Alain Germain

Role of cobalt molecular sieves in the liquid-phase oxidation of cyclohexane to adipic acid

The catalytic activity of CoAPO-5 in the oxidation of cyclohexane to adipic acid has been re-examined in order to specify the actual role of the solid. It was shown that the catalytic activity in acetic acid was ascribable to the leaching of cobalt. The activity of CoAPO-5 was comparable to that of cobalt(II) acetate at very low concentration. Surprisingly, a maximum of activity was found at 0.17 mmol dm−3, which corresponds to the concentration of cobalt leached from the solid in the reaction. Such a concentration is far below the concentration usually used for homogeneous catalysis. Variations in adipic acid selectivity, which followed the variations in activity, were interpreted by changes in mechanism.

Vapour-phase nitration of fluorobenzene with N2O4 over aluminosilicates. Effects of structure and acidity of the catalyst

Abstract The vapour-phase nitration of fluorobenzene with dinitrogen tetroxide has been investigated over amorphous silica-alumina and zeolites with various structures and aluminium contents. The activity of the catalysts increases with the number and the strength of the acid sites, but is also very dependent on the accessibility controlled by the pore structure and the size of the crystals. Except, the zeolite BEA which is the most active and the most stable, the deactivation of the catalysts is fast since the activity is high. The addition of water to the feed increases the activity and the stability of all the zeolites, but decreases the activity of amorphous silica-alumina. A large part of deactivation is attributed to the marginal formation of 2,4-dinitrofluorobenzene which stays on the surface of the catalyst, but can be eliminated by ‘steam distillation’. No evidence of shape selectivity was obtained. Zeolite BEA proved to be a remarkably efficient catalyst.

The catalysis of the Ruff oxidative degradation of aldonic acids by titanium-containing zeolites

Ti‐BEA and Ti‐FAU, obtained by post‐synthesis treatment, and TS‐1, obtained by direct hydrothermal synthesis, have been tested as catalysts for the Ruff oxidative degradation of calcium d‐gluconate to d‐arabinose using diluted hydrogen peroxide as oxidant. Only large‐pore zeolites Ti‐BEA and Ti‐FAU were found to be active. It was shown, in particular, that a very rapid leaching of titanium occurred and that the titanium species present in the solution were responsible for the catalytic activity observed.

Liquid-phase oxidation of cyclohexane to adipic acid catalysed by cobalt containing β-zeolites

Abstract Cobalt exchanged β-zeolites obtained by impregnation and solid state ion exchange and cobalt substituted β-zeolites obtained by incorporation of cobalt in the synthesis gel were studied towards the oxidation of cyclohexane into adipic acid. The Co-substituted β-zeolites were found to be effective catalysts for the oxidation of cyclohexane in acetic acid. In contrast, the use of Co-exchanged β-zeolites always led to inhibition of the oxidation. It was demonstrated that the catalytic activity came as a result of the dissolved cobalt in the reaction medium, while inhibition was ascribed to the accessible uncompensated aluminic sites of the zeolites.

Electrochemical oxidation of perfluoroalkenes in fluorosulfuric acid

Abstract The electrochemical oxidation in fluorosulfuric acid has been shown to be an effective and useful method to functionnalize perfluorinated organic compounds, which are generally extremely difficult to oxidize by conventionnal routes. We have already reported such oxidations of primary linear perfluorinated compounds CF 3 (CF 2 ) n X with X = H, Br, CH 2 OH, CO 2 H and SO 3 H, and of some secondary hydroperfluoroalkanes and cycloalkanes. The present communication deals with the study of the electrochemical behaviour of perfluoroalk-1-enes in fluorosulfuric acid and of the indirect oxidation of such olefins with the peroxide (FSO 3 ) 2 . Linear and cyclic voltamperometric studies show that perfluorooct-1-ene C 6 F 13 CFCF 2 is electroactive in FSO 3 H (E 1/2 ( Cu/Cu )2+ = 2.01 volts) according to an irreversible electrochemical process. Preparative direct electrochemical oxidation leads to bis (fluorosulfato) perfluoroalkanes, The action of the peroxide (FSO 3 ) 2 (preliminary prepared by electrochemical oxidation of FSO 3 H) on the olefin yields these esters in the same proportions, i.e. 25% of the 1-1 adduct (I) and 75% of the 2-1 adduct dimer (II). Such results can be explained by the intervention of the same mechanism, an electrochemical or chemical oxidation of the olefin, in the two cases. This assumption is discussed.

C–C bond formation from dimethyl ether via a radical mechanism in the presence of strong acid

The selective radical dimerization of dimethyl ether by peroxodisulphuryl difluoride in fluorosulphuric acid, suggests that a radical intermediate for initial C–C bond formation in the conversion of methanol in the conversion of methanol into hydrocarbons is a possibility.

Solvent effects in the two-phase nitration of anisole

Depending on the nature of the organic solvent, anisole can be quantitatively nitrated by 65% nitric acid in a nitrite-catalysed two-phase system.

Functionalisation of secondary and tertiary hydrofluorocarbons by electrooxidation in fluorosulphuric acid: novel route to perfluoroketones and tertiary alcohols

Aliphatic and alicyclic secondary and tertiary hydrofluorocarbons are indirectly electro-oxidised in fluorosulphuric acid. Thus, 2H-heptafluoropropane and undecafluorocyclohexane are transformed into the corresponding perfluorosulphates. Pyrolysis of these latter compounds over caesium fluoride afforded the corresponding ketones. This method constitutes a novel route to perfluoro ketones particularly hexafluoroacetone. Tertiary hydroperfluoroalkanes are less reactive than secondary compounds vis-a-vis electro-oxidation. Nevertheless, the reaction of 1H-undecafluoronorbornane with the peroxide (FSO3)2, followed by hydrolysis of the ester so obtained, yielded perfluoronorbornan-1-ol.