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This study analyzes the selectivity of Pd (1 wt %) catalysts supported on different activated carbons to produce olefins from hydrodechlorination of chloroform. It was found that selectivity to olefins was favored by a higher zerovalent to electrodeficient Pd ratio (Pd0/Pdn+) and by a lower amount of oxygen-containing surface functional groups on the activated carbon supports. Thus, the highest selectivity to olefins was obtained by catalysts supported on FeCl3- and ZnCl2-activated carbons. Conversely, the catalysts supported on KOH-, NaOH-, and H3PO4-activated carbons gave the lowest selectivity to olefins. These catalysts showed higher surface concentrations of electro-deficient Pd as well as high concentrations of oxygen functional groups that enhance the adsorption of reactants and intermediates. This leads to complete hydrogenation of reaction intermediates and poisoning of active sites by the adsorption of chlorocarbon compounds. ZnCl2-derived catalysts with the highest selectivity to olefins also showed an outstanding stability, most likely due to redispersion into very small and well-distributed Pd particles during the reaction. However, FeCl3-derived catalysts gave rise to sintering of Pd particles, resulting in a marked loss of activity.

Conversion of chloroform (TCM) by gas-phase catalytic hydrodechlorination (HDC) has been addressed to maximize the selectivity to ethane and propane. Several own-made Pd (1 wt%) catalysts have been tested. The catalysts were prepared by incipient wetness impregnation of five different activated carbons. These carbons were obtained by chemical activation of lignin with different activating agents, namely, H3PO4, ZnCl2, FeCl3, NaOH and KOH. The catalysts were fully characterized by N2adsorption–desorption at −196 °C, CO2adsorption at 0 °C, TPR, NH3-TPD, XRD, XPS and TEM. The activating agents provided important differences in the characteristics of activated carbon supports, and hence in the resulting catalysts, in terms of their porous texture, surface acidity, Pd oxidation state and Pd particle size distribution. NaOH and KOH activation led to carbons with the highest surface areas (2158 and 2991 m2g−1, respectively) and low Pd0/Pdn+ratios, while ZnCl2- and H3PO4-activated carbons yielded the highest surface acidity and mean Pd particle sizes. The analysis of the TOF values revealed that the HDC of TCM on these catalysts is a structure-sensitive reaction, increasing TOF values with Pd particle size. The best results, in terms of selectivity to ethane and propane, were obtained with the catalysts supported on KOH- and NaOH-activated carbons. The former allowed 80% selectivity to the target compounds at almost complete dechlorination (>99%) at 300 °C. The KOH-based catalyst showed fairly good stability at a reaction temperature of 200 °C.

Metronidazole is a nitroimidazole antibiotic that is increasingly detected in aquatic bodies. Therefore, there is an urgent need to research methodologies to remove this and other antibiotics. One of the alternatives is the application of solar photocatalysis, which requires the use of an efficient photocatalyst. In this work, UiO-66-NH2was synthesized by a facile solvothermal method and evaluated for the degradation of metronidazole under simulated solar light. The effects of catalyst dosage, initial pH, and metronidazole concentration were discussed, establishing the best operation conditions. In addition, the stability and reproducibility of UiO-66-NH2activity were also verified. The quenching reaction showed that holes and superoxide radicals coexisted as the main active species, being responsible for the metronidazole degradation. The pathway of metronidazole photodegradation was proposed by means of density functional theory calculations and LC/ESI-MS analysis. It is noteworthy that this study detected for the first time C6H11N3O4, C4H6N2O3,and C4H8N2O4as metronidazole photodegradation byproducts. ECOSAR toxicity analysis showed that all byproducts were less toxic than the original metronidazole, supporting the potential feasibility of this method for treating water polluted with this antibiotic.

The performance of 61 global climate models participating in CMIP5 and 6 is evaluated for the Southern Hemisphere extratropics in terms of typical regional‐scale atmospheric circulation patterns. These patterns are known to be linked with a number of key variables in atmospheric physics and chemistry and provide an overarching concept for model evaluation. First, hemispheric‐wide error and ranking maps are provided for each model and regional details are described. Then, the results are compared with those obtained in a companion study for the Northern Hemisphere. For most models, the average error magnitude and ranking position is similar on both hemispheres, ruling out systematic tuning toward either of the two. CMIP6 models perform better on average than CMIP5 models and the interactive simulation of more climate system components does not deteriorate the results for most model families. Better performance is associated with higher resolution in the atmosphere, following a non‐linear relationship. This letter provides a survey on the capability of global climate models to reproduce the regional atmospheric circulation in the Southern Hemisphere in present climate conditions. Climate models from the latest model generation are found to perform better on average than those of the previous generation and the obtained model ranking is similar to that found for the Northern Hemisphere in a companion study. While model performance is found to be generally unrelated to model complexity in terms of covered climate system components, better results are associated with higher model resolution in the atmosphere. CMIP6 models perform better than CMIP5 models on averageSouthern Hemisphere model ranking similar to Northern Hemisphere rankingMore complex model versions perform similar to less complex ones CMIP6 models perform better than CMIP5 models on average Southern Hemisphere model ranking similar to Northern Hemisphere ranking More complex model versions perform similar to less complex ones

A novel method for the preparation of stable Pt/C catalysts with size-controlled nanoparticles has been developed. The method is based on in situsynthesis of the nanoparticles (reduction with NaBH4in the presence of a support and PVP). Compared to the conventional ex situroute (colloidal synthesis followed by impregnation), this in situroute yields smaller nanoparticles (2.5–3.9 nm) of narrower size distribution. The catalysts prepared by the in situsynthesis showed a higher stability in water at 80 °C, indicating a stronger interaction between the support and the metallic phase. Hydrothermal stability tests were also conducted under conditions equivalent to those of aqueous phase reforming (200 °C, 17 bar and water and diluted acetic acid). Hydrothermal treatment proved to be an excellent method to improve the resistance to leaching of the catalysts. Metal loss was negligible while PVP was almost completely removed from the catalyst; hence, most of the porosity was recovered and the dispersion measured by CO chemisorption increased from 5 to 34–75%. Water at 200 °C was more effective than diluted acetic acid for the removal of PVP. TEM images confirmed that the Pt nanoparticles did not undergo significant changes either in size or morphology upon the hydrothermal treatment, and XPS analysis showed a homogeneous distribution of Pt nanoparticles within the catalyst granules.

This work reports the solvothermal synthesis of UiO-66-based MOFs with three different ligands and its application to the breakdown of aqueous acetaminophen under simulated sunlight. This pharmaceutical is a representative contaminant of emerging concern that enters water bodies mainly through wastewater treatment plant discharges. The synthesis approach of the MOFs was fitted using a zirconium alkoxide as metal cluster precursor and 2-aminoterephthalic and 2,5-dihydroxyterephthalic acids as ligands to prepare UiO-66-NH2and UiO-66-(OH)2MOFs, respectively. These new MOFs have enhanced visible light harvesting and narrower band gap than the UiO-66. Among all, UiO-66-NH2yielded the highest removal of acetaminophen under simulated solar irradiation in batch test. The activity and stability of UiO-66-NH2were demonstrated for the first time in a continuous flow test, where stable performance was observed upon 30 h on stream. The degradation pathway of acetaminophen was elucidated based on coupling, ring-opening, and oxidation reactions. DFT calculation confirmed that the indirect semiconductor behavior of UiO-66-NH2upon light excitation occurred through ligand-ligand charge transfer. Overall, promising UiO-66-based MOFs photocatalysts were obtained for effective degradation of acetaminophen with the assistance of solar light.