Examinando por Autor "Torres, Cecilia C."
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Ítem Catalytic pyrolysis of used tires on noble-metal-based catalysts to obtain high-value chemicals: Reaction pathways(Elsevier B.V., 2022-07-01) Osorio Vargas, Paula; Campos, Cristian H.; Torres, Cecilia C.; Herrera, Carla; Shanmugaraj, Krishnamoorthy; Bustamante, Tatiana M.; Diaz de Leon, J.N.; Medina, Francisco; Arteaga Pérez, Luis E.A systematic study on the use of noble metals (Pd, Pt, Au) supported on titanate nanotubes (NT-Ti) for selectively producing BTX and p-cymene from waste tire pyrolysis is provided here. All the materials were characterized for chemical, textural and structural properties using a range of analytical techniques. The M/NT-Ti (M: Pd, Pt, or Au) catalysts exhibit low nanoparticle sizes (1.8 support > non-catalyst. The Py-GC/MS suggest that the catalysts participate in the secondary reactions of dealkylation, dehydrogenation, isomerization, aromatization, and cyclization leading to a higher formation of BTX than the uncatalyzed reaction. Finally, a comprehensive reaction pathway describing the catalytic pyrolysis of WT over Pd/NT-Ti was proposed by studying the catalytic pyrolysis of individual polymers constituting the waste tires, and D,L-Limonene. © 2021 Elsevier B.V.Ítem Cobalt Nanoparticles Supported on TiO2 for Highly Selective Formation of N-Benzylideneanilines from Nitroarenes and Benzaldehyde via Reductive Imination Reaction(MDPI, 2024-04-04) González-Vera, Daniela; Bustamante, Tatiana M.; Díaz de León, J. Noé; Torres, Cecilia C.; Campos, Cristian H.The search for active, inexpensive, and stable heterogeneous catalysts to produce desired imines in fine chemistry presents an ongoing challenge for both academia and industry. This work reports the utilization of Co nanoparticles supported on TiO2 derived from the H2-assisted reduction of the perovskite-type mixed oxide CoTiO3. The entire preparation process is operationally simple and straightforward, enabling scalability for practical applications. The resulting catalyst comprises metallic cobalt nanoparticles responsible for the hydrogenation process, whereas the TiOx thin layer surrounding the cobalt promotes the adsorption of C=O, thereby enhancing the formation of desired products. Notably, at lower temperatures, the reaction yields the target imine product. Our study demonstrates a synergistic effect between nitrobenzene and benzaldehyde in the presence of a Co-TiOx interface, which reduces the apparent activation energy for the hydrogenation of the-NO2 group. Furthermore, under moderate reaction conditions, the catalytic system offers applicability to various nitrobenzene compounds substituted at the 4-position and benzaldehyde, resulting in high yields of the corresponding imines with electron-density-donating substituent groups. Finally, the catalyst exhibits facile separation for subsequent reuse, displaying moderate stability with minimal selectivity for the desired product.Ítem Liquid Phase Hydrogenation of Pharmaceutical Interest Nitroarenes over Gold-Supported Alumina Nanowires Catalysts(MDPI AG, 2020-02) Shanmugaraj, Krishnamoorthy; Bustamante, Tatiana M.; Campos, Cristian H.; Torres, Cecilia C.In this work, Au nanoparticles, supported in Al2O3 nanowires (ANW) modified with (3-aminopropyl)trimethoxysilane were synthetized, for their use as catalysts in the hydrogenation reaction of 4-(2-fluoro-4-nitrophenyl)-morpholine and 4-(4-nitrophenyl)morpholin-3-one. ANW was obtained by hydrothermal techniques and the metal was incorporated by the reduction of the precursor with NaBH4 posterior to superficial modification. The catalysts were prepared at different metal loadings and were characterized by different techniques. The characterization revealed structured materials in the form of nanowires and a successful superficial modification. All catalysts show that Au is in a reduced state and the shape of the nanoparticles is spherical, with high metal dispersion and size distributions from 3.7 to 4.6 nm. The different systems supported in modified-ANW were active and selective in the hydrogenation reaction of both substrates, finding for all catalytic systems a selectivity of almost 100% to the aromatic amine. Catalytic data showed pseudo first-order kinetics with respect to the substrate for all experimental conditions used in this work. The solvent plays an important role in the activity and selectivity of the catalyst, where the highest efficiency and operational stability was achieved when ethanol was used as the solventÍtem PAMAM-grafted TiO2 nanotubes as novel versatile materials for drug delivery applications(Elsevier Ltd, 2016-08) Torres, Cecilia C.; Campos, Cristian H.; Diáz, Carola; Jiménez, Verónica A.; Vidal, Felipe; Guzmán, Leonardo; Alderete, Joel B.PAMAM-grafted TiO2 nanotubes (PAMAM-TiO2NT) have been synthesized and evaluated as new drug nanocarriers, using curcumin (CUR), methotrexate (MTX), and silibinin (SIL) as model therapeutic compounds. TiO2NT were surface-modified using a silane coupling agent and subsequently conjugated with PAMAM dendrimer of the third generation. The characterization of PAMAM-TiO2NT nanomaterials was performed by FTIR, TEM, N2 adsorption-desorption isotherms, XRD, and TGA techniques, which accounted for a 2.6 wt.% of PAMAM grafting in the prepared materials. The drug loading capacity, drug release properties, and cytotoxicity of PAMAM-TiO2NT showed a significant improvement compared to pristine TiO2NT, thus revealing the promising properties of these new materials for drug delivery purposes. © 2016 Elsevier B.V. All rights reserved.Ítem TiO2 nanorods doped with g-C3N4 – Polyethylene composite coating for self-cleaning applications(Elsevier Ltd, 2022-09-01) Osorio Vargas, Paula; Pais Ospina, Daniel; Marin Silva, Diego A.; Pinotti, Adriana; Damonte, Laura; Cánneva, Antonela; Donadelli, Jorge A.; Pereira da Costa, Luiz; Pizzio, Luis R.; Torres, Cecilia C.; Campos, Cristian H.; Rengifo Herrera, Julián A.Visible-light-absorbing graphitic carbon nitride–TiO2 nanorod nanomaterials (g-C3N4@TiO2NR) were successfully immobilized using a one-step UVA-induced photocatalytic procedure on commercially obtained flexible low-density polyethylene (LDPE) films. Self-cleaning properties were evaluated in solid–liquid and solid–gas phases using malachite green as a model molecule under UV-A and visible light irradiation. For comparison purpose, LDPE films containing P25 TiO2 nanoparticles was prepared using the same synthetic strategy (P25/LDPE). Among the fabricated films, the g-C3N4@TiO2NR/LDPE films exhibited the highest photocatalytic activity both in solid–liquid and solid–gas phases after 120 min of visible light irradiation (λ > 455 nm) removing efficiently malachite green stains probably due to the attack of photoinduced reactive oxygen species (ROS) such as singlet oxygen (1O2), hydroxyl radical (•OH) and superoxide anion radical (O2−•). Furthermore, the g-C3N4@TiO2NR/LDPE films retained their visible-light-photoinduced photocatalytic properties after four reuse cycles. The g-C3N4@TiO2NR/LDPE films also exhibited significant visible-light-photoinduced hydrophilicity. The high visible-light-photoinduced photocatalytic capacity of g-C3N4@TiO2NR/LDPE films was found to be related to the textural and electronic properties, superior visible-light absorption, and surface roughness of the films. © 2022 Elsevier B.V.