National Institute Of Materials Physics - Romania

Publications

169 articles found

121. Structural changes during toluene complete oxidation on supported EuFeO3 monitored by in situ Eu-151 and Fe-57 Mossbauer spectroscopy

Authors: Florea, M; Alifanti, M; Kuncser, V; Parvulescu, VI

Published: JUN 1 2013, CATALYSIS TODAY, 208, 59, DOI: 10.1016/j.cattod.2012.09.035

Pure EuFeO3 and ceria were prepared via a sol-gel citrate route and were calcined at 700 degrees C. Separately, a 20 wt% EuFeO3/CeO2 was prepared via incipient wetness impregnation of calcined ceria with citrate precursors and calcined in the same conditions. SBET, XRD, toluene chemisorption, toluene-TPD and in situ Eu-151 and Fe-57 Mossbauer investigations were performed. All characterization data indicate the formation of a well-dispersed EuFeO3 at the surface of CeO2. During the oxidation of toluene Eu-151 and Fe-57 Mossbauer spectroscopy suggested a cooperative effect of the cations. The catalysts were tested in total oxidation of toluene. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuFeO3. All structural changes during operation time were reversible. (C) 2012 Elsevier B.V. All rights reserved.

122. Postsynthetic Modification of a Metal-Organic Framework (MOF) Structure for Enantioselective Catalytic Epoxidation

Authors: Candu, N; Tudorache, M; Florea, M; Ilyes, E; Vasiliu, F; Mercioniu, I; Coman, SM; Haiduc, I; Andruh, M; Parvulescu, VI

Published: MAY 2013, CHEMPLUSCHEM, 78, 450, DOI: 10.1002/cplu.201300076

Postsynthetic modification of [Cu2(mand)2(hmt)] (mand=mandelic acid, hmt=hexamethylenetetramine) with a chiral, dimeric chromium(III)salen complex led to a robust structure. Characterization of this new material showed that it perfectly preserved the textural and structural properties of the parent metalorganic framework (MOF). Although epoxidation of trans-methyl cinnamate with hydrogen peroxide led to copper leaching of 23%, experiments performed with N-methylmorpholine-N-oxide indicated no leaching, even after 72h of exposure. The obtained chiral MOF is an effective catalyst for the enantioselective epoxidation of trans-methyl cinnamate and leads to (2R,3S)-phenylglycidate with a high enantiomeric excess at room temperature.

123. A Robust Metal-Organic Framework Constructed from Alkoxo-Bridged Binuclear Nodes and Hexamethylenetetramine Spacers: Crystal Structure and Sorption Studies

Authors: Ilyes, E; Florea, M; Madalan, AM; Haiduc, I; Parvulescu, VI; Andruh, M

Published: AUG 6 2012, , DOI: 10.1021/ic301139j

124. Spectroscopic Analysis of the Interstitial Anions in Some Layered Double Hydroxide Materials

Authors: Frunza, L; Gheorghe, N; Iova, F; Ganea, P; Neatu, F; Parvulescu, VI

Published: AUG 2011, REVISTA DE CHIMIE, 62, 772, DOI:

Layered double hydroxide materials with Zn2+ and Mg2+ as bivalent cations and Al3+ and Ga3+ as trivalent cations were studied. The anions to balance the positive charge of the network were carbonate and/or nitrate. The samples were prepared in laboratory and routinely characterized. Here the investigations by Fourier transform infrared spectra and thermogravimetric measurements are detailed. On the basis of calibration curves for carbonate and nitrate ions obtained from IR spectra of the corresponding salts, the sample analysis of the interlayer anions was performed quantitatively.

125. Benzylation of benzene with benzyl alcohol on zeolite catalysts

Authors: Candu, N; Florea, M; Coman, SM; Parvulescu, VI

Published: FEB 15 2011, , DOI: 10.1016/j.apcata.2010.11.044

126. Unusual Behavior of a Novel Heterogeneous Chiral Dimer Cr(III)-Salen Complex in the Epoxidation/Epoxide Ring-Opening Reaction of trans-Methylcinnamate Ester

Authors: Protesescu, L; Tudorache, M; Neatu, S; Grecu, MN; Kemnitz, E; Filip, P; Parvulescu, VI; Coman, SM

Published: FEB 3 2011, JOURNAL OF PHYSICAL CHEMISTRY C, 115, 1122, DOI: 10.1021/jp106281z

A dimer chromium(III)-salen complex immobilized on modified silica is an effective catalyst for the epoxidation/epoxide ring-opening reaction of trans-methylcinnamate ester and gave significantly high ee in methyl (2R,3S)-2,3-dihydroxy-3-phenylpropionate. For the first time, it is shown that a donor ligand (e.g., Et3N) can be involved into the enantioselective mechanism of the product configuration. It is suggested that the additive is interacting with the reaction intermediate in a manner that prolongs its lifetime, thus affording a free rotation of the C-C single bond in this species and a selective collapse to the cis-epoxide product. In the presence of water, this epoxide led to methyl (2S,3R)-2,3-dihydroxy-3-phenylpropionate. Alternatively, the donor additives may give rise to a new chromium-based oxidant that effects epoxidation and its consecutive ring opening to diols via an unusual pathway.

127. 1-BUTANOL DEHYDRATION AND DEHYDROGENATION OVER VANADIUM ALUMINIUM OXYNITRIDE CATALYSTS

Authors: Florea, M; Delsarte, S; van Keulen, E; Grange, P

Published: FEB 2011, , DOI:

128. Novel Pd heterogeneous catalysts for cycloisomerisation of acetylenic carboxylic acids

Authors: Neatu, F; Protesescu, L; Florea, M; Parvulescu, VI; Teodorescu, CM; Apostol, N; Toullec, PY; Michelet, V

Published: DEC 2010, GREEN CHEMISTRY, 12, 2149, DOI: 10.1039/c0gc00258e

The Pd-TPPTS complex (TPPTS - trisodium salt of 3,3',3 ''-phosphanetriyl benzenesulfonic acid) and PdCl42- salt heterogenised onto Zn2AlNO3 layered double hydroxide (LDH) using an ion-exchange procedure, have been shown to be efficient green catalysts in the cycloisomerisation reaction of acetylenic carboxylic acids to the corresponding 5-membered heterocycles.

129. Modifications of the Catalytic Activity for Cyanoethylation Induced by the Memory Effect of Mg/Al-Type Modified Hydrotalcites

Authors: Pavel, OD; Birjega, R; Angelescu, E; Zavoianu, R; Florea, M; Mitran, G

Published: APR 2010, , DOI:

130. Epoxidation of cyclohexene with O-2 and isobutyraldehyde catalysed by cobalt modified hydrotalcites

Authors: Angelescu, E; Ionescu, R; Pavel, OD; Zavoianu, R; Birjega, R; Luculescu, CR; Florea, M; Olar, R

Published: JAN 15 2010, , DOI: 10.1016/j.molcata.2009.09.009