Study of the miscibility gap in H2SO4/HI/I2/H2O mixtures produced by the Bunsen reaction – Part I: Preliminary results at 308 K

In the framework of the optimization of the sulfur–iodine thermochemical cycle for massive hydrogen production, investigations were performed in order to characterize the liquid phase (HIx and H₂SO_4(aq) phases) separation of solutions resulting from Bunsen reaction. Quaternary H₂SO₄/HI/I₂/H₂O mixtures were prepared at 308 K with different relative proportions of reactants and the chemical composition of each of the two phases formed was analyzed. An increase in iodine concentration and a decrease in water concentration appeared to improve the liquid–liquid equilibrium phase separation. However, a too low concentration of water also promoted the formation of byproducts. An increase in the [H₂SO₄]/[HI] ratio tended to favor the separation and seemed to lead to a dehydration of the HIx phase.