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In this paper, we report that the hydrogenolysis of glycerol can be carried out at atmospheric pressure and low temperature with high selectivity to 1,2-propanediol (1,2-PDO) over reduced copper catalyst. The vapor-phase reaction was carried out over the copper-based catalysts supported on alumina at ambient pressure, and the effects of temperature, space time, and H2 molar fraction in the feed were analyzed. The textural and structural characteristics of the catalysts with increasing copper loading were determined by N2 sorptometry (BET), inductively coupled plasma-atomic spectroscopy (ICP-AES), powder X-ray diffraction (PXRD), temperature-programmed reduction (TPR), and N2O chemisorption (metallic area). On the basis of both characterization and activity results, it was possible to conclude that the hydrogenolysis of glycerol to 1,2-propanediol in vapor phase at atmospheric pressure over copper-based catalysts is a structure sensitive reaction. Activity results suggests that the most probable pathway for the glycerol conversion into 1,2-propanediol under the employed conditions is glycerol is dehydration to hydroxyacetone (acetol), followed by its hydrogenation into 1,2-propanediol. Complete glycerol conversion and a selectivity of 60% to 1,2-propanediol was achieved, using a catalyst with 15 wt % CuO at 200 °C, H2 molar fraction of 61%, and atmospheric pressure. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to study the catalytic activity of Ni(10%) based catalysts supported over ã-Al2O3 modified with Mg (3%) for the steam reforming of glycerol. Catalysts have been prepared by incipient wetness impregnation method; analysing the effect of the calcination temperature of the modified support and the calcination temperature of the catalysts. Catalysts were characterized by temperature programmed reduction, (TPR), x-ray diffraction (DRX) and BET surface area. All catalysts were tested for this reaction in a fixed bed reactor. The best performance was achieved with the catalyst calcined at 500 °C being the optimum calcination temperature for the modified support of 900 °C This behaviour is ascribable to the formation of MgAl2O4 spinel which favours the dispersion of Ni°, responsible of the catalytic activity. [Copyright &y& Elsevier]

Electrochemical energy conversion devices are considered key in reducing CO 2 emissions and significant efforts are being applied to accelerate device development. Unlike other technologies, low temperature electrolyzers have the ability to directly convert CO 2 into a range of value-added chemicals. To make them commercially viable, however, device efficiency and durability must be increased. Although their design is similar to more mature water electrolyzers and fuel cells, new cell concepts and components are needed. Due to the complexity of the system, singular component optimization is common. As a result, the component interplay is often overlooked. The influence of Fe-species clearly shows that the cell must be considered holistically during optimization, to avoid future issues due to component interference or cross-contamination. Fe-impurities are ubiquitous, and their influence on single components is well-researched. The activity of non-noble anodes has been increased through the deliberate addition of iron. At the same time, however, Fe-species accelerate cathode and membrane degradation. Here, we interpret literature on single components to gain an understanding of how Fe-species influence low temperature CO 2 electrolyzers holistically. The role of Fe-species serves to highlight the need for considerations regarding component interplay in general., (© 2023 Wiley-VCH GmbH.)

In this work we present a systematic computational study of the structural and magnetic properties of a layered family of Co(II) hydroxichlorides, obeying to the general formula Co(OH) 2- x Cl x (H 2 O) y . This solid contains both octahedral and tetrahedral cobalt ions, displaying a complex magnetic order arising from the particular coupling between the two kinds of metallic centers. Here, supercells representing concentrations of 12, 20, and 40% of tetrahedral sites were modeled consistently with the compositions reported experimentally. Our simulations show that the two types of cobalt ions tend to couple antiferromagnetically, giving rise to a net magnetic moment slightly out of the plane of the layers. The band gap reaches its minimum value of 1.4 eV for the most diluted fraction of tetrahedral Co(II) sites, going up to 2.2 eV when the content is 40%. Moreover, our results suggest that the presence of interlayer water stabilizes the material and at the same time strongly modifies the electronic environment of tetrahedral Co(II), leading to a further drop of the band gap. To our knowledge, this is the first theoretical investigation of this material.

Synchrotron X-ray and neutron diffraction experiments at various temperatures, down to 3 K, along with ab initio calculations, are carried out to elucidate the magnetic order of layered β-cobalt-hydroxide. This combination of techniques allows for the unambiguous assignment of the magnetic structure of this material. Our results confirm that below the Néel temperature high-spin cobalt centers are ferromagnetically coupled within a layer, and antiferromagnetically coupled across layers (magnetic propagation vector k = (0,0,½)), in agreement with the indirect interpretation based on magnetic susceptibility measurements. A paramagnetic/antiferromagnetic transition is observed at around 15 K. Moreover, the thermal expansion behavior along the c-lattice direction, perpendicular to the layers, shows an inflection slightly above this temperature, at around 30 K. The neutron diffraction patterns and the non-collinear DFT+U calculations indicate that the magnetization forms an angle of about 35° with the cobalt planes. In particular, for an isolated ferromagnetic layer, the electronic structure calculations reveal sharp cusps on the potential energy surface when the spins point parallel or perpendicular to the planes, suggesting that the ferromagnetic superexchange mechanism is strongly sensitive to the orientation of the magnetic moment.

A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl)-1,1-dimethylurea) (DCMU) and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

A structural study of the thermal evolution of Ni(0.69)Cr(0.31)(OH)(2)(CO(3))(0.155) x nH(2)O into NiO and tetragonal NiCr(2)O(4) is reported. The characteristic structural parameters of the two coexisting crystalline phases, as well as their relative abundance, were determined by Rietveld refinement of powder x-ray diffraction (PXRD) patterns. The results of the simulations allowed us to elucidate the mechanism of the demixing process of the oxides. It is demonstrated that nucleation of a metastable nickel chromite within the common oxygen framework of the parent Cr(III)-doped bunsenite is the initial step of the cationic redistribution. The role that trivalent cations play in the segregation of crystalline spinels is also discussed.