Papers by Reinaldo Atencio
Mineral coals from Guasare Paso Diablo Mine, specifically from coal seams IV and V, were activate... more Mineral coals from Guasare Paso Diablo Mine, specifically from coal seams IV and V, were activated with potassium hydroxide (KOH), and then characterized through ASTM Standard Test Methods, for instrumental determination of carbon, hydrogen, nitrogen, oxygen, moisture and ash. A low ash percentage was obtained, which made these materials perfect to be used in chemical activation of mineral coal. Surface Area was determined through the Brunauer-Emmett-Teller (BET) method. The morphology of the material was studied by Scanning Electron Microscopy (SEM), and the information about functional groups was obtained with Infrared Spectroscopy (FT-IR). Surface areas of 1386 m 2 /g and 652 m 2 /g, were obtained after chemical activation of mineral coal from layer IV and V, respectively, after activation with 60% m/m KOH solution. 30% m/m KOH solution produced activated carbon with lower surface area. This KOH concentration was unable to break the carbon bonds and form a real porous structure i...
Avances en Química, 2013
Hydantoin-L-aspartic acid, C5H6N2O4, crystallize in the orthorhombic system with space group P212... more Hydantoin-L-aspartic acid, C5H6N2O4, crystallize in the orthorhombic system with space group P212121 (No19), Z=4, and unit cell parameters a= 7.597(1) A, b= 8.591(1) A, c= 9.447(1) A, V= 616.6(2) A3. In the crystal structure of the title compound the molecules are joined by N---H···O and O---H···O hydrogen bonds into chain and cyclic structures with graph-set C(4), C(6), C(8), R33(15), R44(20) forming a three-dimensional network.
Acta Crystallographica Section E-structure Reports Online, Jun 30, 2004
ABSTRACT The crystal structure of the title compound, [Co(NO3)(bipy)2]2[MoO4]·7H2O (bipy is 2,2′-... more ABSTRACT The crystal structure of the title compound, [Co(NO3)(bipy)2]2[MoO4]·7H2O (bipy is 2,2′-bipyridine, C10H8N2), contains the isomers Δ and Λ of the cation [Co(NO3)(bipy)2]+, self-assembled through complementary –, C—H… and C—H…O interactions, leading to an intricate two-dimensional array. The final three-dimensional network is sustained via extensive hydrogen bonding among the cations, uncoordinated water molecules and molybdate anions, which are accommodated in between adjacent cationic two-dimensional arrays. In the cations, the metal centres adopt a distorted octahedral geometry due to the coordination of the N atoms of two bipy molecules and one bidentate nitrate ligand.
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, 2012
The aim of this study was to modify a synthetic clay with MgO and a non-ionic surfactant (Igepal ... more The aim of this study was to modify a synthetic clay with MgO and a non-ionic surfactant (Igepal CA-720), impregnated with Cu or Fe to evaluate the H2S removal. The Cu and Fe content was: 1.0; 8.0 and 15wt.%, bimetallic Cu-Fe solids were also prepared. The obtained materials were characterized by N2 adsorption, X-ray diffraction (XRD), X-ray fluorescence (XRF), temperature programmed reduction (TPR) and thermogravimetic analysis (TGA). An increase of surface area, pore volume and mesoporosity was observed after clay modification with surfactant and MgO. The modified clay impregnated with Cu showed, by XRD, CuO phases which were confirmed by TPR profiles. The highest H2S removal was obtained for clay sample containing 15% of Cu. It was established that the surface reaction occurred over metallic sites while the porous structure of the material was kept intact after reaction.
Acta Crystallographica Section E-structure Reports Online, Jul 24, 2003
View of the title complex, showing the atom-labelling scheme. Displacement ellipsoids are drawn a... more View of the title complex, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 35% probability level. metal-organic papers m634 Edgar Ocando-Mavarez et al. [Rh(C 5 H 7 O 2)(C 10 H 19 P)(CO)]
Acta Crystallographica Section E-structure Reports Online, Feb 28, 2004
The structure of diammonium tetramolybdate, [(NH4)2(Mo4O13)]n, consists of puckered layers built... more The structure of diammonium tetramolybdate, [(NH4)2(Mo4O13)]n, consists of puckered layers built up from the self-assembly of chains of tetrameric units [Mo4O13]2− linked through corner-sharing octahedra. The ammonium cations are located between consecutive layers, yielding a three-dimensional array via extensive N—H⋯O hydrogen bonding, in which terminal oxo groups of the surface network are involved.
Dalton Transactions, 2013
Novel MoO(2)/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbon... more Novel MoO(2)/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of polyoxometalates (POMs: phosphomolybdic acid [H(3)PMo(12)O(40)] and ammonium heptamolybdate tetrahydrate [(NH(4))(6)Mo(7)O(24)]·4H(2)O). The structural characterization by FT-IR, XRPD, SEM and TEM analyses revealed the controlled formation of hierarchical MoO(2)/C composites with different morphologies: strawberry-like, based on carbon microspheres decorated with MoO(2) nanoparticles; MoO(2)/C core-shell composites; and irregular aggregates in combination with ring-like microstructures bearing amorphous Mo species. These composites can be fine-tuned by varying reaction time, glucose/POM ratio and type of POM precursor. Subsequent transformations in the solid state through calcinations of MoO(2)/C core-shell composites in air lead to hollow nanostructured molybdenum trioxide microspheres together with nanorods and plate microcrystals or cauliflower-like composites (MoO(2)/C). In addition, the MoO(2)/C composite undergoes a morphology evolution to urchin-like composites when it is calcined under nitrogen atmosphere (MoO(2)/C-N(2)). The MoO(2)/C strawberry-like and MoO(2)/C-N(2) composites were transformed into Mo carbide and nitride supported on carbon microspheres (Mo(2)C/C, MoN/C, and MoN/C-N(2)). These phases were tested as precursors in thiophene hydrodesulphurization (HDS) at 400 °C, observing the following trend in relation to the thiophene steady-state conversion: MoN/C-N(2) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; MoN/C &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Mo(2)C/C &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; MoO(2)/C-N(2) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; MoO(2)/C. According to these conversion values, a direct correlation was observed between higher HDS activity and decreasing crystal size as estimated from the Scherrer equation. These results suggest that such composites represent interesting and promising precursors for HDS catalysts, where the activity and stability can be modified either by chemical or structural changes of the composites under different conditions.
Acta Crystallographica Section C-crystal Structure Communications, Jul 5, 2007
![Research paper thumbnail of Synthesis, reactivity and catalytic activity of [RuH(η<sup>1</sup>-OCMe<sub>2</sub>)(CO)<sub>2</sub>(PPr<sup>i</sup><sub>3</sub>)<sub>2</sub>]BF<sub>4</sub>](https://attachments.academia-assets.com/118341160/thumbnails/1.jpg)
Journal of The Chemical Society-dalton Transactions, 1995
Reactions of the zirconium-sulfide metallocene anion [Cp tt 2 ZrS 2 ] 2-(Cp tt) η 5-1,3-di-tertbu... more Reactions of the zirconium-sulfide metallocene anion [Cp tt 2 ZrS 2 ] 2-(Cp tt) η 5-1,3-di-tertbutylcyclopentadienyl) with [{M(µ-Cl)(diolefin)} 2 gave the d 0-d 8 complexes [Cp tt 2 Zr(µ 3-S) 2-{M(diolefin)} 2 ] (M) Rh, diolefin) 2,5-norbornadiene (nbd) (1), 1,5-cyclooctadiene (cod); M) Ir, diolefin) cod) with a triangular ZrM 2 core capped by two symmetrical µ 3-sulfido ligands. The rhodium complexes [Cp tt 2 Zr(µ 3-S) 2 {Rh(diolefin)} 2 ] (diolefin) tetrafluorobenzobarrelene (tfbb), nbd, cod) can also be prepared by the additive-deprotonation reactions of the mononuclear [Rh(acac)(diolefin)] (diolefin) nbd, tfbb) and the dinuclear [{Rh(µ-OH)(cod)} 2 ] complexes with [Cp tt 2 Zr(SH) 2 ]. These compounds exist as two rotamers in solution due to a hindered rotation of the cyclopentadienyl rings and the relative disposition of the substituents of the Cp tt groups in the sandwich moiety. The reaction of [Cp tt 2 Zr(SH) 2 ] with [Ir(acac)(cod)] gave the complex [Cp tt (acac)Zr(µ 3-S) 2 {Ir(cod)} 2 ] (5) with release of HCp tt and coordination of acetylacetonate to the zirconium center. Carbonylation of compounds 1 and 5 yielded [Cp tt 2-Zr(µ 3-S) 2 {Rh(CO) 2 } 2 ] (6) and [Cp tt (acac)Zr(µ 3-S) 2 {Ir(CO) 2 } 2 ], respectively, while the complexes [Cp tt 2 Zr(µ 3-S) 2 {M(CO) 2 } 2 ] (M) Rh, Ir) resulted also from the reaction of [Cp tt 2 Zr(SH) 2 ] with (PPh 3 Bz)[MCl 2 (CO) 2 ] in the presence of triethylamine. Reactions of the carbonyl complexes with 1 molar equiv of bis(diphenylphosphino)methane (dppm) gave the cisoid complexes [Cp tt 2-Zr(µ 3-S) 2 {M(CO)} 2 (µ-dppm)] (M) Rh (9), Ir) with evolution of carbon monoxide. Monodentate phosphites, P(OMe) 3 and P(OPh) 3 , react with 6 to give mixtures of the transoid and cisoid isomers [Cp tt 2 Zr(µ 3-S) 2 {Rh(CO)(P(OR) 3)} 2 ], which also exhibit a restricted rotation of the Cp tt rings. The molecular structures of complexes 6 and 9 have been determined by X-ray diffraction methods. Compound 6 in the presence of P-donor ligands, P(OMe) 3 , P(OPh) 3 , and PPh 3 , is a precursor of the catalyst for the hydroformylation of oct-1-ene under mild conditions of pressure and temperature. No Zr-Rh synergic effect is observed in this case, and the precursor breaks down after catalysis.
Organometallics, Apr 1, 1995
ABSTRACT
Acta Crystallographica Section C: Structural Chemistry, Aug 30, 2020
A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phos... more A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phosphines has been prepared in good to excellent yields by the reaction of [Rh(acac)(CO)2] (acac is acetylacetonate) with the corresponding allyl-, cyanomethyl- or cyanoethyl-substituted phosphines. All compounds were fully characterized by 31P, 1H, 13C NMR and IR spectroscopy. The X-ray structures of (acetylacetonato-κ2 O,O′)(tert-butylphosphanedicarbonitrile-κP)carbonylrhodium(I), [Rh(C5H7O2)(CO)(C8H13N2)] or [Rh(acac)(CO)(tBuP(CH2CN)2}] (2b), (acetylacetonato-κ2 O,O′)carbonyl[3-(diphenylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C15H14N)(CO)] or [Rh(acac)(CO){Ph2P(CH2CH2CN)}] (2h), and (acetylacetonato-κ2 O,O′)carbonyl[3-(di-tert-butylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C11H22N)(CO)] or [Rh(acac)(CO){tBu2P(CH2CH2CN)}] (2i), showed a square-planar geometry around the Rh atom with a significant trans influence over the acetylacetonate moiety, evidenced by long Rh—O bond lengths as expected for poor π-acceptor phosphines. The Rh—P distances displayed an inverse linear dependence with the coupling constants J P-Rh and the IR ν(C[triple-bond]O) bands, which accounts for the Rh—P electronic bonding feature (poor π-acceptors) of these complexes. A combined study from density functional theory (DFT) calculations and an evaluation of the intramolecular H...Rh contacts from X-ray diffraction data allowed a comparison of the conformational preferences of these complexes in the solid state versus the isolated compounds in the gas phase. For 2b, 2h and 2i, an energy-framework study evidenced that the crystal structures are mainly governed by dispersive energy. In fact, strong pairwise molecular dispersive interactions are responsible for the columnar arrangement observed in these complexes. A Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots indicated that the structures are stabilized by H...H, C...H, H...O, H...N and H...Rh intermolecular interactions.
Revista Latinoamericana de Metalurgia y Materiales, Aug 16, 2017
Se sintetizaron bajo condiciones hidrotermicas y caracterizados por difraccion de rayos X de cris... more Se sintetizaron bajo condiciones hidrotermicas y caracterizados por difraccion de rayos X de cristal unico, IR-TF y analisis elemental dos compuestos hibridos. El compuesto 1 ([[NH 4 ] 2 [{Cu(OH 2 ) 2 (en) 2 }][{Cu(en) 2 } 3 H 2 W 12 O 42 ]·7H 2 O] n ), consiste en apilamientos de redes polimericas 2D. La red de polimero en 1 se extiende a traves de enlaces de coordinacion entre los grupos oxo perifericos del cluster paradodecatungstato B y complejos metal-organicos, [Cu(en) 2 ] 2+ . La estructura cristalina del compuesto 2 ([Mo 8 O 26 Ag 4 (4,4'-bipi) 6 (H 2 O) 2 ] n ) consiste en cadenas de polimeros, 1D de complejos de coordinacion, [Ag(4,4´-bipi) 3 H 2 O], conectadas a traves de atomos oxigeno terminales de cluster de β-octamolibdato, generando una red 3D. Two hybrid compounds were synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, FT-IR and elemental analysis. Compound 1 ([[NH 4 ] 2 [{Cu(OH 2 ) 2 (en) 2 }][{Cu(en) 2 } 3 H 2 W 12 O 42 ]·7H 2 O] n ) consists of 2D polymer framework stacks. The polymer framework in 1 extends through coordination bonds between the peripheral oxo groups of the paradodecatungstate B cluster and metal-organic complexes [Cu(en) 2 ] 2+ . Crystalline structure of compound 2 ([Mo 8 O 26 Ag 4 (4,4'-bipi) 6 (H 2 O) 2 ] n ) consists of 1D polymeric chains of coordination complexes, [Ag(4,4'-bipi) 3 H 2 O], connected through terminal oxygen atoms of β-octamolybdate cluster, resulting in a 3D network.
Acta Crystallographica Section A, Aug 8, 1996
Acta Microscopica, 2019
Lithium-ion batteries have been widely used as a key alternative in the advancement of new energy... more Lithium-ion batteries have been widely used as a key alternative in the advancement of new energy generation and storage technologies. However, some of their features can still be improved. Nanostructured electrode materials are at the forefront of research in the field of energy storage, showing superior performances, higher energy, power densities, and a more significant number of charge-discharge cycles. In this work, electrochemical reversibility studies were carried out through the cyclic voltammetry technique applying the Nicholson and Shain criteria in a cell constructed from an anode of multi-walled carbon nanotubes (MWCNT) and lithium tetraoxomanganate(VI) (LiMn2O4) as the cathode, using lithium tetrafluoroborate (LiBF4) as support electrolyte dissolved in propylene carbonate and an Ag/AgCl reference electrode. The products were also characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and X-ray Diffraction (XRD) analysis. Combinations of binders were used in the composites to improve the electrical conductivity in the electrodes, the mechanical properties, and the reversibility process. The electrochemical characterization reported the existence of a pair of characteristic anodic and cathodic peaks associated with the intercalation/deintercalation process of lithium ions at the electrode/electrolyte interface, expected behavior in Li-ion cells. Results showed that combinations of 70% LiMn2O4/25% Carbon (C)/5% polytetrafluoroethylene (PTFE) for the cathode material and 90% MWCNT/10% PTFE at the anode presented optimal results both for the intercalation and deintercalation of lithium, as well as for the adherence of the composite.
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, Apr 1, 2011
Se prepararon compuestos de aluminio reforzados con nanotubos de carbono de pared múltiple (NTCPM... more Se prepararon compuestos de aluminio reforzados con nanotubos de carbono de pared múltiple (NTCPM) utilizando la técnica de pulvi-metalurgia. Los NTCPM se sintetizaron por deposición química de vapor (DQFV), utilizando C 2 H 2 como gas precursor, Ar como gas de arrastre y Fe-Co / CaCO 3 como catalizador. El polvo de aluminio se mezcló con NTCPM en un dispositivo de molienda de bolas planetaria para diferentes relaciones de peso, de 0% a 2% y diferentes etapas de tiempo en el proceso de mezcla (3 min y 60 min). Los compuestos en polvo se prensaron en caliente, recocidos en atmosfera inerte y analizados usando un microscopio electrónico de barrido de emisión de campo (MEB-EC), difracción de rayos X en polvo y dureza Vickers. Se examinaron un total de 80 muestras para evaluar el efecto de los NTCPM sobre la dureza. Los resultados mostraron un aumento de la dureza para los compuestos de ~ 15% a 24%. Se consideró la desviación estándar de las medidas de dureza para evaluar la dispersión de MWCNT en los compuestos. Se aplicó un ajuste lineal a los datos de dureza para evaluar la influencia de la temperatura en el proceso de consolidación de granos y un análisis de varianza. Los resultados exhibieron una dispersión sustancial de la dureza de 13.13% a 24.57% de error. El análisis de los resultados obtenidos en varias condiciones sugirió condiciones óptimas para un tiempo de mezcla de 3 min y una temperatura de sinterización de 760 ° C.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, 2016
Carbones minerales de la mina Paso Diablo en Guasare, especificamente aquellos ubicados en los ma... more Carbones minerales de la mina Paso Diablo en Guasare, especificamente aquellos ubicados en los mantos IV y V de la mina Paso Diablo, fueron activados quimicamente con hidroxido de potasio (KOH). La caracterizacion fue realizada por medio de normas ASTM, para la determinacion del porcentaje de carbono, hidrogeno, nitrogeno, oxigeno, azufre, humedad y cenizas, obteniendose porcentajes bajos de cenizas, lo cual es ventajoso para el uso de estos materiales como precursores en la preparacion de carbon activado. El area superficial fue determinada por el metodo Brunauer-Emmett-Teller (BET). El estudio morfologico y quimico se realizo mediante microscopia electronica de barrido (MEB) y espectroscopia de infrarrojo (IR-TF). El tratamiento del carbon mineral con KOH al 60% m/m produjo su activacion. Las areas superficiales de los materiales obtenidos fueron de 1386 m2/g y 655 m/g para los carbones activados procedente del manto IV y manto V, respectivamente. La activacion con KOH al 30 % m/m...
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Papers by Reinaldo Atencio