Effect of slurry processing on the properties of catalytically active copper-alumina aerogel material for applications in three-way catalysis

This study examines the catalytic performance of copper-alumina (CuAl) aerogel which is a possible alternative to the use of precious metals in automotive exhaust treatment systems which require simultaneous conversion of carbon monoxide, unburnt hydrocarbons and nitrogen oxides. To be a viable alternative, the aerogel materials need to withstand a slurrying process to enable coating onto a substrate and they need to maintain performance in a humid environment typical of what is seen in automotive exhaust. In this study, we slurried heat-treated copper-alumina aerogels in an acidic (pH ~4) aqueous solution under mechanical stirring. The solution was subsequently dried at 60 °C under ambient pressure conditions. Physical properties of slurried CuAl aerogel (surface area, X-ray diffraction, morphology) were similar to those of non-slurried materials. Catalytic testing in a simulated automotive exhaust environment demonstrated that the aerogels can survive exposure to humidity. The ability of the slurried and non-slurried aerogels to oxidize propene and carbon monoxide was similar under dry and humid conditions. In a high-O 2 environment adding humidity degraded catalytic performance while in a low-O 2 environment the humidity improved performance. The catalytic performance toward nitrogen monoxide was less consistent: the slurried sample did not perform as well as the non-slurried sample under any conditions. Copper-alumina aerogels can be slurried and exposed to a humid exhaust stream and maintain three-way catalytic performance. The figures on the left show images of the material as prepared, and after heat treatment. Pore volume is reduced after heat treatment and slurrying. The images on the right show catalytic performance for CO in dry and humid conditions.