Abstract: A hydrocarbon synthesis catalyst is for reacting a raw material gas including hydrogen and carbon dioxide to convert to hydrocarbons, wherein when elemental analysis of a surface of the hydrocarbon synthesis catalyst to be brought into contact with the raw material gas is performed by energy dispersive X-ray spectroscopy (SEM-EDX), 15 to 65% by mass of Fe, 10 to 40% by mass of O, 0.04 to 30% by mass of Na, 0 to 15% by mass of Ni, and 5 to 30% by mass of Cr are detected.

Abstract: An object of the invention is to provide titanium dioxide coloring particles capable of developing colors other than red and yellow while maintaining non-toxicity of titanium dioxide and a titanium dioxide particle mixture containing the titanium dioxide coloring particles, and to provide a method capable of producing the titanium dioxide coloring particles exhibiting the excellent properties by a simple process with a small environmental load. The invention relates to titanium dioxide coloring particles having a brookite type or rutile type crystal structure and co-doped with at least nitrogen and boron, a titanium dioxide particle mixture containing the titanium dioxide coloring particles, and a method for producing the titanium dioxide coloring particles in which a hydrothermal reaction of titanium diboride is caused in presence of an acid or urea, and then a nitriding treatment is performed in an ammonia gas atmosphere or by mixing with urea or carbon nitride.