Effects of modifying Ni/Al2O3 catalyst with cobalt on the reforming of CH4 with CO2 and cracking of CH4 reactions

Alumina supported nickel (Ni/Al2O3), nickel–cobalt (Ni–Co/Al2O3) and cobalt (Co/Al2O3) catalysts containing 15% metal were synthesized, characterized and tested for the reforming of CH4 with CO2 and CH4 cracking reactions. In the Ni–Co/Al2O3 catalysts Ni–Co alloys were detected and the surface metal sites decreased with decrease in Ni:Co ratio. Turnover frequencies of CH4 were determined for both reactions. The initial turnover frequencies of reforming (TOFDRM) for Ni–Co/Al2O3 were greater than that for Ni/Al2O3, which suggested a higher activity of alloy sites. The initial turnover frequencies for cracking (TOFCRK) did not follow this trend. The highest average TOFDRM, H2:CO ratio and TOFCRK were observed for a catalyst containing a Ni:Co ratio of 3:1. This catalyst also had the maximum carbon deposited during reforming and produced the maximum reactive carbon during cracking. It appeared that carbon was an intermediate product of reforming and the best catalyst was able to most effectively crack CH4 and oxidize carbon to CO by CO2.