Keywords: catalyst, oxygen, rate constant, sulphur trioxide, sulphuric acid, thermal decomposition, hydrogen production, chemical kinetics, nuclear energy, nuclear power, hydrogen energy
Thermal decomposition of SO3
The iodine–sulphur and the Westinghouse methods are recognised as thermochemical methods for producing hydrogen from water. Thermal decomposition of SO3 is an important process in both methods. This study used a flow-type apparatus to evaluate the decomposition of SO3 to SO2 and O2. The SO3 decomposition rate was measured by the temperature dependence of oxygen concentration using a chemical kinetic model and the reaction was assumed to be a homogeneous reaction of first order. The decomposition rate constant without catalyst was estimated to be 2.23 × 1012 exp(–39,295/T) s-1. When hematite was used as the catalyst, the decomposition rate constant increased to 6.79 × 105 exp(–20,021/T) s-1. A chemical dynamics calculation showed the decomposition ratio of SO3 for cases with the catalyst reached 0.9 within about 20 sec at 1173 K. Catalyst use would be effective for decreasing the size of a SO3 decomposer at temperatures lower than 1273 K.