Catalytic activity and characterization of Ni/Al2O3 and NiK/Al2O3 catalysts for CO2 methane reforming Original Research Article

The effect of potassium in the catalytic activity and structural properties of a Ni/Al2O3 catalyst used for the CO2 reforming of methane has been analyzed. To determine the catalytic activity, two types of catalytic test were carried out: (i) temperature programmed reaction (TPR) up to 1173 K and (ii) isothermal reaction (IR) at 973 K. Several techniques were used to characterize the catalysts before and after the reforming reaction: SEM, temperature programmed oxidation (TPO), temperature programmed reduction (TPR–H2), XPS and XAFS. The presence of potassium facilitates the reduction of nickel during the activation treatment (heat treatment in H2 at 773 K, 2 h) previous to the reforming reaction, although a further activation of the potassium free catalyst takes place at the reaction condition. Ni/Al2O3 and NiK/Al2O3 catalysts show very similar CH4 and CO2 conversion at 973 K (under TPR and isothermal conditions) and the XAFS analysis of the used samples reveals a similar nickel structure. However, the whole process is different because in Ni/Al2O3 catalysts the formation of coke is much higher.