Purification process crystallization

Raw Materials. Eor the first decade of PET manufacture, only DMT could be made sufficiently pure to produce high molecular weight PET. DMT is made by the catalytic air oxidation of -xylene to cmde TA, esterification with methanol, and purification by crystallization and distillation. After about 1965, processes to purify cmde TA by hydrogenation and crystallization became commercial (52) (see Phthalic ACID AND OTHER... 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

When a melt-zone is moved through a long crystal, an impurity concentration builds up in the melt zone due to rejection by the crystal as it resolidifies. We can also say that the distribution coefficient favors a purification process, i.e.- k 1. Another reason (at least where metals are concerned) is that a solid-solution between impurity and host ions exists. It has been observed that the following situation, as shown in the following diagram, occurs ... 

There is a great number of separation and purification processes to choose from in process development, but classical separations such as crystallization, filtration, drying, liquid-liquid extraction and distillation are still predominantly used. For solid products crystallization, filtration, and drying are the first options although vacuum distillation and extraction combined with the other techniques are also possible. For liquid products, liquid-liquid... 

High or ultrahigh product purity is obtained with many of the melt-purification processes. Table 20-1 compares the product quality and product form that are produced from several of these operations. Zone refining can produce very pure material when operated in a batch mode however, other melt crystallization techniques also provide high purity and become attractive if continuous nigh-capacity processing is desired. Comparison of the features of melt crystallization and distillation are shown on Table 20-2. 

This chapter provides an introduction to the pharmaceutical sector, and the business of developing new active pharmaceutical ingredients (API). Crystallization is the preferred method of isolating commercial API products because it offers a highly efficient means of purification. The crystallization process is also where the physical properties of the drug substance are defined. These properties can have a significant impact on the formulated product and process, and eventually on the drug release profile in the patient. 

The aim of this section is to provide a generic step by step methodology for the design of a final purification process for a non-salt form API using crystallization. The process objective is to consistently manufacture API of the desired purity and polymorphic form, within the constraints of a typical batch production facility. A brief outline of the analytical techniques that may be required is presented in section 4.6. 

The first successful synthesis of polycrystalline Mg CoH and its deuteride MgjCoDj was reported by Zolliker et al. [57]. The 2Mg-Co elemental mixture was sintered under 4.0-6.0 MPa of hydrogen at temperatures between 350 and 500°C. The formation of the hydride was not complete and the main remaining phases, MgH and Co had to be removed by a separate purification process. X-ray and neutron diffraction data suggested a tetragonally distorted CaF -type crystal structure... 

Purification processes, such as crystallization, sieving, filtration, and preparative chromatography, are widely used. 

Ciystallization from solution is an important separation and purification process in a wide variety of industries. These range from basic materials such as sucrose, sodium chloride and fertilizer chemicals to pharmaceuticals, catalysts and specialty chemicals. The major purpose of crystallization processes is the production of a pure product. In practice however, a number of additional product specifications are often made. They may include such properties as the ciystd size distribution (or average size), bulk density, filterability, slurry viscosity, and dry solids flow properties. These properties depend on the crystal size distribution and crystal shape. The goal of crystallization research therefore, is to develop theories and techniques to allow control of purity, size distribution and shape of crystals. 

There are several companies and groups that are developing bio-based succinic acid production for commercial use. The Showa group possesses a unique technology for purification of succinic acid from fermentation broth. This is the fractional crystallization method starting from sodium succinate. The yield by this method is around 70%, but we can recycle the residual solution so that we can minimize the loss of the product. We also compared the cost-effectiveness of this method with the bipolar electrodialysis method. The cost of our purification process seemed to be about half (our internal data). 

New applications of zeolite adsorption developed recently for separation and purification processes are reviewed. Major commercial processes are discussed in areas of hydrocarbon separation, drying gases and liquids, separation and purification of industrial streams, pollution control, and nonregenerative applications. Special emphasis is placed on important commercial processes and potentially important applications. Important properties of zeolite adsorbents for these applications are adsorption capacity and selectivity, adsorption and desorption rate, physical strength and attrition resistance, low catalytic activity, thermal-hydrothermal and chemical stabilityy and particle size and shape. Apparent bulk density is important because it is related to adsorptive capacity per unit volume and to the rate of adsorption-desorption. However, more important factors controlling the raJtes are crystal size and macropore size distribution. 

F or some time the United States Department of the Interior has been carrying out a program aimed toward the selection of an economical method of obtaining potable water from sea water. One method investigated at the Battelle Memorial Institute (1) is an adaptation of the zone-purification process which had previously been used satisfactorily in the purification of metals (5). In the process, as applied to purification of sea water, a narrow zone of water is frozen in a tube containing sea water. As this zone is made to traverse the length of the tube, the formation of ice crystals tends to concentrate the salt in the solution ahead of the crystals. This results in the concentration of the salt at one end of the tube and the depletion of salt at the other end. 

The yellow crystals of compound 23 (Equation 6) are routinely obtained in a yield of 10-30%. However, replacement of benzamidine with fV,iV,./V -tris(trimethylsilyl)benzamidine gives compound 23 in a 60% yield without the requirement for any acid scavengers, thus improving the ease of the purification process <1989J(P1)2495>. The mechanism and labile nature of the trimethylsilyl groups is illustrated in Scheme 2 (modified from <1989J(P1)2495>). On the basis of these findings, silylated amidines remain an attractive route to dithiadiazoles. 

In biochemical assays, additives such as detergents, DMSO, urea, BSA, and glycerol are commonly used to improve reaction performances and enzyme stability. However, these additives also act as crystallization disturbing agents preventing the formation of optimal crystals for the MALDI process. Analytical sensitivity and mass accuracy can be affected. The challenge is to develop bioassays that can perform optimally without crystallization disturbing additives. Often, it is necessary to use elaborate purification processes prior to analysis. 

The exudation process is a modified purification by crystallization. At present it is applied to purify grade m TNT and to recover impurities present in TNT for use as TNT oil in the preparation of explosive compositions. The process may be carried out in two ways. 

The use of these asymmetric hydrogenation catalysts gives the C-2 chiral center in about 80% optical purity. The same value would apply also to the chiral methyl. For further purification, a crystallization process was used. The optically impure lactic acid (an oil) was dissolved in an approximately equal volume of boiling diethylether diisopropyl ether, 1 1 on standing at 5°C large, colorless, crystals of optically pure chiral methyl chiral lactic acid, 162, were deposited. The recovery of the purified material was 60%. Because of the inherent relationship between the two chiral centers, optical purity at C-2 guarantees optical purity at C-3. 

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