As one important separation and purification method in ethyl vanillin (EVA) production process, solute crystallization from organic solution is the last step controlling the crystal product quality. Generally, nucleation could play a critical role in the initial stage of crystallization process, determining the crystal polymorph, crystal habit and size distribution of the particles. Nucleation behavior of ethyl vanillin (EVA) was studied in three different organic solvents, ethanol, n-propanol and n-butanol, by measuring the metastable zone widths (MSZWs) in cooling crystallization. The supersaturation was expressed by the critical supercooling △Tmax, which is a function of saturated temperature T0 and cooling rate R. Compared to The Nývlt's semiempirical model and Sangwal's theory, the nucleation behavior of three unseeded ethyl vanillin organic systems was better described by the modified model proposed by Xu et al. The dependence of the nucleation parameters on saturation temperature T0 and nucleation temperature T1 is eliminated. Moreover, the relative pre-exponential A and crystal-liquid interfacial energy γ were calculated. At the same time, the critical nucleus size and critical Gibbs free energy were obtained based on the Classical Nucleation Theory and the relationship between the nucleation barrier and pre-exponential A also could be established according to the Sangwal's theory.

Nucleation behavior of Ethyl vanillin in three solvents from the metastable zone widths in cooling crystallization

2019 Spring National Meeting

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