Benchtop Scale Testing of Aerogel Catalysts: Preliminary Results

Aerogels are nanoporous structures with physical characteristics that make them promising for use in automotive exhaust catalysis systems: highly porous with low densities (<0.1 g/mL) and high surface area per unit mass (>300 m²/g) - features that provide favorable characteristics for catalysis of gaseous pollutants. Ceramic aerogels are also highly thermally insulating (∼0.015 W/mK) and able to withstand high temperatures. Aerogels can be made of a wide variety of ceramics (e.g. alumina, silica, titania) with other catalytically active metals (e.g. copper, cobalt, nickel) incorporated into their structures. This paper provides a brief overview of the rapid supercritical extraction (RSCE) method employed in this work for aerogel preparation, describes in detail the benchtop scale testbed and methods used to assess the catalytic activity of RSCE fabricated aerogels, and presents data on the catalytic ability of some promising aerogel chemistries. Catalyst performance in simulated gasoline engine exhaust was examined over temperatures ranging from 200 - 750°C, and space velocities of 15-30 s^-1. Alumina aerogels fabricated via RSCE processing and incorporating non-precious metals such as copper and cobalt catalyze the oxidation of CO and UHCs, and the reduction of NO under conditions similar to those involved in automotive exhaust after-treatment applications. Copper-alumina aerogels show particular promise, yielding conversion percentages of NO and CO in excess of 90% over a wide range of experimental conditions, and appear to manifest potentially valuable oxygen storage capability.