Activity study of NiO-based oxygen carriers in chemical looping steam methane reforming
•Metallic Ni on ZrO2, Al2O3 and NiAl2O4 is active and stable in reforming.•Use of SiO2 and TiO2 support results in fast catalyst deactivation.•Ni on TiO2 easily reoxidizes to NiO during reforming conditions.•NiO/ZrO2 shows excellent activity and stability in chemical looping steam reforming.
This study evaluates the performance of NiO-based oxygen carriers supported on ZrO2, TiO2, SiO2, Al2O3 and NiAl2O4 as conventional reforming catalysts at low temperature (650 °C) as well as oxygen transfer materials (OTMs) for chemical looping steam methane reforming. Conventional reforming experiments with pre-reduced OTMs demonstrated satisfactory performance of NiO/Al2O3, NiO/ZrO2 and NiO/NiAl2O4 at 650 °C, with less than 8% relative decrease in conversion after 10 h time-on-stream. On the other hand, NiO/SiO2 and NiO/TiO2 were found to have low activity (<50% initial CH4 conversion) and deactivated rapidly, eventually dropping to less than 10% CH4 conversion after 2 h on stream. The three most promising materials were tested under chemical looping steam methane reforming conditions for twenty consecutive redox cycles in a fixed bed flow unit. NiO/ZrO2 exhibited good activity with initial CH4 conversion higher than 80% and had very good stability. Deactivation was minimal after 20 consecutive redox cycles, corresponding to 20 h exposure to CH4/steam. NiO/Al2O3 and NiO/NiAl2O4 demonstrated similar high initial activity, but also high deactivation, leading to methane conversion of 59 and 63% conversion respectively at the end of the test.
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Journal: Catalysis Today - Volume 272, 1 September 2016, Pages 32–41