1,2-propanediol and 1,3-propanediol homogeneous nucleation rates and phase transitions in the new phase critical embryos

Abstract

Nucleation rates of supersaturated vapors near the conditions for the critical line for each pair of 1,2- or 1,3-propanediol and carbon dioxide or sulfur hexafluoride at total system pressures of P=0.10, 0.20, and 0.30 MPa have been measured in a flow diffusion chamber. Critical parameters, i.e., temperatures and pressures, of the binary systems versus compositions were semiempirically evaluated. It was found experimentally that there is an area of parameters in the PTx phase diagram, for each pair of vapor and carrier gas investigated in the present research, for which critical embryo phase transitions of the first order take place (where P, T, and x are pressure, temperature, and embryo composition, respectively). The nucleation rate surface singularity and a gap in the number of molecules in critical embryos reflect this area. Shifts of the phase transition temperatures can be initiated by increasing the pressure (or concentration) of the carrier gas. This behavior is peculiar for binary systems. It is well-known that no liquid–liquid phase transitions can exist for a one-component system. At least a binary solution is required for liquid–liquid phase transitions. This means that vapor nucleation of the investigated substances in the carrier gas atmosphere can be considered as nucleation of a binary vapor–gas system. A schematic diagram for the possible metastable vapor conditions is presented. On the basis of our experimental results, one can assume that there exists a surface describing the parameters related with a phase transition of the first order in critical embryos. This surface is located within the volume of the possible vapor metastable conditions.

Vapor–gas/liquid nucleation experiments: A review of the challenges

“…These measurements have been made using a static diffusion cloud chamber at pressures up to 4.0 MPa with H 2 , He, N 2 , and Ar as the carrier gases. Other experimental results have supported a dependence of the nucleation rate on the nature and total pressure of the carrier gas (Anisimov, Koropchak et al, 2000;Luijten, Peeters, & van-Dongen, 1999;Lihavainen & Viisanen, 2001). Gas-pressure effects were detected by van Remoortere, Heath, Wagner, and Strey (1996) although most of the measurements from this research group (i.e., Viisanen, Strey, & Reiss, 1993; did not observe carrier gas influences on nucleation rate.…”

An Additional Condition of Efficiency of the Supercritical Fluid Extraction Process

“…The experimental study [28] at sufficiently high temperatures of 398.2, 423.2, and 453.2 K at a pressure up to 55 MPa showed that this is type V-VI of phase behavior with a discontinuous critical curve. However, Anisimov et al [29], in their study concerning only nucleation in the supersaturated vapor of this system near the critical line, stated that this line is continuous. To be sure, this statement was not grounded in the results of experimental investigations of the phase space, but was formulated only based on some theoretical and calculated concepts.…”

Nucleation: theory and experiment

“…By contrast, according to Eqn (25), this value is inverse to the cube of the logarithm of supersaturation. However, the linear regressions of the experimental nucleation rates both as the functions (lnS) 73 and (lnS) 72 give equally good approximations.…”