Effect of Cobalt Oxide Content on the Activity of NiO-Co2O3/γ-Al2O3 Catalyst in the Reaction of Dry Reforming of Methane to Synthesis Gas

Abstract

The effect of cobalt oxide content on the activity of NiO-Co₂O₃/γ-Al₂O₃ catalyst was investigated in process of dry reforming of methane (DRM) to synthesis gas. It was found that among the studied catalysts the highest activity is shown by the NiO-Co₂O₃/ γ-Al₂O₃, where methane conversion is 89%. It was determined by the scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) there are oxides of Ni and Co in the form of nanosized particles on active NiO-Co₂O₃/γ-Al₂O₃ catalyst and Co-Ni alloys, formed after the reaction of DRM, the size of 17‒23 nm. Thermogravimetric Analysis (TGA)/ Differential Thermal Analysis (DTA)/ Differential Scanning Calorimetry (DSC) of catalyst showed that the highest weight loss (2.7%) is observed at a degree from 30 to 260 °C after DRM. After heating above 300 °C there is a slight increase in weight, accompanied by an exothermic effect on the DSC curve due to the gas adsorption used to purge the unit. The data indicate the absence of coke formation on NiO-Co₂O₃/γ-Al₂O₃ surface. According to TPR-H₂ there are peaks at relatively low temperatures of Т¹_mах = 205 °C and Т2mах = 497 °C on thermally programmed reduction (TPR) TPR-Н₂ spectrum of NiO-Со₂О₃/γ-Al₂O₃, which are associated with the formation of easily reducible cobalt and nickel oxides, indicating the presence of active and mobile oxygen in the catalyst. These results confirm that the activity of NiO-Co₂O₃/γ-Al₂O₃ is due to the formation of nanophases, the presence of active oxygen, and the absence of coke on the catalyst surface.