US Patent 7858066 Method of making titanium dioxide particles

The disclosure provides a process for preparing nanocrystalline titanium dioxide, in particular rutile nanocrystalline titanium dioxide, comprising: (a) precipitating a mixture comprising hydrated titanium oxide and a separable filtering agent; (b) filtering the precipitated mixture to form a filter cake comprising the precipitated hydrated titanium dioxide and a separable filtering agent, (c) calcining the precipitated hydrated titanium oxide and separable filtering agent at a temperature of greater than about 300° C.; and (d) removing the separable filtering agent thereby recovering titanium dioxide particles.