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1

Vanadium-containing Mesoporous Molecular Sieves: Synthesis, Properties and Catalytic Performance in Oxidative Activation of Light Alkanes

Cortés Corberán V., Sulikowski B.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 9

1823-1837

EN

Vanadium-containing mesoporous molecular sieves (MMS) are quasi-crystalline solids with interesting catalytic properties in the oxidative activation of light alkanes. In the present work, the methods of their synthesis, physico-chemical properties and catalytic behaviour in the oxidative dehydrogenation and selective oxidation of C2-C4 alkanes are reviewed. It is concluded that, as with conventional supported vanadium contacts, the catalytic performance in these reactions is related to the number and environment of vanadium centres, and the best selectivity and yield are obtained over isolated vanadium sites exhibiting tetrahedral coordination.

2

Oxidative Dehydrogenation of Propane over Mechanochemically Activated V2O5-Cr2O3 System

Wieczorek-Ciurowa K., Gomułczak A., Zazhigalov V. A.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 1-2

191-198

EN

High-energy ball milling of V2O5-Cr2O3 mixture (V/Cr molar ratio = 1/10) initially causes dispersion of vanadium oxide on the surface of chromium oxide grains resulting in an active phase-support system. The increase of both, the V/Cr ratio on the surface and acidity of active sites is observed. Thus, this system mechanically treated for only 30 minutes has lower selectivity of propane conversion to propylene than the non-milled one. Due to homogenization resulting from longer milling time, the vanadium layer on the surface is destroyed and therefore the lower V/Cr ratio on the surface and decrease in acidity are observed. Simultaneously, the formation of Cr2VO5.5 phase takes palce. It was concluded that these phenomena were responsible for a significant increase of selectivity in conversion of propane to propylene in contrast to the non-activated sample.

3

Oxidative Dehydrogenation of Isobutane on VOx/Oxide Support Catalysts: Effect of the Potassium Additive

Samson K., Grzybowska-Świerkosz B.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 7

1345-1354

EN

Effect of the potassium additive on physicochemical and catalytic properties in oxidative dehydrogenation (ODH) of isobutane has been studied for a series of vanadia-based catalysts supported on different oxides (SiO2, Al2O3, TiO2, MgO). The catalysts (denoted as VS where S is a cation of a support), containing 1 or 1.5 monolayer (mnl) of V2O5 were prepared by impregnation method, characterized by BET, XPS, isopropanol decomposition (probe reaction for acido-basic properties) and tested in isobutane ODH in the temperature range 250-450_C. For all the catalysts the K additive decreased the acidity and increased the basicity, decreased the total acitivity, and increased (with the exception of VMg catalyst) the selectivity to isobutene. The increase in the selectivity was attributed to the decrease in acidity and increase in basicity of the catalysts. For VMg, different distribution of carbon oxides and different kinetic scheme were observed (dominance of CO2 formed by a consecutive path over CO formed by a parallel route) as compared with other catalysts (dominance of CO over CO2). These facts suggest, that the decrease in the selectivity to isobutene by the K additive observed for VMg catalyst is due to modification by K of other than acido-basic properties (most probably interaction of the catalysts with oxygen), which control the selectivity in this case.

4

Conversion of ethane on the Na+/CaO catalyst under reaction conditions suitable for oxidative coupling of methane

Machocki A., Denis A.

Polish Journal of Chemical Technology

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2006

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Vol. 8, nr 2

54-58

EN

It was found that under the reaction conditions suitable for oxidative coupling of methane over a half of ethylene formed from the ethane-oxygen feedstock in the presence of Na+/CaO catalyst may derive from thermal transformations of ethane rather than from its oxidative dehydrogenation. The total selectivity of ethane conversion towards all hydrocarbons formed is high and at 1073 K is close to 99%. The selectivity of ethylene formation is about 86 - 88% at 873 K. An increase in the temperature to 923 K causes an approximately 10% decrease in the ethylene selectivity. However, at about 973 K ethylene selectivity returns to the level of 87 - 90% which is sustained until 1073 K. The minimum selectivity of ethylene formation is accompanied by the corresponding maxima in C3+ hydrocarbons and methane selectivities, which suggest that disproportionation of C2 species is favoured at 873 - 973 K.

5

Oxidative dehydrogenation of n-butane over transition metal containing hydrotalcite derived catalysts.

Kuśtrowski P., Chmielarz L., Węgrzyn A., Surman J., Dziembaj R.

Prace Naukowe Instytutu Chemii i Technologii Nafty i Węgla Politechniki Wrocławskiej. Konferencje

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2002

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Vol. 10, nr 57

247-252

EN

Mg-Al layered double hydroxides containing carbonates and nitrates in theinterlayer gallery were used as parent materials for anion exchange. NO-3 and CO2-3 anions were exchanged with oxoanions containing vanadium, chromium, molybdenum and tungsten. Ion-exchange in basic solution led to introduction of V2O 4-7, CrO2-4, MoO2-4 and WO2-4 anions, while V10O286-, Cr2O2-7, Mo7O6-24 and W7O6-24 forms were intercalated in acidic solution. The intercalation was confirmed by X-ray diffraction and FTIR spectroscopy. Oxidative dehydrogenation of n-butane was carried out over hydrotalcite-derived catalysts. The catalysts obtained by thermal decompn. of V2O4-7-contg. Hydrotalcites appeared to be the most active ones in a prodn. of 1,3-butadiene. However, the highest yield of butenes was achieved over Mg-Al-Cr oxides catalyst in the low temp. range (Ł550C).

6

Mg-Al hydrotalcite modified with V3+ and/or V5+ cations as precursors of catalysts for oxidative.

Węgrzyn A., Kuśtrowski P., Rafalska-Łasocha A., Dziembaj R.

Prace Naukowe Instytutu Chemii i Technologii Nafty i Węgla Politechniki Wrocławskiej. Konferencje

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2002

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Vol. 10, nr 57

253-258

EN

The chemical composition of Mg-Al hydrotalcite was modified either by introduction of V3+ cations into the brucite-like sheets of double layered hydroxide or by exchange of the interlayer NO3- and CO32- anions with polyoxovanadate species. Pyrovanadate (V2O74-) and decavanadate (V10O286-) intercalated into Mg-Al hydrotalcite were obtained from the parent aqueous NH4VO3 solution by adjustment of pH to the value of 9.5 or 4.5, respectively. All the as-synthesized samples were characterized with respect to their structure by powder x-ray diffraction and IR spectroscopy. The calcined materials were used as catalysts in oxidative dehydrogenation of iso-butane performed in the excess of oxygen.

7

Physico-Chemical Characteristic of Sulfated Mixed Oxides of Sn with Some Rare Earth Elements

Jyothi T., Sreekumar K., Talawar M., Mirajkar S., Rao B., Sugunan S.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 6

801-812

EN

A series of binary mixed oxides of tin with three rare earth elements viz. La, Ce and Sm were prepared by co-precipitation method and sulfate treatment was performed by treating the mixed hydroxides with sulfuric acid or ammonium sulfate. The physicochemical characterization has been done by XRD, BET-S.A., SEM, EDX, TG-DTA and IR spectroscopy. Adsorption of n-butylamine was used to probe the acidic properties of the catalysts. The strength and distribution of acid sites depend on the mixed metal oxide composition, as well as on the preparation method. The rare earth modified sulfated tin oxide catalysts are more active in the oxidative dehydrogenation of cyclohexanol and cyclohexane, compared to the corresponding mixed oxide systems and sulfated tin oxide. Among the different sulfated oxide systems investigated , cerium prooted catalysts displayed a better selectivity towards dehydrogenation products.

8

Oxidative Dehydrogenation of Ethylbenzene over Zn1-xNixFe2O4 (x=0,0.2, 0.5, 0.8 and 1.0) Type Systems : Effect of Composition on Surface Properties and Catalytic Activities

Sreekumar K., Thomas M., Jyothi T., Biju M., Sugunan S., Rao B.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 4

509-517

EN

The activity and selectivity of this reaction were correlated well with the surface acid-base and redox properties the catalyst. Basicity of the systems was studied based on the adsorption studies using electron acceptors with different electron affinity values. The surface acidity of the system was evaluated using cyclohexanol decomposition studies.

9

Oxidative dehydrogenation of isobutane on chromium oxide-titania catalysts

Grzybowska B., Słoczyński J., Grabowski R., Wcisło K., Kozłowska A., Stoch J., Serwicka E.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 9

2159-2171

EN

Oxidative dehydrogenation of isobutane has been studied at 250 degreeC for a series of chromium oxide-TiO2 (anatase) samples containing 5-50 Cr at per nm(2) of the support surface and for pure chromia. The catalysts have been characterized by XPS, Raman, ESR spectroscopies and by probe reactions for acido-basic properties and the catalyst oxygen reactivity. The maximum activity and selectivity to isobutene have been observed for a catalyst containing 1 theoretical monolayer of the chromia phase on titania. Higher selectivity to isobutene for this catalyst as compared with unsupported chromia or catalysts with higher Cr loading has been ascribed to lower acidity and lover reactivity of oxygen.