TITANIUM OXIDE GRAIN, PROCESS AND APPARATUS FOR PRODUCING THE SAME, AND METHOD OF TREATING WITH THE TITANIUM OXIDE

摘要

Titanium oxide grains of large specific area and high crystallinity with reduced internal defects, whose high photocatalytic activity as a photocatalyst is promising; and titanium oxide grains which even when heated at high temperature, exhibits low tendency of transformation to rutile crystal structure and exhibits low rate of sintering. As titanium oxide grains for composing a photocatalyst, use is made of those of the shape of a boxy polyhedron. The polyhedron constituting the titanium oxide grains is composed of one or more titanium oxide single-crystal polyhedrons. The crystallinity can be enhanced by causing the flatness ratio of single-crystal polyhedrons to fall within the range of 0.33 to 3.0. It is preferred that the polyhedron be a hexa- to decahedron. The rutile transformation ratio R (700-24) is to be 7.5% or less while the rutile transformation ratio R (500-24) is to be 2.0% or less. Titanium oxide grains of the above configuration are produced through a process comprising feeding titanium tetrachloride vapor and oxygen into a synthetic tube of quartz glass and heating them from the exterior of the synthetic tube by means of an oxyhydrogen flame burner so as to effect thermal oxidation.