Anne-Marie Le Govic

Validity of using isopropanol decomposition as a test-reaction for the characterization of metal oxides basicity; comparison with results obtained from methylbutynol decomposition

Abstract Isopropanol and methylbutynol decomposition have been studied under He stream, at 483 K and 453 K, respectively, on different solids to characterize their basicity. The oxides studied included MgO, ZnO and the corresponding aluminates ZnAl 2 O 4 , Zn 4 Al 2 O 7 , MgAl 2 O 4 , Mg 4 Al 2 O 7 . We observe that isopropanol decomposition only occurs on ZnO and Zn aluminates, and is not observed on MgO and Mg aluminates, well known as basic oxides. In contrast, all the oxides studied are active towards methylbutynol with formation of acetone and acetylene.

Catalysis by rare earth phosphate II: Selective o-methylation of phenols by methanol in vapor phase

Abstract Vapor phase catalytic alkylation of phenols with methanol was carried out on various phosphates as catalysts. The best activity and selectivity was observed on soron, rare-earth and niobium phosphate. With boron phosphate, the reaction is very selective for O-alkylation even at high temperature. On this catalyst o-methoxy-phenol is selectively obtained from 1–2-dihydroxybenzene. With rareearth phosphate calcinated at 400°C and with niobium phosphate, O-alkylation selectivity decreases with an increase of reaction temperature. For rare-earth phosphates it is possible to improve the selectivity by calcination at higher temperature or by a wetness impregnation of cesium hydrogenophosphate. An explanation of these results is proposed.

Catalysis by rare earth phosphate III. Characterisation of samarium phosphate and samarium phosphate-cesium hydrogenophosphate as key catalysts for o-alkylation of phenols

Summary Samarium phosphates, impregnated or not by cesium hydrogenophosphate, selective catalysts for O-alkylation of phenols, have been characterised by various techniques. This study has shown that: u - the cesium salt added by wetness impregnation (10 % w/w) has a sintering effect on its calcination. The examination of structural and textural datas shows that the cesium does not enter the crystalline network. The cesium salt is uniformly distributed on the crystalline surface and the special morphology of samarium phosphate makes the cesium retained in the porosity of the solid. - Samarium phosphate has an intrinsic acidic activity which can only be observed on products calcinated at a temperature of 700°C and which therefore possess a monoclinic structure. Samarium phosphate calcinated at lower temperatures, with an hexagonal structure has acido-basic characteristics highly dependant on the synthetic route use: - a totally basic activity is observed for samarium phosphate being neutralized with ammonia after precipitation. - products which have not been treated according to the previous step present an acidic activity - the addition of cesium by wetness impregnation on the dry catalyst produces a totally basic behavior.