Behavior of Ni‐base alloy 625 in methanol‐supercritical water systems

Methanol reacts with water under supercritical conditions to form a hydrogen rich gas. This reforming reaction can be performed without the addition of a catalyst. Typical reaction conditions are 25 MPa pressure and 600°C temperature and short residence times. The tubular flow reactor used was made of the nickel base alloy 625. The reactor was operated continuously for more than 1000 hours without problems. The feed concentration was 5 weight‐% methanol. The major component of the product gas was hydrogen (up to more than 70 vol‐%). Methanol conversion was higher than 99% and the liquid effluent was clear and free of soot. After exposure, the reactor has been sectioned and each section has been analyzed. No major corrosion phenomena were observed. Severe ductility loss of the material could be measured in the higher temperature section of the reactor.