A polythermal methodology to assess the mechanisms and the kinetics of solution crystallisation is described and used in connection with a recently proposed model for the

In situ studies of methyl stearate growing from supersaturated n-dodecane, kerosene, and toluene solutions reveal strong evidence that solvent choice influences the crystal morphology and crystal growth kinetics. Crystals with similar habit are observed in all solvents, with the exception of lower supersaturations in kerosene, where a less symmetric morphology was observed. BFDH analysis based on the monoclinic C2 crystal structure of methyl stearate yielded the morphological indexation to be (110), (1–10), (−110), and (−1–10) for the dominant observed habit and (110) (1–10) (−1–10) (−240) (−3–10) for the less symmetric habit observed in kerosene solvent. Measurements of the growth rate for the (110) and (1–10) faces are similar for all solutions ranging from 0.02 to 1.13 μm/s, for significantly lower values of supersaturation in the case of toluene. The tendency of the growth rate dependence on σ was consistent with the Burton-Cabrera-Frank (BCF) growth mechanism in n-dodecane, the Birth and Spread (B&S) mechanism in kerosene and diffusion controlled in toluene solvent.

A1. Morphological analysis A1. BFDH and zone axis methods A1. Crystal growth kinetics and rates A1. In-situ optical microscopy A1. Kinetic roughening B1. N-alkanes a b s t r a c t A detailed analysis of the crystal morphology of triclinic n-docosane (C 22 H 46 ) is presented together with a preliminary assessment of the supersaturation-dependence of the growth rates for the predicted hkl ð Þ faces. A methodology to index the experimentally observed crystal faces, based on a combined BFDH and zone axis methodology is defined. Analysis using this methodology yields the morphological indexation of n-docosane to be (001), (112), (102), (010), and (1 À 33) or (130) based on the expected triclinic crystal structure. Crystals of n-docosane growing from supersaturated n-dodecane (C 12 H 26 ) solutions, as studied using in-situ optical microscopy, at three different supersaturation (σ) levels 0.01, 0.02 and 0.05, reveal that the crystal morphology changes with increasing in supersaturation, evolving from a habit consistent with a triclinic crystal system to a habit that is perhaps more representative of an orthorhombic structure. Growth rates determined for the (112) and (102) faces as well as for those less dominant faces range between 0.51 and 9.85 mm/s, in good agreement with previously reported data for other organic molecules including n-alkanes.

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Crystallization studies of methyl stearate from supersaturated dodecane, kerosene, and toluene solutions reveal strong evidence that solvent choice influences solubility and nucleation behavior. Solute solubility is less than ideal with toluene, kerosene, and dodecane, respectively, exhibiting the closest behavior to ideality, the latter consistent with the highest solvation. Polythermal crystallization studies using the Kashchiev–Borissova–Hammond–Roberts (KBHR) model [J. Phys. Chem. B20101145441; J. Cryst. Growth2010312698; CrystEngComm201416974] reveal a progressive nucleation (PN) mechanism with crystallite interfacial tension (γeff) values between 0.94 and 1.55 mJ/m2, between 1.21 and 1.91 mJ/m2, and between 1.18 and 1.88 mJ/m2 for dodecane, kerosene, and toluene, respectively. Nucleation rates at the critical undercooling lie between 4.56 × 1016 and 1.79 × 1017 nuclei/mL·s, with the highest rates associated with crystallization from kerosene solutions. Iso-supersaturation nucleation rates are the highest for dodecane ranging from 2.39 × 1017 to 3.63 × 1018 nuclei/mL·s. Nucleation in toluene appears to be hindered by its relatively higher interfacial tension, which is associated with nucleation rates about an order of magnitude less than those obtained for dodecane.