Titanium dioxide having a variable sintering stability

Abstract

Provided is a crystalline TiO 2 powder in the form of aggregated primary particles having a variable sintering stability at a BET surface area of 70-100 m 2 /g and a rutile content of greater than 10% but less than or equal to 40%, and a process for preparing the crystalline TiO 2 powder, which involves: introducing a TiCl 4 vapor and, separately therefrom, H 2 and a primary air into a mixing chamber to produce a gaseous mixture; igniting the gaseous mixture in a burner to produce a flame, which is burned into a reaction chamber to produce the crystalline TiO 2 powder and gaseous substances; and separating the crystalline TiO 2 powder from the gaseous substances, wherein the relative amounts of TiCl 4 vapor, H 2 and primary air are selected to provide crystalline TiO 2 powder having the aforementioned BET surface area and rutile content, with the proviso that factor A has a value of 0.1-0.4·10 5 g/m 2 in accordance within the following formula: factor A=10 5 {[(TiCl 4 vapor×H 2 )/(primary air×gaseous mixture)]/BET]}.

1 . A crystalline titanium dioxide powder in the form of aggregated primary particles having a variable sintering stability at a BET surface area of 70-100 m 2 /g and a rutile content of greater than 10% but less than or equal to 40%. 
   
   
       2 . The crystalline titanium dioxide powder according to  claim 1 , wherein the amount of aggregated primary particles having an average particle diameter of more than 45 μm is 0.0001-0.05 wt. %. 
   
   
       3 . The crystalline titanium dioxide powder according to  claim 1 , wherein the BET surface area is 80-90 m 2 /g. 
   
   
       4 . The crystalline titanium dioxide powder according to  claim 1 , wherein the rutile content is 16-30%. 
   
   
       5 . The crystalline titanium dioxide powder according to  claim 1 , wherein the crystalline titanium dioxide powder has a chloride content of less than 0.1 wt. %. 
   
   
       6 . The crystalline titanium dioxide powder according to  claim 1 , wherein the crystalline titanium dioxide powder has a chloride content of 0.01-0.05 wt. %. 
   
   
       7 . The crystalline titanium dioxide powder according to  claim 1 , wherein the crystalline titanium dioxide powder has a tamped density of 20-200 g/L. 
   
   
       8 . The crystalline titanium dioxide powder according to  claim 1 , wherein the crystalline titanium dioxide powder has a tamped density of 30-120 g/L. 
   
   
       9 . A process for preparing the crystalline titanium dioxide powder according to  claim 1 , 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 70-100 m 2 /g and a rutile content of greater than 10% but less than or equal to 40%,   with the proviso that factor A has a value of 0.1-0.4·10 5  g/m 2  in accordance within the following formula:
   factor A=10 5 {[(TiCl 4  vapor×H 2 )/(primary air×gaseous mixture)]/BET]} 
   wherein TiCl 4 , H 2 , primary 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 10 5  g/m 2 .   
   
   
       10 . The process according to  claim 9 , wherein the process further comprises introducing a secondary air into the mixing chamber,
 wherein   the secondary air comprises air and/or oxygen enriched air,   a volume ratio of primary air to secondary air is 10:0.1, and   the primary air and/or the secondary may optionally be preheated to a temperature of 50-500° C.   
   
   
       11 . The process according to  claim 10 , wherein the volume ratio of primary air to secondary air is 4.5:0.3. 
   
   
       12 . The process according to  claim 9 , wherein the process further comprises igniting in the burner and burning into the reaction chamber a secondary air,
 wherein   the secondary air comprises air and/or oxygen enriched air,   a volume ratio of primary air to secondary air is 10:0.1, and   the primary air and/or the secondary may optionally be preheated to a temperature of 50-500° C.   
   
   
       13 . The process according to  claim 12 , wherein the volume ratio of primary air to secondary air is 4.5:0.3. 
   
   
       14 . The process according to  claim 9 , wherein a ratio of the amount of hydrogen introduced to a stoichiometric amount of hydrogen required to react with chloride of titanium tetrachloride to form hydrochloric acid is referred to as gamma (γ) in accordance with the following equation:
   gamma (γ)=H 2  introduced (mole)/stoichiometric H 2  (mole)   wherein gamma (γ) has a value of 1-9.   
   
   
       15 . The process according to  claim 9 , wherein a ratio of the amount of oxygen introduced to a stoichiometric amount of oxygen required to react with titanium of titanium tetrachloride to form titanium dioxide and convert any excess unreacted hydrogen to water is referred to as lambda (λ) in accordance with the following equation:
   lambda (λ)=O 2  introduced (mole)/stoichiometric O 2  (mole).   wherein lambda (λ) has a value of 1-9.   
   
   
       16 . The process according to  claim 9 , wherein the process further comprises steam treating the crystalline TiO 2  powder, after separating the crystalline TiO 2  powder from the gaseous substances, with steam and an optional air. 
   
   
       17 . The process according to  claim 16 , wherein the steam and the optional air, which is present, are flowing in a concurrent direction or a countercurrent direction. 
   
   
       18 . The process according to  claim 16 , wherein the steam treating is carried out at a temperature of 250-750° C. 
   
   
       19 . A catalyst comprising the crystalline titanium dioxide (TiO 2 ) powder according to  claim 1 . 
   
   
       20 . A catalyst support comprising the crystalline titanium dioxide (TiO 2 ) powder according to  claim 1 .