Water-CO2 system

Z.F. Zhang, W.Z. Wu, H.X. Gao, B.X. Han, B. Wang and Y. Huang, Tri-phase behavior of ionic liquid-water-CO2 system at elevated pressures, Phys. Chem. Chem. Phys. 6, 5051-5055(2004). 

Comparison of the pure neutral water / CO2 system to the acidic one to which uranyl salts and increasing amounts of TBP and acids have been added reveals important evolutions which are of particular significance in the context of assisted extraction of uranyl. 

The pure water / CO2 system in pH neutral versus nitric acidic conditions (A - C)... 

The systems A - C have been simulated with "standard" MD simulations, starting from a prebuilt interface (i.e. without mixing / demixing procedures). As shown in Figure 3, the pH-neutral neat water / CO2 system A consists of two well defined phases, separated by an interface of about 12 A thick. A few CO2 molecules... 

It is also important to note that in most cases the stationary phase cannot be regarded as an irmocent component of the reaction mixture. The interactions of substrates, catalyst, or CO2 with the stahonary phase can all influence the course of the reaction. In ophmal cases this can be a useful factor, for example in the hydrovinylation system discussed below, where the ionic hquid (I L) acts as a catalyst activator which must otherwise be added separately. In water—CO2 systems, however, the formation of carbonic acid when CO2 is dissolved in water means that the pH of the aqueous phase can be as low as 3. Thus all reagents and catalysts must be stable under acidic conditions when using this approach. 

Figure 14 Absorbance of methyl orange in the PFPE + water + CO2 system as a function of added water. (From Ref. 73.)...

Supercritical fluid extraction — During the past two decades, important progress was registered in the extraction of bioactive phytochemicals from plant or food matrices. Most of the work in this area focused on non-polar compounds (terpenoid flavors, hydrocarbons, carotenes) where a supercritical (SFE) method with CO2 offered high extraction efficiencies. Co-solvent systems combining CO2 with one or more modifiers extended the utility of the SFE-CO2 system to polar and even ionic compounds, e.g., supercritical water to extract polar compounds. This last technique claims the additional advantage of combining extraction and destruction of contaminants via the supercritical water oxidation process."... 

Where water supplies are inadequate for conventional firefighting and foam making, automatically activated fixed clean agent or CO2 systems may be considered for seal fire protection. The agent should be discharged into the seal area below the secondary seal. Fire detection options for these automatic systems include reusable thermal wires and pneumatic tube devices. Thermal wire is typically the more economical choice. 

Mole Fractions from VLLE of the Glucosc+2-Propanol+Water+CO-) System P/MPa Glucose 2-Prp. Water CO2 T/K... 

Fine water spray systems may be potentially superior to CO2 applications and may replace halon environments such as telephone central offices and computer rooms. In the fine spray delivery system, water is delivered at relatively high pressure (above 100 psi [0.689 MPa]) or by air atomization to generate droplets significantly smaller than those generated by sprinklers. Water flow from a fine spray nozzle potentimly extinguishes the fire faster than a sprinkler because the droplets are smaller and vaporize more quickly. Preliminary information indicates that the smaller the droplet size, the lower the water flow requirements and the less chance of water damage. 

The chemoselective 1,2-reduction of a 3-unsaturated carbonyl compounds has been carried out with metal hydride or by hydrogenation. However, chemoselective 1,4-reduction of a (B-unsaturated carbonyl compounds is challenging. Recently, a(B-unsaturated carbonyl compounds 1.23, 1.25 and 1.27 were selectively reduced to the corresponding saturated carbonyl compounds 1.24, 1.26 and 1.28, respectively, by cobalt octacarbonyl and water [Co2(CO)8-H20 system]... 

SAFETY PROFILE Poison by ingestion, subcutaneous, and possibly other routes. Moderately toxic by inhalation. Causes injury to kidneys, Kver, and cardiovascular system. Mutation data reported. Flammable hquid when exposed to heat, flame (sparks), and oxidizers. Moderately explosive when exposed to heat. To fight fire, use alcohol foam, water, CO2, or dr chemical. When heated to decomposition it emits toxic fumes of Cr and NOx. See also other chloropropane entries and CHLORIDES. 

The cumulative display below shows how the supercritical carbon dioxide system provided the best economic solution at the end of the first full year of operation. The net present value of the two systems at a 12% cost of capital was deionized water, 425,000 supercritical CO2, 215,000 economic savings utilizing supercritical CO2 system, 210,000. 

ATh has the units M atm its values for the CO2 system are given in Table 4.3. The concept of gas-water partitioning equilibria (Henry s law) is discussed more fully in Chapter 5. 

In addition, because the net reaction at converts Fe to Fe, the measured potential exhibits a slow drift. Such mixed potentials are of little worth in determining equilibrium values. Many important redox couples in natural waters are not electroactive. No reversible electrode potentials are established for N03T-N0 -NH4-H2S or CH4-CO2 systems. Unfortunately, many measurements of Eh (or pe) in natural waters represent mixed potentials not amenable to quantitative interpretation. 

The term speciation is used to describe the reactions that take place when an electrolyte is dissolved in water. Water dissociates, sour gases hydrolyze, some ions dissociate, and other ions associate until thermodynamic equilibrium is attained. The liquid phase of the ternary H2O-NH3-CO2 system contains at least the following nine species HjO, NH3(aq), COjiaq), H", OH, NH4, HCOj, COj , and NHjCOO. (aq) indicates that the species is in aqueous solution to avoid ambiguity. In order to adequately model this system, interaction parameters for the interaction between each pair of species need to be determined thus, speciation calculations are performed simultaneously with the parameter estimation, and the calculated amount of each species is compared with experimental data. Some models also require ternary parameters and consequently an additional amount of data to determine these parameters. 

Simulations of ternary systems were performed using the pure component parameters in Table I and the cross parameters for the systems acetone/ CO2 and water/C02 determined previously (fi j - 1 and 0.81 respectively). Because of expected difficulties similar to the ones mentioned for the water/C02 system, no attempt was made to simulate the system acetone/water near room temperature. Thus, we set the acetone/water interaction parameters to the values from the Lorenz-Berthelot rules with fi j-l. Direct simulations of ternary phase equilibria have not been previously reported to the best of our knowledge. 

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