Patent ID: 8679449

Claim:
A method for producing decahedral titanium oxide particles, wherein the decahedral titanium oxide particles are produced by allowing a reaction gas containing titanium tetrachloride to flow into a reaction pipe having a partial double-pipe structure in which a hollow internal cylinder is inserted into an upstream portion of a hollow external cylinder, the method comprising: performing a preheating on the reaction gas containing titanium tetrachloride and a barrier gas not containing metal chlorides but including water vapor in a region of the reaction pipe, wherein the region exists on the upstream side of a downstream end of the hollow internal cylinder, while allowing the reaction gas to flow into the hollow internal cylinder and the barrier gas to flow between the hollow internal cylinder and the hollow external cylinder; and performing a main heating on a mixed gas, which includes the reaction gas and the barrier gas, in a downstream region apart from the downstream end of the hollow internal cylinder to thermally decompose the titanium tetrachloride; wherein a sectional area of a passageway for the barrier gas between the hollow external cylinder and the hollow internal cylinder is equal to or more than four times a sectional area of a passageway for the reaction gas of the hollow internal cylinder, wherein the time until the reaction gas discharged from the downstream end of the hollow internal cylinder arrives at the most upstream end of a main heating region heated to be equal to or more than 800° C. is equal to or less than 250 milliseconds, and the time during which the reaction gas stays at the main heating region is equal to or more than 2 milliseconds and equal to or less than 300 milliseconds.