Small titania/titanates

Certain difficulties in the application of titania enamels arise as a result of their reduced colour stability. Even small amounts of Fe cause undesirable yellow colouring. Of some help is oxidation to Fe which does not form the ferrous--titanate colouring complex. Similar unfavourable efiects are also exhibited by other impurities (Cr, Ta, >Jb, W). 

Support modification has been reported earlier in the open literature [5,6,7,8,9]. Zirconia modification of silica supports was used to prevent the formation of unreducible cobalt-silicates [5]. Zr, Ce, Hf, or U modification of titania supports was reported to prevent the formation of cobalt-titanates during regeneration [6]. To increase the porosity of titania supports, they were modified with small amounts of binders, e.g. silica, alumina or zirconia [7]. Lanthanum oxide promotion of alumina was reported to be beneficial for improved production of products with higher boiling points [8], and zirconia modification of alumina supports was carried out to decrease the interaction of cobalt with alumina [9]. All these modified supports were either used for fixed bed cobalt based Fischer-Tropsch synthesis catalysts or they were used for slurry phase cobalt catalysts, but not tested under realistic Fischer-Tropsch synthesis conditions in large scale slurry bed reactors. 

Ilmenite. Ferrous titanate, Fe0.Ti02 m.p. 1365°C. This mineral is the principal constituent of the heavy minerals in the beach sands of Australia and elsewhere it is thus the chief source of titania, which is used in the ceramic industry as an opaciher and as a constituent of some ceramic dielectrics. Image Furnace. Apparatus for the production of a very high temperature in a small space by focusing the radiation from the sun (solar furnace) or from an electric arc (arc-image furnace) by means of mirrors and/or lenses. Such furnaces have been used for the... 

Sol-gel routes for binary titanium dioxide, tertiary titanates, and other mbced metal oxide systems not only employ various Ti(lV) alkoxides and modified alk-oxides but also Ti(IV) chlorides, oxychlorides, oxynitrates, and so on. The microstructure of the resulting titania and titanates depends on the morphology and interactions between primary particles (clusters) forming upon hydrolysis-condensation of Ti(IV) precursors. An apparent lack of crystalline order and very small size of primary particles and clusters (<1 nm) is observed in the early stages of reaction. At a more advanced stage, the morphology is determined by interparticle interactions and aggregation mechanisms. 

X-ray patterns of the products formed by the reaction between strontium carbonate and anatase, rutile, and nonstoichiometric rutile each showed SrTiOj to be the only phase present. X-ray patterns of partially reacted compacts revealed the presence of strontium titanate, strontium carbonate, and titania. The absence of strontium oxide indicates that the carbon dioxide evolution was associated with the reaction between SrCOj and Ti02 to form a product phase and not with the decomposition of SrCOj to SrO. The data of Wanmaker and Radielovic for the rate of dissociation of strontium carbonate indicates that interference from dissociation in measuring the kinetics of interaction between SrCOj and Ti02 is negligible below 900°C. Above this temperature a correction may be necessary for the dissociation of SrCOj. However the fact that the same kinetic model can be used to represent the data above and below this temperature suggests that the correction term is small. 

---