J. Phys. IV France 09 (1999) Pr3-337-Pr3-342
A two-step thermochemical conversion of CH4 to CO, H2 and C2-hydrocarbons below 1173 KA. Aoki, T. Shimizu, Y. Kitayama and T. Kodama
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-21, Japan
A high-temperature thermochernical process using a redox system of metal oxide is proposed for converting CH4 to CO, H2, and C2-hydrocarbons (C2-HCs). Reactions were performed in a two-step redox cycle. In the first high-temperature and endothermic step, methane is reacted with metal oxide to produce C2-HCs and the reduced metal oxide : 2CH4 + metal oxide→C2Hn + (4-n/2)H2O + reduced metal oxide. In the second step, H2O or CO2 is reacted with the reduced metal oxide to generate H2 or CO at lower temperatures : H2O + reduced metal oxide→H2 + metal oxide. CO2 + reduced metal oxide→CO + metal oxide. The net rations are 2CH4→C2Hn + (4-n/2)H2, and 2CH4 + (4-n/2)CO2→C2Hn + (4-n/2)(CO + H2O). A thermodynamic analysis showed that redox systems of Fe3O4/FeO, SnO2/SnO and WO3/WO2 are promising for the two-step process. The redox system of Fe3O4 was experimentally examined. Methane was selectively converted to C2-HCs, H2, and CO by the two-step process using the SiO2-supported Fe3O4 (Fe3O4/SiO2) in the temperature range from 1123 to 1173 K. It was found that the high-temperature methane decomposition to bulk carbon was efficiently suppressed over Fe3O4/SiO2. This process offers the efficient endothermic net reaction for converting natural gas to C2H4, H2, and CO with upgraded calorific values, utilizing concentrated solar radiation as the energy source of high-temperature process heat below 1173 K.
© EDP Sciences 1999