Experimental study of SnO₂/SnO/Sn thermochemical systems for solar production of hydrogen

Abstract

Abstract A novel two‐step thermochemical water‐splitting cycle based on SnO 2 /SnO is proposed from the detailed study of the whole tin oxide systems involving three redox pairs. The thermal reduction of tin(IV) oxide occurs in the temperature range 1400–1600°C following a zero order kinetic law of Arrhenius with an activation energy of 394.8 kJ mol −1 and a pre‐exponential factor of 8.32 × 10 8 g s −1 at atmospheric pressure. The operating conditions that prevent gaseous stannous oxide (SnO) from recombining with O 2 are defined. The effect of a quenching device (water‐cooled finger) is negligible whereas operation at low total pressure or low O 2 and SnO partial pressures leads to nearly pure SnO product. The comparison of SnO and metallic tin hydrolysis in a fixed bed reactor reveals a higher reaction rate in the case of SnO. Hydrolysis of these reduced compounds shows nearly complete conversion producing hydrogen by a solid/gas reaction proceeding at moderate temperature, thus easy to implement in a common reactor technology. © 2008 American Institute of Chemical Engineers AIChE J, 2008