The behaviour of nickel manganese catalysts Ni0.05Mn0.95O for the dry (carbon dioxide) reforming of methane was investigated from 500 to 800 degrees C. Prepared catalysts showed ex-solution nickel nanoparticles on the manganese surface, which sintered during reaction, deactivating the catalyst. By pre-sintering the catalyst at 750 degrees C in an inert atmosphere, deactivation from sintering and carbon deposition was avoided at temperatures below 800 degrees C. The resistance of the sintered catalyst against carbon deposition was assumed to be caused by SMSI effects. After dispersing the Ni0.05Mn0.95O catalyst on silica, the catalyst exhibits a leap in activity at 6000 degrees C followed by slow deactivation, attributed to a spontaneous phase change to Ni/Mn2SiO4. (C) 2014 Elsevier B.V. All rights reserved.