TITANIUM OXIDE PRODUCTION METHOD
The present invention provides a method of producing titanium oxide capable of maintaining a high content of an anatase form crystal phase at a low cost even under a high temperature environment. The method of producing titanium oxide includes a step of synthesizing titanium oxide by using an aqueous solution obtained by dissolving titanium tetrachloride and an α-hydroxycarboxylic acid having 3 carboxy groups as a reaction liquid and bringing the reaction liquid to a reaction temperature of 60° C. or higher and the boiling point of the reaction liquid or lower, wherein the ratio of the amount (mol) of the α-hydroxycarboxylic acid to the amount (mol) of Ti in the reaction liquid is 0.006 or more and 0.017 or less, and the concentration of Ti in the reaction liquid is 0.07 mol/L or more and 0.70 mol/L or less.
1 . A method of producing titanium oxide, the method comprises a step of synthesizing titanium oxide by using an aqueous solution in which titanium tetrachloride and an α-hydroxycarboxylic acid having 3 carboxy groups are dissolved as a reaction liquid and bringing the reaction liquid to a reaction temperature of 60° C. or higher and a boiling point of the reaction liquid or lower,
wherein a ratio of an amount (mol) of the α-hydroxycarboxylic acid to an amount (mol) of Ti in the reaction liquid is 0.006 or more and 0.017 or less;
a Ti concentration of the reaction liquid is 0.07 mol/L or more and 0.70 mol/L or less;
when the Ti concentration of the reaction liquid is 0.07 mol/L or more and less than 0.20 mol/L, the reaction temperature is 60 to 75° C.;
when the Ti concentration of the reaction liquid is 0.20 mol/L or more and less than 0.45 mol/L, the reaction temperature is 65° C. or more and the boiling point of the reaction liquid or lower; and
when the Ti concentration of the reaction liquid is 0.45 mol/L or more and 0.70 mol/L or less, the reaction temperature is 60 to 75° C., and
wherein the method further comprises a dilution step of obtaining the reaction liquid by diluting an aqueous solution of titanium tetrachloride and the α-hydroxycarboxylic acid in a concentration of 10% by mass or more as a precursor aqueous solution prior to the synthesizing step with water.
2 . The method of producing titanium oxide according to claim 1 , wherein the α-hydroxycarboxylic acid is citric acid.
3 . A method of producing titanium oxide, the method comprises a step of synthesizing titanium oxide by using an aqueous solution in which titanium tetrachloride and an α-hydroxycarboxylic acid having two carboxy groups are dissolved as a reaction liquid and bringing the reaction liquid to a reaction temperature of 60° C. or higher and a boiling point of the reaction liquid or lower,
wherein a ratio of an amount (mol) of the α-hydroxycarboxylic acid to an amount (mol) of Ti in the reaction liquid is 0.034 or more and 0.065 or less;
a Ti concentration of the reaction liquid is 0.07 mol/L or more and 0.70 mol/L or less;
when the Ti concentration of the reaction liquid is 0.07 mol/L or more and less than 0.20 mol/L, the reaction temperature is 60 to 75° C.;
when the Ti concentration of the reaction liquid is 0.20 mol/L or more and 0.45 mol/L or less, the reaction temperature is 65° C. or more and the boiling point of the reaction liquid or lower; and
when the Ti concentration of the reaction liquid is 0.45 mol/L or more and 0.70 mol/L or less, the reaction temperature is 60 to 75° C.
4 . The method of producing titanium oxide according to claim 3 , wherein the α-hydroxycarboxylic acid is tartaric acid or malic acid.
5 . The method of producing titanium oxide according to claim 3 , wherein the method further comprises a dilution step of obtaining the reaction liquid by diluting an aqueous solution of titanium tetrachloride and the α-hydroxycarboxylic acid in a concentration of 10% by mass or more as a precursor aqueous solution prior to the synthesizing step with water.
6 . The method of producing titanium oxide according to claim 1 , wherein the method further comprises a step of preparing the aqueous solution of titanium tetrachloride and the α-hydroxycarboxylic acid as the precursor aqueous solution by mixing an aqueous solution of titanium tetrachloride having a Ti concentration of 10% by mass or more with the α-hydroxycarboxylic acid prior to the dilution step.
7 . The method of producing titanium oxide according to claim 1 , wherein the dilution step is performed by adding water to the precursor aqueous solution.
8 . The method of producing titanium oxide according to claim 1 , wherein the precursor aqueous solution is held at 35° C. or lower until the dilution step is started.
9 . The method of producing titanium oxide according to claim 1 ,
wherein in the dilution step, a temperature of water used for dilution is lower than the reaction temperature; and
in the synthesizing step, the reaction liquid is heated to the reaction temperature.
10 . The method of producing titanium oxide according to claim 9 , wherein in the synthesizing step, the reaction liquid is heated at a temperature rise rate of 0.1 to 1.5° C./min.
11 . The method of producing titanium oxide according to claim 1 , wherein the reaction liquid is held at the reaction temperature for 0.5 hours or more.
12 . The method of producing titanium oxide according to claim 3 , wherein the method further comprises a step of preparing the aqueous solution of titanium tetrachloride and the α-hydroxycarboxylic acid as the precursor aqueous solution by mixing an aqueous solution of titanium tetrachloride having a Ti concentration of 10% by mass or more with the α-hydroxycarboxylic acid prior to the dilution step.
13 . The method of producing titanium oxide according to claim 3 , wherein the dilution step is performed by adding water to the precursor aqueous solution.
14 . The method of producing titanium oxide according to claim 3 , wherein the precursor aqueous solution is held at 35° C. or lower until the dilution step is started.
15 . The method of producing titanium oxide according to claim 3 ,
wherein in the dilution step, a temperature of water used for dilution is lower than the reaction temperature; and
in the synthesizing step, the reaction liquid is heated to the reaction temperature.
16 . The method of producing titanium oxide according to claim 15 , wherein in the synthesizing step, the reaction liquid is heated at a temperature rise rate of 0.1 to 1.5° C./min.
17 . The method of producing titanium oxide according to claim 3 , wherein the reaction liquid is held at the reaction temperature for 0.5 hours or more.