In this work, we describe a novel design for a H2SO4 decomposer. The decomposition of H2SO4 to produce SO2 is a common processing operation in the sulfur-based thermochemical cycles for hydrogen production where acid decomposition takes place at 850°C in the presence of a catalyst. The combination of a high temperature and sulfuric acid creates a very corrosive environment that presents significant design challenges. The new decomposer design is based on a bayonet-type heat exchanger tube with the annular space packed with a catalyst. The unit is constructed of silicon carbide and other highly corrosion-resistant materials. The new design integrates acid boiling, superheating, decomposition, and heat recuperation into a single process and eliminates problems of corrosion and failure of high-temperature seals encountered in previous testing using metallic construction materials. The unit was tested by varying the acid feed rate and decomposition temperature and pressure.