No abstract

Amino acids are widely used in food, chemical, agricultural, cosmetic, and pharmaceutical products. Crystallization is one of the key steps in their manufacturing processes. However, for a complex multicomponent system with solvates and compounds, it is not clear how to recover a specific amino acid or its salt. To address this issue, this article proposes a general framework for the conceptual design of amino acid crystallization processes. It is based on the representation and experimental determination of solid−liquid equilibrium (SLE) phase diagrams. Glutamic acid and its sodium salt, monosodium glutamate, are chosen as a model system to illustrate this framework. SLE experiments were performed to estimate the location of the boundaries between different crystallization compartments in each of which a single component can be recovered.

Liquid−liquid extraction is usually used along with other separation processes for the recovery of pure components. It is desirable that the liquid−liquid equilibrium (LLE) phase behavior, which is the thermodynamic basis for liquid−liquid extraction, be represented in a phase diagram. This is because the visualization of process limitations has a crucial role in the construction of feasible separation schemes for achieving the overall separation objective. However, because most applications involve multicomponent mixtures, visualization of the LLE phase diagram in its entirety becomes difficult or even impossible. Therefore, a visualization approach to represent high-dimensional LLE phase diagrams based on projections and cuts to reduce dimensionality is proposed. In such an approach, the liquid−liquid immiscibility regions are represented as a collection of projected tie lines. By superimposing the resulting diagram with any other map of process boundaries in composition space, such as a solid−liquid equilibrium phase diagram, one can clearly observe the possible use of liquid−liquid extraction in crossing the boundaries, an option that is not apparent when only numerical data are presented. Two common separation scenarios are used to demonstrate the applicability and advantages of this approach, particularly in illustrating the close interactions of liquid−liquid extraction with distillation and crystallization.