Studies of Thermochemical Hydrogen Production. VII. Vapor-Liquid Equilibrium for Sulfur Dioxide–Bromine–Hydrobromic Acid–Sulfuric Acid–Water System

Abstract

Abstract In order to eliminate SO2 from HBr gas produced by the reaction between SO2, Br2, and H2O, vapor-liquid equilibrium measurements of the Br2–H2SO4–H2O system saturated with HBr have been made over a wide range of the constituent concentrations. Experiments were carried out in a semi-flow system at 25 °C under atmospheric pressure. The relative concentration of HBr saturated in the liquid phase decreased from 0.31 to 0.05 [mol]/[mol] with an increase in the relative H2SO4 concentration from 0.0 to 0.40 [mol]/[mol]. The solubility of Br2, as defined by Henry’s law constant, varied from 1.1 to ca. 150 atm/mol/mol with the above-mentioned decrease in the HBr concentration. The relation between the partial pressure of SO2 in the gas phase and the composition of the liquid phase was found to be expressed by the following empirical formula: PSO2=K·CHBr·CH2SO4⁄CBr2, where the value of K is 8×10−4 when C is expressed as a relative molar concentration for each species in the liquid phase. The unconverted SO2 can be effectively removed by bringing the effluent gases from the reactor into contact with a HBr-saturated aqueous solution containing an excess of Br2.