Separation of Complex Feed Streams of a Product by Layer Melt Crystallization

Abstract

The purification of a complex feed stream of a multicomponent product, i.e., two isomers and impurities, by melt crystallization was evaluated by studying different optimization parameters like crystal growth rate, crystallization time, and purity. First, a phase diagram was established and on this basis different crystallization experiments were carried out. A laboratory-scale solid layer melt crystallizer, a so-called cold finger, was used to determine the purity and separation of the components, i.e., the ratio of the components, from the product at different crystallization times and temperatures as a function of layer thickness and a sweating process. The desired composition of the final product was achieved by adding components resulting from the second stage of crystallization since the first crystallization gave only the desired purity but not the right mixture of the two compounds of the wanted product.

Chiral Purification of S-2-Phenylpropionic Acid from an Enantiomer Mixture by Stripping Crystallization

“…Shiau and co-workers have introduced a new separation technology, stripping crystallization (SC), to separate some mixtures with close boiling temperatures, including mixed xylenes − and enantiomer mixtures. , Basically, SC applies melt crystallization and vaporization to a liquid mixture by lowering temperature and pressure, leading to the formation of a crystalline product and vapor mixture via a three-phase transformation. During melt crystallization, a pure desired crystalline solid is formed due to the solid–liquid transformation in a liquid mixture at normal pressure during the cooling process. − On the other hand, during SC, a pure desired crystalline solid along with the vapor mixture is formed due to the three-phase transformation in a liquid mixture at low pressures during the cooling process. − As the vapor mixture can be removed and collected, a pure desired crystalline solid is obtained as the product. If no liquid remains at the end of SC, neither crystal/liquid separation nor crystal washing is required after SC.…”

Purification of 2-Pyrrolidone by Falling Film Melt Crystallization

“…Melt crystallization is an environmentally friendly purification technology in which separation and purification are achieved according to the melting point difference between the main component and the impurities in the liquid mixture. , The principle of melt crystallization technology is to obtain crude crystals by gradually reducing the temperature below the crystallization temperature at a certain cooling rate, and subsequently, the sweating process is necessary to purify the crude crystals because of some impurities entrapped between crystals. − In recent years, melt crystallization technology has been attracting much attention and is widely applied in separation and purification of isomers, heat-sensitive materials, and mixtures exhibiting azeotropes because of its advantages including low energy consumption, no requirement for a solvent, no damage to heat-sensitive materials with a low melting point, and safe operation. − Various substances, including milk fat, p -xylene, phosphoric acid, dodecanedioic acid, p -cresol, caprolactam, ethylene glycol, chlorobromobenzene, and N -vinylpyrrolidone, were successfully purified by melt crystallization.…”

Purification of Chlorophenol Isomers by Stripping Crystallization Combining Melt Crystallization and Vaporization

“…In principle, SC combines melt crystallization and vaporization at reduced pressures. As opposed to the solid-liquid transformations involved during melt crystallization [13][14][15][16][17][18][19][20][21][22][23][24], a series of three-phase transformations occur in a liquid mixture during SC. Consequently, the desired component is crystallized as the solid product while the unwanted components are vaporized and removed.…”