Methane Decomposition to Hydrogen Over Zirconia-Supported Fe Catalysts-Effects of the Modified Support

Abstract

Methane decomposition is a promising route to synthesize CO_x -free hydrogen and carbon nanomaterials (CNM_s ). In this work, the impregnation method was employed for the preparation of the catalysts. Systematic investigations on the activity and stability of Fe-based catalysts were carried out in a packed-bed micro-activity reactor at 800 °C with a feed gas flow rate of 18 mL/min. The effect of doping Y₂ O₃ , MgO, SiO₂ and TiO₂ over ZrO₂ on the catalytic performance was also studied. BET revealed that the specific surface areas and pore volumes are increased after SiO₂ , TiO₂ , and Y₂ O₃ are added to ZrO₂ while MgO had a negative impact and hence a little decrease in specific surface area is observed. The catalytic activity results showed that the Fe-based catalyst supported over TiO₂ -doped ZrO₂ that is, Fe-TiZr, demonstrated the highest activity and stability, with a maximum methane conversion of 81.3 % during 180 min time-on-stream. At 800 °C, a maximum initial methane conversion of 73 %, 38 %, 64 %, and 69 % and a final carbon yield of 121 wt. %, 55 wt. %, 354 wt. %, and 174 wt. % was achieved using Fe-MgZr, Fe-SiZr, Fe-TiZr and Fe-YZr catalysts, respectively. Moreover, bulk deposition of uniform carbon nanotubes with a high degree of graphitization and different diameters was observed over the catalysts.

Keywords: hydrogen generation; iron catalyst; methane decomposition; modified support; zirconia.