New CoO−SiO₂-Sol Pillared Clays as Catalysts for NOx Conversion

New CoO−SiO 2 -sol pillared montmorillonite (Co−SiM) is synthesized by interlamellar hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in the presence of Co 2+ ion via an alkylammonium intercalated montmorillonite. The silicate layers of Na + −montmorillonite are expanded in advance with hexadecyltrimethylammonium cation up to ∼22 Å, followed by reaction with a mixed sol solution of TEOS and CoCl 2 ·6H 2 O in the presence of n -dodecylamine as a cotemplate. A microporous Co−SiM is obtained after removing the organic templates at 550 °C. The nitrogen adsorption−desorption isotherm for the pillared sample reveals that a large number of micropores are created between the silicate layers, giving rise to a high BET specific surface area ( S BET = ∼570 m 2 /g) and a pore volume ( V = ∼0.65 mL/g). According to the X-ray photoelectron and X-ray absorption spectroscopy, the incorporated cobalt species is found to be CoO, which is homogeneously dispersed on the surface of the SiO 2 pillars. The Co−SiM exhibits an excellent NO conversion rate of ca. 50% at 200 °C, which continuously increases up to 80% at 500 °C.