The rate of reaction of CCl4 with lattice oxygen atoms of the TT-phase niobium oxide (TT-Nb2O5) at 453 K was limited by the diffusion of CCl4 through the layer of a solid reaction product, NbOCl3, formed around the outer surface of niobium oxide. This contrasts to the reaction occurring on the amorphous niobium phosphate in which an inner niobium phosphate participates in the reaction leading to the complete oxidation of CCl4 to CO2. For the reaction of CCl4 on TT-Nb2O5 at temperatures above 573 K, the chemical reaction occurring on the surface of the niobium oxide controls the decomposition rate due to the disappearance of the layer of NbOCl3 by its sublimation.