Effect of Copper Loading in Copper-Alumina Aerogels on Three-Way Catalytic Performance

Abstract

Aerogels are high surface area, low density, low thermal mass, nanoporous materials that are stable at high temperatures. This unique combination of physical characteristics makes them promising for use in three-way catalyst systems. Their high surface area has the potential to result in more active sites and improved gas/solid interaction. Their high temperature stability may reduce active site diffusion/sintering and allow for close coupling, which combined with the low thermal inertia may lead to a reduced time to light-off. It is relatively easy to incorporate a variety of metals, including non-precious group metals, into an aerogel backbone. We have developed a series of copper-alumina (CuAl) aerogels via sol-gel synthesis and rapid supercritical extraction drying. Different amounts of copper were incorporated into the alumina gel, resulting in materials with 20% to 40% copper by mass. Scanning electron microscopy imaging shows copper-containing particles distributed in the material, and powder X-ray diffraction indicates that the copper may be in the copper aluminate spinel phase after heat treatment. The materials were tested in the Union Catalytic Aerogel Testbed (UCAT), which evaluates catalytic material performance for conversion of NO, HCs, and CO over a range of temperatures from 200 to 700 °C using a simulated exhaust gas mixture with and without air. UCAT test results indicate that adding more copper to the aerogel lowers the light-off temperature from 350 to 225–250 °C for the conversion of CO and from 500 to 425–450 °C for the conversion of HCs (in the presence of air) and from 425 to 325 °C for NO (without air).