We demonstrated recently that CuPd/TiO 2 –Na bimetallic catalysts synthesized by sequential wet impregnation are active, selective, and stable for the hydrodeoxygenation (HDO) of glycerol into propylene glycol at low H 2 pressure. The present study reports on the nature and distribution of Cu and Pd surface species in CuPd/TiO 2 –Na bimetallic catalysts using different scanning transmission electron microscopy techniques that supply cluster-specific alloying details. In particular, we used atomic-resolution Z -contrast imaging, X-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy. We also include X-ray photoelectron spectroscopy results. Our analysis shows that the metallic nanoparticles adopt mainly five different structures according to how the Cu and Pd atoms coordinate among themselves: a homogeneous CuPd alloy structure (45–61%), a Cu shell/CuPd core (15–23%), a smaller number of particles formed by Cu on the surface and Pd in the nucleus (10–17%), and there are also nanoparticles formed only by Pd (4–7%) or by Cu (8–13%). We determined that there is a inhomogeneous distribution of Cu and Pd in the bimetallic nanoparticles, with Cu being predominant on the surface (between 76 and 90% of the total area analyzed for each particle). Most bimetallic nanoparticles have sizes below 6 nm, the Pd monometallic nanoparticles are in the 2–4 nm range, whereas the monometallic Cu nanoparticles are larger than 8 nm. Bimetallic nanoparticles with sizes smaller than 6–7 nm are fundamentally made up of Cu 0 –Pd 0 and Cu 1+ –Pd 0 . The nanoparticles with sizes greater than 7 nm consist of Cu 2+ and Cu 2+ –Pd 2+ . Our obtained results also help describe reports about the activation of HDO by Pd–Cu in the absence of H 2 , an effect apparently not observed with other bimetallic systems.

Hydrodeoxygenation (HDO) kinetics of glycerol into 1,2-propanediol (1,2-PDO) in the liquid phase is studied on Cu-Pd/TiO 2 catalysts. At a stirring speed higher than 480 rpm and an average diameter of the catalyst particles smaller than 89.5 μm, no mass transfer resistance artifacts are observed. The increasing temperature and H 2 concentration promote the glycerol conversion and the selectivity to 1,2-PDO and disfavor the selectivity to acetol. Based on the experimental data, empirical kinetic pseudo-homogeneous expressions are proposed for glycerol disappearance, 1,2-PDO formation, and acetol formation in the catalytic system. Dependence of the disappearance rate of glycerol is closer to 1 with respect to glycerol and nonmeaningful with respect to H 2 . The formation rate of 1,2-PDO is not highly dependent on the initial concentration of glycerol or H 2 , and the formation rate of acetol is directly dependent on glycerol and inversely dependent on H 2 , since it accelerates acetol conversion to 1,2-PDO. The activation energies for glycerol disappearance (77.8 kJ/mol), 1,2-PDO formation (51.2 kJ/mol), and acetol formation (84.6 kJ/mol) evidenced the selective formation of 1,2-PDO in this catalytic system.

Cellulose fibers were obtained from banana pseudostem residues by two different chemical routes: 30% sodium hydroxide and 8% hydrogen peroxide. The average yields obtained were 24.4% and 49.3%, respectively. Additionally, according to the SEM results, more fibrillous material is obtained under alkaline conditions. On the other hand, XRD diffractograms of the materials obtained by both methods, show similarities, however, a peak in 2θ = 16 ° in the material treated with H2O2, suggests that the material that was not completely degraded and therefore concluding greater effectiveness with the alkali treatment. Thus, the results obtained to date are not conclusive, therefore, the fibers obtained are still characterized by other complementary SEM analyzes and other techniques to define their dimensions and morphology with greater precision and from these results determine the possible products of the paper industry for which said fibers could be used.

Eichhornia crassipes es una planta considerada una plaga para los diferentes ecosistemas acuáticos en el mundo. Además el Cr (VI) es un contaminante acuático altamente tóxico. Se estudió la capacidad de adsorción de la Eichhornia crassipes como bioadsorbente para la remoción de Cr (VI) presente en un agua residual simulada. La concentración del ion en solución, pH y temperatura fueron estudiadas como variables en un diseño experimental factorial simétrico, y mediante análisis ANOVA. La mayor capacidad de adsorción Cr (VI) (2.5 mgꞏg-1) se obtuvo a 75 ppm de Cr (VI), pH de 1.5 y 45 °C. Se observaron grupos funcionales superficiales que mediante atracción electrostática y formación de puentes de hidrógeno favorecieron la adsorción de Cr (VI). Esto permite concluir que el bioadsorbente es efectivo para la remoción de Cr (VI) en solución con un proceso simple y de bajo costo. Eichhornia crassipes commonly called water hyacinth, is a plant considered a pest for the different aquatic ecosystems in the world. Furthermore, Cr (VI) is a highly toxic aquatic pollutant. In order to contribute to the solution of these two environmental problems, the adsorption capacity of water hyacinth as a bioadsorbent was studied for the removal of Cr (VI) in a simulated wastewater. The ion concentration in solution, pH y temperature were studied using a symmetric factorial experimental design y applicating an ANOVA analysis. The highest Cr (VI) adsorption capacity (2.5 mgꞏg-1) was obtained at 75 ppm of Cr (VI), pH of 1.5 y 45 ° C. Surface functional groups were observed that, through electrostatic attraction y formation of hydrogen bonds, favored the adsorption of Cr (VI). This allows to conclude that this bioadsorbent is effective for the elimination of Cr (VI) in solution using a simple y low-cost process.