Solubility behaviour, crystallisation kinetics and pour point: A comparison of linear alkane and triacyl glyceride solute/solvent mixtures

Abstract

Mixtures of either a hydrocarbon wax in a hydrocarbon solvent or a long chain triacyl glyceride (TAG) in a TAG solvent show complex solubility boundary temperature hysteresis and precipitated crystal network formation leading to gelation. For these industrially-important systems, we show how the equilibrium solubility and its hysteresis, crystallisation kinetics and pour point temperature vary with solute concentration for representative examples of both hydrocarbon (n-tetracosane (C24) solute in n-heptane (C7) solvent) and TAG (tristearin (SSS) solute in tricaprylin (CCC) solvent) mixtures. The behaviour is modelled with good accuracy; thereby providing a useful aid to formulation and process optimisation.

Visual Measurements of Solid–Liquid Equilibria and Induction Times for Cyclohexane + Octadecane Mixtures at Pressures to 5 MPa

“…The time was then recorded until the first crystals were visually observed on the copper tip. The results are presented in and show that increased subcooling exponentially shortened the induction time, halving approximately every 0.25 K. These observations are consistent with those generally observed in the nucleation experiments 78 where formation of a new condensed phase requires to overcome an activation energy barrier associated with the interfacial energy between the new and parent phases; no such energy penalty exists for the melting process where the energy bound in the interfacial region is released [79][80][81][82][83].…”

“…The results are presented in Figure 6 and show that increased subcooling exponentially shortened the induction time, halving approximately every 0.25 K. These observations are consistent with those generally observed in the nucleation experiments 78 where formation of a new condensed phase requires an activation energy barrier associated with the interfacial energy between the new and parent phases be overcome; no such energy penalty exists for the melting process in which the energy bound in the interfacial region is released. 79 7a shows results from the low pressure experiments regarding the SLVE for the binary mixture of cyclohexane and octadecane. The results are consistent with the SLE data measured at 0.1 MPa by Domanska et al, 61 which confirms that solid equilibria are comparatively insensitive to pressure.…”

Ultra-stable self-foaming oils

“…Several isolated crystals can be discerned however (right hand side of image) and these are plate-like of side length around 10 m (see also Figure S11(a)). It was shown recently that the crystals were exclusively those of the  polymorph (Fletcher, Roberts & Urquhart, 2016). Since we were limited to low volumes (due to the expensive tristearin), we aerated the dispersion using a rotor-stator homogeniser.…”