http://precedings.nature.com/tags/high%20pressure Recently posted documents tagged with 'high pressure' Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://dx.doi.org/10.1038/npre.2008.2649.1 Acquiring a comprehensive understanding of the behaviour of carbon dioxide under reservoir conditions is essential for optimizing its usage in enhanced oil recovery (EOR) and for developing sequestration schemes. In order to obtain this understanding, it is necessary to study the physical properties and phase behaviour of mixtures of carbon dioxide with hydrocarbons and brines under conditions of high pressure. In this work we are addressing both the experimental and the theoretical aspects of this problem. A new apparatus, based on the static-analytical method, has been developed to measure phase equilibrium. The equipment comprises a high-pressure cell with sapphire windows for visual observation and phase sampling, with on-line gas chromatography analysis, for measuring the phase compositions. The experimental work is complemented with a theoretical modelling for these mixtures, using the statistical association fluid theory for potentials of variable range (SAFT-VR). As an example of the predictive capabilities of the equation, the fluid phase behaviour of the mixture (carbon dioxide + n-decane) is presented. http://dx.doi.org/10.1038/npre.2008.2649.1 Fri, 12 Dec 2008 17:33:17 UTC Measurement & Prediction of Phase Behaviour of Carbon Dioxide Mixtures doi:10.1038/npre.2008.2649.1 2008-12-12 Esther Forte Nature Precedings 2008-12-12T17:33:17Z Poster Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/2476/version/1 The chemical nature of aqueous electrolyte ionization is illustrated by a simple relationship with water as a reactant believed to correlate ionization of aqueous sodium chloride approaching infinite dilution over the entire range of temperature and pressure [0 to 1000oC; 0.1 to 1000 MPa (10000 Atm)]. The derived equation accurately and smoothly describes the ionization constant of sodium chloride [K(NaCl)] in both water and water strongly diluted by inert solvent. Effects of water density on ionization are quantitatively and simply described that oppose conventional theory that ionization is a function only of dielectric constant, and theorists should apply this simplicity with density in understanding aqueous electrolyte ionization. There appears to be no substantive evidence for Pitzer’s earlier proposal (1983) that K(NaCl) with decreasing very low densities (if known) would diverge sharply downward by several orders of magnitude. Classical ionization theories are limited in universal application, and it seems that theory must adjust to this observed simple fundamental relationship. http://precedings.nature.com/documents/2476/version/1 Thu, 06 Nov 2008 18:08:50 UTC Aqueous Electrolyte Ionization over Extreme Ranges as Simple Fundamental Relation with Density and Believed Universal; Sodium Chloride Ionization from 0o to 1000oC and to 1000 MPa (10000 Atm.) hdl:10101/npre.2008.2476.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T18:08:50Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/2474/version/1 Examinations of past complex theoretical equations describing isothermal dielectric constants (ε) of liquids show that none describe experiments throughout and that only a two-constant equation of density is required. The dielectric susceptibility (ε – 1) as a simple exponential function of density is shown here to describe ε for both polar and non-polar organic liquids over all available experimental ranges from 0.50 to 1.2 g cm-3 and temperatures to 400oC. For water above 0.25 g cm-3, the equation describes the excellent dielectric-constant formulation of Fernández, et al., (1997) throughout its experimental range [-35 to +600oC; to 1000 MPa (10000 Atm)] and even when diluted by “inert” solvents (Marshall, 2008). At lower densities at all temperatures, water susceptibilities converge to an even more simple unit proportionality to density below 0.003 g cm-3, not yet verified for organics without experiment. While the past Born, Tait, Clausius-Mossotti, and Owen-Brinkley theories describe ε equally well over a limited 10% change in density, all are shown to fail over greater ranges. The simple density relation presented here should be useful in clarifying and reducing complexity of theory applied to liquid structure. http://precedings.nature.com/documents/2474/version/1 Thu, 06 Nov 2008 17:59:24 UTC Dielectric Constant of Liquids (Fluids) Shown to be Simple Fundamental Relation of Density over Extreme Ranges from – 50o to + 600oC, Believed Universal hdl:10101/npre.2008.2474.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T17:59:24Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.2472.1 The experimental static dielectric constants (ε) of water formulated by Fernández, et al., (1997-International Association for the Properties of Water and Steam, IAPWS), –35 to 600oC; 0.1 to 1200 MPa, are discovered to be closely described throughout by a simple equation of density (ρ), presented here, and agreeing with their reported calculated (extrapolated) values to 923oC. Eight limiting boundary conditions are observed. Values of ε follow isothermal straight-line slopes of log (ε – 1) vs log ρ down to densities of 0.25 g cm-3 water, even in dioxane-water solutions. At lower densities, all slopes curve asymptotically in approaching unity, while becoming unity throughout at –35oC (near metastable freezing point). Slopes above 0.25 g cm-3 asymptotically approach 1 2/3 at high temperatures that numerically proportionates (ε – 1) to volume times surface densities, with a proposed explanation given. Values for ε of water dissolved in dioxane down to 0.006 g cm-3 water (25-300oC) and in benzene to 0.014 g cm-3 water (300-400oC) extend uninterrupted from those for pure water. The Deul-Franck (1984, 1991) values of ε for benzene (25-400oC; to 400 MPa) by the relationship fall on a single straight-line independent of temperature. Theorists should evaluate this simple relationship of water and other liquids to density that appears to be universal. http://dx.doi.org/10.1038/npre.2008.2472.1 Thu, 06 Nov 2008 17:56:46 UTC Dielectric Constant of Water Discovered to be Simple Function of Density over Extreme Ranges from – 35 to + 600oC and to 1200 MPa (12000 Atm.), Believed Universal doi:10.1038/npre.2008.2472.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T17:56:46Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1771/version/4 A compressibility study was carried out of calcium nitride using a powdered sample in a diamond anvil cell with a Debeye-Scherrer camera at Cornell High Energy Synchrotron Source (CHESS) in 1992. This is the first such high pressure study of the equation of state of calcium nitride reported in the literature. http://precedings.nature.com/documents/1771/version/4 Fri, 09 May 2008 13:44:33 UTC Compressibility of Calcium Nitride to 137 Kb hdl:10101/npre.2008.1771.4 2008-05-09 Michael J. Bucknum Nature Precedings 2008-05-09T13:44:33Z Manuscript Chemistry http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1771/version/3 A compressibility study was carried out of calcium nitride using a powdered sample in a diamond anvil cell with a Debeye-Scherrer camera at Cornell High Energy Synchrotron Source (CHESS) in 1992. This is the first such high pressure study of the equation of state of calcium nitride reported in the literature. http://precedings.nature.com/documents/1771/version/3 Thu, 08 May 2008 16:32:20 UTC Compressibility of Calcium Nitride to 137 Kb hdl:10101/npre.2008.1771.3 2008-05-08 Michael J. Bucknum Nature Precedings 2008-05-08T16:32:20Z Manuscript Chemistry http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1771/version/2 A compressibility study was carried out of calcium nitride using a powdered sample in a diamond anvil cell with a Debeye-Scherrer camera at Cornell High Energy Synchrotron Source (CHESS) in 1992. This is the first such high pressure study of the equation of state of calcium nitride reported in the literature. http://precedings.nature.com/documents/1771/version/2 Wed, 30 Apr 2008 16:06:06 UTC Compressibility of Calcium Nitride to 137 Kb hdl:10101/npre.2008.1771.2 2008-04-30 Michael J. Bucknum Nature Precedings 2008-04-30T16:06:06Z Manuscript Chemistry http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1771/version/1 A compressibility study was carried out of calcium nitride using a powdered sample in a diamond anvil cell with a Debeye-Scherrer camera at Cornell High Energy Synchrotron Source (CHESS) in 1992. This is the first such high pressure study of the equation of state of calcium nitride reported in the literature. http://precedings.nature.com/documents/1771/version/1 Tue, 08 Apr 2008 17:50:05 UTC Compressibility of Calcium Nitride to 137 Kb hdl:10101/npre.2008.1771.1 2008-04-08 Michael J. Bucknum Nature Precedings 2008-04-08T17:50:05Z Manuscript Chemistry http://creativecommons.org/licenses/by/3.0/