Effect of preparation methods on the performance of Co/Al2O3 catalysts for dry reforming of methane

Abstract

Two methods, dry impregnation (DI) and controlled adsorption (CA), are used for the preparation of Co/Al₂O₃ catalysts for methane dry reforming reactions. Point of zero charge (PZC) measurements, pH-precipitation studies, and adsorption isotherms are used to develop a synthesis procedure in which deposition of Co²⁺ takes place in a more controlled manner than metal deposition during drying in synthesis by dry impregnation. The possible adsorption phenomena that occur during preparation of Co/Al₂O₃ catalysts by controlled adsorption are discussed. H₂ chemisorption and TEM show that catalysts prepared by CA have smaller average particle sizes and higher dispersions. TPR studies show that for the sample prepared by CA a higher amount of cobalt is reduced to its metallic state and that more CoAl₂O₄ spinel species are present relative to DI samples. The catalyst prepared by CA shows higher activity and slower deactivation for methane dry reforming than the catalyst prepared by DI. XPS and C, H, N analysis on spent catalysts confirm two types of carbonaceous deposits are formed depending on the preparation method.