Stepwise production of syngas and hydrogen through methane reforming and water splitting by using a cerium oxide redox system

Stepwise production of syngas and hydrogen from ZrO2-supported CeO2 through methane reforming and water splitting was investigated in order to find proper operating conditions under which carbon deposition could be minimized. Recommendable operating temperature and time were 1073 K and 30 min for both the methane reforming and the water splitting. Even though the H2/CO ratio during the methane reforming was maintained close to the desired ratio of 2, undesirable methane cracking occurred to a small extent and further reduction of Ce2O3 to metallic Ce by CH4 and H2 occurred to some extent. When the methane reforming-water splitting cyclic operations were repeated, the yields of syngas and hydrogen decreased considerably from the first cycle to the second cycle, but from the second cycle to the fifth cycle the gas yields were maintained nearly constant. As the CeO2 content in the sample increased, the gas yields per mole of CeO2 decreased but the gas productions per gram of sample increased.

► CeO2/ZrO2 for stepwise production of syngas and hydrogen by a redox cycle. ► Proper conditions for methane reforming with minimal carbon deposition are examined. ► A small amount of metallic Ce is produced during the methane reforming. ► Reduced Ce2O3 and Ce can be fully re-oxidized by water splitting. ► Constant gas yields are obtained in repeated cyclic operations.