METHANATION OF CO ON SOME NI CATALYSTS

The kinetics of methanating CO on a number of nickel catalysts was investigated in the range up to 10% or 20% CO in H2 in a once-through differential reactor where the catalyst particles of size 0.3-0.5 mm were fluidized. The order with respect to CO was less than zero and approached -0.5 at higher CO concentrations. At low CO concentrations there was detected in most cases a maximum in rate, which could not be interpreted definitely as an intrinsic or a diffusion phenomenon. The measured rates at CO concentrations above the maxima were not influenced by diffusion; the rates in this region fitted well with the empirical, general rate equation r= Zi exp(- E1 RT)pH2n [1+Z2 exp( 16 650 RT)( Pco PH2)]0.5 Carrier and promoter oxides showed a significant effect on the kinetics, as z2, and E1 increased in the following order: γ- or η-Al2O3, SiO2 < MgAl2O4, α-Al2O3, Co2O3 < MgO ≪ K2O. E1 was in the 18-28 kcal/mole range and z2 in the range of approximately 10-3 to 10-6. For Ni on MgAl2O4 we found n = 0.15 by measurements in the pressure range of 1-15 atm. A kinetic model is proposed with a step in the H2 adsorption determining the rate. Methanation rates and the specific capacity for adsorption of H2S are compared, showing that K2O decreases the methanation activity without decreasing this capacity. The rates of methanation of CO, CO2, and CH3OH are compared. © 1969.