“ … of Surface Waters in the Schenectady County Watershed Fiona Fitzgerald ‘20, Margot O’Brien ‘19, and Thomas … ”
Abstract
The Schoharie River and Hans Groot's Kill are both tributaries into the Mohawk River. Thus, it is likely that they all have similar chemical compositions. One-third of the volume of the Mohawk River is contributed by the Schoharie River, while Hans Groot's Kill also feeds into the Mohawk River after passing through the residential homes of the "GE Plot" and Union College. Some chemicals are naturally occuring while others are introduced to the bodies of water via anthropogenic products.
Over one billion automobiles are in use around the world, the majority of which employ internal combustion engines. Catalytic converters are used to convert the toxic compounds found in car exhaust -- carbon monoxide, nitrogen oxides (NOx) and hydrocarbons -- to less harmful gases. The typical catalytic converter employs, as three-way catalysts, expensive raw materials such as platinum, palladium and/or rhodium. Aerogel materials have high surface area and thermal stability, properties that make them attractive for catalysis applications. Aerogels made with transition metal oxides (TMOs) are candidates to replace platinum in the catalytic converter. Chromium oxide (chromia) materials have demonstrated catalytic activity in other applications due to favorable redox chemistry, stability and selectivity. In this work, sol-gel synthesis techniques, using a 1:5 mole ratio of chromium(III) to aluminum, are adapted to a patented rapid supercritical extraction (RSCE) method to fabricate chromia-alumina catalytic aerogels. Physical characterization via several methods, including XRD and SEM, is performed on the chromia-alumina aerogels as prepared and following heat treatment. Catalytic performance of these promising materials is evaluated using an in-house-constructed testbed in which the aerogel materials are exposed to simulated automotive exhaust under temperature conditions that approximate those experienced in a catalytic converter. Initial tests demonstrate that chromia-alumina aerogels act as three-way catalysts.
“ … Fitzgerald,Fiona , Development of Catalytic Chromia Based Aerogels, 2020. Acknowledgments ● FionaFitzgerald, Chris Avanessian, Bassem … ”
Abstract
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.
“ … i ABSTRACT Fitzgerald,Fiona Development of catalytic chromia-based aerogels. … (NOx) … Development of Catalytic Chromia-based Aerogels By Fiona T. Fitzgerald *********** Submitted in partial … ”
Abstract
Over one billion automobiles are in use around the world, the majority of which employ internal combustion engines. Catalytic converters are used to convert the toxic compounds found in car exhaust -- carbon monoxide, nitrogen oxides (NOx) and hydrocarbons -- to less harmful gases. The typical catalytic converter employs as catalysts expensive raw materials (platinum, palladium and/or rhodium) wash-coated onto an alumina-based ceramic substrate. Aerogel materials have high surface area and thermal stability, properties that make them attractive for catalysis applications. Aerogels made with transition metal oxides are candidates to replace platinum in the catalytic converter. Chromium oxide (chromia) materials have demonstrated catalytic activity in other applications due to favorable redox chemistry, stability and selectivity. In this work, sol-gel synthesis techniques are adapted to a patented rapid supercritical extraction (RSCE) method to fabricate chromia and chromia-based catalytic aerogels. In one example of a co-precursor technique, a mixture (1:5 mole ratio) of chromium(III) to aluminum salt in ethanol is reacted with a weak base or proton scavenger to induce gelation. Following solvent exchanges of the wet gels with absolute ethanol, and RSCE processing yields chromia-alumina aerogels. Observed shrinkage is higher than for copper-containing aerogels fabricated via the same process. Physical characterization via several methods, including XRD and SEM, reveals post-calcination chromia-alumina aerogels contain ?- Cr<sub>2</sub>O<sub>3</sub> nanocrystals within the alumina backbone. Catalytic testing is evaluated using an in-house-constructed testbed in which the aerogel materials are exposed to simulated automotive exhaust under temperature conditions that approximate those experienced in a catalytic converter. Chromia-alumina aerogels completely convert HC and CO gases at 400 °C under high air conditions and completely convert NO at 450 °C under low air conditions.
