Direct synthesis of vertically oriented Co-Mg-Al layered double hydroxide on spherical γ-Al2O3 for passive NOx adsorber

초록

Co-Mg-Al layered double hydroxides (LDHs) are directly synthesized on spherical γ-Al2O3 using a hydrothermal treatment method with urea for low-temperature NOx adsorber, and the formation mechanism of LDHs is studied. γ-Al2O3 acts as an Al3+ source and a support, and urea provides CO32– and OH– during hydrothermal treatment. During the hydrothermal reaction, a gibbsite-like amorphous aluminum hydroxide (AOH) phase is formed on the γ-Al2O3 surface, and Co2+ and Mg2+ are dissolved into AOH layers to form LDHs. The urea concentration is a critical factor for nucleation and particle growth during LDH synthesis, affecting the properties and NOx storage/release performance of LDH-derived mixed metal oxides. Sintering of LDH-derived mixed metal oxide particles is prevented during calcination and regeneration at elevated temperatures owing to chemical bonding between the LDHs and the AOH layer, thus enhancing NOx adsorption performance.

키워드