With further development this technology, which employs a Fe-TAML® activator, may provide an attractive alternative to existing methods that rid fuels of sulfur contaminants, which are associated with serious human health problems and contribute to acid rain. These same contaminants also cause engines to burn fuel less efficiently.
Results of this laboratory research will be presented by Colin Horwitz, research associate professor at Carnegie Mellon, on Wednesday, Sept. 10, at the 226th annual meeting of the American Chemical Society (paper 160, "Oxidation of sulfur compounds in fuels using Fe-TAML® activators and hydrogen peroxide," Industrial and Engineering Chemistry Division). This research was funded by the Department of Energy.
"We are working to develop Fe-TAML activators to clean fuels to the point where they will comply with stringent EPA sulfur standards slated to go into effect by 2006," said Horwitz. "This technology could aid significantly in the development of cleaner burning, more fuel-efficient automobile engines."
Most diesel fuels on the market in the United States contain 500 parts per million (ppm) of sulfur contaminants. By approximately 2010, the EPA will require all transportation fuels to contain no more than 30 ppm of these pollutants. Sulfur contaminants interfere with other technologies designed to prevent release of soot particles. As a result, these particles are released into exhaust fumes, along with sulfur contaminants (sulfur oxides). The particles have been linked to asthma, while sulfur oxides contribute to acid rain.
Fe-TAMLs (TAML stands for tetra-amido macrocyclic ligand) are synthetic catalysts made with elements found in nature.
When Fe-TAMLs and hydrogen peroxide are added to automotive fuel models, the recalcitrant sulfur compounds are rapidly converted into substances that are easily extracted so that a nearly sulfur-free fuel remains, according to Horwitz. This process is accomplished rapidly and effectively under moderate conditions, such as slightly elevated temperature (60 °C), ambient pressure and neutral pH.
Fe-TAMLs provide a promising green alternative to current sulfur extraction techniques based on the same chemistry--oxidative desulfurization. Existing methods are very corrosive and require more hydrogen peroxide to achieve the same sulfur reduction seen with Fe-TAML technology. The Fe-TAML approach appears to be highly selective for attacking the sulfur compounds and leaving other components of the fuel untouched.
Fe-TAML activators originated at Carnegie Mellon's Institute for Green Oxidation Chemistry under the leadership of Terry Collins, the Thomas Lord Professor of Chemistry at the Mellon College of Science (MCS) and a strong proponent of green chemistry to create environmentally friendly, sustainable technologies. Fe-TAML activators show enormous potential to provide clean, safe alternatives to existing industrial practices. They also provide ways to remediate other pressing problems that currently lack solutions.
As part of this September's American Chemical Society meeting symposium, "Green Chemistry: Multidisciplinary Science and Engineering Applied to Global Environmental Issues," the Collins group will present results of Fe-TAML activators' effectiveness in cleaning wastewater from textile manufacturing, killing a simulant of a biological warfare agent, treating pulp and paper processing byproducts, and detoxifying pesticides. At the symposium, the Collins group also will highlight how Fe-TAML activators can work with oxygen rather than hydrogen peroxide, thereby extending tremendously the range of potential applications of these catalysts.