Thermodynamics and mass-balance studies indicate the following reaction scheme for the H₂S-sulfuric acid gas-liquid system from room temperature to 120°C:​

H₂S + H₂SO₄ → S + SO₂ + 2H₂O (1)

2H₂S + SO₂ → 3S + 2H₂O (2)

The measured stoichiometry of the two reactions depends on the acid concentration. Under appropriate conditions the two reactions may occur stoichiometrically such that they remove H₂S and recover sulfur without any sulfur emission. The possible chemical reactions between sulfuric acid (from 80 to 96 wt%) and other components likely present in sour gases requiring sulfur removal, i.e., methane, ethylene, CO, CO2, COS, CS2, mercaptan and thiophene, were investigated.

The kinetics for each of the two reactions was studied separately by measuring the total pressure-drop rate in a closed and constant-volume batch reactor enabling an initial-rate analysis. Reaction (1) under acid concentrations from 88 to 100 wt% behaves first order with respect to the pressure of H₂S. The reaction order with respect to sulfuric acid cannot be expressed in terms of an integer. The temperature (20-60°C) dependence of the global rate constant fits the Arrhenius equation. A formula correlating the rate constant with acid concentration and temperature is determined based on the kinetics measurements and an empirical rate equation is proposed. Reaction (2) in presence of sulfuric acid solution (from 30 to 60 wt%) is first order with respect to the pressure of H₂S and to the concentration of SO2 in the solution, respectively. Its rate constant also depends on the temperature (20-60°C) in accordance with the Arrhenius equation but it is independent of the concentration of sulfuric acid solution, which merely provides a liquid medium for the reaction. The rate function for the second reaction may be extrapolated to acid concentrations larger than 60 wt%. Both reactions are found occurring at the interface between gas and liquid.

The reaction rate equations obtained provide a basis for the simulation of the overall reaction rate in a batch reactor. The behaviors of the reactions in a packed column reactor are also studied. And the structure of the technology using these reactions is suggested.