J.P. Nogier

Green and selective epoxidation of alkenes catalysed by new TiO2–SiO2 SBA mesoporous solids

New catalysts TiO2–SiO2 n(Ti–SBA) with pore sizes of 37 and 65 A have been synthesized by grafting titanium on a structured mesoporous SBA15 (SBA for Santa BArbara and 15 for hexagonal structure) by means of titanium tetrachloride in the gas phase. These catalysts have been tested in the selective epoxidation of cyclooctene, cyclohexene, (R)-limonene and α-pinene. Whatever the oxidant, hydrogen peroxide (H2O2), tert-butyl hydroperoxide (TBHP) or cumyl hydroperoxide (CHP), the selectivity is 100%. However, the yield is low with H2O2 and the catalyst is partially leached out. In the case of TBHP and CHP the epoxide yields can reach practically 100% and no leaching of titanium is observed after four successive reaction cycles. An effect of pore size on the epoxidation kinetics of α-pinene and cyclooctene has been found.

Oxidative ring opening of epoxides by tert-butyl hydroperoxide in the presence of AISBA-15

Oxidative ring opening of epoxides by tert -bytyl hydroperoxide was carried out in the presence of AISBA-15 under mild conditions (acetonitrile, 353 K). Various materials were prepared with different Si/Al molar ratio (5 to 20) in order to compare their catalytic activity. These solids were fully characterized especially by 27 Al NMR and NH 3 adsorption. This work emphasizes the influence of the method used for the incorporation of aluminium (grafting (AISBA(PS)) or direct synthesis (AlSBA(DS))) on the conversion of cyclohexene oxide to adipic acid. The best yields of the diacid (40–50%) were obtained in the presence of aqueous TBHP and AlSBA(DS) materials.

Comparative study of the catalytic activity of Al-SBA-15 and Ga-SBA-15 materials in α-pinene isomerisation and oxidative cleavage of epoxides

Materials of the SBA-15 type with well dispersed Ga or Al atoms were prepared successfully by using different procedures (direct synthesis or grafting). Depending on the heteroelement sources, gallium-based samples displayed different catalytic activities in the isomerisation of α-pinene but led to better selectivities than Al-solids did. However, these last ones turned out to be more adapted to the formation of adipic acid (AA) by the oxidative cleavage of cyclohexene oxide (CHO) in the presence of tert-butylhydroperoxide (TBHP).

New efficient catalysts Ti-SBA15 and Ti-ALSBA15 for green chemistry application to selective oxidation of alkenes

Abstract New structured mesoporous catalysts TiSBA15 and Ti-A1SBA15 were synthesised by grafting titanium on the pore internal surface of various SBA15 and A1-SBA15 materials by means of titanium tetrachloride in the gas phase. These catalysts were tested in the oxidation of alkenes by alkyl hydroperoxides in mild conditions (343-353 K). The silica based materials lead, in any case, to the selective formation of the epoxides with a high level of conversion over four catalytic runs. Al-based supports afford an efficient acid-catalysed ring opening of oxiranes and allow the direct conversion of cyclohexene to adipic acid with a yield of 80%.