Amine-salt process

Frey et al. [101,102] have shown that an amine-salt solution (EDA with 56% KSCN) at 8% w/w cellulose can be converted into nanofibers (Figure 10.50) by using an electrospinning process. Interestingly, the fiber resembled cotton fibers. Thus, so far these recent, positive achievements indicate that the amine-salt process should be further developed before commercialization. 

Aromatic Isocyanates. A variety of methods are described in the Hterature for the synthesis of aromatic isocyanates. Only the phosgenation of amines or amine salts is used on a commercial scale (5). Much process refinement has occurred to minimise the formation of disubstituted ureas arising by the reaction of the generated isocyanate with the amine starting material. A listing of the key commercially available isocyanates is presented in Table 1. 

Dialkyldimethyl and alkyltrknethyl quaternaries can be prepared direcdy from secondary and primary amines as shown ia equations 7 and 8, respectively. This process, known as exhaustive alkylation, is usually not the method of choice on a commercial scale. This technique requires the continuous addition of basic material over the course of the reaction to prevent the formation of amine salts (223,224). Furthermore, products such as inorganic salt and water must be removed from the quaternary. The salt represents a significant disposal problem. 

Dissociation extraction is the process of using chemical reac tion to force a solute to transfer from one liquid phase to another. One example is the use of a sodium hydroxide solution to extract phenolics, acids, or mercaptans from a hydrocarbon stream. The opposite transfer can be forced by adding an acid to a sodium phenate stream to spring the phenolic back to a free phenol that can be extrac ted into an organic solvent. Similarly, primary, secondary, and tertiary amines can be protonated with a strong acid to transfer the amine into a water solution, for example, as an amine hydrochloride salt. Conversely, a strong base can be added to convert the amine salt back to free base, which can be extracted into a solvent. This procedure is quite common in pharmaceutical production. 

The Zincke reaction is an overall amine exchange process that converts N- 2,A-dinitrophenyl)pyridinium salts (e.g, 1), known as Zincke salts, to iV-aryl or iV-alkyl pyridiniums 2 upon treatment with the appropriate aniline or alkyl amine. The Zincke salts are produced by reaction of pyridine or its derivatives with 2,4-dinitrochlorobenzene. This venerable reaction, first reported in 1904 and independently explored by Konig, proceeds via nucleophilic addition, ring opening, amine exchange, and electrocyclic reclosure, a sequence that also requires a series of proton transfers. By... 

Acid chlorides are very reactive and have as a condensation product hydrochloric acid.4,7 9 This hydrochloric acid can form an amine salt with unreacted amine groups, which should be avoided. To prevent this happening, acid binders, which are more reactive than the amines, are added. Polyamidation can be earned out using a solution and with an interfacial method. With the interfacial method one has the choice between a stirred and an unstirred process. In an unstirred process, the polymerization is at the interface and a rope can be drawn from the interface,... 

Pr)4, " borohydride-exchange resin,and formic acid. When the last is used, the process is called the Wallach reaction. Conjugated aldehydes are converted to alkenyl-amines with the amine/silica gel followed by reduction with zinc borohydride.In the particular case where primary or secondary amines are reductively methylated with formaldehyde and formic acid, the method is called the Esch-weiler-Clarke procedure. It is possible to use ammonium (or amine) salts of formic acid, " or formamides, as a substitute for the Wallach conditions. This method is called the Leuckart reaction,and in this case the products obtained are often the N-formyl derivatives of the amines instead of the free amines. Primary and secondary amines can be iV-ethylated (e.g., ArNHR ArNREt) by treatment with NaBH4 in acetic acid. Aldehydes react with aniline in the presence of Mont-morillonite KIO clay and microwaves to give the amine. Formaldehyde with formic acid converts secondary amines to the N-methyl derivative with microwave irradiation. 

High yielding reactions allowed for through processing from salt 12 to amine salt 2 The only three solid compounds (12, 2,1) allowed for purity upgrades... 

It is estimated that over 100,000 acres in Hawaii and some 250,000 acres in Louisiana each year are treated with herbicides, mostly 2,4-D and TCA (sodium salt of trichloroacetic acid), for pre- and postemergence weed control. Johnson grass on ditch banks on some 50,000 to 75,000 superficial acres in Louisiana is controlled with sodium chlorate or TCA. Some trials with CMU [3-(p-chlorophenyl)-l,l-di-methylurea] are in process. Florida cane growers use 150,000 pounds of 2,4-D amine salt of Karmex W on 43,000 acres of cane and anticipate using up to 100,000 pounds per year. Of the growers in Puerto Rico, 60% are said to use herbicides as either pre- or post-emergence sprays. 

The key to a controlled molecular weight build-up, which leads to the control of product properties such as glass transition temperature and melt viscosity, is the use of a molar excess of diisopropanolamine as a chain stopper. Thus, as a first step in the synthesis process, the cyclic anhydride is dosed slowly to an excess of amine to accommodate the exothermic reaction and prevent unwanted side reactions such as double acylation of diisopropanolamine. HPLC analysis has shown that the reaction mixture after the exothermic reaction is quite complex. Although the main component is the expected acid-diol, unreacted amine and amine salts are still present and small oligomers already formed. In the absence of any catalyst, a further increase of reaction temperature to 140-180°C leads to a rapid polycondensation. The expected amount of water is distilled (under vacuum, if required) from the hot polymer melt in approximately 2-6 h depending on the anhydride used. At the end of the synthesis the concentration of carboxylic acid groups value reaches the desired low level. 

Having formed the amine salt, the solvent can be used for the extraction of uranium. This is shown as an ion exchange process in Eq. (7.3) ... 

The Zincke reaction is an overall amine exchange process that converts N- 2,A-dinitrophenyl)pyridinium salts, known as Zincke salts, to A -aryl or A -alkyl pyridiniums upon treatment with the appropriate aniline or alkyl amine. 

Types of catalysts used include mineral or oiganic acids and latent acids such as ammonurea salts, amine salts, and metal salts (49). One type of catalyst used in early commercial processing was amine hydrochloride. However, the fishy odor evolving from this material has caused this type of catalyst to be discarded. Metal salt catalysts such as magnesium chloride or zinc nitrate have been widely used over the years. However, because of effluent concerns, zinc salts have fallen into disuse. Magnesium nitrate has been suggested as an alternative catalyst (50). 

Diazocompounds. A group of very reactive org compds, many of which are explosive, containing the bivalent radical -N N- or N N-. They are formed when nitrous acid acts at low temp on the salts of primary amines. The process of prepg diazocompds Is called diazo-tization and was discovered about I860 by P. Griess (Ref 4)... 

By far the most important use of amine salt extractants is in the recovery of uranium from acidic leach liquors. The basic process was developed at the Oak Ridge National Laboratory in the USA,195 and essentially similar processes are currently in operation throughout the world. Examples of plant practice in the USA,196 Canada,197 Australia,198 South Africa199 200 and South West Africa201 have been described. 

Interestingly, the extraction of palladium(II) by orf/20-hydroxyoximes can be accelerated sufficiently to be used in a continuous process by the addition of small quantities of amine salts of high molecular mass to the organic phase.230 Presumably these accelerator compounds operate by the initial extraction of palladium in a rapid anion-exchange process involving no ligand exchange... 

The extraction of the PGM by amine salts was first reported some 30 years ago,235 shortly after which a process for the recovery of the PGM by solvent extraction was patented in the Soviet Union.236 The results of pilot-plant operations for the recovery of PGM from copper and nickel refinery slimes have also been described,237-23S and it is probable that such processes are currently in full-scale commercial use. Further extensive studies by Soviet workers have been described in a recent review.239 It has been shown that, in addition to the anion-exchange mechanism, e.g. 

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