CHANGES OF THE METALLIC SURFACE OF FE/AL2O3 DURING EXPOSURE TO CO/HE AND CO/H-2

The evolution of the sites capable of adsorbing hydrogen on 10% Fe/Al2O3 has been studied as a function of time of exposure to CO/He and CO/H2 at 558 K by the temperature-programmed desorption (TPD) method. The sites adsorbing hydrogen change in number but not in nature during reaction. The curve of rate of methanation vs. time of reaction can be understood in terms of a constant concentration of carbonaceous intermediate and a surface concentration of hydrogen that varies with time. The surface hydrogen concentration seems to be linked with the degree of carburization of the iron. During carburization the Fe0/FeyC mixture probably fragments and causes the number of sites capable of adsorbing hydrogen to pass through a maximum. © 1990.