THERMAL DECOMPOSITION KINETICS OF THE THERMAL DECOMPOSITION PRODUCT OF AMMONIUM HEPTAMOLYBDATE TETRAHYDRATE IN AIR AND INERT GAS ATMOSPHERES

Abstract

In this study, ammonium tetramolybdate (ATM) was obtained as the intermediate product of ammonium heptamolybdate tetrahydrate (AHM). The thermal decomposition mechanism of ATM was investigated under nonisothermal and isothermal conditions in air and inert gas atmospheres. Nonisothermal experiments were carried out by TGA/DTA/MS while TG was used for isothermal conditions. Characterization of the decomposition products were carried out by XRD and FT-IR. The thermal decomposition of ATM in air proceeds in a single step and forms MoO3 while [(NH4)(2)O](0.0083)MoO3 and molybdenum suboxide (MoO3-x, x=0.025) were obtained in the first and the second steps of thermal decomposition in He, respectively. Activation energies, frequency factors and kinetic model equations were determined for thermal decomposition reactions. Fractional conversion-time diagrams were compared with diagrams drawn according to kinetic model equation.