Effect of oxides of the IV and VI group metals on the polymorphic transformation of anatase into rutile

Sembaev, D. Kh.; Ivanovskaya, Faina; Saurambaeva, L. I.; Yugay, O. K.; Mikhailovskaya, T. P.

doi:10.1007/s11144-008-5276-8

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…Above about 475°C, rutile is the major stable phase. However, already Dachille et al (1968), supported by new work (Grzmil et al 2007;Sembaev et al 2008) stress that whole rock composition plays an important role in the variation of the transition to rutile. Smith et al (2009) found that the transition from anatase to rutile is thermodynamically favorable at all temperatures, and the formation of anatase requires lowtemperature aqueous conditions.…”

Section: Electronic Supplementary Materialsmentioning

confidence: 97%

Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks

Triebold¹,

Luvizotto

Tolosana‐Delgado

et al. 2010

Contrib Mineral Petrol

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Investigation by Raman spectroscopy of samples from different geological settings shows that the occurrence of TiO 2 polymorphs other than rutile can hardly be predicted, and furthermore, the occurrence of anatase is more widespread than previously thought. Metamorphic pressure and temperature, together with whole rock chemistry, control the occurrence of anatase, whereas variation of mineral assemblage characteristics and/or fluid occurrence or composition takes influence on anatase trace element characteristics and re-equilibration of relict rutiles.Evaluation of trace element contents obtained by electron microprobe in anatase, brookite, and rutile shows that these vary significantly between the three TiO 2 phases. Therefore, on the one hand, an appropriation to source rock type according to Nb and Cr contents, but as well application of thermometry on the basis of Zr contents, would lead to erroneous results if no phase specification is done beforehand. For the elements Cr, V, Fe, and Nb, variation between the polymorphs is systematic and can be used for discrimination on the basis of a linear discriminant analysis. Using phase group means and coefficients of linear discriminants obtained from a compilation of analyses from samples with well-defined phase information together with prior probabilities of groupings from a natural sample compilation, one is able to calculate phase grouping probabilities of any TiO 2 analysis containing at least the critical elements Cr, V, Fe, and Nb. An application of this calculation shows that for the appropriation to the phase rutile, a correct-classification rate of 99.5% is obtained. Hence, phase specification by trace elements proves to be a valuable tool besides Raman spectroscopy.

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Section: Electronic Supplementary Materialsmentioning

confidence: 97%

Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks

Triebold¹,

Luvizotto

Tolosana‐Delgado

et al. 2010

Contrib Mineral Petrol

View full text Add to dashboard Cite

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“…On the other hand, the kind of TiO 2 crystal modification influences on the reduction degree of V 2 O 5 upon the heat treatment of V-Ti catalysts. It is known [6], that the thermal dissociation of V 2 O 5 with the formation of VO 2 takes place during the heating of such catalysts. The reduction rate of V 2 O 5 into VO 2 increases with the rise of a treatment temperature.…”

Section: Resultsmentioning

confidence: 99%

Catalysts for Alkylbenzene and Alkylpyridine Ammoxidation

Sembaev¹,

Ivanovskaya²,

Pochtennaya³

2016

Eur Chem Tech J

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An increase of effectivity of binary and ternary vanadium containing oxide catalysts can be achieved by a regulation of chemical and phase catalyst composition during their preparation. Activity and selectivity of V-Ti catalysts depend on the ratio of V2O5 to VO2 in the succession of substitutional solid solutions VO2- TiO2, as well as on the crystal modification of TiO2. It was investigated the influence of vanadium oxides over the rate of the polymorfous conversion from anatase to rutile and the kind of TiO2 crystal modification over V2O5 reduction degree during the thermal treatment of V-Ti catalysts. The synthesized catalysts offered producing nicotinonitrile from 3-methylpyridine with 93-95% mol. yield. Modifying of V-Ti catalysts by SnO2 increased their activity. The reason is V=O bond weakening under the influence of SnO2. That was verified by increasing of V2O5 dissociation rate almost by an order in comparison with V-Ti catalysts. SnO2 in the ternary catalysts exists as individual phase and acts as a donor of oxygen for the lower vanadium oxides. It provides the high stability of V-Ti-Sn catalysts and possibility of obtaining isonicotinonitrile with 95-97% mol. yield from 4-methylpyridine. The investigation of the mutual influence of starting components in the ternary V-Ti-Zr catalysts showed that ZrO2 prevented the polymorphous transformation from anatase into rutile. In its turn, anatase stabilized baddeleyite, which has a higher catalytic activity than ruffite. Taking into account the mutual influence of the components, it was able to prepare the selective V-Ti-Zr catalyst. It offered obtaining nicotininitrile from 3-methylpyridine with 92-96% mol. yield.

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polymorphism

Muhler¹

2020

Catalysis From a to Z

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Effect of oxides of the IV and VI group metals on the polymorphic transformation of anatase into rutile

Abstract: An effect of some metal oxides on the polymorphic transformation of anatase into rutile and on the rate of dissociation of V 2 O 5 in the systems V 2 O 5 -TiO 2 and V 2 O 5 -TiO 2 -Me x O y has been studied, where Me x O у is SnO 2 , WO 3 , Cr 2 O 3 or ZrO 2 .

Cited by 5 publications

References 4 publications

Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks

Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks

Catalysts for Alkylbenzene and Alkylpyridine Ammoxidation

polymorphism

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