243 Matching Results

Search Results

Advanced search parameters have been applied.

Heterogeneous oxidative and polymerization processes

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). We performed experiments directed at understanding novel catalysts and the use of supercritical carbon dioxide as a reaction medium for catalytic reactions. We participated in program development activities with individual companies and with trade organizations to develop research and funding strategies for catalysis on a national level. This work has helped to identify scientific and technological opportunities for catalysis research in industry and for large national initiatives such as global climate change. Our work has poised the Laboratory to participate in a spectrum of activities where catalysis science and technology will play a role.
Date: November 1, 1998
Creator: Tumas, W.; Ott, K. & Baker, R.T.
Partner: UNT Libraries Government Documents Department

Pulse Radiolysis in Supercritical Rare Gas Fluids

Description: Recently, supercritical fluids have become quite popular in chemical and semiconductor industries for applications in chemical synthesis, extraction, separation processes, and surface cleaning. These applications are based on: the high dissolving power due to density build-up around solute molecules, and the ability to tune the conditions of a supercritical fluid, such as density and temperature, that are most suitable for a particular reaction. The rare gases also possess these properties and have the added advantage of being supercritical at room temperature. Information about the density buildup around both charged and neutral species can be obtained from fundamental studies of volume changes in the reactions of charged species in supercritical fluids. Volume changes are much larger in supercritical fluids than in ordinary solvents because of their higher compressibility. Hopefully basic studies, such as discussed here, of the behavior of charged species in supercritical gases will provide information useful for the utilization of these solvents in industrial applications.
Date: January 1, 2007
Creator: Holroyd, R.
Partner: UNT Libraries Government Documents Department

Supercritical water oxidation data acquisition testing. Final report, Volume II

Description: Supercritical Water Oxidation (SCWO) technology holds great promise for treating mixed wastes, in an environmentally safe and efficient manner. In the spring of 1994 the US Department of Energy (DOE), Idaho Operations Office awarded Stone & Webster Engineering Corporation, of Boston Massachusetts and its sub-contractor MODAR, Inc. of Natick Massachusetts a Supercritical Water Oxidation Data Acquisition Testing (SCWODAT) program. The SCWODAT program was contracted through a Cooperative Agreement that was co-funded by the US Department of Energy and the Strategic Environmental Research and Development Program. The SCWODAT testing scope outlined by the DOE in the original Cooperative Agreement and amendments thereto was initiated in June 1994 and successfully completed in December 1995. The SCWODAT program provided further information and operational data on the effectiveness of treating both simulated mixed waste and typical Navy hazardous waste using the MODAR SCWO technology.
Date: November 1, 1996
Partner: UNT Libraries Government Documents Department

Thermodynamics and kinetics of ion speciation in supercritical aqueous solutions: A molecular based study

Description: Molecular simulation of infinitely dilute NaCl aqueous solutions are performed to study the Na{sup +}/Cl{sup -} ion pairing in a polarizable and a nonpolarizable solvent at supercritical conditions. The Simple Point Charge, Pettitt-Rossky, and Fumi-Tosi models for the water-water, ion-water, and ion-ion interactions are used in determining the degree of dissociation, its temperature and density dependence, and the kinetics of the interconversion between ion-pair configurations in a nonpolarizable medium. To assess the effect of the solvent polarizability on the stability of the ion-pair configurations, we replace the Simple Point Charge by the Polarizable Point Charge water model and determine the anion-cation potential of mean force at T{sub r}=1.20 and {rho}{sub r}=1.5.
Date: May 1, 1997
Creator: Chialvo, A.A.; Cummings, P.T.; Simonson, J.M. & Mesmer, R.E.
Partner: UNT Libraries Government Documents Department

Structure from solute-solvent interactions in supercritical polyatomic molecular mixtures

Description: Solute-solvent and solute-solute microstructures at the sueprcritical state are important in elucidating chemical reaction and spectroscopic data. We can classify the range of pair correlations into two regions: a short range (r {le} r{sub min}) and a long range (r from r{sub min} to 20 {approximately} 50 molecular diameters). The often cited local density enhacement referes to the short range corelations and is shown not to be related to the critical behavior of the mixture. The long-range behavior of the pair correlations is responsible for the buildup of osmotic susceptibility and is related to the closeness to solvent`s critical point. In the class of attractive supercritical mixtures, the solute-solvent short-range pair correlation exhibits complicated bheavior: enhanced solvation (within the first neighborhood) at low to medium densities and peak attenuation followed by peak growth at higher densities. Earlier theor. studies (integral equations) dealt with idealized model of solute molecules as spheres (molecular size effects accounted for, but not molecular shape effects). This study examines behavioral change due to molecular shapes and orientations as the solutes take the shape of polyatomic molecules. For example the case of di-tert-butylnitroxide radicals in supercritical ethylene can be modeled as linear dimeric molecules. Reference interaction site model integral equation is used to produce site-site correlation functions. We map out the density ranges where structural changes take place and elucidate their practical implications.
Date: December 31, 1994
Creator: Lee, L.L. & Cochran, H.D.
Partner: UNT Libraries Government Documents Department