Crystallization Control

A typical flow diagram for pentaerythritol production is shown in Figure 2. The main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive by-product formation and/or reduced yields of pentaerythritol (55,58,59). The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 h at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the Hquors by subsequent filtration. 

The alkah metal perchlorates are either white or colorless, and have increasing solubiUty in water in the order of Na > Li > NH4 > K> Rb > Cs. The high solubiUty of sodium perchlorate, NaClO, makes this material useful as an intermediate for production of all other perchlorates by double metathesis reactions and controlled crystallization. 

A phosphate-sludge conditioner blend may be employed because the deposit control agent or sludge conditioner limits and controls crystal formation (threshold and crystal distortion effects) and ensures particle fluidization (dispersion effect). 

PAN/VACUUM PAN Equipment used for controlled crystallization of sugar solutions by boiling under a vacuum. 

Functional Aspects of Hydrocolloids in Controlling Crystal Structure in Foods... 

NASH—CONTROLLING CRYSTAL STRUCTURE IN FOODS FUNCTIONAL ASPECTS... 

Emulsifiers assist the stabilizing hydrocolloids in controlling crystal structure. They accentuate the function of the homogenizer in reducing the size of the fat globules. They also reduce the interfacial tension between the fat and water phases of the mix. The result is smaller ice particles and air cells when the mix is frozen and a smoother and creamier finished product. 

A typical instrument is equipped with four computer controlled crystal spectrometers, as well as an EDS system for preliminary qualitative analysis. A light microscope is provided for examining the specimen and also for ensuring that the specimen height is adjusted until it is on the Rowland circle. The drawing of... 

US patent 6,759,521, Polarization switching to control crystal form [113]. This patent describes a method to select and prepare polymorphs of materials by switching the polarization state of light and employing non-photochemical laser-induced nucleation. 

Dilchill [Dilute, chill] A process for dewaxing petroleum by controlled crystallization, with cooling accomplished by the incremental addition of a cold solvent. Developed by Exxon Research Engineering Company. 

Valluzzi, R., Szela, S., Avtges, P., Kirschner, D., and Kaplan, D. (1999). Methionine redox controlled crystallization of biosynthetic silk spidroin. J. Phys. Chem. B 103, 11382-11392. 

The latest results of a controlled crystallization of macromolecules are the polymer fibrids which are a completely new modification of synthetic polymers as far as the micro- and macro-structure is concerned. They exist of small fibers having a length of up to some millimeters, which are highly oriented, and which have a macro-morphology similar to that of cellulose pulp. 

Controlled crystallization Natural and synthetic single crystals Crystal growth from solutions, gels and by coarsening of solids... 

It has been reported that pure equatorial chloro- and trideuteriomethoxycy-clohexane were obtained by carefully controlled crystallization of the respective liquids (21). 

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