Structured sulphur trioxide splitting catalytic systems and allothermally-heated reactors for the implementation of Sulphur-based thermochemical cycles via a centrifugal solar particle receiver

Catalytic sulphur trioxide splitting is the highest-temperature (850-900 degrees C), endothermic step of several sulphurbased thermochemical cycles targeted to production of hydrogen or solid sulphur. The demonstrated capability of centrifugal particle solar receivers of heating particle streams at such temperatures, can allow for allothermal implementation of this step via the enthalpy of such particle streams in a catalytic shell-and-tube reactor/heat exchanger decoupled from a solar receiver. In this context, SO3 splitting catalytic systems shaped to spherical particles and flow-through honeycombs and foams were prepared and tested. Long-term (100-950 h) experiments with catalyst-coated SiC honeycombs demonstrated that oxide-supported Pt catalysts suffered from low conversion and severe deactivation at 650 degrees C, contrary to Fe2O3-coated ones. Fe2O3-coated SiC foams demonstrated reproducible near-equilibrium conversion at 850 degrees C, under a broad range of sulphuric acid flow rates, combined with minute pressure drop even under high catalyst loadings (35-45 wt %) being thus in principle suitable for eventual pressurized operation.

Automated summary

Catalytic sulphur trioxide splitting is a crucial step in sulphur-based thermochemical cycles for hydrogen or solid sulphur production. Centrifugal particle solar receivers have been demonstrated to enable high-temperature allothermal implementation of this step. SO3 splitting catalytic systems in spherical particle, honeycomb, and foam shapes have been prepared and tested for this purpose.