Simona M. Coman
University of Bucharest
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Featured researches published by Simona M. Coman.
Green Chemistry | 2013
Iunia Podolean; Victor Kuncser; Nicoleta G. Gheorghe; Dan Macovei; Vasile I. Parvulescu; Simona M. Coman
Ru(III)/functionalized silica-coated magnetic nanoparticles (Ru(III)-MNP) were proven to be a highly active, selective and easily recoverable catalyst for the oxidation of levulinic acid to succinic acid under green conditions.
Applied Surface Science | 1999
Vasile I. Parvulescu; Simona M. Coman; P Palade; Dan Macovei; Cristian M. Teodorescu; G Filoti; R. Molina; Georges Poncelet; Fe Wagner
Ru-zeolites prepared via deposition of aqueous solution of ruthenium chloride on X, L, ZSM-5 and APO-54 were investigated. The impregnated solids were characterized by the following techniques: N-2 sorption, H-2 chemisorption, TPR, XRD, XPS, EXAFS and Mossbauer spectroscopy. It was found that deposition of Ru is influenced by the pore structure and the chemical composition of the supports, in particular the concentration and strength of the protonic sites, with the formation of the different species. The packing of Ru as well as the degree of the reduction and the metal particle size are different according to the penetration depth of the metal and the nature of the zeolite. The amount of chlorine possibly remaining as adatoms of Ru is very low or inexistent. In calcined and reduced catalysts no chloride peak could be evidenced by XPS. The experiments confirmed that the use of large amounts of Ru chloride precursor leads to rather large metal particles
Nature Communications | 2015
Ana Primo; Iván Esteve-Adell; Juan F. Blandez; Amarajothi Dhakshinamoorthy; Mercedes Alvaro; Natalia Candu; Simona M. Coman; Vasile I. Parvulescu; Hermenegildo García
Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C–N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets.
Chemical Communications | 2004
F Iosif; Simona M. Coman; Parvulescu; Paul Grange; Stéphanie Delsarte; Dirk E. De Vos; Pascale Jacobs
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.
Chemsuschem | 2012
Stefan Wuttke; Alina Negoi; Nicoleta Gheorghe; Victor Kuncser; Erhard Kemnitz; Vasile I. Parvulescu; Simona M. Coman
TIN, TAILORED, NOT SOLDER, BUT CAT: Doped hydroxylated fluorides, prepared by a modified sol-gel method, offer enhanced acidity and improved stability against water, and efficiency in the degradation of cellulose. These materials extend the portfolio of acid catalysts for fast and selective hydrolysis of biomass to glucose, which offers a feedstock for bioethanol production.
Chemcatchem | 2010
Simona M. Coman; Vasile I. Parvulescu; Stefan Wuttke; Erhard Kemnitz
The partly hydroxylated MgF2 and AlF3 materials are efficient and selective catalysts for the preparation of two important members of the vitamin K class: vitamin K1 and vitamin K1‐chromanol. The high activity in combination with high selectivity in one of the target products is due to both the acidic strength and the synergistic effect of the presence of both, optimized Brønsted and Lewis sites. Therefore, the best catalyst for a target product can be obtained through a very simple tuning of the acidic properties of the material. Moreover, the results obtained in the present study (Yvitamin K1=57.8 % and Yvitamin K1‐chromanol=71.4 %) are also very encouraging from the environmental standpoint as green elements are introduced by using solid catalysts and a biphasic solvent system.
Chemsuschem | 2013
Alina Negoi; Ioan Teodor Trotus; Olimpia Mamula Steiner; Madalina Tudorache; Victor Kuncser; Dan Macovei; Vasile I. Parvulescu; Simona M. Coman
A sweet catalyst: A catalyst formed of Ru/functionalized silica-coated magnetite nanoparticles is highly efficient in the one-pot production of sorbitol and glycerol, starting from cellulose and in the absence of an external hydrogen source. The ease of recoverability of the catalyst from the solid residues, and its reuse without loss of activity or selectivity for several runs, is an important green element of the process.
Journal of Molecular Catalysis A-chemical | 1999
Simona M. Coman; V.I Pârvulescu; B. Tesche; H Bönnemann; J.F. Roux; P.A. Jacobs
Ru–MCM-41 catalysts were investigated in the diastereoselective hydrogenation of class F prostaglandin intermediates. The catalysts were prepared by deposition of Ru from different precursors (ruthenium acetylacetonate, ruthenium chloride or ruthenium hexaamine chloride). These catalysts were characterized using several techniques: atomic emission spectroscopy with inductively coupled plasma, N2 adsorption–desorption curves at 77 K, H2-chemisorption, temperature-programmed oxidation, temperature-programmed reduction, XPS, XRD and transmission electron microscopy (TEM). The measurements indicated that Ru is homogeneously distributed on the surface of MCM-41 and that using the hexamine chloride complex allows a better penetration of Ru inside the mesoporous tubes then the other two precursors. Hydrogenation of a prostaglandin F intermediate, namely the one with R=H and –R′=CH2–O–C6H4 (m) Cl, showed that the catalysts prepared using ruthenium acetylacetonate and ruthenium chloride exhibit a higher selectivity to allylic alcohol than that prepared using ruthenium hexaamine chloride. In all the investigated catalysts the diastereomeric excess was in the (11R,15S) allyl alcohol and it varied in the same order as the chemoselectivity. A positive effect of pressure was found.
Catalysis Science & Technology | 2015
Octavian Dumitru Pavel; Peter Goodrich; Liliana Cristian; Simona M. Coman; Vasile I. Pârvulescu; Christopher Hardacre
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.
Catalysis Science & Technology | 2015
Natalia Candu; Cristina Rizescu; Iunia Podolean; Madalina Tudorache; Vasile I. Parvulescu; Simona M. Coman
A green alternative, based on the use of an efficient and recyclable chiral ketone@SBILC@MWCNT@Fe3O4 catalytic system (Y = 35%, S = 100% and ee = 100%), was developed for the asymmetric epoxidation of trans-methylcinnamate to (2R,3S)-phenyl glycidate.