Non-equilibrium Kinetics of Dissociation of Molecular Hydrogen in Microwave Discharge in Liquid Hydrocarbons

A semi-empirical level-based model is developed that describes the detailed kinetics of the formation and decay of hydrogen atoms during relaxation of the vibrational energy of hydrogen molecules in the gas phase of a microwave discharge in liquid hydrocarbons in the range of the translational temperature from 600 to 3000 K at atmospheric pressure. It is shown that, depending on the conditions in the gas phase, the monomolecular decomposition of hydrogen can consist of two stages—the early and late stages. At the early stage, the dissociation of a hydrogen molecule occurs with a non-equilibrium energy distribution over the internal degrees of freedom of the molecule. At the late stage, chemical equilibrium in the concentration of hydrogen atoms is established. The specific energy stored in the vibrational degree of freedom of the hydrogen molecule decreases as a result of the dissociation of molecules during the equilibrium between the translational-rotational and vibrational degrees of freedom of the molecule. As a result, the relaxation time of the vibrational energy increases and becomes equal to the time at which the equilibrium of hydrogen atoms concentration is established.