Browsing by Author "Escalona, Nestor"

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    A new porous organic polymer containing Troger's base units: Evaluation of the catalytic activity in Knoevenagel condensation reaction
    (2021) Rodriguez-Gonzalez, Fidel E.; Niebla, Vladimir; Velazquez-Tundidor, M. V.; Tagle, Luis H.; Martin-Trasanco, Rudy; Coll, Deysma; Ortiz, Pablo A.; Escalona, Nestor; Perez, Edwin; Jessop, Ignacio A.; Terraza, Claudio A.; Tundidor-Camba, Alain
    The classic Tro center dot ger's base polymerization of a diamine and dimethoxymethane with trifluoroacetic acid as catalyst generated a Tro center dot ger's base-type polymer (TBP), which exhibited the absolute insolubility in a variety of organic solvents because of its highly aggregated model. A new porous organic polymer was obtained by a simple Tro center dot ger's base polymerization reaction between a diamine and formaldehyde in the form of acetal in the presence of trifluoroacetic acid as catalyst. Tro center dot ger's base-type polymer (TBP) resulted insoluble in a wide range of organic solvents due to its rigid and aromatic structure. TBP was characterized spectroscopically (FT-IR), thermally and morphologically. As result, a thermostable and amorphous polymer bearing pores ranging between 50 and 300 nm and macro-voids of up to 12 mu m was obtained. Due to the insolubility of the TBP, it was tested as a metal-free heterogeneous catalyst in the Knoevenagel condensation reaction, showing a high efficiency. For this, the optimal catalyst load, reaction time and reuse of the catalyst were studied using benzaldehyde and malononitrile as substrates. Furthermore, aldehydes with variable chain sizes and ethyl cyanoacetate replacing malononitrile were tested as substrate with a high percent of conversion (97-99%).
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    Adsorption of low molecular weight food relevant polyphenols on cross-linked agarose gel
    (2022) Raquel Rivera-Tovar, Pamela; Perez-Manriquez, Javiera; Salome Mariotti-Celis, Maria; Escalona, Nestor; Perez Correa, Jose Ricardo
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    Aqueous Phase Hydrogenation of 4-(2-Furyl)-3-buten-2-one over Different Re Phases
    (2024) Diaz, Claudio Ignacio C.; Araya-Lopez, Claudio; Dongil, A. B.; Escalona, Nestor
    4-(2-furyl)-3-buten-2-one (FAc) is obtained by aldol condensation of furfural and acetone and has been used in hydrodeoxygenation reactions to obtain fuel products using noble metal catalysts. The hydrogenation of FAc in the aqueous phase using metallic- and Re oxide-supported catalysts on graphite was studied, within a temperature range of 200-240 degrees C, in a batch reactor over a 6 h reaction period. The catalysts were characterized using N2 adsorption-desorption, TPR-H2, TPD-NH3, XRD, and XPS analyses. Catalytic reactions revealed that metallic rhenium and rhenium oxide-supported catalysts are active for the hydrogenation and Piancatelli rearrangement of FAc. Notably, metallic rhenium exhibited a fourfold higher initial rate than rhenium oxide, which was attributed to the higher dispersion of Re in the Re/G catalyst over graphite. Re/G and ReOx/G catalysts tended to rearrange and hydrogenate FAc to 2-(2-oxopropyl)cyclopenta-1-one in water.
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    CONVERSION OF QUINOLINE ON ReS2 CATALYSTS: EFFECT OF THE SUPPORT AND THE ADDITION OF CS2 IN THE FEED
    (2017) Bassi, Romina; Camu, Esteban; Villarroel, Mirza; Gil-Llambias, Fco. Javier; Garcia-Fierro, J. L.; Escalona, Nestor; Baeza, Patricio
    The effect of supports and the addition of CS2 in the feed were studied on hydrodenitrogenation of Quinoline in a continuous flow reactor over ReS2/support catalysts at 300, 325 and 350 degrees C and 3MPa of H-2. The ReS2 supported on TiO2 displayed the highest activity followed by ZrO2, gamma-Al2O3 and SiO2 supports. The activity trend was correlated with the Re dispersion on the support. The effect of the addition of CS2 was increased activity until 2.5 v/v % content. At higher CS2 content the activity decreased due to competitive adsorption between CS2 and Quinoline on the active sites.
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    COSMO-RS-based solvent screening and experimental analysis for recovering added-value chemicals from the bio-oil aqueous phase
    (ELSEVIER, 2025) Lorenzo Llanes, Junior; Palomar, Jose; Escalona, Nestor; Canales, Roberto I.
    Bio-oil's aqueous phase (BAP) has received particular interest for recovering value-added chemicals. To this end, liquid-liquid extraction (LLE) has proven its suitability for bio-oil fractionation and product recovery. The present work aimed to assess greener solvents (e.g., bio-based and terpene-based) for recovering acetic acid and acetol as model compounds of the BAP via physical and reactive LLE. A solvent screening (>2000 compounds) based on the distribution coefficient (K-d) of each solute in the solvent/water biphasic system estimated by COSMO-RS was used. Then, the solvents' environmental, safety, and human health impacts were assessed. The selected candidates were used to validate the COSMO-RS predictions through LLE measurements. In the reactive LLE, the selected extracting solvents were mixed with trioctylamine (TOA) or tributyl phosphate (TBP) used as the reactive extractants. Finally, the temperature and extractant fraction effects were assessed in terms of the K-d for the best diluent + extractant pairs. For acetic acid, 2-methyltetrahydrofuran (K-d = 1.8) outperformed the rest of the solvents during the physical extraction, whereas for acetol, 2-methyl-2-butanol (K-d = 0.44) was the solvent with the best performance. Moreover, attractive K-d values were obtained for acetic acid (K-d = 0.91) and acetol (K-d = 0.37) using 2-phenylethanol. In the reactive LLE, TOA-based extractants improved the acetic acid K-d up to 10 times compared to the physical extraction, with no improvement on acetol. For TBP-based extractants, no clear improvements were observed. Acetic acid selectivity was maximized at 293 K, and a TOA mass fraction between 40 and 50 % for all the diluents.
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    CuII- and CoII-Based MOFs: {[La2Cu3(μ-H2O)(ODA)6(H2O)3]•3H2O}nand {[La2Co3(ODA)6(H2O)6]•12H2O}n. The Relevance of Physicochemical Properties on the Catalytic Aerobic Oxidation of Cyclohexene
    (2020) Santibanez, Luis; Escalona, Nestor; Torres, Julia; Kremer, Carlos; Cancino, Patricio; Spodine, Evgenia
    The aerobic oxidation of cyclohexene was done using the heterometallic metal organic frameworks (MOFs) {[La2Cu3(mu-H2O)(ODA)(6)(H2O)(3)].3H(2)O}(n)(LaCuODA)) (1) and {[La2Co3(ODA)(6)(H2O)(6)].12H(2)O}(n)(LaCoODA) (2) as catalysts, in solvent free conditions (ODA, oxydiacetic acid). After 24 h of reaction, the catalytic system showed that LaCoODA had a better catalytic performance than that of LaCuODA (conversion 85% and 67%). The structures of both catalysts were very similar, showing channels running along thecaxis. The physicochemical properties of both MOFs were determined to understand the catalytic performance. The Langmuir surface area of LaCoODA was shown to be greater than that of LaCuODA, while the acid strength and acid sites were greater for LaCuODA. On the other hand, the redox potential of the active sites was related to Co-II/Co(III)in LaCoODA and Cu-II/Cu(I)in LaCuODA. Therefore, it is concluded that the Langmuir surface area and the redox potentials were more important than the acid strength and acid sites of the studied MOFs, in terms of the referred catalytic performance. Finally, the reaction conditions were also shown to play an important role in the catalytic performance of the studied systems. Especially, the type of oxidant and the way to supply it to the reaction medium influenced the catalytic results.
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    Degradation of dairy wastewater using sustainable nanotechnology composed of a-Fe2O3/TiO2 rod-shaped material and photocatalytic process: a complementary treatment approach for industrial wastewater
    (2024) Espinoza-Villalobos, Nicole; Rojas, Susana; Barrientos, Lorena; Salazar-Gonzalez, Ricardo; Luna, Damari; Flores, Caetano; Escalona, Nestor
    BACKGROUND: High water consumption and the toxic pollutants found in industrial wastewater are key challenges in achieving a more sustainable development. In this sense, it is crucial to develop sustainable ways to reduce the organic pollutants found in wastewater and to promote its reuse.
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    Effect of Pyrolysis Temperature on Copper Aqueous Removal Capability of Biochar Derived from the Kelp Macrocystis pyrifera
    (MDPI, 2021) Araya, Matias; Rivas, Jorge; Sepulveda, Graciela; Espinoza Gonzalez, Camila; Lira, Sebastian; Meynard, Andres; Blanco, Elodie; Escalona, Nestor; Ginocchio, Rosanna; Garrido Ramirez, Elizabeth; Contreras Porcia, Loretto
    Seaweed biochar is an efficient alternative bioadsorbent for Cu2+ removal due to its low cost and heavy metal removal capacity. Using the slow pyrolysis process, we produced biochars from Macrocystis pyrifera at 300 (BC300), 450 (BC450), and 600 & DEG;C (BC600). The physicochemical and structural properties of the biochar samples improved with increasing pyrolysis temperature from 300 to 450 & DEG;C, whereas no significant differences were observed with further increases in temperature to 600 & DEG;C. The yield ranged between 49% and 62% and had a high ash content (57.5-71.1%). BC450 and BC600 presented the highest surface areas and higher porosities. The FTIR spectra indicated that an increase of temperature decreased the acidic functional groups due to depolymerization and the dehydration processes, increasing the aromatic structures and the presence of calcium carbonate. The fittings of the kinetic models were different for the BCs: for the BC450 and BC600 samples, the Cu2+ adsorption was well-represented by a pseudo-first-order model; for BC300, a better fit was obtained with the pseudo-second-order model. The rate-limiting step of Cu2+ adsorption on BCs was represented by both models, liquid film diffusion and intraparticle diffusion, with surface diffusion being more important in BC300 and BC600, and intraparticle diffusion in BC450, in agreement with the pore size of the biochar samples. The adsorption isotherms of all BCs showed Langmuir behavior, representative of a chemisorption process, which was corroborated by the energy adsorption values determined by the D-R model. The maximum monolayer Cu2+ adsorption capacities were 93.55 and 58.0 mg g(-1) for BC600 and BC450, respectively, whereas BC450 presented the highest affinity. Other mechanisms involved in controlling heavy metal removal from aqueous suspensions using these seaweed biochars remain to be explored. We conclude that BC450 and BC600 from M. pyrifera are the most efficient adsorbents for Cu2+ aqueous removal and are thus an appropriate alternative for bioremediation.
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    Electrodes based on zeolites modified with cobalt and/or molybdenum for pesticide degradation: part II-2,4,6-trichlorophenol degradation
    (2021) Castro, Jorge; Fernandez, Francisco; Olivares, Felipe; Berrios, Cristhian; Garrido-Ramirez, Elizabeth; Blanco, Elodie; Escalona, Nestor; Aspee, Alexis; Barrias, Pablo; Soledad Ureta-Zanartu, M.
    2,4,6-trichlorophenol (TCP) is a persistent pollutant introduced in water by industrial processes and pesticides. We have studied the electrooxidation of TCP on glassy carbon (GC) electrodes drop-coated with a suspension containing Mo- and/or Co-modified zeolite, graphite, and Nafion (R) perfluorinated ion-exchange resin in distilled water. Three zeolites, Linde type A (ZA), Faujasite (ZY) and MFI (ZSM-5), of different hydrophilic/hydrophobic character, were modified with molybdenum and/or cobalt by the wet impregnation method and characterized by Fourier-transform infrared spectroscopy with attenuated total reflection and temperature programmed reduction. The electrochemical study included cyclic voltammetry, electrochemical impedance spectroscopy, and electrolysis at controlled potential. High performance liquid chromatography and mass spectrometry allowed detecting the following reaction products: 2,6-dichloro-1,4-benzoquinone, 2,6-dichloro-1,4-hydroquinone, 3,5-dichloro-2-hydroxy-1,4-benzoquinone, and malic, maleic, picric, and acetic acids. A maximum degradation of about 90% was reached after 4 h of electrolysis at 0.83 V vs Ag/AgCl/KCl 3 M, using a GC/graphite-ZSM5(Mo) electrode. The electrodes modified with Mo, and especially that with ZSM5, the most hydrophobic zeolite, were active for the degradation of TCP. We conclude that the main role of the Mo species is to catalyze the hydrogen peroxide decomposition yielding reactive singlet oxygen, as evidenced by the pink color of 3,5-dichloro-2-hydroxy-1,4-benzoquinoneand confirmed by mass spectrometry.
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    Influence of ex-situ annealing on the friction and wear performance of multi-layer Ti3C2Tx coatings
    (2024) Boidi, Guido; Zambrano, Dario; Broens, Martin I.; Moncada, Daniel; Varga, Markus; Ripoll, Manel Rodriguez; Badisch, Ewald; Escalona, Nestor; Gruetzmacher, Philipp G.; Gachot, Carsten; Rosenkranz, Andreas
    2D materials have gained momentum for lubrication purposes, which holds specifically true under more severe conditions such as elevated temperatures. Among them, MXenes are a new family of 2D materials, which offer an excellent electrical conductivity, tunable surface functionality, and outstanding mechanical properties. In the past five years, MXenes have been significantly studied for tribological applications due to their ability to form easy-to-shear tribofilms with excellent wear resistance. However, little is known regarding MXenes' tribological performance at elevated temperatures. Therefore, we systematically studied the tribological performance of spray-coated Ti3C2Tx coatings after thermal annealing at temperatures between 50 and 400 degrees C using linear-reciprocating ball-on-disc tribometry. Advanced materials characterization demonstrated that thermal annealing of MXenes results in the release of superficial and intercalated water, the removal of surface terminations, and the oxidation of Ti3C2Tx to TiO2. Consequently, the tribological performance of the annealed coatings deteriorated, which is particularly pronounced for thin coatings, high normal loads, and elevated annealing temperatures. Our results provide insight into the thermal stability of Ti3C2Tx coatings as well as the implications on their tribological performance.
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    Modification of a commercial activated carbon with nitrogen and boron: Hydrogen storage application
    (2023) Morande, Arturo; Lillo, Patricio; Blanco, Elodie; Pazo, Cesar; Belen Dongil, Ana; Zarate, Ximena; Saavedra-Torres, Mario; Schott, Eduardo; Canales, Roberto; Videla, Alvaro; Escalona, Nestor
    The present study evaluates the effect of heteroatom doping (N and B) and thermal treatment modification of activated carbon, in different sequences over hydrogen storage capacity. All the materials were characterized by N2-physisorption, XRD, TPD, and XPS. H2 adsorption was measured at-196 degrees C and correlated with physico-chemical properties, while a density-functional theory model was employed to analyze the hydrogen adsorp-tion. Results have shown that there is an effect of the modification order on the storage capacity, which was related to increments of the specific surface area or the nature of the functional groups. An optimum nitrogen doping temperature was detected at 500 degrees C and was associated with the presence of pyridone groups. This sample had the highest hydrogen capacity ca. 2.34 % at 0.93 bar. Such value was extrapolated to 7.86 wt% at 30 bar using the Dubinin-Astakhov adsorption model, making it a promising material for hydrogen storage.
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    Nanostructured Fe-N-C pyrolyzed catalyst for the H2O2 electrochemical sensing
    (2021) Candia-Onfray, Christian; Bollo, Soledad; Yanez, Claudia; Escalona, Nestor; Marco, Jose F.; Menendez, Nieves; Salazar, Ricardo; Recio, F. Javier
    Fe-N-C pyrolyzed materials have been proposed as substitutes of the noble-based catalyst for energy conversion reactions. However, their use as electrochemical sensors has not been deeply explored. In the present work, different Fe-N-C pyrolyzed catalysts were synthesized for the amperometric sensing of the H2O2 reduction in neutral media. The catalysts were characterized by BET, TEM, FESEM, XPS, Mossbauer spectroscopy, and cyclic voltammetry. The catalysts present an N-doped graphitic matrix with a macroporous structure and mesoporous contribution. Different amounts of N-pyridinic, N-pyrrolic, N-graphitic, N-oxides, and FeN4 sites have been detected on the catalysts. Among the different active sites present in the catalysts, the FeN4 structure is proposed as the most catalytic active site for the hydrogen peroxide reduction reaction (HPRR). Under optimal conditions (0.61 V vs. NHE, 0.00 V vs. Ag/AgCl), the materials show a lineal amperometric response in the range of 0.08 and 14 mu M, with a sensitivity of 31.3 mu A mu M-1 cm(-2), and a detection and quantification limits of 0.25 mu M and 0.75 mu M respectively. The amperometric results indicate that the best performance is reached when increasing the amount of FeN4 active sites, and the redox potential of the FeN4 species becomes more positive. The Fe-N-C catalyst stands out for the more positive working potential than other materials proposed in the literature. (C) 2021 Elsevier Ltd. All rights reserved.
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    Novel protein stabilization in white wine: A study on thermally treated zirconia-alumina composites
    (2024) Silva-Barbieri, Daniela; Escalona, Nestor; Salazar, Fernando N.; Lopez, Francisco; Perez-Correa, Jose R.
    A major concern for wineries is haze formation in white wines due to protein instability. Despite its prevalent use, the conventional bentonite method has shortcomings, including potential alteration of color and aroma, slow processing times, and notable wine wastage. Zirconium oxide (ZrO2) effectively removes proteins without affecting wine characteristics. However, producing cost-effective ZrO2 materials with efficient protein removal capabilities poses a significant challenge. This research aims to assess the viability of designing a porous material impregnated with zirconia to remove turbidity-causing proteins effectively. For this purpose, the support material alone (Al2O3) and the zirconia-impregnated support (ZrO2/Al2O3) were subjected to different calcination temperatures. It was observed that high-temperature treatments (750 degrees C) enhanced wine stability and protein adsorption capacity. The optimal adsorbent achieved a notable reduction in turbidity, decreasing the Delta NTU from 42 to 18, alongside a significant 44 % reduction in the total protein content, particularly affecting proteins in the molecular weight range of 10 to 70 kDa. This result is attributed to modifying the textural properties of ZrO2/ Al2O3, characterized by the reduction of acidic sites, augmented pore diameters from 4.81 to 7.74 nm, and the emergence of zirconia clusters across the surface of the porous support. In summary, this study presents the first application of zirconia on the alumina support surface for protein stabilization in white wine. Combining ZrO2/ Al2O3 and a high-temperature treatment emerges as a promising, cost-efficient, and environmentally sustainable strategy for protein removal in white wine.
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    Polymers of intrinsic microporosity containing aryl-phthalimide moieties: synthesis, modeling, and membrane gas transport properties
    (2023) Rodriguez-Gonzalez, Fidel E.; Soto, Cenit; Palacio, Laura; Montero-Alejo, Ana L.; Escalona, Nestor; Schott, Eduardo; Comesana-Gandara, Bibiana; Terraza, Claudio A.; Tundidor-Camba, Alain
    High-performance polymers for membrane gas separation require the careful design of the structure-porous relationship. In this work, five phthalimide-based polymers of intrinsic microporosity (PIMs) were obtained via the double nucleophilic aromatic substitution with the commercially available 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane (TTSBI) monomer. The phthalimide monomers were synthesized considering different sizes and positions of the alkyl-substituents to evaluate their influence on the physical properties of the polymers and their potential use as gas separation membranes. Four polymers were soluble in the low-boiling solvents chloroform and tetrahydrofuran, facilitating the casting of self-standing films to evaluate their gas separation properties. The thermally stable membranes showed 5% weight lost between 537 ? and 549 ?. As powders, these four polymers showed apparent BET surface areas ranging from 434 to 661 m(2) g(-1). The experimental BET surface areas correlated with those obtained by molecular simulation models of the synthesized polymers. A linear function is proposed as a tool to predict, with a known uncertainty, the surface area values of this type of polymer from the corresponding computational models. As a trend, increasing the volume of the ortho-substituent in the aryl-phthalimide group increases the permeability of the membranes, reaching generally better performances than Matrimid (R) and close to those of PIM-1, considering their place on the Robeson diagrams of the O-2/N-2, CO2/CH4 and CO2/N-2 gas pairs. Aging studies between 63 and 122 days showed a decrease in permeability, accompanied by the typical increase in selectivity that tends to move the data parallel to the upper Robeson limits.
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    Reduced alkaline earth metal (Ca, Sr) substituted LaCoO3 catalysts for succinic acid conversion
    (2022) Rojas, Mabel; Bernales, Gabriel; Dongil, Ana Belen; Pecchi, Gina; Escalona, Nestor
    The effect of partial substitution of La by Ca and Sr in the catalytic activity of lanthanum cobaltite (LaCoO3) was studied. Two series of La1-xCaxCoO3 and La1-xSrxCoO3 (x = 0, 0.2, and 0.4) reduced perovskites were prepared, characterized and evaluated in the succinic acid conversion at 200 degrees C and 6 MPa. The characterization results showed a larger Ca substitution in the La1-xCaxCoO3 series, whereas carbonates as segregated phases up to x = 0.2 of Sr were obtained in the La1-xSrxCoO3 series. In the Sr substituted perovskites, the oxidation of Co3+ to Co4+ neutralizes the electronic instability, whereas in the Ca substituted perovskites the presence of Ca2+ generates oxygen vacancies. The succinic acid conversion forms mainly succinic anhydride and 2-hydroxy-tetrahydrofuran by dehydration and hydrogenation processes. The highest initial rate of the reduced LaCoO3 was attributed to the smallest Co crystal size with no segregated phases, compared to substituted catalysts.
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    Removal of Ibuprofen and Diclofenac in Batch Nitrifying Reactors: Effect of Natural Zeolite on the Process
    (2023) Escobar, Jenny; Hernandez, Leslie; Gonzalez, Jorge Leiva; Salazar-Gonzalez, Ricardo; Calzadilla, Wendy; Guerrero, Lorna; Escalona, Nestor; Huilinir, Cesar
    Ibuprofen (IBP) and diclofenac (DFC) are two of the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs) to treat inflammation and pain. However, they can impact the environment if not treated adequately before discharge into waterways. Biodegradation through the nitrification process is an alternative to reducing the concentration of these micropollutants (MPs) in wastewater. Thus, this work aimed to evaluate the effect of natural zeolite on IBP and DFC removal in a nitrifying batch reactor. Mini-reactors were set up with 90 mL of inoculum and 110 mL of synthetic wastewater with a concentration of 25 mg total ammonia nitrogen TAN/L, at 25 & DEG;C and 1 vvm (volume of air/volume liquid & BULL;min) of aeration. Two conditions were tested: high concentrations (IBP = 700 & mu;g/L, DFC = 100 & mu;g/L) and low concentrations (IBP = 30 & mu;g/L, DFC = 20 & mu;g/L). The research used a concentration of 5 g/L of the natural zeolite. Results indicated that the zeolite negatively affected the nitrification rate. At high MPs concentration, the natural zeolite negatively affects the removal of IBP and DFC, where biodegradation and sorption are the mechanisms that eliminate both NSAIDs. Conversely, at low DFC and IBP concentrations, the natural zeolite improves the removal of IBP and DFC, wherein biodegradation is the primary removal mechanism.
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    Role of β-CD Macromolecule Anchored to α-Fe2O3/TiO2 on the Selectivity and Partial Oxidation of Guaiacol to Add-Value Products
    (2021) Espinoza-Villalobos, Nicole ; Rojas, Susana ; Salazar, Ricardo Andrés ; Contreras, David ; Escalona, Nestor ; Vergara, Elizabeth ; Laguna-Bercero, Miguel Angel ; Mendizabal, Fernando ; Barrientos, Lorena
    Biomass is a naturally abundant, sustainable, and clean resource, which has the potential to replace fossil feedstock for sustainable production of high add-value chemicals. However, an efficient conversion process is still difficult to achieve due to the difficult reaction conditions. In this study as a novel and versatile concept, we introduced the use of beta-cyclodextrin (beta-CD) macromolecule to enhance the photocatalytic behavior of a alpha-Fe2O3/TiO2 heterojunction. The selective conversion of guaiacol was evaluated using 0.2, 1.0, and 2.0 molar ratios of beta-CD anchored on 0.7 wt % alpha-Fe2O3/TiO2 under mild reaction conditions. 1.0 molar ratio of beta-CD promoted photo-oxidation of guaiacol to mainly produce p-benzoquinone with similar to 68% selectivity at similar to 10% conversion. To understand this effect, Electron Paramagnetic Resonance Spectroscopy (EPR) in operando mode and Diffuse Reflectance Spectroscopy (DRS) experiments were performed. The results showed that the 1.0 molar ratio of beta-CD decreases the bandgap from 3.06 to 2.76 eV and controls the center dot OH radical concentration due to the formation of a covalent bond between beta-CD and semiconductors. The improved guaiacol adsorption capacity on the photocatalyst resulted in the enhancement of the photochemical activity and selectivity. Additionally, a possible pathway of guaiacol transformation was proposed through the oxidation intermediates. Furthermore, the photocatalyst beta-CD/alpha-Fe2O3/TiO2 can be recycled efficiently and reused three times, without loss in reactivity.
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    STUDY OF THE CATALYTIC CONVERSION AND ADSORPTION OF ABIETIC ACID ON ACTIVATED CARBON: EFFECT OF SURFACE ACIDITY
    (2016) Garcia, Rafael; Peralta, Lorena; Segura, Cristina; Sepulveda, Catherine; Ghampson, I. Tyrone; Escalona, Nestor
    This study reports the adsorption and catalytic conversion of abietic acid as representative compound of tall oil, using activated carbons. Acid functional groups present on CGRAN activated carbons favored the adsorption of abietic acid, probably through a physical adsorption mechanism. In contrast, the conversion of abietic acid was not favored in DARCO activated carbon by increase of acid sites thought HNO3 treatment. The detection of neoabietic, palustric and/or levopimaric acids as reaction products indicate that the transformation of abietic acid was by dehydrogenation and/or isomerization routes. The negative influence of acid sites on the catalytic activity, in addition to the non-detection of volatile products, suggests that the cracking pathway for the conversion of abietic acid over these catalysts can be ruled out. Contrasting effects of the surface groups on the adsorption capacity and the conversion was observed: strong acid sites of CGRAN activated carbon favor the adsorption of abietic acid and decrease competitive adsorption between substrate and solvent, while conversion is not favored by these acid sites.
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    Temperature effect of asphalt production on the thermo-chemical properties of Kraft lignin
    (2024) Marquez, J. Waldo; Fuentes, Valentina; Rueda, Eduardo J.; Tundidor-Camba, Alain; Escalona, Nestor; Norambuena-Contreras, Jose; Gonzalez, Alvaro
    Global warming has triggered a series of strategies and efforts to reduce greenhouse gas emissions and increase the reuse and recycling into asphalt pavements. One of these, is the reduction of production temperatures of asphalt mixtures, and the other is using sustainable antioxidants, such as Kraft lignin, with high phenolic content. Kraft lignin is usually mixed at high temperatures without considering the effect of temperature on its antioxidant properties. This research aimed to study the impact of the production temperatures of asphalt mixtures on the thermo-chemical properties of Kraft lignin and its antioxidant capacity. To evaluate these properties, thermogravimetry, infrared spectroscopy, and DPPH tests were done. To validate the results, bitumen-lignin blends were prepared considering representative temperatures for Hot-Mix-Asphalt (HMA), 160 degrees C, and for Warm-Mix-Asphalt (WMA), 135 degrees C. Bitumen-lignin blends were prepared considering 0% and 20% Kraft lignin by total weight bitumen. The blended samples, unaged and aged. were evaluated considering mechanical, rheological, and chemical properties. The main conclusion of the study demonstrated that although Kraft lignin can be used in HMA, using it in mixtures with lower temperatures conserve its properties. WMA production temperatures preserve Kraft lignin's chemical properties, increasing the durability and resilience of bitumen throughout its service life.
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    Thermal Modification Effect on Supported Cu-Based Activated Carbon Catalyst in Hydrogenolysis of Glycerol
    (2020) Seguel, Juan; Garcia, Rafael; Jose Chimentao, Ricardo; Luis Garcia-Fierro, Jose; Ghampson, I. Tyrone; Escalona, Nestor; Sepulveda, Catherine
    Glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) was performed over activated carbon supported copper-based catalysts. The catalysts were prepared by impregnation using a pristine carbon support and thermally-treated carbon supports (450, 600, 750, and 1000 degrees C). The final hydrogen adsorption capacity, porous structure, and total acidity of the catalysts were found to be important descriptors to understand catalytic performance. Oxygen surface groups on the support controlled copper dispersion by modifying acidic and adsorption properties. The amount of oxygen species of thermally modified carbon supports was also found to be a function of its specific surface area. Carbon supports with high specific surface areas contained large amount of oxygen surface species, inducing homogeneous distribution of Cu species on the carbon support during impregnation. The oxygen surface groups likely acted as anchorage centers, whereby the more stable oxygen surface groups after the reduction treatment produced an increase in the interaction of the copper species with the carbon support, and determined catalytic performances.