Kinetic and thermodynamic studies of the Bunsen reaction in the sulfur–iodine thermochemical process

This work presents the kinetic and thermodynamic studies of the Bunsen reaction in the sulfur–iodine thermochemical cycle for hydrogen production by water splitting. A series of experimental runs have been carried out by feeding the gas mixture SO2/N2 in an I2/H2O medium in the temperature range of 336–358 K. The effects of the various operating parameters on the SO2 conversion ratio have been evaluated. The results showed that the efficiency of SO2 conversion into H2SO4 increased with the amount of I2 or H2O increase. The increasing reaction temperature impeded SO2 conversion into H2SO4. A kinetic model has been developed to fit to the experimental data obtained in a semi-batch reactor. A good fitting can be observed for each experiment, which discloses the overall kinetic mechanism of the complex Bunsen reaction. The apparent activation energies were found to be 23.513 kJ mol−1 and 9.212 kJ mol−1 for the sequential reactions (5) and (6), respectively.