Patent ID: 8071070

Claim:
A process for preparing a crystalline titanium dioxide powder in the form of aggregated primary particles having a variable sintering stability at a BET surface area of 80-90 m 2 /g and a rutile content of 16-30%, wherein the process comprises: introducing a titanium tetrachloride (TiCl 4 ) vapor and, separately therefrom, hydrogen (H 2 ) and a primary air into a mixing chamber to produce a gaseous mixture, wherein the primary air comprises air and/or oxygen enriched air; igniting the gaseous mixture comprising TiCl 4 vapor, H 2 and primary air in a burner to produce a flame, which is burned into a reaction chamber to produce the crystalline titanium dioxide powder and gaseous substances; and separating the crystalline titanium dioxide powder from the gaseous substances, wherein the relative amounts of TiCl 4 vapor, H 2 and primary air are selected to provide crystalline titanium dioxide powder having a BET surface area of 80-90 m 2 /g and a rutile content of 16-30%, with the proviso that factor A has a value of 0.1-0.4 g/m 2 in accordance within the following formula: factor A= 10 5 {[(TiCl 4 vaporÃ—H 2 )/(amount of airÃ—gaseous mixture)]/BET]} wherein TiCl 4 , H 2 , amount of air and gaseous mixture are in units of kmol/h, BET surface area is in units of m 2 /g, and factor A is in units of g/m 2 , and wherein the variable sintering stability is represented by a decrease in BET surface area of 20-90%, based on an original BET surface area prior to sintering.