Solvent Purification

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. 

Solvent recovery with adsorption is most feasible when the reusable solvent is valuable and is readily separated from the regeneration agent. When steam-regenerated activated-carbon adsorption is employed, the solvent should be immiscible with water. If more than one compound is to be recycled, the compounds should be easily separated or reused as a mixture. Only very large solvent users can afford the cost of solvent purification by distillation. ... 

Equimolar amounts (0.5 mmol) of 131 and chloranil in 2 mL of THE were heated at reflux for 4 h before cooling to room temperature and removing the solvent. Purification by preparative TLC gave 132 as an oil in 58% yield. 

A mixture of 1.759 g of 2a.3a-epithio-5Q -endrostan-17 3-ol, 2.3 ml of 1-methoxycyclopen-tene, 20 mg of pyridine salt of p-toluenesulfonic acid and 20 ml of t-butanol is stirred for 4 hours at room temperature. The reaction mixture is poured into an aqueous solution of sodium carbonate and the whole extracted with dichloromethane. The extract is dried over anhydrous sodium sulfate and evaporated to remove solvent. Purification of the residue by chromatography over alumina gives 1.487 g of 17/3-(1-methoxycyclopentyl)oxy-2a,3a-epi-thio-50 -androstane. Yield68.2%. MP98°Cto 101°C. 

Other catalyst systems such as iron V2O5-P2O5 over silica alumina are used for the oxidation. In the Monsanto process (Figure 6-4), n-butane and air are fed to a multitube fixed-bed reactor, which is cooled with molten salt. The catalyst used is a proprietary modified vanadium oxide. The exit gas stream is cooled, and crude maleic anhydride is absorbed then recovered from the solvent in the stripper. Maleic anhydride is further purified using a proprietary solvent purification system. ... 

Figure 6-4. The Monsanto process for producing maleic anhydride from butane (1) reactor, (2) absorber (3) stripper, (4) fractionator, (5) solvent purification.

In contrast, when a THF-acetonitrile solution of [26+jClOj or [113+JC104 was added to the THF solution of K+[2 ], the deep green colour of carbanion [2 ] persisted. After evaporation of the solvent, purification of the residue yielded a dark green salt, [26+2 ] or [113+2 ] (Scheme 3), the IR spectra (KBr disk) of which consisted of the absorptions of [2 ] and [26+] or [113+] superimposed. The visible-near IR region... 

General Considerations. The following chemicals were commercially available and used as received 3,3,3-Triphenylpropionic acid (Acros), 1.0 M LiAlH4 in tetrahydrofuran (THF) (Aldrich), pyridinium dichromate (Acros), 2,6 di-tert-butylpyridine (Acros), dichlorodimethylsilane (Acros), tetraethyl orthosilicate (Aldrich), 3-aminopropyltrimethoxy silane (Aldrich), hexamethyldisilazane (Aldrich), tetrakis (diethylamino) titanium (Aldrich), trimethyl silyl chloride (Aldrich), terephthaloyl chloride (Acros), anhydrous toluene (Acros), and n-butyllithium in hexanes (Aldrich). Anhydrous ether, anhydrous THF, anhydrous dichloromethane, and anhydrous hexanes were obtained from a packed bed solvent purification system utilizing columns of copper oxide catalyst and alumina (ether, hexanes) or dual alumina columns (tetrahydrofuran, dichloromethane) (9). Tetramethylcyclopentadiene (Aldrich) was distilled over sodium metal prior to use. p-Aminophenyltrimethoxysilane (Gelest) was purified by recrystallization from methanol. Anhydrous methanol (Acros) was... 

At Merck KGaA in Darmstadt (Germany), in-line UV spectroscopy has been used for monitoring a distillation setup for solvent purification." A transmission probe was implemented at the top of the column. Solarization-resistant UV fibers guided the light to a diode array spectrometer. From the spectra, a quality parameter was extracted and fed to the process control system (PCS). As an example, the quality parameter would exhibit a transient behavior upon column startup. Below a defined threshold value of the parameter, the PCS would assume sufficient product quality and switch the exit stream from waste to product collection. The operation of the spectrometer does not take place in a direct manner, but rather via the PCS. 

Solvent purification Fractionator bottoms Dissolved and separable organics... 

The usual techniques of the anionic polymerization have been employed for the solvent purification and the syntheses. The monomer is distilled three times from calcium hydride and then once more just before the polymerization. 

We give here details of a one-step, high yield (70% or greater), medium pressure (65 atm) synthesis of Ru3(CO)12 from RuCl3 nH20.4 No solvent purification is necessary and this synthesis can be completed in 1 day. 

For difficult separations, multiple extractions are frequently carried out, although in many cases the background is also coextracted. Using multiple extractions, polar interferences may sometimes be transferred from the aqueous into organic solvents that can dissolve minute amounts of water. This problem cannot be eliminated by simple presaturation of the extraction solvent but only by washing the extract with small amounts of water (58). Another relevant issue to be considered in trace residue analysis concerns the purity of the organic solvents, since they can introduce solvent impurities into the sample extract. Therefore, the need for high solvent purification should not be overlooked in some applications. 

In reporting the potential data, the reference redox system used should be indicated by such symbols as i/2(bct) and prc). Detailed information should also be given concerning the cell construction, solvent purification, impurities in the solution, etc. 

In previous chapters, we dealt with various electrochemical processes in non-aque-ous solutions, by paying attention to solvent effects on them. Many electrochemical reactions that are not possible in aqueous solutions become possible by use of suitable non-aqueous or mixed solvents. However, in order for the solvents to display their advantages, they must be sufficiently pure. Impurities in the solvents often have a negative influence. Usually commercially available solvents are classified into several grades of purity. Some of the highest-grade solvents are pure enough for immediate use, but all others need purification before use. In this chapter, the effects of solvent impurities on electrochemical measurements are briefly reviewed in Section 10.1, popular methods used in solvent purification and tests of impurities are outlined in Sections 10.2 and 10.3, respectively, and, finally, practical purification procedures are described for 25 electrochemically important solvents in Section 10.4. 

Solvents for electrochemical use have been dealt with in the books of Refs [1]-[3]. A series of IUPAC reports [4, 5] concerning methods of solvent purification and tests for impurities is also useful. The book by Riddick, Bunger and Sakano [6] is the most authoritative, covering the properties of about 500 organic solvents and their purification methods. The book by Marcus [7] also contains useful information about solvent properties. For the latest information about the toxicity and... 

T. K. Organic Solvents, Physical Properties and Methods of Purification, 4th edn, Wiley Sons, New York, 1986. Includes detailed data on solvent properties and methods of solvent purification. 

The primary separation of plutonium and uranium from the fission products involves a solvent extraction with 30 vol % TBP at room temperature. The activity levels in this separation are quite high ( 1700 Ci/L for the fission products) and the aqueous waste, which contains 99+% of the fission products, is a high-level waste. Am and Cm are not extracted and Np is partially extracted. Because of the high radiation levels, there are radiolysis problems with TPB, leading to solvent degradation. Primary products of the radiolysis of TBP are the dibutyl- and monobutylphosphoric acids along with phosphoric acid. These degradation products are removed in the solvent purification steps. 

Studies of the photobleaching reaction of chlorophyll have shown that the presence of oxygen practically eliminates the reversibility of the system (79). In such cases as this, extensive degassing and solvent purification are necessary to obtain meaningful data. 

D. Prepurification Of Solvents. Some solvent purification procedures call for some type of wash. For example, saturated hydrocarbons are often washed with concentrated H2S04 to remove alkenes. These washing procedures are generally done first, since they usually involve the use of an aqueous solution or a substance that contains significant amounts of water. Unlike the following procedures, washes can be done in the presence of air, since further treatment usually involves a step designed to eliminate oxygen. 

For drug substances, assure that all starting materials, in-process reagents, stable intermediates, solvents, purification columns, and so on are correct for the process and have been properly released by the quality group for their intended use in the process. All items used... 

Potentiometric redox measurements are often performed in nonaqueous or mixed-solvent media. For such solvents various potentiometric sensors have been developed, which, under rigorously controlled conditions, give a Nemstian response over a wide ranges of activities, particularly in buffered solutions. There are some experimental limitations, such as with solvent purification and handling or use of a reference electrode without salt bridges, but there also ate important advantages. Solutes may be more soluble in such media, and redox... 

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