Nature and evolution of Pd catalysts supported on activated carbon fibers during the catalytic reduction of bromate in water

[EN] Catalytic hydrogenation of bromate using Pd catalysts supported on activated carbon fibers is a smart solution to treat bromate polluted water. These catalysts have been analyzed by different techniques for an in-deep characterization of the active sites. The in situ X-ray absorption spectroscopy and the CO chemisorption studies showed that Pd-0 nanoparticles with different crystal sizes were generated on the support during hydrogen activation at 200 degrees C and that the PdHx-phase was formed during the cooling to room temperature. As PdHx species formed on Pd-0 nanoparticles are responsible for bromate reduction, the most active catalysts are those having Pd-0 nanoparticles with large crystal sizes, where PdHx species are easily formed. The catalysts are fully stable in succesive reaction runs. It has been also shown that bromate reduction rate depends on the bromate concentration and on the hydrogen partial pressure, with a pseudo-first reaction order towards both reactants.Authors thank the Spanish Ministry of Economy and Competitiveness through RTI2018-101784-B-I00 (MINECO/FEDER) and SEV-2016-0683 projects for the financial support. We gratefully acknowledge ALBA synchrotron for allocating beamtime (proposal 2015091414) and CLAESS beamline staff for their technical support during our experiment. C. W. Lopes (Science without Frontiers -Process no. 13191/13-6) thanks CAPES for a predoctoral fellowship. J. L. Cerrillo is grateful to MINECO for the Severo Ochoa contract for PhD formation (SVP-2014-068600). L. Kiwi-Minsker acknowledges financial support provided by Russian Science Foundation (project 15-19-20023). Authors also thank Kynol Europa GmbH for the supply of the activated carbon fibers.Cerrillo, JL.; Lopes, CW.; Rey Garcia, F.; Agostini, G.; Kiwi-Minsker, L.; Palomares Gimeno, AE. (2020). Nature and evolution of Pd catalysts supported on activated carbon fibers during the catalytic reduction of bromate in water. Catalysis Science & Technology. 10(11):3646-3653. https://doi.org/10.1039/d0cy00606hS364636531011Naushad, M., Khan, M. R., ALOthman, Z. A., AlSohaimi, I., Rodriguez-Reinoso, F., Turki, T. M., & Ali, R. (2015). Removal of BrO3 − from drinking water samples using newly developed agricultural waste-based activated carbon and its determination by ultra-performance liquid chromatography-mass spectrometry. Environmental Science and Pollution Research, 22(20), 15853-15865. doi:10.1007/s11356-015-4786-yBUTLER, R., GODLEY, A., LYTTON, L., & CARTMELL, E. (2005). Bromate Environmental Contamination: Review of Impact and Possible Treatment. 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Alkali poisoning of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3

[EN] Fe (2 wt%)-Cu (1.5 wt%)-ZSM-5 SCR catalyst contacted 1.5 wt% of Na and 1.8 wt% of K in order to simulate poisoning by species more specifically contained in exhaust gases from exhaust gases of diesel engines and power plants. Poisoning agents do not cause loss of surface area nor pore occlusion. XRD and SEM results showed that alkali metals introduction did not deteriorate the crystallinity and morphology of zeolite crystals. However, a significant loss of surface acidity was observed upon alkali-poisoned catalysts causing a dramatic deactivation of the NH3-SCR of NO reaction. Na-doped catalyst showed higher low-temperature SCR activity, while potassium has a stronger deactivation effect on Fe-Cu-ZSM-5 than sodium beyond 400 degrees C.Jouini, H.; Mejri, I.; Martinez-Ortigosa, J.; Cerrillo, JL.; Petitto, C.; Mhamdi, M.; Blasco Lanzuela, T.... (2022). Alkali poisoning of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3. Research on Chemical Intermediates. 48(8):3415-3428. https://doi.org/10.1007/s11164-022-04768-93415342848

Copper nanoparticles encapsulated in zeolitic imidazolate framework-8 as a stable and selective CO2 hydrogenation catalyst

Metal–organic frameworks have drawn attention as potential catalysts owing to their unique tunable surface chemistry and accessibility. However, their application in thermal catalysis has been limited because of their instability under harsh temperatures and pressures, such as the hydrogenation of CO2 to methanol. Herein, we use a controlled two-step method to synthesize finely dispersed Cu on a zeolitic imidazolate framework-8 (ZIF-8). This catalyst suffers a series of transformations during the CO2 hydrogenation to methanol, leading to ~14 nm Cu nanoparticles encapsulated on the Zn-based MOF that are highly active (2-fold higher methanol productivity than the commercial Cu–Zn–Al catalyst), very selective (>90%), and remarkably stable for over 150 h. In situ spectroscopy, density functional theory calculations, and kinetic results reveal the preferential adsorption sites, the preferential reaction pathways, and the reverse water gas shift reaction suppression over this catalyst. The developed material is robust, easy to synthesize, and active for CO2 utilization.King Abdullah University of Science and Technology (KAUST) funded this work: BAS/1/1403. The authors acknowledge the KAUST Supercomputing Laboratory for providing high-performance computational resources and support from the KAUST Core Labs

Early assessment of forest restoration techniques using chlorophyll fluorescence and diagnosi of oak (Quercus ilex sub. ballota) seedings vitality

[EN] Chlorophyll a fluorescence has been applied to study the evolution of leaf photoprotection processes to dissipate excess absorbed energy that can not be fully utilized in photochemical reactions, and reflects the plants ability to adapt to environmental conditions. Plants environmental conditions can be modified by forest restoration techniques to ensure successful seedlings establishment, hence chlorophyll a fluorescence can be a useful tool for assessing plant response to planting stress. The objective of this paper was to analyze the chlorophyll a fluorescence as an early indicator of oak seedling response to the establishment stress and as a useful tool for the assessment of different competition control and individualized protection techniques (tillage, herbicide, mulch, tree shelter) used in forest restoration. A field experimental plot with these restoration treatments was established and a monthly monitoring of chlorophyll a fluorescence and a vitality analysis were carried out between August 2003 and October 2004 on oak seedlings. Results showed that fluorescence parameters were sensitive to stress conditions prevailing in each analysed period. On the evaluation of herbaceous competition control techniques, no significant results on the chlorophyll a fluorescence were observed. However, tree shelters exercised a protection effect on seedling limiting the photoinhibition processes during spring and winter periods. Finally, protected plants showed major photochemical efficiency than that showed by unprotected ones according to vitality tests. Therefore, the chlorophyll a fluorescence analysis was proved to be a useful tool for early assessment of oak seedlings establishment stress and for the assessment of certain forest restoration techniques, such as those that combine control of herbaceous competition and individualized seedling protection.[ES] La fluorescencia de la clorofila a se ha aplicado para estudiar la evolución de los procesos de fotoprotección de la hoja para disipar el exceso de energía absorbida que no puede ser totalmente utilizado en las reacciones fotoquímicas, y refleja la capacidad de las plantas para adaptarse a las condiciones ambientales existentes. Las técnicas de repoblación forestal modifican las condiciones ambientales con el objetivo de asegurar el éxito en el establecimiento de los brinzales, por lo que la fluorescencia de la clorofila a puede ser una herramienta valiosa para evaluar la respuesta de las plantas al estrés de establecimiento. El objetivo de este trabajo fue analizar la fluorescencia de la clorofila a como indicador temprano de la respuesta de brinzales de encina al estrés de establecimiento y como una herramienta útil para la evaluación de distintas técnicas de control de la competencia y protección de los brinzales (laboreo, herbicida, mulch, tubo invernadero) utilizadas en restauración forestal. Para ello, entre agosto de 2003 y octubre de 2004, se realizó un seguimiento mensual de la fluorescencia de la clorofila a y un análisis de vitalidad de los brinzales de encina previamente plantados y sometidos a diferentes tratamientos de restauración en una parcela de ensayo bajo condiciones de campo. Los resultados mostraron que los parámetros de fluorescencia resultaron sensibles a las condiciones de estrés imperantes en cada periodo temporal analizado. En cuanto a la evaluación de técnicas de control de la competencia herbácea, no se observaron resultados significativos en relación con la fluorescencia de la clorofila a. Sin embargo, el tubo invernadero ejerció un efecto de protección sobre las plántulas que limitó la aparición de procesos de fotoinhibición durante los periodos de primavera e invierno. Finalmente, las plantas protegidas mostraron mayor rendimiento fotoquímico que las carentes de protección de acuerdo con los análisis de vitalidad realizados. Por tanto, el análisis de fluorescencia de la clorofila se mostró como una herramienta útil para la evaluación temprana del estrés de establecimiento de brinzales de encina y para la evaluación de determinadas técnicas de restauración forestal, como aquellas que combinan el control de la competencia con la protección individualizada de los brinzales.Los autores agradecen al Centro de IFAPA "Alameda del Obispo", y en particular a su director Víctor Ortiz, las facilidades ofrecidas para el desarrollo de este estudio. Este trabajo de investigación se realizó con el apoyo de los proyectos INTERBOS (CGL2008-04503-C03-0l/BOS) y AGL2009-12243-C02-02 "Variability, cataloguing, responses to stresses, and clona! propagation of Holm oak (Quercus ilex, subs. ballota) (DECOVA)" financiados por el Ministerio de Ciencia y Tecnología.Ceacero Ruíz, CJ.; Díaz Hernández, JL.; Campo García, ADD.; Navarro Cerrillo, R. (2012). Evaluación temprana de técnicas de restauración forestal mediante fluorescencia de la clorofila y diagnóstico de vitalidad de brinzales de encina (Quercus ilex sub. ballota). Bosque. 33(2):191-202. https://doi.org/10.4067/S0717-92002012000200009S19120233

Copper nanoparticles encapsulated in zeolitic imidazolate framework-8 as a stable and selective CO2 hydrogenation catalyst

Abstract Metal–organic frameworks have drawn attention as potential catalysts owing to their unique tunable surface chemistry and accessibility. However, their application in thermal catalysis has been limited because of their instability under harsh temperatures and pressures, such as the hydrogenation of CO2 to methanol. Herein, we use a controlled two-step method to synthesize finely dispersed Cu on a zeolitic imidazolate framework-8 (ZIF-8). This catalyst suffers a series of transformations during the CO2 hydrogenation to methanol, leading to ~14 nm Cu nanoparticles encapsulated on the Zn-based MOF that are highly active (2-fold higher methanol productivity than the commercial Cu–Zn–Al catalyst), very selective (>90%), and remarkably stable for over 150 h. In situ spectroscopy, density functional theory calculations, and kinetic results reveal the preferential adsorption sites, the preferential reaction pathways, and the reverse water gas shift reaction suppression over this catalyst. The developed material is robust, easy to synthesize, and active for CO2 utilization