High-pressure miscibility

Polymer solutions at high pressures Miscibility and kinetics of phase separation in near... 

ZHA Zhang, W. and Kiran, E., Phase behavior and density of polysulfone in binary fluid mixtures of tetrahydrofuran and carbon dioxide under high pressure miscibility windows, J. Appl. Polym. Sci., 86, 2357, 2002. 

High-Pressure Miscibility of Polymers in Near- and Supercritical Fluids... 

Kiran, E., Malki, K., POhIcr, H. (1996) High-pressure miscibility and extraction of polymeric coatings and hot melt adhesives with carbon dioxide + pentane mixtures. Towards supercritical recycling of paper-plastic waste. Proc, ACS. Div. Pofym. Mater. Set A Eng., 74,231-232. 

Cyclohexylamine is miscible with water, with which it forms an azeotrope (55.8% H2O) at 96.4°C, making it especially suitable for low pressure steam systems in which it acts as a protective film-former in addition to being a neutralizing amine. Nearly two-thirds of 1989 U.S. production of 5000 —6000 t/yr cyclohexylamine serviced this appHcation (69). Carbon dioxide corrosion is inhibited by deposition of nonwettable film on metal (70). In high pressure systems CHA is chemically more stable than morpholine [110-91-8] (71). A primary amine, CHA does not directiy generate nitrosamine upon nitrite exposure as does morpholine. CHA is used for corrosion inhibitor radiator alcohol solutions, also in paper- and metal-coating industries for moisture and oxidation protection. 

In the previous sections we have been concerned with high-pressure equilibria in systems containing one liquid phase and one vapor phase. We now briefly consider the effect of pressure on equilibria between two liquid phases. In particular, we are concerned with the question of how pressure may be used to induce miscibility or immiscibility in a binary liquid system. 

Fig. 18. Effect of pressure on miscibility, (a) Low pressure no immiscibility. (b) High pressure immiscible for x < Xi < xV...

In the previous sections, we indicated how, under certain conditions, pressure may be used to induce immiscibility in liquid and gaseous binary mixtures which at normal pressures are completely miscible. We now want to consider how the introduction of a third component can bring about immiscibility in a binary liquid that is completely miscible in the absence of the third component. Specifically, we are concerned with the case where the added component is a gas in this case, elevated pressures are required in order to dissolve an appreciable amount of the added component in the binary liquid solvent. For the situation to be discussed, it should be clear that phase instability is not a consequence of the effect of pressure on the chemical potentials, as was the case in the previous sections, but results instead from the presence of an additional component which affects the chemical potentials of the components to be separated. High pressure enters into our discussion only indirectly, because we want to use a highly volatile substance for the additional component. 

Adrian et al. (2000) have reported a novel high-pressure liquid-liquid extraction process with reference to processing in biotechnology the example of cardiac glycosides (digitoxin and digoxin) is cited. A completely miscible, binary system of water and a hydrophobic organic solvent like ethanol can split into two liquid phases when a near-critical gas (e.g. CO2) is added. The near-critical C02/water/l-propanol system is reported, for which possibilities for industrial exploitation exist. 

A cosolvent used as a miscible additive to CO2 changed the properties of the supercritical gas phase. The addition of a cosolvent resulted in increased viscosity and density of the gas mixture and enhanced extraction of the oil compounds into the C02-rich phase. Gas phase properties were measured in an equilibrium cell with a capillary viscometer and a high-pressure densitometer. Cosolvent miscibility with CO2, brine solubility, cosolvent volatility, and relative quantity of the cosolvent partitioning into the oil phase are factors that must be considered for the successful application of cosolvents. The results indicate that lower-molecular-weight additives, such as propane, are the most effective cosolvents to increase oil recovery [1472]. 

The high pressure form of FeOOH is more compact than any other iron oxide hydroxide, hence it has a higher than usual Neel temperature of 470 K. At room temperature, high pressure FeOOH is antiferromagnetic with a collinear spin arrangement parallel to the c-axis (Fernet et al., 1973). High-pressure FeOOH is completely miscible with CrOOH. Substitution with Cr reduces T to the extent that with 80%... 

Numerous methods have been explored to recover at least some of this vast resource. Injection of oil-miscible fluids, gases under high pressure, and steam —either separately or in combination — have all been tried with various degrees of success. This is where microemulsions enter the picture. Under optimum conditions an aqueous surfactant solution — which may also contain cosurfactants, electrolytes, polymers, and so on —injected into an oil reservoir has the potential to solubilize the oil, effectively dispersing it as a microemulsion. 

Phosphate esters are widely used in metalworking and lubricants. A C12 h with 6 mol of ethylene oxide (diester) can be used as an emulsifier but also as an extreme pressure additive - it can reduce wear where there is high pressure metal to metal contact. PEs can also show corrosion inhibiting properties, as with petroleum sulphonates and the emulsifying power of PEs with low foam is used in agrochemical formulations. PEs can act as dispersants or hydrotropes in plant protection formulations, allowing the development of easy-to-handle and dilute formulations of both poorly miscible and insoluble herbicides. 

Liquid/liquid emulsions consist of two (or more) non-miscible liquids. Classical examples for this are oil in water (O/W) emulsions, for example milk, mayonnaise, lotions, creams, water soluble paints, photo emulsions, and so on. As appliances, teeth-rimed rotor-stator emulsifiers and colloid mills, as well as high-pressure homogenizers are used. 

The structure of platinum dioxide and its reactions with some di, tri, and tetravalent metal oxides have been investigated. Ternary platinum oxides were synthesized at high pressure (40 kUobars) and temperature (to 1600°C). Properties of the systems were studied by x-ray, thermal analysis, and infrared methods. Complete miscibility is observed in most PtO2-rutile-type oxide systems, but no miscibility or compound formation is found with fluorite dioxides. Lead dioxide reacts with Pt02 to form cubic Pb2Pt207. Several corundum-type sesquioxides exhibit measurable solubility in PtOz. Two series of compounds are formed with metal monoxides M2PtOh (where M is Mg, Zn, Cd) and MPt306 (where M is Mg, Co, Ni, Cu, Zn, Cd, and Hg). 

For the on-line procedures there are numerous combinations of sorbents and mobile phases. The primary objective is to partially separate the component(s) of interest on one column, followed by diversion of those fractions of interest onto a second column. The sorbents used for each column can be different, but the mobile phases must be miscible. To achieve column switching, high-pressure, low-internal-volume, valves are used. Numerous valve configurations are used and these are discussed below. 

At temperatures below the critical point of C02 (31°C), C02 and TEG exhibit liquid phase immiscibility. This can be seen for the 25°C isotherm shown on figure 7.2. At temperatures greater than 31°C, C02 + TEG mixtures have a miscibility gap. Thus, it is possible to dehydrate C02 at high pressures. 

Hydrogen sulfide and TEG are completely miscible. Thus, at high pressure TEG cannot be used to dehydrate H2S because they completely mix. Dehydration of an H2S stream using TEG must be done at low pressure when the H2S is still in the vapor phase. These... 

For mechanistic studies, ambient pressure experiments on emulsions and foams often offer significant experimental advantages over high-pressure experiments. However, high-pressure measurements are also needed since the phase behavior, physical properties of the fluids, and dispersion flow may all depend on pressure. Experiments under laboratory conditions that closely match reservoir conditions are particularly important in the design of projects for specific fields. Chapter 19, by Lee and Heller, describes steady-state flow experiments on CO2 systems at pressures typical of those used in miscible flooding. The following chapter, by Patton and Holbrook,... 

CO2 floods at pressures above 10 MPa (49). Only flooding experiments were used to choose surfactants in this first extension of low-pressure foam flooding to high-pressure, C02-miscible flooding. 

The purpose of the miscible displacement tests was, primarily, to evaluate the effect of the surfactant on the interaction between the high pressure CO2 and the crude oil. The miscible displacement process is so efficient in linear laboratory tests that any improvement would be minor. However, any interference with the mechanism of miscibility should be detrimental to the recovery efficiency and easily observed. 

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