Monday, June 3, 2019
Texas Ballroom Prefunction Area (Grand Hyatt San Antonio)
The dry reforming of methane (DRM) is a auspicious process to convert biogas or natural gas into CO + H2 syngas. The generation of syngas is of great industrial interest in particular in the production of liquid fuels via Fischer-Tropsch. The major problem in DRM is the catalyst deactivation by the formation of carbon deposits over the metal sites. To overcome this problem the catalyst La2Ce2-xNixO7-λ-LaNiO3 was synthesized using coprecipitation (CP) and hydrothermal (HT) methods. These catalysts were characterized and tested catalytically in the DRM at temperatures between 600 to 900°C, and further, tested at 850°C, over 8 hours. The X-ray diffraction analysis showed, in both synthesis methods, the formation of NiO in addition to LaNiO3 and La2Ce2-xNixO7-d. In the temperature programmed reduction analysis, two main reduction peaks characteristic of the perovskite phase were observed with higher reduction temperatures in the HT sample. Furthermore, this catalyst had higher CH4 and CO2 conversions at all temperatures, and unlike CP the HT catalyst was active at relatively low temperature of 600°C. In the short term stability at 850°C, the HT catalyst showed very close CH4 and CO2 (~90%) conversions suggesting that the reaction is occurring stoichiometrically. In contrast, the CP catalyst showed higher CO2 (~75%) than CH4 (~62%) conversion, due the simultaneous occurrence of reverse water gas shift reaction. Regardless of the synthesis method, all catalysts were stable during 8h of time on stream. Furthermore, thermogravimetric analysis after short-term stability tests revealed no significant carbon deposition (<2%). The results indicate that the pyrochlore-perovskite system is active and stable to catalyze the DRM, since it can effectively suppress the deposition of carbon on the surface of the catalyst.