Sublimation Kinetic Studies of the Zr(tmhd)4 Complex

The thermal behaviour of tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium(IV), [Zr(tmhd)(4)] was investigated by nonisothermal and isothermal thermogravimetric methods in a high pure nitrogen atmosphere. The influence of the heating rate in dynamic measurements (6, 8, 10, and 12 degrees C/min) on activation energy was also studied. The nonisothermal sublimation activation energy values determined following the procedures of Arrhenius, Coats and Redfern, Kissinger, and Flynn-Wall yielded 76 +/- 5, 92 +/- 2, 81 +/- 8, and 72 +/- 7 kJ/mol, respectively, and the isothermal sublimation activation energy was found to be 87 +/- 4 kJ/mol over the temperature range of 411-462 K. Different reaction mechanisms were used to compare with this value. Analysis of the experimental results suggested that the actual reaction mechanism was an R-n type.