Effects of spatially confined nickel nanoparticles in surface-pretreated hydrophobic SBA-15 for dry reforming of CH₄ with CO₂

The efficient methods to preserve original smaller nickel nanoparticles (NP) with its even size distribution of ∼5 nm on a highly ordered mesoporous SBA-15 (NP/SBA-15) were investigated for a high temperature (800 °C) dry reforming of methane with CO₂ (DRM). The suppressed thermal aggregation with less coke deposition and higher catalytic activity were observed by the confined nickel nanoparticles spatially in the mesoporous SBA-15 channels. Especially, two-step surface-pretreated SBA-15 with acetic anhydride followed by successive H₂O treatment showed a higher dispersion of organics-stabilized nickel nanoparticles, which were preferentially deposited in the ordered mesoporous inner SBA-15 channels with its insignificant aggregation. On the optimal NP(10)/SBA-15 with 10 wt%Ni possessing the characteristics of the hydrophobic SBA-15 inner surfaces, as-prepared nickel nanoparticles were selectively and homogeneously distributed in the inner mesoporous SBA-15 channels with its small depositions on the outer SBA-15 surfaces. The spatial confinement effects were realized due to the less mobility of the smaller nickel nanoparticles by keeping its original particle sizes even after a long-term DRM reaction at 800 °C for 120 h. The phenomena were responsible for an enhanced catalytic stability by suppressing a severe sintering of nanoparticles and less coke formation even under a harsh DRM reaction condition.