Stéphanie Delsarte

Ir-Beta zeolite as a heterogeneous catalyst for the one-pot transformation of citronellal to menthol

Beta zeolites, impregnated with Ir, catalyze the one-pot full conversion of citronellal to menthol by consecutive acid-catalyzed cyclization and Ir-catalyzed hydrogenation, with 95% selectivity for the menthol isomers, of which 75% is the desired (-)-menthol.

A novel family of mixed gallium aluminum phosphorus oxynitrides: Their synthesis, characterization and utilization in heterogeneous catalysis

A new family of nitrided phosphates, the oxynitrides (Ga,Al)PON, have been prepared by nitridation under ammonia flow in the 500-1000 degrees C temperature range of galloaluminophosphates obtained by sol-gel route. These (Ga,Al)PON oxynitrides, in which the P/(Ga + Al) atomic ratio and the nitrogen content can vary both, are amorphous powders characterized by high specific surface areas up to 300 m(2) g(-1). These new materials have been tested as supported platinum catalysts in the isobutane dehydrogenation and compared to other catalysts: The Pt/(Ga,Al)PON catalysts present the highest conversion and selectivity rates in isobutene

Isobutane dehydrogenation on various platinum supported mixed metallophosphate oxynitride catalysts MM ' PON (M = Al, M ' = Ga,Cr)

The very first results of isobutane dehydrogenation over metal-supported mixed metallophosphate oxynitrides (AlMPON)-P-III (M-III = Ga, Cr) are presented. Catalytic tests show that the substitution of oxygen by nitrogen in the anionic network involves the appearance of new and more active sites. The substitution of a part of aluminium by gallium in oxynitride compounds increases significantly the activity while chromium does not modify to a great extent the conversion of isobutane

Basic sites on mixed nitrided galloaluminophosphates "AlGaPON": infrared studies of SO2 and CDCl3 adsorption

The basic properties of nitrided galloaluminophosphate “AlGaPON” are documented by FTIR of sulphur dioxide and deuterated chloroform. To evidence the increase in the number of basic sites with nitrogen enrichment, we compared the spectra recorded after adsorption of CDCl3 on the phosphate precursor “AlGaPO” and on four oxynitrides with increasing nitrogen contents. On the oxide, adsorption arises from CDCl3 interacting with surface hydroxyl groups, on the oxynitrides basic sites are shown to be M–NH2 groups. This interpretation is confirmed by FTIR of adsorbed SO2.

Nitrided ultrastable zeolite Y: Identification and quantification of incorporated nitrogen species and their influence on the basic catalytic activity

Novel microporous basic catalysts have been obtained by activation under ammonia flow of an ultrastable zeolite Y at temperatures in the range of 500-900 degrees C. The homogeneity of nitridation was confirmed by comparing the bulk (chemical analysis) and superficial (XPS) nitrogen content. DRIFTS experiments allow us to identify the nature and location of the nitrogen species, and to propose a mechanism of nitridation. The nitrided samples are active in the Knoevenagel condensation between benzaldehyde and malononitrile and their activity increases when the temperature of nitridation increases.

Jasminaldehyde synthesis catalyzed by Al(Ga)PON oxynitrides : influence of the reaction conditions

Nitridation of amorphous aluminium phosphate (AlPO4) and mixed aluminium gallium phosphate (Al0.5Ga0.5PO4) under ammonia flow allows preparing “AlPON” and “AlGaPON” bifunctional acid-base heterogeneous catalysts. Their acid-base bi-functional character allows their use as selective catalysts for the production of jasminaldehyde through the cross-condensation of heptanal and benzaldehyde, followed by the dehydration of the aldol intermediate product. Three parameters enabling to maximize the jasminaldehyde yields in a batch reactor operated at 125°C were investigated: the catalyst composition (Al/Ga and O/N ratio), the reactant concentration and the amount of catalyst in the reactor. Maximum jasminaldehyde selectivities were obtained for intermediate nitrogen contents (7-10 wt.%). Maximum reaction rates were obtained using pure reactants and a catalysts weight equal to 10% of the total reagent weight.

XAS structural and electronic investigation of a new type of catalyst: {AlGaPON}

Substitution of oxygen by nitrogen in galloaluminophosphate oxides leads to compounds, with properties and applications improved as compared to the oxide. The structural and electronic changes induced by the anionic substitution of oxygen by nitrogen on those amorphous compounds have been studied by XAS. The investigation of the EXAFS and XANES data have allowed us to highlight some structural changes; in particular the existence of mixed tetrahedra XOxNy (x being P, Al or Ga) have been demonstrated. Such a study is helpful in understanding the variations in the surface acido-basic properties of these compounds.

Nitridation of ultrastable Y zeolite: influence of experimental parameters

Nitrided zeolites were prepared by thermal treatment of ultrastable zeolite Y (Si/Al ratio equal to 13) under ammonia flow for a prolonged time. The effects of the nitridation parameters on the extent of the nitrogen incorporation and on the structural and catalytic properties of the resulting zeolites were investigated. The amount of nitrogen incorporated in the zeolite increases with temperature and duration. Structural order and porous volume are preserved if the nitridation temperature and the nitridation time do not exceed 800°C and 72 h, respectively. Nitrided zeolites are base catalysts as revealed by the reaction of Knoevenagel condensation between benzaldehyde and malononitrile.

Basic sites on mixed nitrided galloaluminophosphates “AlGaPON”: confrontation of spectroscopic and catalytic data

The nature of the basic sites present at the surface of nitrided galloaluminophosphates “AlGaPON” is still a subject of discussion and their identification requires the confrontation of surface characterisation techniques and catalytic data. In order to better describe the nature of the species that generate the basic catalytic activity in the Knoevenagel condensation between benzaldehyde and malonitrile, we paralleled the activity loss generated by a thermal treatment prior to the reaction with the DRIFTS study of the evolution of the surface species as a function of the pre-treatment temperature. By demonstrating an important activity loss upon pre-treatment we showed that the thermally unstable nitrogen molecules located at the surface play a key role in the catalytic condensation of benzaldehyde with malononitrile.

X-ray photoelectron spectroscopy study of nitrided zeolites

X-ray photoelectron spectroscopy (XPS) was used to observe the changes in the nitrogen, silicon and aluminum local environments occurring upon nitridation of ultrastable Y zeolite (Si/Al = 13) at different temperatures. In the case of nitrogen an identification and quantification of incorporated species was possible. The substitution of oxygen by nitrogen in the immediate vicinity of both silicon and aluminum atoms was also demonstrated. The extent of this substitution was more important at high nitridation temperature.