The sulfur iodine hydrogen production process (SI process) is an efficient thermochemical process. Developing composition data of the Bunsen products that are obtained under pressurized conditions is important for the integrated operation of SI process. We investigated the characteristics of the pressurized Bunsen reaction by varying operating parameters (pressure, temperature, I-2 and H2O feed concentrations). An HIx solution that consisted of HIx I-2 and H2O was used as the reactant. When the pressure increased, the extent of Bunsen reaction was enhanced by increasing the solubility of SO2 gas in the HIx solution. In addition, the amount of H2SO4 phase solution increased due to the decrease in the amount of HIx complex, which has a high degree of hydration. Increasing temperature enhanced the separation performance of the Bunsen products, while the extent of Bunsen reaction decreased. When I-2 feed concentration increased, the occurrence of side reaction was inhibited, but the separation performance of the Bunsen products decreased. Although increasing H2O feed concentration was favorable for the pressurized Bunsen reaction, the H2O feed concentration should be controlled by considering the solubility of I-2 in the HIx solution. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.