Chromia-alumina aerogels for automotive pollution mitigation

Passenger vehicles with internal combustion engines are a major air pollution contributor due to their production of significant amounts of NOx, CO, and unburned hydrocarbons. Catalytic converters are used for automotive pollution mitigation. Aerogels are remarkable materials due to their highly porous nanostructure that is approximately 90-99% air by volume. Their high surface area and thermal stability make them attractive for catalytic applications. In this study, chromia-alumina aerogels were synthesized and characterized in order to evaluate their promise as catalysts for automotive applications. The sol-gel synthesis consisted of combining aluminum chloride hexahydrate, chromium(III) nitrate nonahydrate, ethanol (EtOH), and propylene oxide. The wet gels then underwent EtOH solvent exchanges over a series of days, and were processed by a rapid supercritical extraction method to yield aerogel samples. A heat-treatment process was then performed over 24 h at rising temperature increments to 800‚ÑÉ. The chromia-alumina aerogels were characterized through SEM and XRD, and will further be studied through the use of surface area measurements and IR spectroscopy. In preliminary work, these chromia-alumina aerogels were shown to catalyze the oxidation of CO and hydrocarbons and the reduction of NO.