Octavian Dumitru Pavel

Direct oxidation of amines to nitriles in the presence of ruthenium-terpyridyl complex immobilized on ILs/SILP

The immobilization of a ruthenium complex (Ru2Cl4(az-tpy)2) within a range of supported ionic liquids ([C4C1im]Cl, [C4C1im][NTf2], [C6C1im]Cl, [C4C1pyrr]Br, [C4C1im]Br, [C4C1pyrr]Cl) dispersed silica (SILP) operates as an efficient heterogeneous catalyst in oxidation of long chain linear primary amines to corresponding nitriles. This reaction follows a “green” route using a cheap and easy to handles oxidant (oxygen or air). The conversion was found to be strongly influenced by the alkyl chain length of the amine substrate and the choice of oxidant. No condensation reaction was observed between the starting amines and the selectivity to nitrile is 100%. Moving from a composition of 20 atm N2/5 atm O2 to 5 atm N2/20 atm O2 led to enhancements in the conversion (n-alkylamines) and selectivity (benzonitrile) which have been correlated with an increase of the solubilized oxygen. This was further supported by using different inert gas (nitrogen, helium, argon)/oxygen mixtures indicating that the O2 solubility in the SILP system, has an important effect on conversions and TON in this reaction using SILP catalysts. Experiments performed in the presence of CO2 led to a different behaviour due to the formation of amine-CO2 adducts. The application of the Weisz–Prater criterion confirmed the absence of any diffusional constraints.

New multicomponent catalysts for the selective aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine

Aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine was carried out on new gold-based catalysts using as support bimodal UVM-7-like mesoporous silica containing Ni and Ce (or Sn) as oxide nanodomains partially embedded inside the mesoporous UVM-7 silica walls. These nanodomains acted as effective and stable inorganic anchors favoring the nucleation, growth and stability of supported gold particles. Following the atrane method (a “one-pot” strategy able to harmonize the hydrolytic reactivity of different heteroelements through the use of complexes containing triethanolamine-derived ligands (atranes) as precursors) the stability of the oxide nanodomains during oxidation and thermal treatments was ensured. The catalysts were prepared using a two-step synthesis in which gold was incorporated through impregnation of previously synthesized bimodal porous silicas containing different heteroelements trapped by the silica mesostructure. The versatility of the preparative approach allowed the high surface area and accessibility of mesoporous silica and also an easy and homogeneous inclusion of heteroelements in one pot. Aerobic oxidative condensation of benzylamine on these catalysts occurred selectively only with the formation of N-benzylidenebenzylamine. While selectivity was total, the productivities (molproduct gcat−1 h−1) varied in a wide range as a function of catalyst composition (chemical composition and atomic ratios of the constitutive support elements). The catalytic behavior was merely controlled by the size of gold particles, but the support also exerts an influence. The best results were obtained on the mesoporous Au/Ce60–Ni10–UVM-7 catalyst having a 0.97(wt.%) gold content (in the form of nanoparticles of ca. 4 nm) and preserving a relatively high surface area (566 m2 g−1) and pore volume (0.91 cm3 g−1). The comparison with the individual or bicomponent catalysts led to the conclusion of a cooperative interaction between the catalyst components. However, gold itself exhibits a higher activity than the promoters or co-catalysts (i.e. phases containing Ni and/or Ce).

Synthesis and Characterization of Titanium Dioxide Phases in Mesostructured Silica Matrices with Photocatalytic Activity

An imidazole type ionic liquid (IL), 1‐hexadecyl‐3‐methylimidazolium chloride (I16IL) was used as a template in the preparation of mesoporous silica with incorporated titanium dioxide. In this process, the IL is the structural template as well as the source of the Ti. The steps leading to the formation of the nanocrystalline metal oxide include: a) formation of metal‐containing IL (M‐IL); b) using the M‐IL as a template for the mesoporous silica; c) calcination of the sample to remove the organic moiety, while leaving the metal centers to form oxides on the porous framework. By varying the TiO2–SiO2 calcination temperature, the particle size and phase of TiO2 have been studied. These TiO2–SiO2 hybrid materials were characterized by using various physicochemical techniques, such as UV/Vis diffuse‐reflectance spectroscopy, Raman spectroscopy, X‐ray diffraction, N2 adsorption‐desorption isotherm measurement, Fourier transform infrared spectroscopy, and transmission electron microscopy. The resultant hybrid silica demonstrated effective photocatalytic activity for the oxidation of cyclohexene and styrene.

Effect of Mo/Ce ratio in Mo-Ce-Al catalysts on the hydrogen production by steam reforming of glycerol

Alumina-supported molybdena–ceria catalysts were prepared by a sol–gel method and characterized by X-ray diffraction, N2 sorptometry, UV-vis-NIR diffuse reflectance spectroscopy, SEM and TEM. The effect of the Mo/Ce ratio, reaction temperature, steam to glycerol molar ratio, space velocity and the stability of the catalysts during the reaction were investigated. The results show that the presence of ceria enhances both the activity and the selectivity toward hydrogen. The best reaction temperature was found to be 500 °C for all catalysts, at which the highest hydrogen selectivity of almost 60% was obtained for an optimal cerium loading of 7 wt%; higher ceria loading reduced the capacity to convert glycerol to hydrogen.

Hydrotalcites (HTs) and mesoporous mixed oxides obtained from HTs, basic solid catalysts for cyclohexanone condensation

The effect of the insertion of REE (Y, Gd, Sm and La) in HTs structure to prepare mesoporous mixed oxides with different basic sites to be used as basic solid catalysts is studied. The mixed oxides derived from REE modified HT precursors proved to be active and selective catalysts in cyclohexanone condensation reaction. The catalytic behaviour is associated to basic properties and the presence of structural defects of the prepared catalysts.

Ionic liquids at interfaces: general discussion

Andrew Abbott, Matthew Addicoat, Leigh Aldous, Radha Gobinda Bhuin, Natalia Borisenko, José Nuno Canongia Lopes, Ryan Clark, Samuel Coles, Margarida Costa Gomes, Benjamin Cross, Jeffrey Everts, Millicent Firestone, Ramesh Gardas, Matthieu Gras, Simon Halstead, Christopher Hardacre, John Holbrey, Toshiyuki Itoh, Vladislav Ivaništšev, Johan Jacquemin, Philip Jessop, Robert Jones, Barbara Kirchner, Sichao Li, Ruth Lynden-Bell, Doug MacFarlane, Florian Maier, Markus Mezger, Aǵılio Pádua, Octavian D. Pavel, Susan Perkin, Simon Purcell, Mark Rutland, John M. Slattery, Sefik Suzer, Kazuhisa Tamura, Morgan L. Thomas, Shraeddha Tiwari, Seiji Tsuzuki, Betul Uralcan, William Wallace, Masayoshi Watanabe and James Wishart

Alternative valorization of red mud waste as functional materials with catalytic activity for sulfide oxidation in wastewater

This work investigates the catalytic properties toward sulfide oxidation in wastewater for three composites which are functional materials obtained from red mud waste following its neutralization, chemical activation and functionalization of the iron by treatment with disodium salt of ethylenediaminetetraacetic acid, trisodium citrate or a combination of these two organic ligands. X-ray diffraction and diffuse reflectance Fourier transformed infrared spectroscopy characterizations indicated the coexistence of the corresponding iron chelates phases along with hematite the main crystallographic phase from red mud. The most active catalyst was the red mud-derived material obtained by functionalization with the mixture of ethylenediaminetetraacetate and citrate ligands. The results obtained after its testing in multiple reaction cycles showed that the decrease in conversion after 10 reaction cycles was less than 5%. Considering the results of diffuse reflectance ultraviolet visible narrow infrared spectroscopical analysis which revealed that this solid contains species with lower bond strength, it has been inferred that both the higher catalytic activity, as well as the enhanced stability, is directly related to the versatility of the active species.

Heterocyclic bismuth(III) compounds with transannular N→Bi interactions as catalysts for the oxidation of thiophenol to diphenyldisulfide

The reactions between the diorganobismuth(III) bromides [RCH2N(CH2C6H4)2]BiBr [R = C6H5 (1), C6H5CH2 (2)] and appropriate silver salts resulted in new diorganobismuth(III) compounds of the general formula [RCH2N(CH2C6H4)2]BiX [R = C6H5, X = ONO2 (3), OSO2CF3 (4), OSO2C6H4 (CHCH2)-4 (5); R = C6H5CH2, X = ONO2 (6)], based on a butterfly-like tetrahydro-dibenzo[c,f][1,5]azabismocine heterocyclic framework. The new species were structurally characterized in solution by 1H, 13C{H} and 19F{H} NMR and in the solid state by IR spectroscopy and single-crystal X-ray diffraction. The nitrogen atom is intramolecularly coordinated to bismuth, thus resulting in hypercoordinated species of type 12-Bi-5 (3 and 6) and 10-Bi-4 (4 and 5). In addition, compound 4 shows bismuth⋯π arene and compounds 3 and 6 bismuth⋯oxygen intermolecular interactions, thus leading to dimers in the solid state. These compounds were investigated as catalysts for the oxidation of thiophenol to diphenyl disulfide by using air as an oxidizing agent, both in cyclohexane and in an ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide), at temperatures below 100 °C, affording high reaction rates (TON 34.8, with 100% conversion after 5 h) and a total selectivity to the targeted product.