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Hernandez M.,National Autonomous University of Mexico | Lima E.,National Autonomous University of Mexico | Guzman A.,Laboratorio Of Investigacion En Materiales Porosos | Vera M.,Metropolitan Autonomous University | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2013

Three different amino acids were adsorbed onto the surface of microcrystalline cellulose, which caused changes in the polarity and roughness at the cellulose surface. The adsorptions partially modified the hydrogen bonding network of the cellulose structure, leading to more reactive cellulose residues that were facilely oxidised to gluconic acid by oxygen in the presence of gold zeolite supported catalysts. The conversion of cellulose and the selectivity for gluconic acid was controlled by the identity and amount of amino acid adsorbed onto the cellulose and the extra-framework cation in the zeolite support. © 2013 Elsevier B.V. Source

Guzman-Vargas A.,Laboratorio Of Investigacion En Materiales Porosos | De La Rosa-Pineda J.E.,Laboratorio Of Investigacion En Materiales Porosos | Oliver-Tolentino M.A.,UPIBI IPN | Lima E.,National Autonomous University of Mexico | And 3 more authors.
Environmental Progress and Sustainable Energy | Year: 2015

The discoloration-degradation of yellow 5 dye was achieved through the heterogeneous Fenton reaction using Cu-Y catalysts. Cu-Y materials were prepared by an aqueous ion exchange method from the NH4-Y parent zeolite. The solids are characterized by X-ray diffraction, nitrogen physisorption, EPR and, 27Al and 29Si NMR spectroscopies. Discoloration around 100% with 60% of COD removal was achieved before 90 min at 50°C using the next reaction conditions: 50 mL of colored solution containing 50 ppm of dye, 0.129 mmol of H2O2, catalyst mass/volume of solution ratio (g L-1)= 0.016 and pH = 4-5. The influence of temperature and H2O2 concentration was also studied. The discoloration kinetics were modeled using the pseudo-first order reaction. High catalytic activity was observed even after four reaction cycles, which is credited to the good stability of the Cu species and the zeolite structure. Because the Fenton reaction was favored by the acid media provided by the Cu-Y catalyst and temperature, the addition of any acid was not necessary, avoiding the generation of sludge, resulting in an eco-friendly process. © 2015 American Institute of Chemical Engineers Environ Prog. Source

Guzman-Vargas A.,Laboratorio Of Investigacion En Materiales Porosos | Oliver-Tolentino M.A.,Laboratorio Of Investigacion En Materiales Porosos | Lima E.,National Autonomous University of Mexico | Flores-Morenod J.,Metropolitan Autonomous University
Electrochimica Acta | Year: 2013

The electrocatalytic reduction of nitrite has been studied on the surface of zeolite modified electrodeusing exchanged ZSM-5 with copper (ME/Cu-ZSM-5). The process of reduction and kinetics studies were investigated through cyclic voltammetry and chronoamperometry techniques. The i-E characteristics of ME/Cu-ZSM-5 presented the faradic process associated to redox couple Cu 2+/Cu+with a ΔE = 0.064 V/SCE. On the other hand, voltammetric studies showed that in presence of nitrite, the cathodic peak current of ME/Cu-ZSM-5 increases followed by a decrease in the corresponding anodic current. This indicated thatnitrite species were reduced by a cooperative effect of the acidic properties of zeolite and copper that acts as a redox mediator being immobilized on the electrode surface via an electrocatalytic mechanism. Further experiments showed that electrocatalytic activity increases as Si/Al ratio decreases, the electro-catalytic activity was improved when the material Cu-ZSM-5 was calcined prior to electrode preparation. The values of the rate constant of the catalytic reduction of nitrite and the detection limit obtained were 5.9 × 102 cm3 mol-1s -1 and 1.4 × 10-5mol L-1, respectively. © 2013 Elsevier Ltd. All rights reserved. Source

Oliver-Tolentino M.A.,Laboratorio Of Investigacion En Materiales Porosos | Guzman-Vargas A.,Laboratorio Of Investigacion En Materiales Porosos | Arce-Estrada E.M.,ESIQIE IPN | Ramirez-Rosales D.,ESFM IPN | And 2 more authors.
Journal of Electroanalytical Chemistry | Year: 2013

In the present work the system Cu-ZSM5 was prepared by aqueous ion-exchange method from zeolite H-ZSM5. The solids were characterized by X-ray diffraction, nitrogen physisorption, temperature-programmed reduction with hydrogen (TPR-H2) and electron paramagnetic resonance (EPR). These porous materials were mixed with poly (methacrylic acid methyl ester) and methyl acrylate (MA), and immobilized on a glassy carbon electrode in order to obtain the so-called zeolite-modified electrode (ZME). The as-prepared electrodes were characterized by infrared spectroscopy and electrochemical techniques as cyclic voltammetry and chronocoulometry. The presence of copper in the zeolite was confirmed by TPR-H2. The XRD results indicate not important structural changes in the zeolite ZSM5 due to copper incorporation. The EPR spectroscopy showed that copper in Cu-ZSM5 is as isolated form of Cu 2+ ions. The results of nitrogen physisorption suggest that the Cu2+ cations are occupying the exchange sites in zeolite ZSM5. On the other hand, the IR spectroscopy revealed the presence of C O and C C groups in the mixture Cu-zeolite/polymer. The electrochemical profiles showed that reduction of Cu2+ to Cu0 occurs by two steps in presence of chloride due to stabilization of Cu+. The influence of anion in the electrolyte suggests that the redox processes Cu2+ to Cu + and Cu+ to Cu0 occurs on the zeolite-modified electrode even at nitrate- and sulfate-based solutions at the glassy carbon/zeolite interface. This stabilization is mainly associated to the interactions between Cu+ and C C group and the zeolite framework acting as "electron reservoir". Source

Oliver-Tolentino M.A.,National Polytechnic Institute of Mexico | Vazquez-Samperio J.,Laboratorio Of Investigacion En Materiales Porosos | Manzo-Robledo A.,Laboratorio Of Electroquimica Y Corrosion | Gonzalez-Huerta R.D.G.,Laboratorio Of Electroquimica Y Corrosion | And 3 more authors.
Journal of Physical Chemistry C | Year: 2014

In the present work, the hydrotalcite-like materials known as layered double hydroxides (LDHs) were synthesized. The Ni-Al and Ni-Fe materials with different Ni/Fe ratio were obtained by coprecipitation method at variable pH. The LDH structure was verified by X-ray diffraction, Fourier transform infrared, and Raman spectroscopy. No secondary extra phases were observed for any material. The electronic properties were evaluated by UV-vis spectroscopy, while the magnetic ones were followed by electron paramagnetic resonance (EPR). The results suggested that sample H/Ni-Fe2 (Ni/Fe = 2) has a ferrimagnetic behavior as a result of the combined action of NiII-OH-NiII, FeIII-OH-NiII, and FeIII-OH-FeIII pairs across the layers and ferromagnetic interactions operating between layers. Furthermore, the material H/Ni-Fe1 (Ni/Fe = 1.5) showed a combination of paramagnetic and ferromagnetic interactions which favors a superexchange interaction among metal centers through the OH bridges across the cationic sheets; the superexchange interaction enhances the electrocatalytic activity on the oxygen evolution reaction (OER) in alkaline media. On the other hand, XPS experiments showed that the H/Ni-Fe1 did not exhibit structural changes after electrochemical processes. The activity toward the OER was in the order H/Ni-Fe1 > H/Ni-Fe2 > H/Ni-Al, as was confirmed using in situ linear sweep voltammetry (LSV) coupled with mass spectrometry (differential electrochemical mass spectrometry). © 2014 American Chemical Society. Source

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