Browsing by Author "Pazo Carballo, César Alexander"
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- ItemA new approach to the mechanism for the acetalization of benzaldehyde over MOF catalysts(2020) Camu, E.; Pazo Carballo, César Alexander; Becerra, D.; Hidalgo Rosa, Y.; Paez Hernández, D.; Zárate, X.; Schott Verdugo, Eduardo Enrique; Escalona, Néstor
- ItemAdsorption properties of M-UiO-66 (M = Zr(iv); Hf(iv) or Ce(iv)) with BDC or PDC linker(Royal Society of Chemistry, 2024) González, Diego; Pazo Carballo, César Alexander; Camú Macaya, Esteban Alonso; Hidalgo-Rosa, Yoan; Zarate, Ximena; Escalona, Néstor; Schott Verdugo, EduardoThe increasing CO2 emissions and their direct impact on climate change due to the greenhouse effect are environmental issues that must be solved as soon as possible. Metal-organic frameworks (MOFs) are one class of crystalline adsorbent materials that are thought to have enormous potential in CO2 capture applications. In this research, the effect of changing the metal center between Zr(iv), Ce(iv), and Hf(iv), and the linker between BDC and PDC has been fully studied. Thus, the six UiO-66 isoreticular derivatives have been synthesized and characterized by FTIR, PXRD, TGA, and N2 adsorption. We also report the BET surface area, CO2 adsorption capacities, kinetics, and the adsorption isosteric heat (Q(st)) of the UiO-66 derivatives mentioned family. The CO2 adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, Avrami's kinetic models, and the rate-limiting step with Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The isosteric heats of CO2 adsorption using various MOFs are in the range 20-65 kJ mol(-1) observing differences in adsorption capacities between 1.15 and 4.72 mmol g(-1) at different temperatures due to the electrostatic interactions between CO2 and extra-framework metal ions. The isosteric heat of adsorption calculation in this report, which accounts for the unexpectedly high heat released from Zr-UiO-66-PDC, is finally represented as an increase in the interaction of CO2 with the PDC linker and an increase in Q(st) with defects.
- ItemCatalytic evaluation of MOF-808 with metallic centers of Zr(IV), Hf(IV) and Ce(IV) in the acetalization of benzaldehyde with methanol(Royal Society Chemistry, 2024) Arellano Valderrama, Yazmin Anay; Pazo Carballo, César Alexander; Roa, Vanesa; Hidalgo-Rosa, Yoan; Zarate, Ximena; Llanos, Jaime; Escalona Burgos, Nestor Guillermo; Schott, EduardoIn the context of climate change, it is of utmost importance to replace the use of fossil fuels as raw material in areas of industrial interest, for example, in the production of chemical inputs. In this context, a viable option is biomass, since by subjecting it to chemical processes such as pyrolysis, it is possible to obtain platform molecules that are the basis for the generation of value-added chemical products. Acetals are molecules obtained from biomass derIVatIVes, which have various applications in cosmetic chemistry, in the pharmaceutical industry as intermediates or final compounds, food additIVes, among others. Different catalysts have been used in the acetalization reaction, including MOFs, which have the advantage of being porous materials with high surface area values. The large surface area translates into a greater number of catalytically actIVe sites available for the reaction. Among the MOFs that have been used for this purpose is MOF-808, which is characterized by having a lower number of ligands attached to its metal cluster, therefore, it has a greater exposure of the metals that make up its structure. In this context, the work carried out studied the catalytic performance of MOF-808 when its Zr(IV) metal centers are replaced by Hf(IV) and Ce(IV) atoms in the acetalization reaction of benzaldehyde with methanol. The MOFs obtained by solvothermal synthesis were characterized by powder X-ray diffraction, N-2 adsorption and desorption, FT-IR spectroscopy, acid-base potentiometric titration, XPS and thermogravimetric analysis. The results of the catalysis indicate that the MOF with the best performance was MOF-808-Ce, which achieved conversions greater than 80% in a period of ten minutes. MOF-808-Ce exhibits a higher number of defects and therefore a higher availability of catalytic sites for the reaction to occur, which explains the better performance. Finally, the performance of MOF-808 in the acetalization of benzaldehyde with methanol was also supported by density functional theory (DFT) calculations.
- ItemCobalt-based core@shell catalysts for guaiacol hydro conversion: use of salicylic acid as a sacrificial modulator of the interaction between the metal phase and the silica support(2024) Aguirre Abarca, Diego Alejandro; Pazo Carballo, César Alexander; Laurenti, Dorothee; Karelovic, Alejandro; Dongil, Ana B.; Escalona Burgos, Néstor GuillermoIn this work, four cobalt-based catalysts were obtained using two routes of preparation which differed in the expected degree of interaction with the silica matrix, using salicylic acid as a sacrificial modifier during the synthesis to modulate the interaction between the cobalt phase and the silica support due to its complexing properties. The catalysts were tested for the hydroconversion of guaiacol at 300 degrees C and 5 MPa of H2, with clear differences between each procedure. It is found that the synthesis route has a deep impact on the catalytic activity, with the catalysts prepared using a one-pot route being less active and having an increased selectivity to cyclohexane. In contrast, the ones prepared using a two-step process have increased yield towards phenol and cyclohexanol under the conditions used herein. Salicylic acid increases the catalytic activity in comparison to the untreated material for both families of materials, without changing the observed selectivity between samples with the same preparation., Salicylic acid as a cobalt-based catalyst modifier enhances the activity with increased selectivity towards cyclohexanol. This is linked to changes induced by the modifier over the cobalt surface, allowing for tuning of the catalytic activity.
- ItemConversion of succinic acid over Ni and Co catalysts(2021) Rojas Guerrero, Mabel Natalia; Zarate, X.; Canales Muñoz, Roberto; Dongil, A. B.; Pazo Carballo, César Alexander; Saavedra Torres, M.; Escalona, Néstor
- ItemExtraction of guaiacol from hydrocarbons as an alternative for the upgraded bio-oil purification : Experimental and computational thermodynamic study(2020) Campos-Franzani, M. I.; Gajardo Parra, Nicolás Felipe; Pazo Carballo, César Alexander; Aravena, P.; Santiago, R.; Palomar, J.; Escalona, Néstor; Canales Muñoz, Roberto
- ItemH2 production through aqueous phase reforming of ethanol over molybdenum carbide catalysts supported on zirconium oxide(Wiley, 2024) Pavesi Contreras, Camila Andrea; Blanco, Elodie; Pazo Carballo, César Alexander; Dongil, A.B.; Escalona Burgos, Nestor GuillermoMolybdenum carbide catalysts supported on monoclinic and tetragonal zirconium oxide were studied for hydrogen production through aqueous phase reforming of ethanol. Catalysts were characterized by N2 physisorption, XRD, TPR and XPS. Results showed that 10%Mo2C/m-ZrO2 was less carburized and had a lower surface area than 10%Mo2C/t-ZrO2 and 10%MoC/t-ZrO2. Mo oxide was identified on the surface as well as two types of Mo oxycarbide and Mo oxynitride. The α crystalline phase of the carbide was more active than β phase and was ascribed to its higher relative superficial distribution. However, the α phase generated less H2 probably because there was less oxycarbide presence. 10%Mo2C/m-ZrO2 produced significantly more H2 and was stable for five consecutive reactions. This catalyst showed higher carburization degree after the reaction, which greatly enhanced the generation of H2, suggesting that carbides species improved H2 production compared to oxycarbides.
- ItemH2 production through aqueous phase reforming of ethanol over molybdenum carbide catalysts supported on zirconium oxide(2024) Pavesi Contreras, Camila Andrea; Blanco, Elodie; Pazo Carballo, César Alexander; Dongil, A.B.; Escalona Burgos, Nestor GuillermoMolybdenum carbide catalysts supported on monoclinic and tetragonal zirconium oxide were studied for hydrogen production through aqueous phase reforming of ethanol. Catalysts were characterized by N2 physisorption, XRD, TPR and XPS. Results showed that 10%Mo2C/m-ZrO2 was less carburized and had a lower surface area than 10%Mo2C/t-ZrO2 and 10%MoC/t-ZrO2. Mo oxide was identified on the surface as well as two types of Mo oxycarbide and Mo oxynitride. The α crystalline phase of the carbide was more active than β phase and was ascribed to its higher relative superficial distribution. However, the α phase generated less H2 probably because there was less oxycarbide presence. 10%Mo2C/m-ZrO2 produced significantly more H2 and was stable for five consecutive reactions. This catalyst showed higher carburization degree after the reaction, which greatly enhanced the generation of H2, suggesting that carbides species improved H2 production compared to oxycarbides.
- ItemSeparation of furfuryl alcohol from water using hydrophobic deep eutectic solvents(2023) Cea Klapp, Esteban; Arroyo Avirama, Andrés Felipe; Ormazábal Latorre, Sebastián Alejandro; Gajardo Parra, Nicolás F.; Pazo Carballo, César Alexander; Quinteros Lama, Héctor; Marzialetti, Teresita; Held, Christoph; Canales Muñoz, Roberto; Garrido, José MatíasFurfuryl alcohol (FA) is an important organic chemical feedstock that must be separated from water to upgrade it into high-value-added products. Since FA forms an azeotrope with water, liquid-liquid extraction is a suitable option for separating both compounds. This work evaluates the separation of FA from water using hydrophobic deep eutectic solvents (DES). Three DES were prepared using menthol, thymol, and octanoic acid by combining them in molar ratio as follows: thymol + octanoic acid (1:2), menthol + octanoic acid (1:2), and thymol + menthol (1:1). Experimental liquid-liquid equilibria (LLE) of ternary systems water + FA + DES measured at 313.15 K and 101.13 kPa were used to determine the distribution coefficient and selectivity values for FA when using each DES. The experimental results were compared with molecular dynamics (MD) using Martini 3 force field and modeled using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) without any adjustable binary parameters. According to the results, selectivities and distribution coefficients using hydrophobic DES have comparable values to traditional volatile organic compounds (VOCs) used to separate FA from water. In general, DES shows better distribution coefficients compared with typical organic solvents. According to the results, a good alternative would be menthol + octanoic acid (1:2) or thymol + menthol (1:1) to replace typical VOCs. MD and PC-SAFT provide accurate estimations for ternary LLE in the range of examined thermodynamic conditions, which confirms the predictive consistency of both approaches. Microscopic properties computed with MD simulations evidence a surface activity or absolute adsorption of FA in the interfacial region, which is correlated with favorable distribution coefficients and selectivities.
- ItemSíntesis de productos químicos de alto valor agregado mediante reacciones One-Pot Tándem condensación/hidrogenación sobre catalizadores del tipo MOFS(2024) Pazo Carballo, César Alexander; Escalona Burgos, Néstor Guillermo; Schott Verdugo, Eduardo; Pontificia Universidad Católica de Chile. Escuela de QuímicaLa transformación catalítica de la biomasa se presenta como una ruta eficiente y selectiva para la generación de combustibles no convencionales y de productos químicos con valor agregado. El acoplamiento C-C de moléculas derivadas de la biomasa y posterior hidrogenación se ha planteado hoy día como una reto científico y novedoso. En este trabajo de tesis doctoral se estudió la actividad catalítica de las mallas metal-orgánicas (MOFs por sus siglas en inglés) sobre la condensación aldólica del benzaldehído y acetona sobre catalizadores mono- y bimetálicos-UiO-66 de Zr(IV), Hf(IV) y Ce(IV). Todos los catalizadores fueron sintetizados por el método solvotermal y se caracterizaron utilizando diversas técnicas analíticas. La actividad catalítica de las reacciones de condensación e hidrogenación se llevaron a cabo en un reactor discontinuo. Los resultados mostraron que la mayor actividad se observó sobre el Hf-UiO-66 debido al carácter oxofílico del metal, mostrando una mayor velocidad inicial de reacción para dar benzalacetona sin desactivar sus sitios activos. Efecto contrario se observó al cambiar el enlazador orgánico (ácido-2,5-piridin tereftálico) conllevando a cambios en la actividad catalítica y selectividad. En base a estos resultados, se seleccionó al Hf-UiO-66 como base del MOF con mejor potencial para su uso como soporte de las nanopartículas de ReOx- y ReOx-Pd. La caracterización fisicoquímica puso de manifiesto que las propiedades de estos materiales tras la adición con éxito de estas especies químicas, no alteró la cristalinidad del soporte microporoso. La evaluación catalítica de estos materiales en la hidrogenación de la benzalacetona mostró que todos presentan actividad catalítica con pequeñas variaciones en la selectividad hacia la formación de productos químicos de interés industrial. Finalmente, el ReOx-Pd/UiO-66 se evaluó en la reacción one-pot tándem condensación/hidrogenación mostrando actividad para ambas reacciones partiendo de la mezcla de sustratos benzaldehído/acetona.
- ItemSulfate-modified MOF-808 as a superacid catalyst: a performance evaluation of Zr(iv) and Hf(iv) analogues in acetalization reactions(2025) Roa Gómez, Vanesa Belen; Cea, Sebastián; Pazo Carballo, César Alexander; Llanos, Jaime; Olivares, Douglas; Escalona, Néstor; Leiva Campusano, Ángel; Hidalgo-Rosa, Yoan; Zarate, Ximena; Dongil, Ana Belén; Schott Verdugo, EduardoIn this study, we report the synthesis and characterization of MOF-808-SO4-M (M = Zr(IV), Hf(IV)), derived from MOF-808-M precursors. The introduction of sulfate groups enhances the Brønsted acidity of these materials, significantly improving their catalytic performance in the benzaldehyde acetalization reaction. The materials were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), nitrogen adsorption–desorption analysis, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS), and Hammett indicator tests. Catalytic evaluation revealed that MOF-808-SO4-Zr exhibited significantly higher conversion compared to its Hf-based analogue, a difference attributed to its greater density of acid sites, as confirmed by temperature-programmed surface reaction (TPSR) analysis. These experimental results were further supported by density functional theory (DFT) calculations, which provided insights into the acidic properties and catalytic behavior of the materials.
- ItemTheoretical and Experimental Study for Cross-Coupling Aldol Condensation over Mono- and Bimetallic UiO-66 Nanocatalysts(2023) Pazo Carballo, César Alexander; Blanco, Elodie; Camu, Esteban; Leiva Campusano, Ángel; Hidalgo-Rosa, Yoan; Zarate, Ximena; Dongil, Ana Belén; Schott Verdugo, Eduardo Enrique; Escalona, NéstorMono- and bimetallic UiO-66 nanocatalysts were synthesized using the solvothermal synthesis method and evaluated in the aldol condensation reaction of benzaldehyde and acetone in a batch reactor. N2 physisorption, thermogravimetric analysis, temperature-programmed desorption of ammonia, X-ray diffraction, field-emission scanning electron microscopy–energy-dispersive X-ray, X-ray photoelectron spectroscopy, potentiometric titration, and Fourier transform infrared were used to characterize the nanocatalysts. The higher activity exhibited by the Zr/Hf-UiO-66 catalyst could be attributed to the lower orbital energy interaction with benzaldehyde, as shown by density functional theory. A synergetic effect is observed for the bimetallic UiO-66 nanocatalyst between Zr and Hf, obtaining a higher reaction rate than the monometallic nanocatalysts. Meanwhile, this antagonistic effect was shown in the bimetallic catalysts between Zr and Ce, which was less active than the monometallic UiO-66 catalyst due to free COOH generated during the synthesis. Finally, the selectivity results showed that incorporating Hf and Ce on Zr-UiO-66 favors benzalacetone formation by cross-coupling condensation of benzaldehyde and acetone at isoconversion conditions.