Thermal properties of molybdenum hexacarbonyl: Kinetic and thermodynamic studies

The thermal analysis of molybdenum hexacarbonyl has been performed under helium stream (2 K min(-1)) between room temperature and (1100 +/- 2) K. According to mass spectrometry results, the organometallic sublimates between (330.4 +/- 0.1) K and (339.7 +/- 0.1) K, and the sublimation enthalpy, determined at two particular temperatures (Delta H-sub((298.15 K)) = (73.66 +/- 0.02) kJ mol(-1)), is similar to the activation energy. As a matter of fact, the sublimation of Mo(CO)(6(cr)) follows a perfect-zero order reaction kinetic (E-a = (73.49 +/- 0. 10) kJ mol(-1) and the pre-exponential factor is (8.33 +/- 0.33) x 108 s(-1)). Furthermore, using Langmuir equation and thermogravimetry data, we were able to determine the vaporization constant (alpha) (=8.95 x 10(-5) +/- 1.45 x 10(-7)), the constant k (=80735 J(0.5) mol(-0.5) K-0.5) as well as Delta H-sub ((298.15 K)) (equal to (75.91 +/- 0.37) kJ mol(-1)). In the presence of ZSM-5 zeolite, the temperatures of Mo(CO)(6(cr)) decarbonylation, E-a and Delta H-sub values were succinctly determined. Interestingly, the loss of the first CO ligand in Mo (CO)(6(cr)) occurred between (480 +/- 0.1) K and (532 +/- 0.1) K. (c) 2020 Elsevier Ltd.