THE DYNAMICS OF METHANATION OF CARBON-MONOXIDE ON NICKEL-CATALYSTS

Earlier the author studied methanation kinetics on a 5% Ni/SiO//2-catalyst. The extensive data were described well with a mechanism involving dissociative adsorption of H//2 and CO and stepwise hydrogenation of C//a and O//a. Hydrogen isotope effects were also described with fair accuracy. Since then kinetic data were obtained on two other catalysts, 52% Ni/SiO//2 and 4% Ni/Al//2 0//3. A new mechanism was designed, involving hydrogen-assisted dissociation of adsorbed CO with formation of C//a. With fast H//2O-elimination this step is unidirectional. A new rate equation describes kinetics and isotope effects very well and excludes isotope scrambling. Finally a larger range of catalysts, supported on silica, alumina and titania is tested.