Partial oxidation of methane to syngas with or without simultaneous steam or CO₂ reforming over a high-temperature stable-NiCoMgCeO_x supported on zirconia-hafnia catalyst

Abstract

A NiCoMgCeO_x (Ni/Co/Mg/Ce:1:0.2:1.2:1.2)/zirconia-hafnia catalyst with unusually high thermal stability has been investigated for syngas generation via a process that includes the catalytic partial oxidation of methane (CPOM), the oxidative steam reforming of methane (OSRM) and the oxidative CO₂ reforming of methane (OCRM). The catalyst calcined at 1400°C (for 4 h) showed excellent activity/selectivity for the CPOM, OSRM and the OCRM reactions; furthermore no catalyst deactivation was observed for a period of 20 h. For the CPOM process, the selectivity for H₂ was >95% at reaction temperatures ≥650 °C; however temperatures above 800 °C were required to achieve >95% CO selectivity. While the reaction temperature had a considerable influence on the CPOM product H₂/CO ratio, the space velocity (at 850°C) did not affect it to any significant extent. For the OSRM process, the H₂O/CH₄ ratio and the reaction temperature had a strong effect on the product H₂/CO ratio and the heat of the reaction; depending on the H₂O/CH₄ ratio and reaction temperature, the OSRM process could be operated in a mildly exothermic, thermoneutral or mildly endothermic mode. The CO₂ conversion was very strongly affected by the reaction temperature in the OCRM process; reasonably high CO₂ conversion (>40%) could only be obtained at high OCRM reaction temperatures (>850 °C). The exothermicity of the OCRM reaction was found to decrease with increasing reaction temperature.