Purification ofTiCl4

The chlorides that are solid at room temperature and the entrained dust can be separated from the TiCl4 by simply evaporating (distilling) this off (j). Dissolved chlorine can be removed by heating or reduction with metal powders (Fe, Cu, or Sn).

Removal ofvanadium tetrachloride (VCl4) and vanadium oxychloride (VOCl3) from the TiCl4 by distillation is more challenging owing to the closeness of their boiling points. They are therefore reduced to form solid, low-valence vanadium chlorides (i). An enormous number of reducing agents have been recommended; important examples are copper, titanium trichloride, hydrogen sulfide, hydrocarbons, soaps, fatty acids, and amines. After subsequent evaporation (j) the titanium chloride should contain <5 ppm vanadium. If organic reducing agents are used, the residues may cause problems by baking onto the surfaces of the heat exchanger.

Phosgene and SiCl4 can be removed by fractional distillation.

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