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Catalizadores bimetálicos (Pt-Pd) soportados sobre óxido de zirconio sulfatado y su uso en la hidrodecloración de clorometanos. La presente invención se refiere a catalizadores bimetálicos soportados en zirconia sulfata y a la preparación, activación y operación de los mismos, junto con el uso de los catalizadores mono y bimetálicos para la hidrodecloración de clorometanos en condiciones moderadas de presión y temperatura., Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, pub

Monometallic (Pt or Pd) and bimetallic (Pt–Pd) catalysts supported on zirconia promoted with sulfate (SZ) or tungsten oxide (WZ) were prepared and tested in the gas-phase hydrodechlorination of dichloromethane. The catalysts showed a high selectivity to non-chlorinated products (between 80% and 90% at 250 °C) being methane the main reaction product. As a general trend, the WZ catalysts yielded significantly higher dichloromethane conversion than the SZ ones, yielding all the catalysts initial conversions higher than 80% at a reaction temperature of 250 °C. However, the former showed a very poor stability regardless of the metallic active phase. On the other hand, the presence of palladium in the sulfated zirconia catalyst avoids deactivation as proved in long-term experiments (80-h time on stream). XPS and elemental analyses of the used catalysts suggest that adsorption of organochlorinated species is a cause of deactivation by blocking the active sites. In the monometallic SZ Pt catalyst, deactivation occurs also by poisoning of the Pt sites by the H2S resulting from sulfate reduction under the hydrogen-rich gas atmosphere. The metal particle size appears to be a critical point with regard to stability of the catalysts. The one with the highest dispersion showed the highest stability with no signs of deactivation after more than 80 h on stream., Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub

This work reports for the first time the functionalization of the 2-aminoterephtalate linker of UiO-66-NH2 with cyclopentyl or cyclohexyl rings. The resulting materials displayed reduced bandgaps with enhanced separation of the photogenerated charges due to the inductive electron effect of the cycloalkyl substituent. These functionalized materials displayed higher photocatalytic performance towards the solar abatement of acetaminophen than UiO-66-NH2. The photocatalytic activation mechanism was proposed based on the band alignment and scavenger tests, suggesting the major contribution of holes and superoxide radicals. In particular, UiO-66-NH-C5 exhibited high stability under reaction with low activity loss after reusing. The acetaminophen degradation pathway was also studied indicating that the ACE molecules were coupled to dimers and trimers that were further oxidized. The small bandgap, the band structure, and the photocatalytic performance resulting from the cycloalkyl functionalization of UiO-66-NH2 make it a promising approach to designing novel photocatalysts for solar abatement of emerging contaminants. © 2023 The Author(s)

The upgrading of wasted chloroform in hydrodechlorination for the production of olefins such as ethylene and propylene is studied by employing four catalysts (PdCl/CNT, PdCl/CNF, PdN/CNT, and PdN/CNF) prepared by different precursors (PdCl2 and Pd(NO3)2) supported on carbon nanotubes (CNT) or carbon nanofibers (CNF). TEM and EXAFS-XANES results confirm that Pd nanoparticle size increases in the order: PdCl/CNT < PdCl/CNF ∼ PdN/CNT < PdN/CNF, descending the electron density of Pd nanoparticles in the same order. It illustrates that PdCl-based catalysts show donation of electrons from support to Pd nanoparticles, which is not observed in PdN-based catalysts. Moreover, this effect is more evident in CNT. The smallest and well-dispersed Pd nanoparticles (NPs) on PdCl/CNT with high electron density favor an excellent and stable activity and a remarkable selectivity to olefins. In contrast, the other three catalysts show lower selectivity to olefins and lower activities which suffer strong deactivation due to the formation of Pd carbides on their larger Pd nanoparticles with lower electron density, compared to PdCl/CNT. © 2023 The Authors

An exponential rise in global pollution and industrialization has led to significant economic and environmental problems due to the insufficient application of green technology for the chemical industry and energy production. Nowadays, the scientific and environmental/industrial communities push to apply new sustainable ways and/or materials for energy/environmental applications through the so-called circular (bio)economy. One of today's hottest topics is primarily valorizing available lignocellulosic biomass wastes into valuable materials for energy or environmentally related applications. This review aims to discuss, from both the chemistry and mechanistic points of view, the recent finding reported on the valorization of biomass wastes into valuable carbon materials. The sorption mechanisms using carbon materials prepared from biomass wastes by emphasizing the relationship between the synthesis route or/and surface modification and the retention performance were discussed towards the removal of organic and heavy metal pollutants from water or air (NOx, CO2, VOCs, SO2, and Hg0). Photocatalytic nanoparticle-coated biomass-based carbon materials have proved to be successful composites for water remediation. The review discusses and simplifies the most raised interfacial, photonic, and physical mechanisms that might take place on the surface of these composites under light irradiation. Finally, the review examines the economic benefits and circular bioeconomy and the challenges of transferring this technology to more comprehensive applications.© 2023. The Author(s).

Several sets of reference regions have been used in the literature for the regional synthesis of observed and modelled climate and climate change information. A popular example is the series of reference regions used in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Adaptation (SREX). The SREX regions were slightly modified for the Fifth Assessment Report of the IPCC and used for reporting subcontinental observed and projected changes over a reduced number (33) of climatologically consistent regions encompassing a representative number of grid boxes. These regions are intended to allow analysis of atmospheric data over broad land or ocean regions and have been used as the basis for several popular spatially aggregated datasets, such as the Seasonal Mean Temperature and Precipitation in IPCC Regions for CMIP5 dataset. We present an updated version of the reference regions for the analysis of new observed and simulated datasets (including CMIP6) which offer an opportunity for refinement due to the higher atmospheric model resolution. As a result, the number of land and ocean regions is increased to 46 and 15, respectively, better representing consistent regional climate features. The paper describes the rationale for the definition of the new regions and analyses their homogeneity. The regions are defined as polygons and are provided as coordinates and a shapefile together with companion R and Python notebooks to illustrate their use in practical problems (e.g. calculating regional averages). We also describe the generation of a new dataset with monthly temperature and precipitation, spatially aggregated in the new regions, currently for CMIP5 and CMIP6, to be extended to other datasets in the future (including observations). The use of these reference regions, dataset and code is illustrated through a worked example using scatter plots to offer guidance on the likely range o

Bimetallic Pt:Pd catalysts with different molar ratios and 0.5 wt.% overall metal load supported on sulfated zirconia catalysts were synthesized and tested in the gas-phase hydrodechlorination (HDC) of chloromethanes and their mixtures. The catalysts were characterized by adsorption–desorption of N at −196 °C, X-ray diffraction, X-ray photoelectronic spectroscopy, temperature-programmed reduction, and aberration-corrected scanning transmission electron microscopy (STEM). The effect of the Pt:Pd molar ratio on the activity, stability, and selectivity was analyzed. The high acidity of the sulfated zirconia results in metal particles of small size (mainly <5 nm), as confirmed by STEM. The bimetallic catalysts showed higher stability than the monometallic ones, as demonstrated in long-term experiments (80 h on stream), confirming the positive effect of combining the two metallic phases. Turnover frequency (TOF) values in the range 0.0007–0.0168 s and apparent activation energies between ≈41 and 44 kJ·mol were obtained. TOF values for dichloromethane HDC increased with increasing mean metal particle size within the range of this work (≈1.2–2.3 nm). The catalysts with Pt:Pd molar ratios of 1:3 and 1:1 showed significantly better performance than the 3:1 one for overall dechlorination due to their higher atomic metal content and TOF at the same total metal weight load (0.5%).

Four precious metals supported on activated carbon are compared as catalysts in the gas-phase hydrodechlorination (HDC) of chloromethanes. The intrinsic activity or turnover frequency (TOF) of the catalysts follows the order Pd/C > Rh/C > Pt/C > Ru/C in the HDC of dichloromethane (DCM) while the sequence Pd/C > Pt/C > Rh/C > Ru/C was found for the HDC of chloroform (TCM). High selectivities to non-chlorinated products were obtained in all cases except for the HDC of TCM with Rh/C and Ru/C where the selectivity to DCM greatly depends on the operating conditions. A wider diversity of non-chlorinated hydrocarbons was obtained as reaction products with these two catalysts, especially in the HDC of TCM, favoring the formation of carbonaceous deposits which provoked a marked deactivation of the catalysts. In contrast, CH4 was the only non-chlorinated product obtained with the Pt/C catalysts which showed by far the highest stability. Different reaction pathways were found depending on the catalyst and the starting chloromethane. The different reactivity of the metals is explained in terms of their different electronic structure and the physicochemical properties of the catalysts., MINECO, Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub