Pyrohydrolysis of zirconium tetrafluoride

A study was made on pyrohydrolysis of ZrF4 powder samples with 0.5; 0.8; 1.2 m2/g specific surface and 40-63 μm particle diameter by titrimetric and gravimetric methods with application of X-ray phase and chemical analyses of solid products at 630-800 K, psub(Hsub(2)O)=2.4-100 kPa partial pressures of water vapors, 100 kPa total pressure, 7-20 sm/s linear gas speed in reaction zone. It is shown that the reaction proceeds with formation of ZrO2 and a number of zirconium oxyfluorides- at intermediate stages. The reaction rate slightly depends on the specific surface of samples and at 740-800 K is described by the equation:1-(1-α)sup(1/3)=(3.0+-3.0)x10sup(5)exp[-(120+-30)x10sup(3)/RT]xtauxpsub(Hsub(2)O)/[psub(Hsub(2)O)+(2.6+-2.5)x10sup(6)exp[-(9O+-30)x10sup(3)/RT]], where α- the degree of conversion by tau time. The apparent activation energy of the process decreases from 190 to 120 kJ/mol with temperature growth