VAPO as catalyst for liquid phase oxidation reactions. Part II: stability of VAPO-5 during catalytic operation

Haanepen, MJ; Elemans-Mehring, AM Adelheid; Hooff, van Jhc Jan

doi:10.1016/s0926-860x(96)00349-3

Cited by 47 publications

(22 citation statements)

References 15 publications

(23 reference statements)

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“…[72] Another striking obserProtons are necessary for charge balance, and thus two catalytic functions are formed (Figure 7). If both Co 2ϩ and vation was recently found by Haanepen et al [73] They observed that the leaching process of VAPO-5 molecular sieves Co 3ϩ are in the lattice, they are expected to be in high-spin and in tetrahedral coordination. Redox catalysis requires only occurred in the beginning of the catalytic reaction, and that the heterogeneous contribution steadily stopped due to free coordination sites, and this is impossible in such an ideal situation.…”

Section: Crystallization Processmentioning

confidence: 80%

See 1 more Smart Citation

Transition Metal Ions in Microporous Crystalline Aluminophosphates: Isomorphous Substitution

Weckhuysen¹,

Rao

Martens

et al. 1999

Eur. J. Inorg. Chem.

121

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Microporous crystalline metalloaluminophosphates (MeAPO‐n) represent an important group of molecular sieves because of their potential catalytic and adsorptive properties. Many transition metal ions are claimed to incorporate in the framework of these molecular sieves. Here, the concept of isomorphous substitution, and the different indirect and direct tools available to verify this substitution process for Co, Cr, V, Fe and Mn are reviewed taking the AlPO4‐5 structure as an example. In addition, it will be shown that transition metal ions can be used as a probe to follow the hydrothermal synthesis process of microporous aluminophosphates.

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Section: Crystallization Processmentioning

confidence: 80%

“…[72,73] In this centers, and thus in principle both acid-and redox-catarespect, the composition of the reaction mixture is critical. lyzed reactions can be performed.…”

Section: Crystallization Processmentioning

confidence: 99%

Transition Metal Ions in Microporous Crystalline Aluminophosphates: Isomorphous Substitution

Weckhuysen¹,

Rao

Martens

et al. 1999

Eur. J. Inorg. Chem.

121

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“…a very low concentration of leached metal ions homogeneously catalyzed the reaction. However, this is not true for the VAPO-5-0.03 molecular sieve although it was found by Haanepen and co-workers that the small amount of leached V 5+ ions in VAPO-5 also largely contributed to the observed activity [45]. When the reaction was carried out for 10 h, the cyclohexane conversion was 4.25% over the VAPO-5-0.03 sample.…”

Section: Catalyst Testingmentioning

confidence: 89%

Synthesis, characterization and catalysis of (Co, V)-, (Co, Cr)- and (Cr, V)APO-5 molecular sieves

Fan

Song

et al. 2006

Microporous and Mesoporous Materials

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Synthesis, characterization and catalysis of (Co, V)-, (Co, Cr)-and (Cr, V)APO-5 molecular sieves ) molecular sieves have been hydrothermally synthesized and characterized. The as-synthesized and calcined samples were investigated with XRD, ICP, DRS UV-vis spectroscopy, ESR, 27 Al MAS NMR techniques to explore the valence, coordination and location of the incorporated transition metal ions. It was shown that isomorphous substitution of Co 2+ for Al 3+ convincingly occurred, and V 4+ also anchored to the sample by coordinating to two framework oxygen atoms and most probably occupying P 5+ sites, while no unambiguous spectroscopic evidence was provided for the incorporation of Cr 3+ in the lattice, although chemical analysis suggests this possibility in the case that Co 2+ or V 4+ are added to the synthesis gel. The preferential sequence for the incorporation of these transition metal ions in the AFI framework is: Co 2+ > V 4+ > Cr 3+ . After calcination, almost all V 4+ ions were oxidized to V 5+ , whereas Cr 3+ ions were oxidized to Cr 5+ and Cr 6+ . As catalysts, the (M, N)APO-5 molecular sieves are highly active for the selective oxidation of cyclohexane with a high cyclohexanone/cyclohexanol ratio in the presence of H 2 O 2 . The reaction temperature and solvent significantly influenced the catalytic behavior. Although some leaching of the transition metal ions was observed, the catalytic performance remained stable at least within five repeated runs.

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“…This observation is consistent with other research, outlining that VAPO-5 (and more generally MeAPOs) are not suitable as catalysts for liquid phase oxidation reactions. 6 The supported VO x /SiO 2 catalyst shows a good conversion in a first run (see Fig. S.4w).…”

mentioning

confidence: 92%

The remarkable catalytic activity of the saturated metal organic framework V-MIL-47 in the cyclohexene oxidation

et al. 2010

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The remarkable catalytic activity of the saturated metal organic framework MIL-47 in the epoxidation of cyclohexene is elucidated by means of both experimental results and theoretical calculations.Metal organic frameworks (MOFs) are crystalline porous solids composed of a three-dimensional network of metal ions held in place by multidentate organic molecules. 1,2 Recently, the catalytic applications of MOFs have been reviewed by Hupp et al. and Farrusseng et al. 3,4 However, catalytic reaction mechanisms in metal organic frameworks and in particular at saturated coordinated centres are still poorly understood.In this study, we describe the high catalytic activity of a coordinative saturated V-MOF in the liquid phase oxidation of cyclohexene. The metal organic framework MIL-47 consists of a porous terephthalate framework built from infinite chains of V 4+ O 6 octahedra and has a three-dimensional orthorhombic structure that exhibits large pores. 5 Every structure unit in MIL-47 contains an O-V +IV -O bridge. The linkage of the V +IV to dicarboxylate groups of the terephthalate linkers results in an octahedral structure unit. Hence each vanadium(+IV) centre is saturated.The selective oxidation of cyclohexene is particularly interesting as it can yield, depending on the catalyst and the reaction conditions, several products as shown in Scheme 1. In this study, the reaction was carried out with tert-butyl hydroperoxide (70 wt% TBHP in water) as oxidant and chloroform as solvent. The internal standard used was 1,2,4-trichlorobenzene. The molar ratios were chloroform : cyclohexene : TBHP : 1,2,4-trichlorobenzene = 462 : 1 : 2 : 1. The reaction temperature was kept constant at 323 K. Samples were taken out from the reaction mixture at certain times and analyzed by gas chromatography. Next, MIL-47 was compared with a homogeneous vanadium catalyst vanadyl acetylacetonate VO(acac) 2 . Prior to the reaction, all the catalysts were dried under vacuum. Blank tests were performed without catalyst and no cyclohexene conversion was observed. Fig. 1 depicts the cyclohexene conversion and the detailed product distributions for MIL-47 and the homogeneous VO(acac) 2 catalyst. In both reactions, we used an identical amount of V-sites (0.4 mmol, 0.095 g MIL-47 and 0.106 g VO(acac) 2 ). The four main reaction products formed are cyclohexene oxide 2, cyclohexane-1,2-diol 3, tert-butyl-2-cyclohexenyl-1-peroxide 4 and 2-cyclohexen-1-one 5. From these figures it can be seen that the homogeneous catalyst VO(acac) 2 and the MIL-47 show high reaction rates for the conversion of cyclohexene. The initial turnover frequencies considered at the first 20 min are 57 h À1 and 43 h À1 for the VO(acac) 2 and the MIL-47 respectively. Both catalysts showed an almost linear conversion rate during the first 2 h of reaction and finally topped out at 60% conversion. The turnover numbers calculated at the end of the reaction were 62 and 68 for VO(acac) 2 and MIL-47 respectively. Moreover, considering the product distributions, truly interesting similaritie...

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VAPO as catalyst for liquid phase oxidation reactions. Part II: stability of VAPO-5 during catalytic operation

Cited by 47 publications

References 15 publications

Transition Metal Ions in Microporous Crystalline Aluminophosphates: Isomorphous Substitution

Transition Metal Ions in Microporous Crystalline Aluminophosphates: Isomorphous Substitution

Synthesis, characterization and catalysis of (Co, V)-, (Co, Cr)- and (Cr, V)APO-5 molecular sieves

The remarkable catalytic activity of the saturated metal organic framework V-MIL-47 in the cyclohexene oxidation

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