Nitric Acid-Pretreated Natural Halloysite Nanotubes as Ni Nanoparticle Catalyst Supports for CO₂ Methanation

The CO 2 methanation reaction has attracted more and more attention, which can achieve a carbon cycle and high-valued chemicals, but the development of efficient catalysts remains a big challenge. Herein, the natural halloysite nanotubes (HNTs) pretreated with different concentrations of nitric acid solutions (4, 6, 8, and 10 mol/L) were used as supports for the first time to synthesize Ni-based CO 2 methanation catalysts through the impregnation method. The results revealed that the catalysts prepared with acid-pretreatment HNTs demonstrated more excellent catalytic activity due to the improved dispersion of Ni nanoparticles and more basic sites, which efficiently adsorb and activate the reaction gases H 2 and CO 2 . Moreover, the effects of metal loading on the catalytic performance were also studied. The optimized (Ni(30%)/HNTs-8AC) catalyst with a Ni loading of 30 wt % showed significantly superior CO 2 conversion (95.8%) at 350 °C with CH 4 selectivity of 100% at 15,000 mL/g/h and did not show significant deactivation during a 50 h stability test because of excellent resistance to coking and sintering. This work provides a support of natural materials for preparing a CO 2 methanation catalyst.