Mixed metal oxides titanium compounds

Titanium IV) oxide, T1O2. See titanium dioxide. Dissolves in concentrated alkali hydroxides to give titanates. Mixed metal oxides, many of commercial importance, are formed by TiOj. CaTiOj is perovskite. BaTiOa, per-ovskite related structure, is piezoelectric and is used in transducers in ultrasonic apparatus and gramophone pickups and also as a polishing compound. Other mixed oxides have the il-menite structure (e.g. FeTiOj) and the spinel structure (e.g. MgjTiO ). 

A considerable number of materials called titanates are known, some of which are of technical importance. Nearly all of them have one of the three major mixed metal oxide structures (page 54), and indeed the names of two of the structures are those of the titanium compounds that were the first found to possess them, namely, FeTi03, Hmenite, and CaTi03, perovskite. Other titanites with the ilmenite structure are MgTiOa, MnTi03, CoTi03... 

Another propylene ammoxidation catalyst that was used commercially was U-Sb-0. This catalyst system was discovered and patented by SOHIO in the mid-1960s (26,27). Optimum yield of acrylonitrile from propylene required sufficient antimony in the formulation in order to ensure the presence of the USbaOio phase rather than the alternative uranium antimonate compound USbOs (28-30). The need for high antimony content was understood to stem from the necessity to isolate the uranium cations on the surface, which were presumed to be the sites for partial oxidation of propylene. Isolation by the relatively inactive antimony cation prevented complete oxidation of propylene to CO2. Later publications and patents showed that the activity of the U-Sb-0 catalyst is increased by more than an order of magnitude by the substitution of a tetravalent cation, tin, titanium, and zirconium (31). Titanium was found to be especially effective. The promoting effect results in the formation of a solid solution by isomorphous substitution of the tetravalent cation for Sb + within the catalytically active USbaOio- phase. This substitution produces o gen vacancies in the lattice and thus increases the facility for diffusion of lattice o gen in the solid structure. As is discussed below, the enhanced diffusion of o gen is directly linked to increased activity of selective (amm)oxidation catalysts based on mixed metal oxides. 

A mixture of the 3 compounds exploded violently during mixing. Previously the mixture had been accidentally ignited by a spark. Aluminium powder is incompatible with oxidants, and its mixture with titanium dioxide is a thermite-like combination. See Aluminium Metal oxides See also THERMITE REACTIONS... 

For pressing as well as extrusion, the solid electrolyte precursor particles (e.g., zirconia) are often mixed or reacted with an inorganic cementing substance. It is preferred that such adhesive materials also have ion permselective properties as the precursor particles. Phosphates of zirconium, titanium and zinc are examples of such cements although other materials such as calcium aluminate and calcium aluminosilicates are candidates as well [Arrance et al., 1969]. For these cementing materials to be effective, the metal oxides must be only partially hydrated so that they are reactive with the bonding compounds. 

Inorganic Titanates. Titanium forms a series of mixed oxide compounds with other metals. Only in one of these, Ba2Ti04, ate there discrete TiOJ ions (99). Compounds of the general formula M" 2Ti02 or M " Ti02 are known as metatitanates those having AU TiO and are called... 

The two most important sources of uranium are the minerals carnotite, where uranium occurs in the hexavalent oxide or hydrated oxide, and pitchblende, where uranium occurs mostly in the tetravalent state as a compound salt with other metals. It also occurs as a mixed oxide with titanium, thorium, and niobium in the tetravalent form. The tetravalent uranium minerals appear to have been geologically formed in the presence of reducing agents such as hydrocarbon minerals, graphite, native metals, and sulfide minerals, while such association is rarely observed with the hexavalent uranium minerals. 

The synthesis of a mixed Ti(iv) complex based on Gp and the small carborane ligand C2B42 has been reported. The compounds Gp[2,3-R2-2,3-G2B4H4]TiCl are prepared by reduction of Cp2TiCl2 with /aw-m -Li-l-Li[2,3-R2-2,3-C2B4H4] and subsequent chemical oxidation with anhydrous TiCl4 in THF (Scheme 740). The crystal structure shows a distorted tetrahedral environment about the metal center similar to those of bis-Cp titanium derivatives (Figure 31). 

O-Donor Ligands. Table 1 summarizes the results of some studies concerning titanates and Ti mixed oxide compounds. The corrosion of titanium metal by liquid sodium containing dissolved oxygen has been shown to take place... 

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