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Papers by claudio pirovano

Enantioselective hydrogenation of prochiral substrates in catalytic membrane reactors

Catalysis Science & Technology, 2011

... 10, P. Barbaro, C. Bianchini, F. Liguori, H. Sawa and F. Vizza, PCT/JP, 056288 ... Rev., 2009... more ... 10, P. Barbaro, C. Bianchini, F. Liguori, H. Sawa and F. Vizza, PCT/JP, 056288 ... Rev., 2009, 38, 695 RSC Article ; JI García, B. López-Sánchez, JA Mayoral, E. Pires ... 4-yl)dimethylamine; MAA = methyl 2-acetamidoacrylate; DMI = dimethyl itaconate; ANL = α-angelica lactone; EMC ...

Catalysis Today, 2012

In the present study, various VO x containing catalysts were prepared using nanoporous glass and ... more In the present study, various VO x containing catalysts were prepared using nanoporous glass and mesoporous silicas (e.g. MCM-41 and SBA-15) as supports. The solids were characterised and tested towards partial oxidation of methane to oxygenates at 923 K. The catalysts were synthesised using two different methods such as (i) wet impregnation (WI) and (ii) incipient wetness impregnation (IWI). BET-surface areas depend on the nature of the support and the type of method of preparation. UV-vis spectra clearly disclose the formation of mainly monomeric VO x species in the samples prepared through IWI. Pyr-FTIR reveals that all the catalysts irrespective of the method of preparation contain both Brønsted and Lewis sites. However, the distribution of these sites again depends on the method of preparation. TEM analysis indicates that the catalysts prepared through IWI provide high dispersion of molecular VO x species on the surface of the support compared to WI. Thus, the catalytic activity and selectivity were also found to depend strongly on the method of preparation. Among the two preparation methods, the catalysts synthesised through IWI revealed higher selectivity and higher space-time-yields to formaldehyde. VO x supported on SBA-15 exhibits superior performance compared to MCM-41. Nanoporous glass supported VO x only show poor performance.

Catalysis Today, 2011

Pt and Ni catalysts supported on SiO 2 were prepared with different metal content in order to app... more Pt and Ni catalysts supported on SiO 2 were prepared with different metal content in order to apply them in steam reforming of glycerol at temperatures between 350 • C and 450 • C.

Applied Catalysis B: Environmental, 2012

Mg(Al)O supported Ru catalysts with low loading of active metal (0.6 wt.%), obtained from simple ... more Mg(Al)O supported Ru catalysts with low loading of active metal (0.6 wt.%), obtained from simple inorganic salts, were tested, for the first time, in the steam reforming (SR) of glycerol to hydrogen rich mixtures. The catalysts, obtained by simple wet impregnation of Ru salts on a Mg(Al)O mixed oxide followed by high temperature oxidation/reduction treatments, were systematically characterized by numerous complementary techniques, both before and after their use in SR reaction. The changes of the performances (activity, selectivity and stability) of Ru/Mg(Al)O catalysts were studied, produced by varying reaction temperature (450-650 • C) at fixed glycerol concentration (10 wt.% in water), and by varying glycerol concentration (10-40 wt.% in water) at fixed reaction temperature (550 • C). The best performances (in terms of glycerol conversion, H 2 yield and CO 2 selectivity), at lowest reaction temperature, were obtained operating at 10 wt.% glycerol and 550 • C. Correspondingly, catalysts showed glycerol conversion, H 2 yield and CO 2 selectivity close to 100%. Methane was practically absent, CO selectivity was lower than 3.5% and coke deposition quite scarce (1.1 mg C g cat −1 h −1 ). However, at this temperature, catalysts exhibited stable, although lower, performances up to 40 wt.% glycerol concentrations. Significantly, catalytic performances could be improved increasing reaction temperature up to 650 • C keeping other advantages.

Benzene Hydrogenation by Silica-Supported Catalysts Made of Palladium Nanoparticles and Electrostatically Immobilized Rhodium Single Sites

Organometallics, 2008

... Pierluigi Barbaro , Claudio Bianchini* , Vladimiro Dal Santo , Andrea Meli , Simonett... more ... Pierluigi Barbaro , Claudio Bianchini* , Vladimiro Dal Santo , Andrea Meli , Simonetta Moneti , Claudio Pirovano § , Rinaldo Psaro* , Laura Sordelli and Francesco Vizza . ICCOM-CNR, Area di Ricerca CNR di Firenze, Via Madonna del Piano 10, 50019 Sesto ...

Green Chemistry, 2009

The epoxidation of cyclohexene with aqueous hydrogen peroxide over mesostructured Ti(Cp) 2 Cl 2 -... more The epoxidation of cyclohexene with aqueous hydrogen peroxide over mesostructured Ti(Cp) 2 Cl 2 -grafted silica catalysts is described for the first time. Three kinds of Ti-containing systems with different textural properties have been employed: Ti/SiO 2 , Ti/MCM-41 and Ti/MCM-48. A minimal local H 2 O 2 concentration in the surroundings of Ti sites, obtained by a controlled dropwise addition of aqueous H 2 O 2 (4.17 mmol H 2 O 2 h -1 g cat -1 ), is crucial for an effective and highly selective epoxidation. Excellent selectivity (>98%) in cyclohexene epoxide is obtained at the end of the slow H 2 O 2 addition in acetonitrile. Higher yields in epoxide are found over Ti/MCM-48 than over Ti/MCM-41 or Ti/SiO 2 thanks to better isolation, dispersion and stability of Ti(IV) sites.

Advanced Synthesis & Catalysis, 2009

Titanium-silica catalysts have been prepared by supporting titanium(IV) precursors with different... more Titanium-silica catalysts have been prepared by supporting titanium(IV) precursors with different nuclearity {mononuclear titanocene dichloride Ti(Cp)2Cl2, dinuclear titanium diethyl tartrate and the tetranuclear titanium peroxo complex (NH4)8[Ti4(C6H4O7)4(O2)4]⋅8 H2O} onto the surface of silica materials with different textural characteristics. The supported catalysts have been explored as highly active and reusable catalysts for the oxidation of 2,3,6-trimethylphenol (TMP) and 2,6-dimethylphenol (DMP) to 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate) and 2,6-dimethyl-1,4-benzoquinone (DMBQ), respectively, using aqueous hydrogen peroxide as green oxidant. Catalysts prepared by grafting mononuclear Ti(Cp)2Cl2 revealed a strong dependence of the product selectivity on the surface concentration of titanium active centers. Mesoporous materials with titanium surface concentration in the range of 0.6–1.0 Ti/nm2 were identified as optimal catalysts for the transformation of alkylphenols to benzoquinones. Catalysts having <0.6 Ti/nm2 produced a mixture of benzoquinones and dimeric by-products. Conversely, when di-/tetranuclear titanium precursors were employed for the catalyst preparation, a diminution of the titanium surface concentration had no impact on the benzoquinone selectivity, which was typically as high as 96–99%. DR-UV spectroscopic studies revealed that the catalysts capable of producing alkylbenzoquinones with nearly quantitative yields possess titanium dimers and/or subnanometer-size clusters homogeneously distributed on a silica surface. On the contrary, catalysts with isolated titanium sites give a considerable amount of dimeric by-products. This is the first example which clearly demonstrates the advantages of titanium cluster-site catalysts over titanium single-site catalysts in hydrogen peroxide-based selective oxidation reaction.

Molecules, 2010

Nanostructured single-site heterogeneous catalysts possess the advantages of classical solid cata... more Nanostructured single-site heterogeneous catalysts possess the advantages of classical solid catalysts, in terms of easy recovery and recycling, together with a defined tailored chemical and steric environment around the catalytically active metal site. The use of inorganic oxide supports with selected shape and porosity at a nanometric level may have a relevant impact on the regio-and stereochemistry of the catalytic reaction. Analogously, by choosing the optimal preparation techniques to obtain spatially isolated and well-characterised active sites, it is possible to achieve performances that are comparable to (or, in the most favourable cases, better than) those obtained with homogeneous systems. Such catalysts are therefore particularly suitable for the transformation of highly-functionalised fine chemicals and some relevant examples where high chemo-, regio-and stereoselectivity are crucial will be described.