Phase behavior critical

Beyond the basics, there are a number of efforts underway to advance the role of critical phase behavior in chemical processing. A few of these are already making an impact, but most remain as concepts under development. We briefly summarize key elements of these and provide links that should facilitate a broader understanding on subjects of interest. This list does not aspire to be comprehensive. Rather, it reflects the author s biased impressions of subjects that might resonate with developers of chemical processes. It is hoped that this brief survey will improve with feedback from readers and the passage of time. 

Much of the traditional theory behind critical phase behavior has been discussed in the context of phase... 

The studies most commonly identified with supercritical fluids and critical phase behavior are those concerned with extraction of natural products. No review of this subject would be complete without... 

We have summarized briefly the key concepts and applications of a broad and complex subdiscipline of thermodynamics. Necessarily, selective judgments have been made as to what aspects of critical phase behavior are most important to chemical processing. Alternative perspectives on the role of critical phase behavior in chemical processing are readily available. For example, the role of reactive synthetic processes at critical conditions has received little attention here. As one prospective source for further links, the article by Perrut provides an especially relevant survey. Readers are encouraged to survey this literature for themselves and keep abreast of the latest developments. 

Chialvo, A. A. and P. T. Cummings. 1995. Comment on Near critical phase behavior of dilute mixtures Molecular Physics. 84,41. 

In Fig. 7, the critical phase behavior of binary aqueous solutions of several selected hydrocarbons and additionally fluorobenzene is shown, most of them having been measured in our laboratory [3]. The dashed curve is the vapor pressure curve of pure water, and the solid lines are parts of the branches of the binary critical p T) curves that start from the critical endpoint llg (systems 9 and 10) or from the critical point of pure water CP(H20). Whereas naphthalene H- water (system 9) and biphenyl -f water (system 10) show class-II behavior, all other systems belong to class III according to the classification of van Konynenburg and Scott, and thus exhibit gas-gas equilibria of the second kind. The consequence is that naphthalene and biphenyl are completely miscible with water already at quite low pressures near the vapor pressure curve of pure water. This behavior is of interest for measurements in mixed solvents and for separations. 

Chialvo, A. A. Cummings, P. T. (1995a) Comments on "Near Critical Phase Behavior of Dilute Mixtures", Molecular Physics 84, 41-48... 

Because the hydrophobic segments on polymer chains are partly exposed to water in the postgel regime, the solution tends to separate into two macroscopic phases by hydrophobic association. Thus gelation and phase separation compete as the temperature goes up. The solution reveals an interesting multi-critical phase behavior [33]. 

Arbabi, S., and A. Firoozabadi Near-Critical Phase Behavior of Reservoir Fluids Using Equations of State, SPE Advanced Techology, p. 139, March 1995. 

Due to their technological importance, polymer blends have attracted considerable attention during the past decade. For thermodynamic reasons, most polymer pairs are immiscible and their degree of compatibility is of underlying importance to the microphase structure and consequently, to the mechanical properties of the blend. The Floiy Huggins % interaction parameter for the polymer pair plays a dominant role in explaining critical phase behavior of a compatible pair and in estimating interfacial tension and interfacial thickness for semicompatible or incompatible pairs. Direct measurement of this parameter is not always possible, thus the obtained information, in conjunction with suitable theoretical models of polymer solutions may lead to an assessment of the interaction parameters for the actual polymeric case. 

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