Crystal Product Engineering in the Seeded Cooling Crystallization of Adipic Acid from Aqueous Solution

The Couette-Taylor (CT) crystallizer was developed to promote the size distribution of L-Lysine crystal product in cooling crystallization. When using the CT crystallizer, the size distribution of crystal product was much narrower than that of the conventional Stirred tank (ST) crystallizer. Here, the coefficient size distribution (n) in CT crystallizer was quite large as 3.43, while it was only 2.17 in ST crystallizer at the same 360 rpm of agitation or rotation speed. This result indicated that the CT crystallizer was much more effective than the ST crystallizer in terms of the size distribution of L-lysine crystal products in cooling crystallization. The advantage of CT crystallizer over the ST crystallizer was explained in terms of the high energy dissipation of Taylor vortices flow, where it was 7.6 times higher than that of random fluid motion in conventional ST crystallizer. As such, the supersaturation profile in the CT crystallizer was much more homogeneous than that in the ST crystallizer, which resulted in promotion of size distribution L-lysine crystal product.

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Nucleation control and separation of vanillin polymorphs I and II through the swift cooling crystallization process

CrystEngComm ◽

10.1039/d0ce01557a ◽

2021 ◽

Vol 23 (7) ◽

pp. 1634-1642

Author(s):

Supriya Sundareswaran ◽

Srinivasan Karuppannan

Keyword(s):

Aqueous Solution ◽

Crystallization Process ◽

Stable Form ◽

Cooling Crystallization ◽

Metastable Form ◽

Pure Aqueous Solution

Stable form-I and metastable form-II polymorphs of vanillin are identified through morphology and separated in terms of supersaturation ranges from pure aqueous solution without the use of nucleation selecting materials.

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Structures Formed by Cryoprotective Agents Used in Freezc-Etching

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066292 ◽

1971 ◽

Vol 29 ◽

pp. 448-449

Author(s):

G. G. Cocks ◽

C. E. Cluthe

Keyword(s):

Aqueous Solution ◽

Polyethylene Oxide ◽

Liquid Nitrogen Temperature ◽

Ice Crystals ◽

Etching Technique ◽

Structural Constituent ◽

Cryoprotective Agents ◽

Quick Freezing ◽

Freeze Etching ◽

Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

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