- Alumina-mediated mechanochemical method for simultaneously degrading perfluorooctanoic acid and synthesizing a polyfluoroalkene
-
The design of large-scale processes for disposing harmful perfluorooctanoic acid (PFOA) is an important issue, since it was listed as a persistent organic pollutant in 2015. In this work, we developed an alumina-mediated solid-state mechanochemical (MC) method to simultaneously degrade PFOA and synthesize 1H-perfluorohept-ene (1H-1-PFHp), which is a valuable organofluorine block. A 2.5 h MC treatment resulted in a nearly complete removal (99.4%) of PFOA and a high yield (92.5%) of 1H-1-PFHp. In this transformation, the surface hydroxyl groups on alumina are critical for anchoring the PFOA molecules during the defluorination reaction, and the milling process promotes the dehydration of alumina to produce reactive Lewis acid sites for activating the C-F bonds. Moreover, the high energy ball milling initiates simultaneously the release of lattice oxygen from alumina, producing oxygen vacancies (in alumina) and free electrons, the latter of which can induce the breakage of C-F bonds via a reductive pathway. The combination of the mechanocaloric effect and the triple roles of alumina drives PFOA to a controlled defluorination. This MC process shows promising applications in the green treatment of PFOA solid wastes.
- Lv, Hanqing,Wang, Nan,Zhu, Lihua,Zhou, Yuqi,Li, Wenjing,Tang, Heqing
-
-
Read Online
- Radical additions to fluoroolefins. Thermal reaction of perfluoroallyl chloride with perfluoroalkyl iodides as a selective synthesis of terminal perfluoroolefins
-
Reaction of perfluoroallyl chloride with perfluoroalkyl iodides, RFI (RF = C4F9, C6F13, C8F17), in an autoclave at 180-250 deg C gave terminal perfluoroolefins, CF2=CF-CF2-RF (2-4) as the sole reaction products.Isomeric fluoroolefins containing an internal double bond and telomeric products were not observed in the reaction mixture.The yields were dependent on the reaction temperature and on the chain length of RFI: the highest preparative yield of olefin 2 (RF = C4F9) was obtained at 200 deg C (26percent), while in the syntheses of olefins 3 and 4 (RF = C6F13 and C8F17, respectively) highest yields were achieved at 250 deg C (41percent and 74percent, respectively).The presence of CuI or a peroxide initiator had a negative influence on the yield of products.Formulae have been assigned to the fragments in the mass spectra of products 2-4, and fragmentation sequences have been proposed. - Keywords: Perfluoroallyl chloride; Perfluoroalkyl iodides; Perfluoro-1-alkenes; Radical addition; Thermal initiation; Mass spectrometry
- Cirkva, Vladimir,Paleta, Oldrich,Ameduri, Bruno,Boutevin, Bernard
-
-
Read Online
- PERFLUOROALKENYL ETHERS OF SIMPLE STEROLS
-
Base-catalyzed addition of simple sterols to perfluoroalkenes, to give a variety of perfluoroalkenyl steroidal ethers, has been investigated.The outcome of the reaction was dependent on the base used for deprotonation of sterols.With potassium hydride, a mixture of 1- and 2-perfluoroalkenyl steroidal ethers was obtained in a low yield, whereas with n-butyllithium, preferential formation of 1-perfluoroalkenyl steroidal ethers was achieved in high yields.
- Malik, A. A.,Sharts, C. M.,Shellhamer, D. F.
-
-
Read Online
- Gas-phase NMR studies of the thermolysis of perfluorooctanoic acid
-
The thermolysis of perfluorooctanoic acid (CF3(CF 2)6COOH) has been studied kinetically by high-temperature gas-phase NMR in both sodium borosilicate glass and quartz ampoules. In both cases, 1-H-perfluoroheptane is the major product, but the decomposition is considerably slower in quartz. The decomposition in borosilicate ampoules at 307°C is greatly accelerated by the presence of crushed borosilicate glass and the reaction appears to be completely heterogeneous. Perfluoro-1-heptene is produced as a minor product and time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination of the inner surface of the borosilicate glass ampoule after reaction reveals the presence of NaF. The thermolysis in quartz ampoules was studied by ex situ heating in the temperature range 355-385°C and produced moderate amounts of perfluoro-1-heptene and SiF4 in addition to 1-H-perfluoroheptane. Thermolysis in the presence of added crushed quartz accelerates the decomposition, as does increasing the concentration of perfluorooctanoic acid or carrying out the thermolysis in the presence of water. The thermolysis of perfluorooctanoic acid thus proceeds at widely different rates depending on concentration and on the physical and chemical environment. By contrast, the pyrolysis of ammonium perfluorooctanoate is more facile by orders of magnitude and proceeds by first-order kinetics at essentially the same rates in both quartz and borosilicate ampoules with an estimated half-life of 2 s at 307°C.
- Krusic, Paul J.,Marchione, Alexander A.,Roe, D. Christopher
-
-
Read Online
- Chlorotrifluoroethylene-derived fluids. I. Model compound synthesis
-
A series of chlorofluoroalkanes having chlorines on adjacent carbon atoms has been prepared, i.e. n-C5F11CFClCCl3, n-C6F13CFClCCl3, n-C5F11CFClCFCl2, n-C6F13CFClCFCl2, n-C5F11CFClCF2Cl, n-C2F5CFClCFClC3F7 and n-CF3CFClCFClC4F9, by a combination of halogen exchange, dehalogenation and chlorine addition reactions.An attempt to synthesize n-C6F13CFClCF2CFCl2 by the coupling of n-C6F13CFClI with an excess of ICF2CFCl2 under UV radiation in the presence of Hg gave only n-C6F13CFClCFClC6F13 together with CFCl2CF2CF2CFCl2.Under parallel conditions from n-C6F13CFClI and CF2ClCFClI, n-C6F13CFClCFClCF2Cl was obtained in 48percent yield.
- Paciorek, K. J. L.,Kratzer, R. H.,Nakahara, J. H.,Lin, W.-H.
-
p. 271 - 282
(2007/10/02)
-
- FREE-RADICAL INITIATED ADDITION OF CARBON TETRACHLORIDE TO FLUORO OLEFINS
-
The reaction between carbon tetrachloride and unsymmetrical fluoro olefins, e.g.RCF=CF2, where R=n-C5H11 and C6F5, has led to the addition product, RCFClCF2CCl3.Addition was apparently unidirectional under the conditions used since the isomeric adduct RCF(CCl3)CF2Cl could not be detected.The effects of experimental conditions such as free radical initiators, temperature, and time are discussed for the different reactions studied.A probable mechanism is suggested for these additions.
- Chen, Loomis S.
-
p. 261 - 272
(2007/10/02)
-
