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-O₂ environment adding humidity degraded catalytic performance while in a low-O₂ 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.