•Synthesis of Na2ZnSiO4 via a facile and low-cost solid-state method.•Na2ZnSiO4 evaluated as heterogeneous catalysts in soybean oil transesterification.•Transesterification reaction parameters ...optimized using Box-Behnken design.•99% FAMEs conversion achieved under optimized conditions at 65 °C after 45 min.•Optimized conditions using 5.3 wt% catalyst, 500 RPM and 1:14 MeOH:oil ratio.
This study synthesizes a Na2ZnSiO4 phase as efficient and low-cost heterogeneous catalyst for biodiesel production. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) along with Energy Dispersive X-Ray Spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area analysis isotherms are herein conducted to characterize the structure, texture, composition and surface area of the catalyst, respectively. A Box-Behnken design (BBD) is performed to screen out: the methanol: oil ratio (6:1 to 14:1), catalyst load (0.5 to 5.5 wt%) and stirring rate (500 to 800 RPM), affecting the transesterification reaction using commercial soybean oil as a triglyceride source while fixing the temperature reaction at 65 °C. The oil and its fatty acid methyl esters (FAME) are characterized using Fourier Transform Infrared Spectroscopy with an Attenuated Total Reflectance modulus (FT-IR-ATR). XRD and SEM confirm the successful synthesis of the monoclinic Na2ZnSiO4 phase with low traces of ZnO (<5 wt%) and undetectable for Na2SiO3; presenting a BET surface area around 1.9 m2 g−1. The material is quite active towards the biodiesel production since a conversion superior to 99% is achieved in 45 min, using the statistical optimization conditions estimated with the BBD, 500 RPM, 5.30 wt% and 14:1 MeOH: Oil ratio. According to the response surface methodology, the sensitivity of the parameters increases in the following order: catalyst load > methanol: oil ratio > stirring rate. The FAME conversions drop to 48.4 and 62.42% after 5 cycles of continuous catalyst reuse, according to FT-IR-ATR and proton nuclear magnetic resonance (1H NMR) measurements, respectively.
BiOCl/BiVO4 photocatalysts with different ratios of gold particles were synthesized by a facile method at room temperature. The gold was in situ incorporated on the BiOCl/BiVO4 powders through the ...chemical reduction of HAuCl4 using ascorbic acid as reducing agent. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy were conducted to perform the textural, structural and composition characterizations of the materials; while their photoactivities were evaluated using the methyl orange degradation under visible-light irradiation. The detailed morphology and microstructure of the 1.50Au-(BiOCl/BiVO4) catalyst reveals nanometer and micrometer sized particles in a range from 20 to 500 nm with sphere and elongated-like shapes. Polycrystalline features are observed with preferred (121) surface orientation and interplanar distance values corresponding to (112), (004) and (022) planes of monoclinic BiVO4, while (011), (110), (102) planes can be related to tetragonal BiOCl with the direction (111). The surface chemical analysis showed that the most active Au-(BiOCl/BiVO4) catalyst presents the highest V4+/V5+ ratio (0.85), a 43 at.% BiOCl content and a percentage of Au-decoration of about 1 at.%. A synergic behavior between these chemical compositions enhances the MO photocatalytic degradation. It was found that photodegradation rates strongly relied on the gold content, and the Au-(BiOCl/BiVO4) photocatalyst was highly stable after six reuses and easy to be recovered by centrifugation. A possible electronic transfer mechanism in the different as-synthesized photocatalysts upon visible illumination is proposed, thus elucidating the roles of Au, BiOCl and BiVO4 components. Presumably, the synergistic interaction arising between semiconducting and metallic nanoparticles induces the charge separation responsible for the enhanced photocatalytic behavior.
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•Hybrid ternary systems of Au-(BiOCl/BiVO4) were synthesized by a simple method.•Visible-light photoactivity was evaluated towards methyl orange degradation.•The photoactivity strongly depends on the gold content.•Photomineralization of methyl orange is feasible.•A possible electronic transfer mechanism is proposed.
Ytterbium oxide (Yb
2
O
3
) ceramic powders at different Eu
3+
mol concentrations, co-doped with a low molar ratio of Tb
3+
, were synthesized by the sol–gel process for study before and after the ...inclusion of the organic ligand thenoyltrifluoroacetone (TTA). The luminescent properties caused by the interactions between the Tb
3+
–Eu
3+
ions before and after the antenna effect caused by the TTA were studied to investigate the relationships among their chemical, physical, structural and optical properties. Before the surface adhesion of TTA, the ceramic powders were composed of cubic crystalline structures that, in turn, consisted of large numbers of agglomerated particles exhibiting xerogel morphologies. The materials presented well-defined dispersive energy spectra, which indicated a suitable chemical composition. Subsequently, changes were induced through the superficial inclusion of TTA, these were characterized by promoting a greater luminescent intensity, especially for the emission bands corresponding to the
5
D
0
→
7
F
0-3
transition levels of the Eu
3+
ion.
Evidence to what it is identified in the literature as “active chlorine” in indirect oxidation processes occurring on Ti/ZrO2-RuO2-Sb2O3 anodes is provided in this study. To discriminate such ...behavior, different catalysts are prepared using the Pechini method varying ZrO2 content, at different Zr/Ru molar ratios: 1, 0.5 and 0.3. The characterization of the materials using X-ray photoelectron spectroscopy (XPS) reveals that no solid solution (Ru-Zr) or any doping that affects the crystalline phase of Zr are obtained, while Sb2O3 was surface-segregated from the bulk to the anode surface affecting the outmost 3–5 nm surface layers. There are enormous impacts on the catalytic activity and adsorption properties of the structures as ZrO2 content is increased. The presence of ZrO2 and Sb2O3 shrink the number of favorable oxygen adsorption sites in Ti/ZrO2-RuO2-Sb2O3 catalysts, whence the adsorption energies for oxygen-metal interactions became lower than for Ti/RuO2. Differential electrochemical mass spectroscopy (DEMS) and electrochemical experiments qualitatively indicate that a lower amount of ZrO2 in the ternary electrode induce a better catalysis towards the oxygen evolution reaction (OER, O2 production), while the ionic currents for ClO− and HClO species drop. This behavior suggests that chloride oxidation needs to encompass the mitigation of the OER as the percentage of ZrO2 is increased in the anode. Active chlorine could stem from HClOads species since it was produced in larger amounts than ClOads− according to the pH of the electrolyte, and in adequate levels to generate the degradation of organic compounds.
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•Impacts on the catalytic activity and adsorption properties due to ZrO2.•Adsorption energies for O2-metal interactions became lower due to ZrO2 and Sb2O3.•Active chlorine could stem from HOClads according to the electrolyte pH.•Chloride oxidation involves the inhibition of the oxygen evolution reaction.•A higher amount of ZrO2 in Ru-Zr material catalyzes the active chlorine production.
In this work, compact and porous SiO
2
nanoparticles (NPs) were synthesized using the Stöber and the modified Stöber methods. Water-based nanofluids were characterized by dynamic light scattering, ...scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, and the porosity of the compact and porous SiO
2
samples was measured by N
2
adsorption–desorption isotherms. Thermal wave resonator cavity and inverse photopyroelectric configuration novel techniques were used for the first time to obtain the porous nanoparticles thermal diffusivity (
D
) and effusivity (
e
), respectively. Thermal conductivity (
k
) was obtained from the relationship between them
k
=
e
D
. An increase in the thermal conductivity of the porous SiO
2
NPs was obtained compared to the thermal conductivity of the compact NPs fluids with an enrichment of 14.7 %. Our results are supported by a theoretical model with a thermodynamic approach adapted for the thermal conductivity of porous SiO
2
governed by the parameters of the porosity and nanoparticle size.
In this work, solid solutions of general formula Ce1−x(Zr + Y)xO2−δ were chemically synthesized through the so-called citrate-EDTA complexing method, wherein the doping cations Zr and Y were ...substituted in the ceria lattice with an equimolar amount of 0.05 ≤ x ≤ = 0.25. The ternary oxides were heat-treated, and those that showed the best textural properties were superficially impregnated with Fe2O3 particles by the thermal decomposition method using a metalorganic precursor. The X-ray diffraction results suggest that co-doping with Zr4+ and Y3+ promotes a slight distortion of the CeO2 cubic cell. Nevertheless, the fluorite cubic structure of the oxides remains stable after being exposed to heat treatments. Furthermore, using scanning electron microscopy and Raman techniques, the presence of deposited Fe2O3 and the formation of extrinsic vacancies in the materials could be corroborated. Finally, the oxides’ catalytic evaluation in the soot oxidation reaction was carried out using the thermogravimetry technique. The ternary oxide with cerium molar content equal to 0.9 and impregnated with Fe2O3 presented excellent catalytic behavior for soot oxidation. T10, T50, and T90 temperatures were 310, 383, and 416 °C, respectively.
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► Barium sulfate/polyurethane nanocomposites were prepared by melt extrusion. ► Morphology of nanoparticles (spherical and fibers) modified the rheological behavior. ► Convenient ...levels of radio-opacity were found maintaining the mechanical properties. ► BaSO4 nanoparticles do not diminish the transparency of the polyurethane matrix.
Barium sulfate spherical agglomerates and fibers in the nanometric size range were used to prepare polyurethane (PU) nanocomposites (with 1wt.% concentration) via melt extrusion. A detailed analysis on the effect of the morphology of the barium sulfate phase upon the mechanical, rheological and optical properties was carried out. Results show that the inclusion of the dispersed phase (with various morphologies and sizes) in the polymer matrix does not decrease the polymer mechanical properties, as is observed when particles in the micrometric size range are included. Rheological studies show that the nanocomposite containing spherical particles presents a slightly higher shear viscosity than that of the polymer matrix, in contrast to the nano-fibers viscosity which presents lower values. This is reflected in the effect of the particle morphology on the processability of the material; in contrast, the morphology has no effect on the radio-opacity of the samples. The structure and dispersion of the particles were analyzed using scanning and transmission electron microscopy. The sample with 1wt.% nanofibers presents better processability than the system with spherical agglomerates maintaining the X-ray opacity properties.
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