Perfluorocarboxylic acids production

The 3M company uses electrochemical fluorination (ECF) technology for the production of over lOOt/year perfluorocarboxylic acid, sulphonic acids, alkanes, trialkylamines, alkyl ethers [48]. 

Under the agreement, companies will reduce emissions of these compounds from their facilities and consumer products by 95 per cent by 2010, and work towards eliminating the sources of PFOA by no later than 2015. Furthermore, PFOS and PFOA as well as other perfluorocarboxylic acids (PFCAs) are stable degradation products and/or metabolites of neutral PFCs such as fluorotelomer alcohols (PFTOHs), perfluorinated sulphonamides (PFASAs) and perfluorinated sulphonamide ethanols (PFASEs) [22]. Therefore, the largest global manufacturer and supplier of fluorotelomers such as Capstone, DuPont have adapted its entire product line to utilise short-chain chemistry because short-chain molecules cannot break down to PFOA in the environment. 

Employment of Zn—Cu couple is representative of another approach. For example, reaction of perfluoroalkyl iodides with carbonates gives fluorocarboxylic esters (equation 107)132. Similarly, reaction of perfluoroalkyl iodides with Zn—Cu couple and C02 or S02 in DMSO affords the perfluorocarboxylic acids and sulfonyl chlorides, respectively133. A double methylene inserted product is formed when dibromomethane is used as a substrate (equation 108)134. 

The products of the electrochemical perfluorination of aliphatic or cyclic ethers are the corresponding perfluorinated ethers. Byproducts are perfluorinated ethers with shorter carbon chains, perfluoroalkanes, perfluorocarboxylic acid fluorides and oxygen difluoride. Cyclic perfluorinated ethers can be produced by electrochemical fluorination of alcohols,32 aliphatic carboxylic acids33 or of their acid halides34 containing not less than four carbon atoms in the chain. 

If esters arc perfluorinated the main products are perfluoroalkanes or perfluoroacyl fluorides byproducts are carbon dioxide and oxygen difluoride. The acyl and the alkyl groups in the ester give perfluorocarboxylic acids.41 A comparison of the results obtained from butyl acetate and ethyl butyrate, and from butyl propionate and propyl butyrate, indicates that perfluoro-butanoic acid is obtained in better yield from ethyl and propyl butyrate than from butyl acetate and butyl propionate. Thus, perfluorocarboxylic acids are formed more readily from the acyl than from the alkyl group of the ester. 

The effluent gases from the cell were passed over NaF pellets and then bubbled through two consecutive bottles containing H20 (for collection of the perfluorocarboxylic acids which were formed as a result of the hydrolysis of the pcrfluoroalkanoyl fluorides). The gaseous products which did not react with H20 were led into an alkaline solution of K2S03, and finally collected in traps immersed in liquid N2. Products pcrfluoro(2.4-dimethyltetrahydrofuran) (20%), perfluoi o(2-methyltetrahydropyran) (5.5%), perfluoro(3-methyltetrahydropyran) (10%) and perfiuoro(2-methylpentanoyl fluoride) (7%). 

Like perfluorocarboxylic acid fluorides, perfluoroalkyl chlorosulfonates react with 2-aminophenols, 2-aminothiophenols, and 1,2-diaminobenzene to give A -acylated products. On subsequent heating ring closure occurs with formation of 2-perfluoroalkyl-substituted benzoxazoles, benzothiazoles, and benzimidazoles [90JFC(49)197] (Scheme 44). 

Simply changing the solvent in the Pd-based catalytic system from water to a mixture of water and a perfluorocarboxylic acid (some water is necessary for the reaction see Scheme 6) had no significant effect on product composition formic acid was still the principal product from methane. However, the addition of Cu or Cu chloride to the reaction mixture had a dramatic effect. Methanol and its ester now became the preferred products, with virtually no acetic and little formic acid being formed [40 b]. The activation parameters for the overall reaction determined under the condition when the rate was first order in both methane and carbon monoxide were A = 2 X [O sfa = 15.3 kcal mol . Since methyl trifluoro-acetate is both volatile and easily hydrolyzed back to the acid and methanol, it should be possible to design a system where the acid is recycled and methanol is the end product. Lee and co-workers have recently reported on the further characterization of the catalyst in this bimetallic Pd/Cu system [41]. 

In April 1975, Asahi Chemical started operation of a membrane chlor-alkali plant with a capacity of 40,000 MT/Y of caustic soda using Nafion perfluorosulfonic acid membrane. In 1976, this membrane was replaced by perfluorocarboxylic acid membrane developed by Asahi Chemical. The total caustic production capacity of plants based on Asahi Chemical s membrane chlor-alkali technology using perfluorocarboxylic acid membrane will reach 520,000 MT/Y in 1982, at seven locations in various countries. 

The perfluorocarboxylic acid esters of difluorophosphine, Rj.C(0)0PFa," undergo nucleophilic cleavage with halide ion to give acyl halides RfC(0)X, and similar products result when the latter is replaced by a phosphorus(v) species such as POF2X. With P2O3F4, however, the product is the carboxylic anhydride RfC(0)OPOF2. 

In the past years, elucidation of transformation products of per- and polyfluorinated compounds (PFC) has been a task frequently approached by analytical chemists. It has been estimated that biotransformation contributes to approximately 0.1-5% with respect to perfluorocarboxylic acid (PFCA) historical global emissions [1]. For perfluorooctanesulfonyl fluoride (POSF)-based compounds such as perfluorooctane sulfonic acid (PFOS), biotransformation products probably affect environmental burden marginally, although no distinct estimations have been made so far [2]. 

Some oxidation systems have been reported to decompose perfluorocarboxylic acids (PFA) and the corresponding sulfonic acids (PFS) at bench scale. The primary products are PFAs with shorter chain length, CO2 and fluoride. The reaction is often proposed to be initiated by electron transfer from the ionic head group to an appropriate electron acceptor. In that regard, especially sulfate radical anions and electrolysis using boron-doped diamond electrodes have been reported to degrade PFA respectively PFS. 

Possibly one of the most complex deliberately designed of all polymer products is the family of membranes described by Seko for the selective passage of sodium (Na+) ions and repulsion of hydroxide ions in a chlorine cell. These perfluorocarboxylic acid membranes are claimed to represent an improvement on the Dupont Nafion class of perfluorosulphonic membranes designed for the same purpose, in that CF/OH" segregation is practically complete. Industrially, the implications for chlorine and caustic soda technology are profound. 

Ionic polymers usually used for the IPMC are perfluorosulfonic acid or perfulorocar-boxylic acid polymers, of which the typical chemical structures are shown in Figure 5.2 [10]. Commercially available products of thin films made from perfluorosulfonie acid can be obtained from E.I. Dupont de Nemours Co. (Nafion). Several other companies supply similar compounds. Asahi Glass Co. produces perfluorocarboxylic acid type (Hemion). 

Ohmori K, Kudo N, Katayama K et al (2003) Comparison of the toxicokinetics between perfluorocarboxylic acids with different carbon chain length. Toxicology 184(2-3) 135-140 Okada E, Sasaki S, Saijo Y et al (2012) Prenatal exposure to perfluorinated chemicals and relationship with allergies and infectious diseases in infants. Environ Res 112 118-125 Olsen GW, Burris JM, Burlew MM et al (2000) Plasma cholecystokinin and hepatic enzymes, cholesterol and lipoproteins in ammonium perfluorooctanoate production workers. Drug Chem Toxicol 23(4) 603-620... 

Electrochemical fluorination of carboxylic acids in anhydrous hydrofluoric acid was invented by Simons [106,107]. A process developed by the 3M Co. [108,109] yields perfluorocarboxylic acid fluoride, which can be converted to esters, amides, or other intermediates for the production of repellents ... 

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