Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation co-precipitation method

Ni based catalysts supported on gamma-Al2O3 that was unpromoted (Ni/gamma Al2O3) or promoted (Ni-Fe/gamma Al2O3, Ni-Co/gamma Al2O3, and Ni-Fe-Co/gamma Al2O3) were prepared using by the impregnation - co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H-2/CO = 3 and in the temperature range between 130 and 350 degrees C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni-Co/gamma Al2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 degrees C). The temperatures for the 20% CO conversion over Ni-Co/ gamma Al2O3, Ni-Fe/gamma Al2O3, Ni-Fe-Co/gamma Al2O3 and Ni/gamma Al2O3 catalysts were 205, 253, 263 and 270 degrees C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of / type nickel species which had an appropriate interacting strength with alumina support in the Ni-Co/gamma Al2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni-Fe/gamma Al2O3. Moreover, it was found that there was no synergetic effect from the binary Fe-Co promotors in the Ni-Fe-Co/gamma Al2O3 on catalytic activity for CO methanation.