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- Andersson, Arne, et al.
(författare)
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Activities of V-Ti-O Catalysts in the Ammoxidation of 3-Picoline
- 1980
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 1090-2694 .- 0021-9517. ; 65:1, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- Ammoxidation of 3-picoline was studied on reduced V-Ti-O catalysts with V6O13 as the major vanadium oxide. The results showed that the initial activity as a function of the TiO2 content reached a maximum at 50–60 mole% TiO2. It is proposed that there is maximum contact between the vanadium and titanium phases at this composition, which results in a weakening of the (VO)3+ surface bond. The selectivity of formation of nicotinonitrile exhibited a maximum of 83% at 10 mole% TiO2 and minima of 73 and 75% at 0 and 30 mole% TiO2, respectively. At higher TiO2 concentrations the selectivity increased continuously to 83% at 90 mole% TiO2. The variation of the selectivity of formation of nicotinonitrile depends on the View the MathML source ratio in the TiO2 phase. It was also found that the conversion and yields varied with the reaction time, which could be explained by the fact that reduced vanadium oxides were oxidized to V2O5 during the ammoxidation process. This oxidation leads to the formation of active and highly selective boundary surfaces between the TiO2-promoted vanadium oxides V6O13 and V2O5.
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| 2. |
- Andersson, Arne, et al.
(författare)
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Activities of Vanadium Oxides in Ammoxidation of 3-Picoline
- 1979
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Ingår i: Journal of Catalysis. - 1090-2694. ; 58:3, s. 383-395
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Tidskriftsartikel (refereegranskat)abstract
- Ammoxidation of 3-picoline to nicotinonitrile was studied on V2O5, V6O13, and V2O4 catalysts in a fixed-bed integral reactor. The activity studies showed that V6O13 was the most active and selective catalyst of the pure oxides, with a maximum yield of 76% nicotinonitrile at 365 °C. The maximum yield on V2O5 catalyst was 34%, and was obtained at a higher temperature, 458 °C. V2O4 was found to be inactive under the conditions studied. The activities and selectivities of the oxides changed rapidly with reaction time when V6O13 and V2O4 were studied. By means of X-ray diffraction and a titrimetric method, the average oxidation number of vanadium was determined, V6O13 was both oxidized and reduced during the reaction; V2O4 was oxidized, while a relatively smaller reduction of V2O5 could be detected. The experiments showed that the V6O13 catalyst used, with both V2O5 and V6O13 phases present, was more selective than any of the pure oxides. This may be explained by active boundary surfaces. Also a mechanism of formation of nicotinonitrile is proposed, which includes a step in which an adsorbed aldehyde complex reacts with ammonia.
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