Abstract
Size-dependent growth kinetics of vitamin C crystals in water solutions of L(+)-ascorbic acid with the addition of methanol and ethanol Growth kinetics of vitamin C crystals during the batch mass crystallization process in L(+)-ascorbic acid - methanol - ethanol - water system was determined. The linear growth rate values were estimated on the basis of the product crystal size distributions. The kinetic model of the continuous process in a MSMPR crystallizer was adopted for the batch mode description according to Nyvlt's conception, taking the sizedependent growth (SDG) rate effects into consideration. The kinetic parameter values were determined with a Rojkowski hyperbolic SDG model. A good compatibility between the experimental product crystal population density distributions and the SDG model predictions was observed. The interpretation of the kinetic data was presented and discussed.
Highlights
Vitamin C (L(+)-ascorbic acid, denoted later in the text as LAA) for the medical needs is synthesized from D-glucose[1, 2], the most often, according to Reichstein, procedure[3]
It results from this figure that in a lnn(L) – L coordinate system for the crystals of the L < 100 μm size, the experimentally determined population density distributions are concave to top
This specific shape can be interpreted as an evidence of a more complex intrinsic kinetics of crystals growth than it can result from the most simplified Size-Independent Growth (SIG) model[27]
Summary
Vitamin C (L(+)-ascorbic acid, denoted later in the text as LAA) for the medical needs is synthesized from D-glucose[1, 2], the most often, according to Reichstein, procedure[3]. The calculation results – effects of adopting the most simplified model of a continuous mass crystallization process kinetics in a theoretical MSMPR (Mixed Suspension Mixed Product Removal) crystallizer for the batch mode description, according to a Nyvlt's conception, is presented in the authors' work[27] (SizeIndependent Growth – SIG kinetics) is, not adequate to correctly reflect the experimentally detected, characteristic initial curvature of the population density distribution in a coordinate system lnn(L) – L within the range of the smallestsize crystals (of L < 100 μm) Taking this fact into account in the presented work, the research results, with their kinetic interpretation (G(L) ≠ const. Taking this fact into account in the presented work, the research results, with their kinetic interpretation (G(L) ≠ const. indicating Size-Dependent Growth, SDG, phenomena), making allowance for the intrinsic nonlinearity of the population density course in a lnn – L coordinate system, are presented
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