Effect of spinel inversion and metal-support interaction on the site activity of Mg-Al-Ox supported Co catalyst for CO2 reforming of CH4

摘要

The active metal-support interaction, as well as spinel inversion was studied for site formation, properties, activity and site resistance to carbon deposition in dry reforming of methane (DRM) using Al-O-x and Mg-Al-O-x supported Ni and Co monometallic catalysts. A change in support from Al-O-x to Mg-Al-O-x led to transformation of hysteresis loop from H2 to H4 as revealed by the N-2 adsorption results, while additional MgO phase was observed from the XRD results of the catalysts. Phase quantification of the XRD showed a reduction from 100% to 45% spinel with the introduction of Mg in the support. Al and Mg K-edge XANES results revealed changes in the co-ordination number (CN) of Mg and Al inside the support, leading to spinel inversion, which ultimately affected the distribution of Ni and Co, as well as site formation on the support system. STEM EDX revealed different interaction/distribution of active metals on the support system. Co showed a uniform distribution, while Ni showed a heterogeneous distribution in addition to the isolated NiO formed on the surface of the support. The K-edge XANES results showed that more Ni sites were generated than Co sites during reduction, but Co sites showed better conversion rate for CO2, CH4, in DRM, and resistance to deactivation, which was also confirmed by the calculated TOF. This improved performance of Co sites was attributed to the better basicity per active site generated from its interaction with MgO (from the support) as compared to the Ni sites.