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Fluid-phase behavior of binary mixtures in which one component can have two critical points
Swaroop Chatterjee1, Pablo G Debenedetti
1Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
The Journal of Chemical Physics
|May 6, 2006
Summary
This study explores water-like fluid mixtures, revealing that a second critical point in water could lead to observable liquid-liquid transitions. The findings suggest experimental possibilities for detecting this phenomenon in aqueous mixtures.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Fluid Phase Behavior
Background:
- Water exhibits complex fluid-phase behavior, including potential for multiple critical points.
- Understanding mixture phase diagrams is crucial for various chemical and physical processes.
Purpose of the Study:
- To theoretically investigate the binary fluid-phase behavior of mixtures with a water-like component possessing two critical points.
- To compare phase behavior using different water parameter sets (two-critical-point vs. singularity-free).
- To analyze the influence of nonpolar solutes with varying dispersive interactions on mixture critical lines.
Main Methods:
- Theoretical investigation of binary fluid mixtures.
- Utilizing two sets of water parameters: one with a second critical point and one without.
- Analyzing the impact of three nonpolar solutes with differing van der Waals attractive parameters (a1 < a2 < a3).
Main Results:
- All investigated mixtures exhibited five critical lines, irrespective of water parameter set.
- A critical line originating from water's second critical point was observed for mixtures with solutes 1, 2, or 3.
- For solutes 1 and 2, this line relates to the vapor-liquid critical line, indicating accessible upper and lower consolute points.
- The second critical point's influence shifts to higher temperatures (up to ~310 K at ~200 bar) with solute 2, suggesting experimental observability.
- Differences in phase behavior between the two water parameter sets were minimal for solute 3 at experimentally accessible conditions.
Conclusions:
- The existence of a second critical point in water can lead to distinct liquid-liquid transitions in aqueous mixtures.
- These transitions may be experimentally observable, particularly for mixtures involving solutes with moderate dispersive interactions.
- The findings highlight the importance of considering multiple critical points in water for accurate phase behavior predictions.
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