Temperature Programmed Reduction Behavior of Copper Promoted Fe_3O_4

摘要

One analyzed the temperature-programmed reduction of Cu/Fe_3O_4 in hydrogen. The values of the activation energy characteristic to this process were determined using the most known iso-conversional methods. In all cases one noted a variation of the activation energy as a function of the degree of reduction. The values of the pre-exponential factor were evaluated assuming various kinetic models. For the most of them the values of the kinetic parameters vary correlated, according to the relationship known in the literature as compensation effect: In A = a·E + b. The dependence of the activation energy on the degree of conversion suggested that the reduction of Cu/Fe-3O_4 takes place passing through three consecutive stages, in which the reduction mechanisms are different. The existence of these reduction stages was tentatively explained taking into account the structural changes which accompany the increase of the reduction degree.