Particle size does not affect the intrinsic activity of silica-supported nickel nanoparticles in dry reforming at 500°C. Display omitted ► Different silica supported nickel catalyst prepared with varying particle size (1.6–7.3nm). ► Neutral silica support favours a very high reduction degree (> 90%) at 500°C. ► Intrinsic Ni/SiO2 performances are independent of nickel particle size in dry reforming at 773K. ► The H2/CO ratio is controlled by the thermodynamic of the fast reverse water gas shift reaction. The influence of nickel particle size in the range of 1.6–7.3nm on catalyst performance in low temperature CO2 reforming of methane reaction has been investigated using well-defined catalysts based on a neutral silica support. XAS and XPS studies indicated a reduction degree greater than 90%. The intrinsic Ni/SiO2 performances were found to be independent of nickel particle size in dry reforming at 773K using a CH4/CO2 ratio of 1.3 at 1atm, both at an early stage and in steady state conditions. The H2/CO ratio was also found to be structure in sensitive but is controlled by thermodynamics through the faster reverse water gas shift reaction.