Thermal properties of molybdenum hexacarbonyl: Kinetic and thermodynamic studies

Abstract

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 (ΔsubH(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 (Ea = (73.49 ± 0.10) kJ mol−1 and the pre-exponential factor is (8.33 ± 0.33) × 108s−1). Furthermore, using Langmuir equation and thermogravimetry data, we were able to determine the vaporization constant (α) (=8.95 × 10−5 ± 1.45 × 10−7), the constant k (=80735 J0.5 mol−0.5 K−0.5) as well as ΔsubH(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, Ea and ΔsubH 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.