Search results for: Adriana Echavarría

Items from 1 to 13 out of 13 results

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Effect of synthesis conditions on zeolite Beta properties and its performance in vacuum gas oil hydrocracking activity

Cecilia Manrique, Alexander Guzmán, Joaquín Pérez-Pariente, Carlos Márquez-Álvarez, more

Microporous and Mesoporous Materials > 2016 > 234 > C > 347-360

The influence of synthesis conditions such as crystallization time, temperature and gel composition on crystallization of zeolite Beta was studied. Optimal temperature for the synthesis was 170 °C. A crystallization time from 24 to 36 h and 25 and 70 SiO₂/Al₂O₃ ratio in the synthesis gel were used. In this way, three pure zeolite Beta samples were obtained under hydrothermal conditions. Change of...

article

Vacuum gas-oil hydrocracking performance of Beta zeolite obtained by hydrothermal synthesis using carbon nanotubes as mesoporous template

Cecilia Manrique, Alexander Guzmán, Joaquín Pérez-Pariente, Carlos Márquez-Álvarez, more

Fuel > 2016 > 182 > C > 236-247

Beta zeolite was synthesized under hydrothermal conditions using multi-walled carbon nanotubes with an outer diameter of 8–15nm as a nanometric template. The textural, structural, and acidic properties were characterized by X-ray diffraction, thermogravimetric and differential thermal analyses, chemical analysis, N₂ physisorption, scanning and transmission electron microscopies, ²⁷Al solid-state nuclear...

article

Platinum–tin/carbon catalysts for ethanol oxidation: Influence of Sn content on the electroactivity and structural characteristics

Franz E. López-Suárez, Carlos T. Carvalho-Filho, Agustin Bueno-López, Johana Arboleda, more

International Journal of Hydrogen Energy > 2015 > 40 > 37 > 12674- 12686

Carbon-supported Pt–Sn catalysts commonly contain Pt–Sn alloy and/or Pt–Sn bimetallic systems (Sn oxides). Nevertheless, the origin of the promotion effect due to the presence of Sn in the Pt–Sn/C catalyst towards ethanol oxidation in acid media is still under debate and some contradictions. Herein, a series of Pt_x–Sn_y/C catalysts with different atomic ratios are synthesized by a deposition process...

article

Influence of the sulfidation temperature in a NiMoW catalyst derived from layered structure (NH4)Ni2OH(H2O)(MoO4)2

Sandra L. Amaya, G. Alonso-Núñez, J. Cruz-Reyes, S. Fuentes, more

Fuel > 2015 > 139 > C > 575-583

NiMoW-O mixed oxide was obtained by calcination of the ϕy layered precursor (NH₄)Ni₂OH(H₂O)(MoO₄)₂ (NiMoW-L). Unsupported catalysts were obtained from porous NiMoW-O activated ex-situ under a H₂S/H₂ (15% v/v) mixture at temperatures in the range of 673–823K. Activation temperature was crucial in catalytic activity for dibenzothiophene (DBT) hydrodesulfurization (HDS). The best temperature of activation...

article

Effect of the divalent metal and the activation temperature of NiMoW and CoMoW on the dibenzothiophene hydrodesulfurization reaction

Sandra L. Amaya, G. Alonso-Núñez, T.A. Zepeda, S. Fuentes, more

Applied Catalysis B: Environmental > 2014 > 148-149 > C > 221-230

α and β trimetallic mixed oxides were obtained from ϕ_y layered phase precursors with (NH₄)H_1.4Ni_2.3O(OH)(MoO₄)_1.4(WO₄)_0.6 and (NH₄)H₂Co₂O(OH)(MoO₄)_1.6(WO₄)_0.4 formulas by calcination at temperatures as low as 673K. At this temperature, phase transition was confirmed by (TGA and DSC) thermal analysis. Oxides were activated ex-situ under a H₂S/H₂ (15%, v/v) mixture at two temperatures: 673K and 798K,...

article

V–Mg–Al catalyst from hydrotalcite for the oxidative dehydrogenation of propane

Julian Antonio Valverde, Adriana Echavarría, Jean-Guillaume Eon, Arnaldo C. Faro, more

Reaction Kinetics, Mechanisms and Catalysis > 2014 > 111 > 2 > 679-696

Mixed oxides obtained by the calcination of hydrotalcite precursors intercalated with 30, 70 and 100 % of decavanadate (theoretical percentages) were used as catalysts for the oxidative dehydrogenation of propane. Propene selectivity values up to 80 % were reached under conditions of deficiency and excess of oxygen at 400 °C with the catalyst derived from the 70 % vanadium-intercalated precursor....

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Decavanadate-intercalated Ni–Al hydrotalcites as precursors of mixed oxides for the oxidative dehydrogenation of propane

Julian Antonio Valverde, Adriana Echavarría, Maria Filipa Ribeiro, Luz Amparo Palacio, more

Catalysis Today > 2012 > 192 > 1 > 36-43

Two nickel–aluminum hydrotalcite type precursors were synthesized with molar ratio Ni/Al=3, using hydroxyl and carbonate as compensation anions. These precursors were intercalated by 30% (theoretical) decavanadate anion. The catalysts were obtained after calcination at 550°C and their performance was evaluated in propane oxidative dehydrogenation at 400°C using space velocities of 100, 150, 200 and...

article

Total oxidation of toluene over calcined trimetallic hydrotalcites type catalysts

Luz A. Palacio, Juliana Velásquez, Adriana Echavarría, Arnaldo Faro, more

Journal of Hazardous Materials > 2010 > 177 > 1-3 > 407-413

Two trimetallic ZnCuAl and MnCuAl hydrotalcites have been successfully synthesized by a co-precipitation method. The manganese based material was identified as a new hydrotalcite phase. Both lamellar precursors were calcined at 450 and 600°C and the resulting catalysts were tested on reaction of total oxidation of toluene. The solids were characterized by X-ray diffraction, thermal analysis, atomic...

article

Limonene epoxidation by molecular sieves zincophosphates and zincochromates

Alejandra M. Santa A., Juan Camilo Vergara G., Luz Amparo Palacio S., Adriana Echavarría I.

Catalysis Today > 2008 > 133-135 > Complete > 80-86

Conversion of limonene in its derivatives has been an interesting process due to its high value for cosmetic, pharmaceutical and food industries. The use of molecular sieves based on transition metals in heterogeneous catalysis, and specifically in oxidative processes, has shown good results. Oxidation of limonene has been studied using zinc based catalyst, hydrogen peroxide as oxidative agent and...

article

Cu, Mn and Co molybdates derived from novel precursors catalyze the oxidative dehydrogenation of propane

Luz Amparo Palacio, Adriana Echavarría, Ligia Sierra, Eduardo A. Lombardo

Catalysis Today > 2005 > 107-108 > Complete > 338-345

The activity of various transition metal molybdates in the oxidative dehydrogenation of propane was tested. A series of nine molybdates of Zn, Cu, Co, Fe and Mn were synthesized by either a hydrothermal or a precursor method. The catalysts were characterized by X-ray diffraction (XRD), atomic absorption (AA), laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM). The reaction was...

article

Synthesis, characterization and structural data of an ammonium manganomolybdate type ΦX

Luz Amparo Palacio, Adriana Echavarría, Dora Ángela Hoyos, Carlos Saldarriaga

Solid State Sciences > 2005 > 7 > 9 > 1043-1048

NH ₄ [Mn ₂ Mo ₂ O ₈ (OH)(H ₂ O)] was prepared at room temperature in alkaline media from solutions of manganese and molybdenum. The solid was characterized by means of X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Atomic Absorption (AA) and CHN Analysis. Besides, the IR frequencies of the vibrational modes...

article

Catalytic performance and stability of isomorphic molybdates used for the oxidative dehydrogenation of propane

Luz A. Palacio, Adriana Echavarría, Eduardo A Lombardo

Reaction Kinetics, Mechanisms and Catalysis > 2005 > 85 > 1 > 175-182

SummaryCo and Mn molybdates were used for this reaction. After use, their structure remained the same. However, only the Co molybdate maintained the surface area and the catalytic properties after 48 h on stream.

article

Synthesis and structure of a porous zinc vanadate, Zn3(VO4)2·3H2O

Dora Angela Hoyos, Adriana Echavarría, Carlos Saldarriaga

Journal of Materials Science > 2001 > 36 > 22 > 5515-5518

A zinc vanadate with the formula Zn₃(VO₄)₂·3H₂O was synthesized by hydrothermal reaction of a gel of composition [(CH₃CO₂)₂Zn·2H₂O] : 0.5V₂O₅: 0.4 [1,3-diaminepropane] : 1.5 NaOH : 114 H₂O, held at 170°C for 24 hours. The structure was determined ab initio by means of the EXPO direct methods program and refined with GSAS. The pale yellow solid crystallizes in the hexagonal space group P-6 with a=...

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