Simulation study on the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water-splitting IS process

Catalytic decomposition of hydrogen iodide in a membrane reactor was investigated theoretically for the application to the hydrogen production step in the thermochemical iodine–sulfur (IS) process. Characteristics of the membrane reactor were evaluated using observed permeances of H2 and HI in a homemade silica membrane that was prepared by chemical vapor deposition (CVD) method (selectivity of H2/HI: 650). The effect of the H2/I2 selectivity on the performance of the membrane reactor was evaluated by simulation since I2 permeance through the homemade silica membrane could not be determined so far because of the difficulty of the measurements. It was found from the simulation study that the conversion of over 0.9 would be attainable using the membrane reactor with the homemade silica membrane. Design criterion of the membrane reactor was discussed using the relationships between the ratio of reaction zone volume to the membrane surface area, the dimensionless reactor length and the conversion.