Hydrogen production tests by hydrogen iodide decomposition membrane reactor equipped with silica-based ceramics membrane

The decomposition of hydrogen iodide in the thermochemical water splitting iodine–sulfur process at an intermediate temperature (400 °C) using a catalytic membrane reactor was reported here, for the first time. The performance of a catalytic membrane reactor based on a hexyltrimethoxysilane-derived silica membranes (H₂ permeance of 9.4 × 10⁻⁷ mol Pa⁻¹ m⁻² s⁻¹ and H₂/N₂ selectivity of over 80.0.) was evaluated at 400 °C by varying the HI flow rates of 2.6, 4.7, 6.9, 8.4, and 9.7 mL min⁻¹. The silica membranes were prepared by counter-diffusion chemical vapor deposition method on γ-alumina-coated α-alumina tubes. Hydrogen was successfully extracted from the membrane reactor using the silica membrane at 400 °C. A significant increase in HI conversion was achieved. The conversion achieved at an HI flow rate of 2.6 mL min⁻¹ was approximately 0.60, which was greater than the equilibrium conversion in HI decomposition (0.22).