三氯三氨合铑的热解机理及非等温动力学研究

Studies on the Thermal Decomposition Mechanism and Non-isothermal Kinetics of Fac-[Rh(NH_3)_3CI_3] and Mer-[Rh(NH_3)_3Cl_3]

用TG-DTA、IR及X-射线衍射方法研究fac-和mer-[Rh(NH_3)Cl_3]的热解机理。在氮气气氛中加热至315～375℃二者均出现分解并失重约60％,相应的分解活化能分别为596和627kJ/mol。mer-[Rh(NH_3)_3Cl_3]在氢气气氛中以加热速度2℃/min加热时,则热解温度范围更宽,并分三步失重,其相应的活化能分别为336.24,307.42及1380kJ/mol。

Thermodecoraposition mechanism of fac-and mer-[Rh(NH_3)_3Cl_3] in air and nitrogen atmospheres is studied with the aid of the TG-DTA, IR and X-ray diffraction data. The two decomposition steps of mer- and fac- are different at heating rates of 2,5,10 and 20℃/min. When fac- and mer- are heated in nitrogen(150ml/min), they decompose in the range of 315～375℃ with a maximum of 365℃. The weight-loss in this endothermic stage (≈60wt%) indicates that 3 moleculae NH_3 and 3/2 moleculae Cl_2 is losted. The calculated activation energies for decomposition of the fac- and mer- are 596kJ/mol amd 627kJ/mol respectively. Mer-[Rh(NH_3)_3Cl_3] heated at the rate of 2℃/min in nitrogen atmosphere decomposes in a complex multi-step manner, which is different from that of fac-[Rh(NH_3)_3Cl_3].The decomposition extends over a wide temperature range, with three stage weight-loss at 294～401℃ (loss 39.0 wt%, correspond to loss 2 molecule NH_3, 1 molecule Cl_2 ), 534～603℃(loss 14.9 wt%, correspond to loss 1 molecule HCl) and 975～1010℃ loss 5.0 wt%, correspond to loss 1 molecule H_2 , 1/2 molecule N_2 ). The activation energies of the three decomposition steps are 336.24, 307.42 and 1380 kJ/mol respectively.