Hydrotalcite-type anionic clays: Preparation, properties and applications.

The hydrogenation of CO2 over Ru catalysts is structure sensitive, the selectivity of the process can be driven either to the production of CH4 or CO depending on Ru particles and support features. Herein, Ru-based MgAl-HT (HT=hydrotalcite) derived catalysts with different Ru loadings (0.5, 1.0 and 2.0 wt%) and promoted with La3+ were prepared, characterized, and tested for CO2 methanation at high Gas Hourly Space Velocity values (480 L/gcat h) feeding a CO2/H2/N2 = 1/4/1 v/v mixture. The MgAlOx mixed oxide obtained after calcination at 600 °C and reduction provided weak, medium and mainly strong basic sites, able to activate the CO2 molecule, and hosted very small Ru nanoparticles (1–3 nm). However, the catalysts displayed a low activity in the low temperature range and a poor selectivity to CH4. The addition of La3+, despite contributing to the basicity, did not have any significant effect on performance. In a comparison between Ru- and Ni-HT-derived catalysts, tested under similar reaction conditions, Ni largely overperformed Ru.