Induction time for surface nucleation

Crystallization of L-SCMC (S-Carboxymethyl-L-cysteine) from DL-SCMC solution, wluch sodium chloride is contained, has been studied for the purpose to develop an optical resolution process by crystallization. In a crystallization process, crystal size and purity and product amount of crystal are important. Grow rates of L-SCMC seeds and surface nucleation of D-SCMC on the surface of L-SCMC seed crystals, which affect crystal size and purity, were reported by Yokota et al. (1). Using an optical resolution process, the product amount of L-SCMC crystal was studied by the decrease of the concentration of L-SCMC in a DL-SCMC solution. In this study, the concentration change of D-SCMC and L-SCMC in a DL-SCMC supersaturated solution, in which L-SCMC seeds were suspended, were observed. The decreasing rate of the concentration of L-SCMC was different depending on whether the solution was classified by dominant component of L-SCMC or D-SCMC. Particular correlative equations were obtained for either case. The operational conditions at which an L-SCMC seed crystal grew without crystallization of D-SCMC were studied by the induction time for surface nucleation of D-SCMC and a method for deciding the volume of crystallizer for optical resolution process was discussed based on the data obtained in this study. 

Induction time for surface nucleation of D-SCMC on L-SCMC seed surface. 

In order to estimate the volume of a crystallizer, V, W/V and Cdo or Clo should be assumed at first, and then the volume of a crystallizer is estimated as follows (Example is shown for L-SCMC). From equations 8, and 9, operational time for L-SCMC, 0 1 and 2 are easily estimated. Then total operational time, 6, for one batch is obtained from equation 7. The amount of product crystal of L-SCMC Pi or P2 is also estimated for assumed volume of Vl from equation 5, or 6, for either case of Cl Cd or Cl Cd. Then total product amount of P for one batch is also obtained by equation 10. On the other hand, desired production rate of L-SCMC,P, should be equal to (P / 0 ) and then volume of crystallizer for L-SCMC,Vl, is easily decided. In this process, 0 should be less than the induction time for surface nucleation of D-SCMC, 0, estimated from equation 1. Therefore, assumed WA and Cuo should be finally decided from these restrictions. 

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