Marcelo Eduardo Domine

Water-resistant solid Lewis acid catalysts: Meerwein–Ponndorf–Verley and Oppenauer reactions catalyzed by tin-beta zeolite

Abstract The catalytic activity of Sn-beta zeolite in the Meerwein–Pondorf–Verley (MPV) reduction of carbonyl compounds with secondary alcohols as reductants and Oppenauer oxidation of alcohols were performed with quantitative yields to the corresponding product. This catalyst exhibits a behavior not observed with Ti- and Al-beta zeolites, with excellent activity and selectivity even after four catalytic recycles, and good stereoselectivities to the thermodynamic less favorable cis-alcohol isomer when alkyl-cylohexanones were used as substrates. Axa0prochiral ketone has been reduced within an enantiomeric excess close to 50% when using a chiral alcohol as the reducing reactant. Other transition metals incorporated in the beta zeolite framework (V or B) led to poor catalytic activities for this reaction. IR studies using cyclohexanone as probe molecule over beta zeolites demonstrated that the more specific Lewis acid sites in the framework of Sn-beta are responsibles for its better catalytic activity with respect to Ti- or Al-beta. The influence of the structure of the alcohol and ketone shows that reaction transition states that by size can be fitted within the pore of beta may have problems forming on the Lewis acid sites due to the shielding effect of the neighbor framework oxygen atoms. Finally, Sn-beta containing organic groups attached to the structure is able to perform the MPV in the presence of water, offering a real alternative to conventional aluminum iso-propoxide catalysts.

Gold supported on a mesoporous CeO2 matrix as an efficient catalyst in the selective aerobic oxidation of aldehydes in the liquid phase.

Gold supported on CeO2 catalyses the selective aerobic oxidation of aliphatic and aromatic aldehydes better than other reported catalysts such as Pt/C/Bi materials; the activity is due to the nanometric particle size of Au and CeO2.

On the dehydroindigo contribution to Maya Blue

A series of data from voltammetric, spectral, and UPLC–MS and Py–GC–MS analyses of extracts from synthetic Maya Blue-type specimens provides evidence on the presence of a significant amount of dehydroindigo, identified on the basis of its MS, FTIR, and UV–Vis signatures, accompanying indigo and other minority compounds, supporting the view of this material as a complex polyfunctional organic–inorganic hybrid material. Estimates of dehydroindigo/indigo in-depth distribution and thermochemical data for the dye association to the clay from chromatographic and voltammetric data are provided.

Ultra fast and efficient synthesis of Ti-ITQ-7 and positive catalytic implications

Incorporation of germanium into a zeolite framework allows the nsynthesis of Ti-Ge-ITQ-7 without seeding in <12 h, instead of 12 days nwhen seeding or >40 days without seeding for the Ge-free ITQ-7; the nsynthesis reported also increases the efficiency of Ti incorporation and nallows the preparation of almost nanocrystaline Ti-ITQ-7 materials with a ncorresponding beneficial effect on the final catalytic activity.

Ti-ferrierite and TiITQ-6: synthesis and catalytic activity for the epoxidation of olefins with H2O2

A new zeolitic material TiITQ-6 has been obtained by the direct synthesis of a layered titanosilicate precursor, followed by delamination; titanium is tetrahedrally coordinated in framework positions and, while the zeolite derived from the precursor has little activity owing to geometrical constraints, the delaminated TiITQ-6 material is active and selective for the epoxidation of hex-1-ene with H2O2.