Chemistry and catalysis in supercritical media Page: 4 of 16
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solvents. A more detailed description of the motivation for this research, experimental
considerations as well as a summary of many of the results from this work can be found in two
chapters we have recently written.'' The attraction of supercritical fluids for chemical synthesis
lies both in their unique solvating capabilities and in their relatively benign nature. There are a
number of inherent properties of supercritical fluids that distinguish them as superior reaction
" High diffusivity
- High compressibility
" Continually adjustable "solvent strength"
" Thermochemical (kinetics/thermodynamics) effects
- Ion-Product (equilibria)
" Solvent participation.
The promise of controlling reaction pathways and even opening up new reactivity patterns
by controlling reaction conditions in supercritical media has been laid out in several recent
reviews,3,4 and several studies have demonstrated that controlling properties such as solvent
strength and solvent participation can impact the selectivity of reactions. Despite a clear
understanding of the potential advantages of supercritical reaction media and their industrial
significance, this extremely promising technology area is in its infancy -- a wide range of organic
reactions and catalytic processes has remained largely unexplored. We have chosen to explore
several catalytic processes in supercritical fluids, particularly CO2. Initial work focused on
selective catalytic oxidations5 of olefins, aromatics and alkanes due to their rich chemistry and
industrial importance. In addition, we have expanded the scope of this project to include studies
on catalytic hydrogenation reactions, particularly asymmetric hydrogenation and transfer
hydrogenation, as well as the development of photochemical and spectroscopic probes of solvation
effects and the use of C02 as a solvent and a reagent for isocyanate synthesis.
2. Importance to LANL's Science and Technology Base and National R&D
U.S. industries must accelerate development of new methods for chemical processing and
synthesis to maintain global competitiveness. Our research has provided much valuable
information on what types of catalytic processes can proceed in supercritical fluids, and also has
begun to delineate the potential advantages of this reaction medium. This research could lead to
conceptually new methods for direct oxidative functionalization, the introduction of asymmetric
centers into molecules and new methods for forming carbon-carbon bonds, which could have
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Tumas, W.; Morgenstern, D. & Feng, S. Chemistry and catalysis in supercritical media, report, July 1, 1997; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc692902/m1/4/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.