Observation of pressure-induced phase transitions in rapeseed oil with methyl alcohol mixtures

Abstract

A high-pressure research on rapeseed oil and mixtures of rapeseed oil with methyl alcohol has been made. In all cases, at least one occurrence of the first order phase transition similar to that in castor oil was noticed [R.M. Siegoczyński, Reports of the Institute of Physics. No. 46, Publishing House of the Warsaw University of Technology (1998)]. Experiments were performed in a cylindrical chamber with a simple piston system, working together with 20 ton hydraulic laboratory press. The pressure in those experiments was approaching 1 GPa. Changes of pressure, volume, temperature and capacitance were recorded using an advanced data acquisition system. In this article, the changes of the relative electric permittivity ε r as function of pressure and also the compressibility of investigated liquids have been presented. Abnormal rise of the dielectric constant in the mixture of rapeseed oil with methyl alcohol was observed. These results suggest the occurrence of a new phase transition apart from the one observed earlier in rapeseed oil [A.J. Rostocki, R. Wiśniewski and T. Wilczyńska, J. Mol. Liq., in press].

Compressibility studies of some vegetable oils up to 1 GPa

“…The experiments were carried out in a 17 mm chamber, as described in [1][2][3][4]. The chamber was connected to an automatic measuring multichannel system.…”

“…A possibility of irreversible changes caused by phase transitions observed in both fatty acids and their triglycerides is bringing the risk of such modifications, which can be dangerous for human health. The high-pressure properties of vegetable oils have been the subject of intensive research in our laboratory since 2004 [1][2][3][4][5][6] and are the continuation of earlier works on castor oil [7][8][9][10]. In all investigated oils, the first-order phase transition has been observed due to the solidification of those oils.…”

Could RME biodiesel be potentially harmful to modern engine? solidification process in RME

“…As it has been presented, scattered light method has a great application potential in determination of phase transition in broad spectrum of liquids [19,29,30,36], including RME. The phase transition causes the sudden change of physical properties like density, viscosity and compressibility.…”

“…Such phase transitions were observed first in castor oil [18] then in most of the vegetable oils used for production of biodiesel [19][20][21][22]. In all of them, a discontinuous phase transition has been observed [23][24][25].…”

Relative permittivity behavior and temperature changes in linoleic acid during the phase transition

“…During the return to the initial phase temperature decreases and free dipoles align according to the electric field again. Analysis of the relative permittivity changes was our main tool which let us to investigate phase transitions in fatty liquids [4][5][6][7][8]. To find out more about the phenomenon that we deal with, the authors decided to consider investigated liquid using the Fröhlich theory of dielectrics [9].…”