VOx species on alumina at high vanadia loadings and calcination temperature and their role in the ODP reaction

Steinfeldt, Norbert; Müller, D.; Berndt, H.

doi:10.1016/j.apcata.2004.05.050

Cited by 59 publications

(46 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Activity and selectivity in the oxidative dehydrogenation sensitively depend on the dispersion and structure of the vanadia species on the support material. Consequently, a detailed characterisation of the tested catalyst is necessary for optimisation of the catalytic material [6] and [7]. Selectivity behaviour of VO x /Al 2 O 3 catalysts in the ODP reported in literature differs remarkably.…”

Section: C3h8+05o2→c3h6+h2omentioning

confidence: 99%

Characterisation and catalytic testing of VO /Al2O3 catalysts for microstructured reactors

Schwarz

Frank

Heß

et al. 2008

Catalysis Communications

View full text Add to dashboard Cite

With regard to the application in a microstructured reactor, a special VO x /Al 2 O 3 catalyst powder (3 μm) was prepared and characterised by BET, XRD, UV/Vis DRS, and Raman spectroscopy. The higher the vanadium content, the higher the degree of polymerisation of the vanadium species on the support surface and the lower the BET surface area. Pelletised powders were tested in conventional tubular reactors for their catalytic performance in the oxidative dehydrogenation of propane. Their activity increases with vanadia loading, whereas selectivity towards propene decreases at iso-conversion. Catalytic benchmarking was performed to choose a reasonable catalyst for further investigations in a microreactor.

show abstract

Section: C3h8+05o2→c3h6+h2omentioning

confidence: 99%

Characterisation and catalytic testing of VO /Al2O3 catalysts for microstructured reactors

Schwarz

Frank

Heß

et al. 2008

Catalysis Communications

View full text Add to dashboard Cite

show abstract

“…Furthermore, support acidity can adversely affect catalyst selectivity when low V loading leaves uncovered Lewis acid sites, especially in the case of alumina-supported samples. However, V2O5 segregation is usually observed at high V loading, sometimes accompanied by the formation of the AlVO4 phase [12,13].…”

Section: Introductionmentioning

confidence: 99%

V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

et al. 2009

View full text Add to dashboard Cite

A flame pyrolysis (FP) procedure has been set up for the preparation of V/Al/O catalysts to be employed for the oxidative dehydrogenation of propane to propylene. The samples have been characterised by means of various techniques (FT-IR, Raman, EPR, ICP-MS, TGA, XRD, SEM) and their catalytic activity has been evaluated in two different operating modes, i.e. under anaerobic conditions and by co-feeding oxygen. The particle size distribution became progressively more homogeneous with increasing V concentration, due to the catalytic effect of the V ions during the FP synthesis. Some V2O5 segregation was observed even at low V loading. However, higher V dispersion was attained with respect to a reference sample prepared by impregnation of the FP-prepared alumina support. 2The increase of V concentration always led to an improvement of propane conversion, though selectivity showed different trends depending on the operating conditions. The comparison with the sample prepared by impregnation showed similar catalytic activity, with a bit higher selectivity for the FP-prepared sample under anaerobic conditions.

show abstract

“…At even higher V loading V2O5 segregation occurs, forming three-dimensional V-based structures with inaccessible V-atoms. Therefore, the maximum ODH rate (per V ion) would occur at intermediate V surface densities [1][2][3]. A monolayer can form at particular V loading (or surface density) depending on the nature of the support.…”

Section: -Introductionmentioning

confidence: 99%

“…Oxidative dehydrogenation (ODH) of propane to propylene represents an interesting alternative to the energy demanding dehydrogenation process and supported VOx demonstrated promising catalysts for this reaction [1][2][3][4][5][6][7][8][9][10]. Different supports have been tested, such as ZrO2 [11,12], TiO2 [13], V-substituted zeolites or silicalites [14], SiO2 [7,9,11] and Al2O3, usually as the -phase [3,[4][5][6]8,10,11,13].…”

Section: -Introductionmentioning

confidence: 99%

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

Oliva

Cappelli

Rossetti

et al. 2009

Chemical Engineering Journal

View full text Add to dashboard Cite

In the oxidative dehydrogenation (ODH) of propane to propylene VOx-based catalysts prepared by flame pyrolysis (FP) showed more selective than those prepared by impregnation. Furthermore, samples prepared by the same method were less active, but more selective when VOx was supported on SiO2 than on Al2O3. In order to assess V local structure, V 4+ ions showed useful labels to characterise these catalysts by EPR spectroscopy. Indeed, the spectrum of a (10 wt%V2O5) FP-prepared VOx/SiO2 catalyst was typical of isolated, tetragonally distorted, paramagnetic complexes of V 4+ forming a monolayer on the sample surface with a strong out-of-plane V 4+ -O bond. In a sample with identical composition, but prepared by impregnation, this bond showed a bit weaker.Furthermore, ferromagnetic domains of clustered V ions formed in the latter sample, hindering at least in part the accessibility to the catalytically active V-based centres. This gives evidence of the higher dispersion of V in the sample bulk provided by the FP preparation method with respect to conventional ones. A by far weaker V 4+ -O bond was revealed by the EPR spectrum of a (10%V2O5) VOx/Al2O3 sample, accounting for its higher oxygen availability, leading to higher activity, but lower selectivity. However, the same catalyst, when prepared by impregnation, showed a ferromagnetic resonance pattern so intense that no EPR spectrum was detectable at all and no information on the V 4+ -O bond strength was available in that case.Such semi-quantitative index of the V-O bond strength can be used as an index of oxygen availability, as a tool to assess catalytic activity and selectivity to the desired olefin.

show abstract

VOx species on alumina at high vanadia loadings and calcination temperature and their role in the ODP reaction

Cited by 59 publications

References 36 publications

Characterisation and catalytic testing of VO /Al2O3 catalysts for microstructured reactors

Characterisation and catalytic testing of VO /Al2O3 catalysts for microstructured reactors

V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

Contact Info

Product

Resources

About