic angle spinning NMR in VOPO₄ phases

Catalytic activity of vanadyl phosphate supported on TiO₂ (anatase) and SiO₂ (silica)

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Some selectivity criteria in mild oxidation catalysis V$z.sbnd;P$z.sbnd;O phases in butene oxidation to maleic anhydride

Cited by 245 publications

References 14 publications

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

Surface Dynamics of A Vanadyl Pyrophosphate Catalyst for n‐Butane Oxidation to Maleic Anhydride: An In Situ Raman and Reactivity Study of the Effect of the P/V Atomic Ratio

51V magic angle spinning NMR in VOPO4 phases

Catalytic activity of vanadyl phosphate supported on TiO2 (anatase) and SiO2 (silica)

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⁵¹V magic angle spinning NMR in VOPO₄ phases

Catalytic activity of vanadyl phosphate supported on TiO₂ (anatase) and SiO₂ (silica)