The kinetics of the chlorination of titania modified by alkali and/or phosphorous additives, were studied by thermogravimetric methods using COCl2 and gaseous CCl4 as chlorinating agents. The chlorination of pure titania was compared with that of phosphorous-containing compounds, TiO2 · nP2O5 and K3P3O9 were also investigated. Apparent activation energies and reaction orders were calculated from the dependence of the initial rates on temperature and partial pressure. With COCl2 as chlorinating agent and increased alkali content of the samples resulted in an increase in the reaction rate, whereas the phosphorous additive behaved as a retardant, and their inhibiting effects became more and more pronounced in the course of the reaction. On the other hand when chlorinating with CCl4, high amounts of K or Na additives retarded the reaction, and Li enhanced the chlorination.
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