Reforming and cracking of CH4 over Al2O3 supported Ni, Ni-Fe and Ni-Co catalysts

Abstract

Supported Ni, Ni-Fe and Fe catalysts of the same total metal loading and different Ni to Fe ratios were studied for the dry reforming and cracking of methane (CH4). The supported Ni-Fe catalysts containing Ni and Fe in the ratio of 3:1 (75Ni25Fe/Al2O3) was the most active for both reactions and was slightly more active than the supported Ni catalyst. The same Ni to Co ratio of 3:1 was present in the most active Ni-Co catalyst (75Ni25Co/Al2O3). Characterization of 75Ni25Fe/Al2O3 revealed the formation of Ni3Fe alloy, whose surface properties were different from the Ni1-xCox alloy present in 75Ni25Co/Al2O3. The presence of Ni based alloys of specific composition seemed responsible for the enhanced activity of 75Ni25Fe/Al2O3 and 75Ni25Co/Al2O3 relative to supported Ni catalyst for both the reactions. Furthermore, 75Ni25Co/Al2O3 was the most active catalyst for both reactions though deactivation occurred. In contrast, lower deactivation occurred with 75Ni25Fe/Al2O3. The turnover frequency during reforming and cracking were closely related for the supported Ni, Ni-Fe and Ni-Co catalysts. The higher activity of the 75Ni25Co/Al2O3 for the dry reforming reaction appeared to be due to the higher turnover frequency of this catalyst for the cracking reaction. Thus, the formation of alloys with specific composition, which improved the CH4 cracking capability, seems to be the key factor for determining the best catalytic performance for the reforming reaction over the promoted Ni catalysts.