Reactive crystallization

Berry, D.A. and Ng, K.M., 1997. Synthesis of reactive crystallization processes. American Institute of Chemical Engineers Journal, 43, 1737. 

Kotaki, Y. and Tsuge, H., 1990. Reactive crystallization of calcium carbonate by gas-liquid and liquid-liquid reactions. Canadian Journal of Chemical Engineering, 68, 435 42. 

Momonaga, M., Yazawa, H. and Kagara, K., 1992. Reactive crystallization of methyl Q-methoxyimino acetoacetate. Journal of Chemical Engineering of Japan, 25, 237-242. 

Reverse-flow reactors Reactive distillation Reactive extraction Reactive crystalization Chromatographic reactors Periodic separating reactors Membrane reactors Reactive extrusion Reactive comminution Fuel cells... 

The reactive crystallization has some peculiar characteristics like insoluble product, initiation of reaction by change in pH and conductivity. In this case the solution becomes saturated and eventually supersaturated with respect to reactant nucleation [30], The ultrasound assisted decomposition precursors includes dissolving metal organic precursors in organic solvents/water with the assistance of surfactants leads to monodisperse and reduced metal/metal oxide nanoparticles. 

Some of the reports are as follows. Mizukoshi et al. [31] reported ultrasound assisted reduction processes of Pt(IV) ions in the presence of anionic, cationic and non-ionic surfactant. They found that radicals formed from the reaction of the surfactants with primary radicals sonolysis of water and direct thermal decomposition of surfactants during collapsing of cavities contribute to reduction of metal ions. Fujimoto et al. [32] reported metal and alloy nanoparticles of Au, Pd and ft, and Mn02 prepared by reduction method in presence of surfactant and sonication environment. They found that surfactant shows stabilization of metal particles and has impact on narrow particle size distribution during sonication process. Abbas et al. [33] carried out the effects of different operational parameters in sodium chloride sonocrystallisation, namely temperature, ultrasonic power and concentration sodium. They found that the sonocrystallization is effective method for preparation of small NaCl crystals for pharmaceutical aerosol preparation. The crystal growth then occurs in supersaturated solution. Mersmann et al. (2001) [21] and Guo et al. [34] reported that the relative supersaturation in reactive crystallization is decisive for the crystal size and depends on the following factors. 

Lin R, Zhang J, Bai Y (2006) Mass transfer of reactive crystallization in synthesizing calcite nanocrystal. Chem Eng Sci 61(21) 7019-7028... 

Crystallization of magnesium hydroxide by a continuous mixed suspension mixed product removal crystallizer was conducted to make clear the characteristics of reactive crystallization kinetics of magnesium hydroxide, which was produced by the precipitation from magnesium chloride with calcium hydroxide. The following operating factors were investigated affecting the crystallization kinetics the initial concentration of feeds, residence time of reactants, feed ratio of reactants, and concentrations of hydroxide and chloride ions. 

The production of sparingly soluble materials by simultaneous reaction and crystallization has been used widely in the chemical industries. To make clear the characteristics of crystallization of sparingly soluble materials by chemical reactions is important for better design and more efficient operation of reactive crystallizers. Many works on... 

The present work deals with the reactive crystallization of magnesium hydroxide, a well-known sparing soluble material, from magnesium chloride with calcium hydroxide. Magnesium hydroxide is produced industrially by the precipitation from brine with... 

Dabir et al showed that the kinetic order i is written by Equation 11 for the reactive crystallization of Mg(OH)2 produced by magnesium chloride and sodium hydroxide. 

Reactive crystallization experiments of magnesium hydroxide were conducted to clarify the characteristics of reactive crystallization kinetics by a continuous MSMPR crystallizer. 

Heterogeneous reactions of the type A+B = AB can, in principle, occur in two ways. 1) The product molecule AB is formed from A and B in the surrounding solvent or immediately at the surface of the AB crystal. These AB molecules are then added to the crystal on its external surface. This is additive crystal growth. 2) The solid product AB forms between A and B and separates the reactants spatially. Further reaction is possible only via (diffusional) transport across the reaction layer AB. This is reactive crystal growth [H. Schmalzried (1993)]. The moving AB interfaces in additive crystal growth are inherently unstable morphologically (see Chapter 11). 

Figure 11-1. Scheme of a) additive and b) reactive crystal growth. 

Usually conversion in a pure reactive crystal must be held to less than 1% to assure the kind of uniformity necessary for establishing a detailed mechanism. This poses obvious problems for classical chemical analysis of product mixtures. For spectroscopic investigations we typically limit conversion to less than 0.1%. 

The mounting of highly reactive crystals may require the use of a glove box. 

Reactive crystallization, or precipitation, has been investigated by numerous research groups. Processes of industrial relevance include liquid-phase oxidation of para-xylene to terephthalic acid, the acidic hydrolysis of sodium salicylate to salicylic acid, and the absorption of ammonia in aqueous sulfuric acid to form ammonium sulfate (60). A very special type of reactive crystallization is diastereomeric crystallization, widely applied in the pharmaceutical industry for the resolution of enantiomers (61). Another fine example of reactive precipitation is the earlier-described production of nano-size particles of CaC03 in high-gravity fields (46). 

Reactive distillation Membrane-based reactive separations Reactive adsorption Reactive absorption Reactive extraction Reactive crystallization... 

Somewhat similar are the so-called adductive crystallization processes, often (wrongly) called extractive crystallization, where reactions of complex/ adduct formation are used to separate compounds that are otherwise difficult to separate. Examples of adductive crystallization include separation of p- and m-cresols (137), separation of o- and p - n i troch I oro ben zcn cs (138), separation of quinaldine and isoquinoline (139), separation of nonaromatic compounds from naphtha-cracking raffinate (140), and separation of p-cresol from 2,6-xylenol (141). Other examples of reactive crystallization/precipitation reported in the literature are listed in Table 5. 

Reactive crystallization/precipitation can also be conducted in high-gravity (Higee) fields using rotating equipment. In China this technique has been used successfully for the production of nano-size particles of CaC03. Ultraline particles... 

Am Ende DJ, Crawford TC, Weston NP. Reactive crystallization method to improve particle size. EP 1157726, Pfizer Products Inc., 2001. 

Kelkar VV, Ng KM. Design of reactive crystallization systems incorporating kinetics and mass-transfer effects. AIChE J 1999 45 69-81. 

It is multifunctional and can also be used for reactive crystallization and has a much wider range of application.. 

Antisolvent and Reactive Crystallization with In-Line Mixing... 

Fig. 11.1. Overall workflow for the development of a reactive crystallization process.

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