Key Roles of Nucleation and Impurity Migration Behavior in Layer Melt Crystallization: Case Study of 4,5-Dimethyl-1,3-dioxol-2-one

In melt crystallization, how the cooling rate and initial concentration affect metastable zone width (MSZW), thus altering the impurity distribution coefficient, remains elusive. To explore the above problem, the layered melting crystallization of 4,5-dimethyl-1,3-dioxol-2-one is taken as a research case here. In this work, first, we show that when the composition decreases or the cooling rate increases, the value of interfacial energy (gamma) increases and the pre-exponential factor (A) decreases, leading to a wider MSZW. Second, the faster the cooling rate or the higher the impurity content of the raw material, more impurity will be entrapped in the crystal layer, leading to a larger impurity distribution coefficient. More interestingly, we found that the relationship between K-BS and K-AS is linear for K-AS = 0.422 to 0.875 within the cooling rate 1-40 K/h, which increases with the increase of cooling rate and tends to be consistent. Finally, we highlight that the essential relationship between the impurity distribution coefficient before and after sweating is a straight line and unless the impurity distribution in the cooling stage reaches 0.377, it is impossible to obtain the product that approaches 100% purity through sweating.