Catalytic decomposition of sulfuric acid for thermochemical water splitting processes

Several promising thermochemical or thermochemical/elecirochemical water splitting processes used to generate hydrogen and oxygen using a high temperature heat source such as a very high temperature nuclear reactor (VHTR) or a solar concentrator employ a high-temperature catalytic sulfuric acid decomposition reaction step. This decomposition reaction, shown below, is identical for the General Atomics, Westinghouse and Ispra Mark 13 cycles. 2H ₂SO ₄ → 2SO ₂ + 2H ₂O + O ₂ The reaction takes place from 750 to 900°C and is facilitated by heterogeneous catalysts to improve the efficiency of the process and the safety of operation. Catalysts increase reaction kinetics by orders-of-magnitude significantly reducing the size of reactors and resulting in lower capital and maintenance costs. Further, reactor size reduction lowers the volume of in-process sulfuric acid, which lowers the potential safety consequences of this reaction step. The Idaho National Engineering and Environmental Laboratory (INEEL) is currently exploring the limitations of the sulfuric acid decomposition catalysts for the purpose of developing highly active, stable catalysts for this reaction step. This presentation will provide an overview of the INEEL nuclear hydrogen project and focus on the sulfuric acid catalytic decomposition studies. A comparison of catalyst activities and stabilities under decomposition conditions will be presented.