Nucleation kinetics of pentaerythritol (original) (raw)
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Crystal growth kinetics of pentaerythritol
The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995
The growth kinetics of pentaerythritol (PE) in aqueous solutions were determined from batch and continuous experiments; growth rate values about two orders of magnitude lower were obtained operating in batch mode. This behaviour, which agrees with previous results reported by various authors, validates the hypothesis that some impurity adsorbed on the crystal surface is capable of strongly depressing the growth kinetics. This influence is also confirmed by the remarkable decrease in PE growth rate observed on adding selected impurities (1% formaldehyde or 2% formic acid) to the solution. The inhibiting effect of the impurity on the growth process is substantially reduced when a threshold supersaturation value equal to about 0.06 gpE per gsolution is exceeded. The growth process can also be improved by increasing the temperature, which reduces the adsorption rate of the impurity, or by washing the crystal seeds, i.e. partially removing the impurity adsorbed over the crystal surface.
Crystallization of Pentaerythritol I. Solubility, Density and Metastable Zone Width
Collection of Czechoslovak Chemical Communications, 1994
Solubility of pentaerythritol in water has been determined using literature data, the polythermal method and the dry residue method. Densities of its aqueous solutions have been measured using a pycnometer. Kinetics of crystallization of the pentaerythritol has been determined in laboratory experiments. In this paper, metastable zone width measurements have been employed for the assessment of the primary nucleation rate.
Growth rate of pentaerythritol crystals from purified aqueous solution
Chemical Engineering Research and Design, 2008
Pentaerythritol crystals were grown by batch desupersaturation of a seeded solution of the purified material in a draft tube crystalliser of 0.25 × 10 −3 m 3 capacity. First and second order rate constants in the high and low supersaturation regions respectively were correlated in terms of the activation energies. The activation energies were found to be 42 and 64 kJ mol −1 respectively with the driving force expressed as relative supersaturation. The very high value for the activation energy in what is normally considered to be the diffusion zone suggests that some impurity was still present.
Short communication Growth rate of pentaerythritol crystals from purified aqueous solution
c h e m i c a l e n g i n e e r i n g r e s e a r c h a n d d e s i g n 8 6 ( 2 0 0 8 ) 951-956 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h e r d a b s t r a c t Pentaerythritol crystals were grown by batch desupersaturation of a seeded solution of the purified material in a draft tube crystalliser of 0.25 × 10 −3 m 3 capacity. First and second order rate constants in the high and low supersaturation regions respectively were correlated in terms of the activation energies. The activation energies were found to be 42 and 64 kJ mol −1 respectively with the driving force expressed as relative supersaturation. The very high value for the activation energy in what is normally considered to be the diffusion zone suggests that some impurity was still present. (D.E. Creasy).
Drying of Pentaerythritol obtained from Batch Crystallization
Chemical Engineering & Technology, 2010
This work was aimed at investigating the kinetics of vacuum drying pentaerythritol obtained by batch crystallization from aqueous solution. The quality of the crystals dried after rinsing with ethanol and acetone was analyzed, and then compared with the data obtained from the unrinsed crystals. Drying was carried out in the laboratory vacuum dryer under different pressures and temperatures. The experimentally‐obtained drying curves were successfully approximated by the two‐parameter Page model. Parameters, k and n, of the mathematical model were correlated with the process conditions. The parameter k grew with increasing drying rate. The parameter n was influenced by the type of solvent that was removed. It decreased with the increase of the boiling point of the solvent.
Homogeneous nucleation rates of 1-pentanol
The Journal of Chemical Physics, 2004
We have measured isothermal homogeneous nucleation rates J for 1-pentanol vapor in two different carrier-gases, argon, and helium, using a two-valve nucleation pulse chamber. The nucleation rates cover a range of 10 5 ϽJ/cm Ϫ3 s Ϫ1 Ͻ10 9 at temperatures between 235ϽT/KϽ265. We observed no influence of the carrier gas on location and slope of the nucleation rate isotherms. These measurements are part of an international effort to examine 1-pentanol using various experimental techniques, which was initiated in Prague in 1995. In the present paper nucleation rate data obtained by several groups are compared to each other and to the classical nucleation theory. As expected, the classical theory is not able to quantitatively predict the experimental results. Nevertheless, relating the experimental data to the classical theory provides a suitable way to compare data of widely differing nucleation rates obtained by different experimental techniques. This comparison helps judging mutual support of the data and, at the same time, provides a rather interesting insight into the accuracy of the individual experimental techniques.
Langmuir, 2009
The solvent type strongly affects the nucleation behavior of 12HSA and therefore strongly influences the peak nucleation rate, fiber length, spatial distribution of mass, and degree of branching. Using nonisothermal kinetic models, a correlation was established among the activation energy of nucleation, fiber length, and induction time of 12HSA nucleation in different solvents. However, there was no correlation between any measurable parameter and solvent polarity. Activation energies varied from 2.2 kJ/mol in methyl oleate to 15.8 kJ/mol in glycerol. Nucleation behavior and structure were strong functions of the cooling rate, with distinct regions observed above and below 5-7°C/min for fiber length, induction time, rate constant, and peak nucleation rate. The abrupt changes in the rate of nucleation, crystal growth rate constant, and degree of branching around this cooling rate are related to whether the nucleation and crystal growth processes are governed by mass transfer or thermodynamics. Furthermore, the Avrami equation accurately predicted several structural features of the fibrillar network such as fiber length and, to a lesser extent, induction time.
Homogeneous nucleation rates of n-pentanol measured in an upward thermal diffusion cloud chamber
The Journal of Chemical Physics, 1999
Homogeneous nucleation rates of n-pentanol as functions of both supersaturation and temperature were measured in two different upward thermal diffusion cloud chambers, by research groups in Prague and Baltimore. The measurements were made at temperatures between 280 K and 320 K. The nucleation rates obtained are compared to the rates measured by Luijten et al. ͓J. Chem. Phys. 106, 4152 ͑1997͔͒, by Hrubý et al. ͓J. Chem. Phys. 104, 5181 ͑1996͔͒, and by Strey et al. ͓J. Chem.
Kinetics of Crystallisation of Polymers - A Review
Progress in Rubber Plastics and Recycling Technology, 2002
A review covering nucleation modes and models of polymer crystallization kinetics. The classical models assume the rate of crystallization to be related to temperature only. For materials exhibiting low molecular mobility, e.g., polymers, time effects appear justified. Ziabicki's model (51-53) allows the rate to be related to time. In thermal nucleation, this relation stems from the delay of the steady-state condition to become established under specific external conditions. The athermal mechanism of nucleation produces another time effect. It involves no potential barriers to be overcome by a cluster to become a nucleus and proceeds only on account of the change in the criterion for the nucleus stability (critical size) as external conditions are modified. Experiments showed the (iso and non-isothermal) crystallization rate to be directly related to time. The underlying phenomenon involves the athermal nucleation occurring on crystal residues left in the melt and the relaxation effect upon subsequent thermal nucleation. The applicability of Ziabicki's model is demonstrated. MECHANISMS OF NUCLEATION IN THE CRYSTALLIZATION OF POLYMERS The crystallisation of polymers is usually regarded as a transformation comprising two stages: (primary) nucleation, and growth of crystals. Taking into account that the stage of crystal growth can be analysed in categories of (secondary) nucleation on the surface of already existing crystals, crystallisation can be regarded as processes of nucleation occurring in the bulk and on the surface of a crystal. The classical theory of nucleation (1-3) examines the one-dimensional process of formation and growth of aggregates as a result of the This paper was originally published in 'Polimery', Volume 46, No.11-12, p768 (in Polish).
Influence of History of Solution in Crystal Nucleation of Fenoxycarb: Kinetics and Mechanisms
Crystal Growth & Design, 2014
Nearly 1800 induction time experiments have been performed on crystal nucleation of fenoxycarb in isopropanol to investigate the influence of solution pretreatment. For each preheating temperature and preheating time, at least 80 experiments were performed to obtain statistically valid results. The relationship between the inverse of the induction time and the preheating time can be reasonably described as an exponential decay having time constants ranging up to days depending on the temperature. This dependence on the preheating temperature corresponds to an activation energy of over 200 kJ/mol. Given sufficiently long preheating time and high temperature, the solution appears to reach a steady-state where the "memory" effect has disappeared. Density functional theory modelling suggests that the molecular packing in the crystal lattice is not the thermodynamically stable configuration at the level of simple dimers in solution, while modelling of the first solvation shell reveals that solute aggregation must exist in solution due to the low solvent to solute molecular ratio. It is thus hypothesized that the dissolution of crystalline material at first leaves molecular assemblies in solution that retain features of the crystalline structure which facilitates subsequent nucleation. However, the longer the solution is kept at a temperature above the saturation temperature and the higher the temperature, the more these assemblies disintegrate, and transform into molecular structures less suited to form critical nuclei. .