REGULARITY OF THE OXIDIZING ACTIVITY OF Mo6+ IONS IN VARIOUS 12-HETEROPOLYMOLYBDATES

Akimoto, Masamichi; Tsuchida, Yoshitaka; Echigoya, Etsuro

doi:10.1246/cl.1980.1205

Cited by 2 publications

(1 citation statement)

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“…Several attempts have been made to link the activity of a catalyst with the physical and chemical properties of the associated cations and these include: ionic radius [35], ionic potential [34], electronegativity [95][96][97][98][99][100][101], enthalpy of oxide formation [99,102,103], electronic polarisability [95,104,105] and optical basicity [106][107][108][109][110][111][112][113]. All of these parameters are listed in Table 9.…”

Section: Investigation Into Correlationsmentioning

confidence: 99%

Comprehensive Study of Isobutane Selective Oxidation Over Group I and II Phosphomolybdates: Structural and Kinetic Factors

Kendel

Brown

2011

Catal Lett

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Various phosphomolybdates were synthesized using cations from Groups 1 and 2 of the periodic table. These compounds were of the form M x H 3-xn [PMo 12 O 40 ], with n being the cationic charge (?1 or ?2). XRD analysis shows pure phosphomolybdic acid has a triclinic structure. A body centered cubic (BCC) structure gradually develops with addition of Group 1 cations, and the triclinic phase is completely replaced by the BCC phase once metal cations occupy a volume greater than 9-11 Å 3 per phosphomolybdate anion. The Group 2 compounds do not form a cubic phase, however the triclinic phase distorts once cationic volume is greater about 5 or 6 Å 3 and appears to become somewhat amorphous. Isobutane selective oxidation over the compounds yielded methacrolein (primary product), 3-methyl-2-oxetanone (lactone), acetic acid, propene, methacrylic acid, carbon dioxide and water as products. Propene was formed over the Group 1 compounds exclusively and methacrylic acid formation was observed with BaH[PMo 12 O 40 ] only. Products form via two distinct processes: Category 1 product has an exponential profile and coverage is consistent with a Langmuir model, Category 2 formations are consistent with desorptions from within the bulk of the substrates. Methacrolein forms via both Category 1 and 2 processes, whilst all other products are formed by Category 2 exclusively. A rigorous kinetic analysis yielded accurate activation parameters. Category 1 methacrolein formation apparent activation energies ranged from 34.7 ± 1.3 to 119 ± 4 kJ mol -1 . Category 2 formations ranged from 34.3 ± 0.4 to 726 ± 172 kJ mol -1 . No relationship between activity and composition or structure could be ascertained, despite investigation into correlations using several different models.

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Section: Investigation Into Correlationsmentioning

confidence: 99%

Comprehensive Study of Isobutane Selective Oxidation Over Group I and II Phosphomolybdates: Structural and Kinetic Factors

Kendel

Brown

2011

Catal Lett

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Effects of cations introduced into 12-molybdophosphoric acid on the catalyst properties

1982

Applied Catalysis

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REGULARITY OF THE OXIDIZING ACTIVITY OF Mo6+ IONS IN VARIOUS 12-HETEROPOLYMOLYBDATES

Abstract: The oxidizing activity of Mo6+ ions in 12-heteropolymolybdates was found to correlate with the electronegativity of counter ion (H+, alkali, and alkali-earth metal ions) as well as of hetero atom (P5+, As5+, and Si4+).

Cited by 2 publications

References 5 publications

Comprehensive Study of Isobutane Selective Oxidation Over Group I and II Phosphomolybdates: Structural and Kinetic Factors

Comprehensive Study of Isobutane Selective Oxidation Over Group I and II Phosphomolybdates: Structural and Kinetic Factors

Effects of cations introduced into 12-molybdophosphoric acid on the catalyst properties

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