Investigation of ceria-nickel containing aerogels for catalytic converter applications

Aerogels have physical properties that make them appealing for automotive exhaust catalysis: they are highly porous with low density and high surface area. Current catalytic converter technology uses precious metals (Pt, Pd and Rh) to oxidize CO and unburned hydrocarbons and reduce NO. Catalytic-metal-containing aerogel can potentially be a less expensive alternative for use in catalytic converters. Prior work with nickel-alumina aerogels indicated promise for this application; the goal of including ceria is to increase oxygen storage and thereby enhance catalytic ability. Here, cerium- and nickel-containing aerogels, with an alumina backbone and silica backbone, are fabricated using an epoxide-assisted recipe and characterized for this application. The precursors for the aerogel, hydrated salts of aluminum chloride, cerium(III) chloride and nickel (II) nitrate, are dissolved in reagent-grade ethanol, to which propylene oxide is added. Wet gels are prepared with different molar ratios of cerium to nickel (25:75, 50:50, 75:25). Following solvent exchange, the metal-containing wet gels are processed into aerogels using a rapid supercritical extraction method and calcined at 800 ?C for24 h. Physical characterization of the aerogels before heat treatment, after heat treatment, and after UCAT testing involved FTIR, XRD, SEM, and EDX. Catalytic testing of the aerogels is performed using an in-house-constructed catalytic testbed under exposure to simulated automotive exhaust.

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