The ageing of grease in bearings is partially due to its thermochemical degradation. It can lead to lubrication defects and bearing deterioration. To establish the kinetics of this ageing, an experimental study is conducted using the RapidOxy device. Fresh grease or grease containing powdered iron (catalyst incorporated into grease in case of bearing wear) is exposed to gaseous oxygen. The model comprises the kinetic modelling of the three chemical reactions taking place within the grease, as well as gas-liquid transfer of oxygen and water, as well as energy and mass balances of each phase in the Rapidoxy 100 system. The resulting system of ordinary differential equations is numerically solved. Dynamic simulation results are compared with experimental data to obtain kinetic and gas-liquid mass transfer parameters via a parametric optimization method. This model represents an initial step towards comprehending the kinetics of thermochemical grease degradation.