The Effect of Cation Type and H+ on the Catalytic Activity of the Keggin Anion [PMo12O40]3− in the Oxidative Dehydrogenation of Isobutyraldehyde

Hu, Jeremy; Burns, Robert C.

doi:10.1006/jcat.2000.2987

Cited by 27 publications

(24 citation statements)

References 39 publications

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“…The NLDFT surface areas ranged from 0.387 to 28 [27,36,98], although work by Okuhara et al supports our finding [41]. The surface area also decreases with respect to increased cation size, which also contrasts with established findings [25,30,37,38,64]. The aluminum salts have a greater number of lower width pores than the pure acid and the lanthanum and cerium phosphomolybdates.…”

Section: Discussionsupporting

confidence: 45%

“…This shows that a decrease in ionic radius is associated with an increase in surface area. In contrast, previous studies have shown that phosphomolybdates containing larger isovalent cations generally possess greater surface areas[39,64]. Therefore factors other than cation radius…”

mentioning

confidence: 50%

“…may be beneficial for catalysis by protonating the organic component [64] or creating reactive Brønsted acid centres [91,92]. Indeed, the acidity of heteropoly acids is much stronger than H 2 SO 4 , HBr, HCl, HNO 3 and HClO 4 [93].…”

Section: Discussion Of Activity Factorsmentioning

confidence: 98%

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Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

et al. 2010

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Twelve phosphomolybdate compounds were synthesized via cationic exchange and were of the form: M x H 3-3x [PMo 12 O 40 ] (M = Al, La or Ce; 0 B x B 1). These compounds were analyzed by XRD and adsorption isotherm. Aluminum addition causes a primitive cubic phase, while lanthanum and cerium yield body-centered structures. La and Ce addition reduces surface area of phosphomolybdate structure. Temperature-programmed experiments for the selective oxidation of isobutane yielded methacrolein, 3-methyl-2-oxetanone (lactone), acetic acid (not with aluminous compounds), propene (only with aluminous compounds), carbon dioxide and water. The preference for propene rather than acetic acid formation with Al 3? may be due to the smaller cation size, or primitive cubic structure. These products form via two distinct reaction processes, labeled categories 1 and 2. Category 1 formation is associated with isobutane forming products on the surface, but reaction rate determined by bulk migration of charged particles. Category 2 formation is concerned with isobutane penetrating deep within the bulk of the substrate and forming products which subsequently desorb in a series of bell-shaped humps. Methacrolein forms via both category 1 and 2, whilst all other products form via category 2 exclusively. Kinetic analysis showed apparent activation barriers for category 1 methacrolein formation range from 67 ± 2 kJ mol -1 to [350 kJ mol -1 , and occur in groups with small, medium and large activation barriers. The addition of ?3 metal cations to the phosphomolybdate anion increase thermal stability, significantly decreasing deactivation; IR spectroscopy shows that the Keggin structure remains intact during temperature-programmed experiments with the Al, La and Ce salts.

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Section: Discussionsupporting

confidence: 45%

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confidence: 50%

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Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

et al. 2010

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“…Other, more recent analyzes have been reported by Hu and Burns [34] and Langpape et al [6] with cesium derivatives, of varying compositions of the form Cs x H 3-x [PMo 12 O 40 ]. These have shown that for x \ 2, two distinct phases are observed in XRD patterns, while for x C 2 only the cubic phase is detectable.…”

Section: Group 1 Phosphomolybdatesmentioning

confidence: 94%

“…The generally larger unit cell dimensions are probably due to differing extents of hydration. The samples were calcined at 350°C for 5 h by Langpape et al [6], at 300°C for 6 h by Hu and Burns [34] and at 300°C for 4 h for this work. Unit cell dimensions for non-cubic phases observed from the XRD data were unable to be determined.…”

Section: Unit Cell Dimensionsmentioning

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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Methacrylic Acid and Derivatives

Wilczynski

Juliette

2003

Kirk-Othmer Encyclopedia of Chemical Technology

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Methacrylic acid (MAA) and its derivatives exhibit a rich array of chemistries and have found wide use in commercial applications, especially as monomers for making various types of polymer products. The predominant manufacturing route to the two simplest methacrylates continues to be via the conversion of acetonecyanohydrin (ACH) in sulfuric acid to methacrylamide followed by either hydrolysis to MAA or esterification with methanol to give methyl methacrylate (MMA). Alternative routes have reached or are now approaching commercialization. These include processes based on either ethylene (C‐2), propylene (C‐3), methylacetylene (C‐3), or isobutylene (C‐4) feedstocks, as well as a separate ACH process which does not involve sulfuric acid. The later route, which starts with catalyzed hydration of ACH to hydroxyisobutyramide followed by esterification and dehydration steps to MMA, has an added benefit of recycling HCN as a raw material. The ethylene‐based routes typically involve formaldehyde condensation on either a propionaldehyde or propionic acid intermediate. The isobutylene‐based routes involve oxidation processes to reach the methacrylate backbone, often passing through methacrolein as an intermediate. The propylene‐based routes typically involve isobutyric acid or isobutyraldehyde intermediates. The methylacetylene‐based process appears to be the most selective overall, where a single reaction with carbon monoxide and methanol leads directly to MMA. All of the synthetic routes require various types of catalysts to promote the separate steps involved. In addition to providing more details on each of these processes, the following article also provides information on volumes, costs, health and safety for methacrylic acid and its derivatives.

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The Effect of Cation Type and H+ on the Catalytic Activity of the Keggin Anion [PMo12O40]3− in the Oxidative Dehydrogenation of Isobutyraldehyde

Cited by 27 publications

References 39 publications

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

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

Methacrylic Acid and Derivatives

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