The effect of the starting material on the thermal decomposition of iron oxyhydroxides

The effect of the iron precursor on the thermal decomposition of iron oxyhydroxides was studied by DSC, DTA and TG in this work. Samples were prepared from iron nitrate, iron sulfate and iron chloride and the thermal curves obtained were analyzed by specific area measurements, X-ray diffraction and Mössbauer spectroscopy. It was found that the iron oxyhydroxide precursors affect the temperatures of the hematite formation as well as the textural properties of the final hematite producing particles with different diameters as following: iron sulfate (3.3 nm)<<iron nitrate (15 nm)<iron chloride (24 nm).Centro de Investigación y Desarrollo en Ciencias Aplicada

Selective Catalytic Reduction of NOx by CO over Cu(Fe)/SBA-15 Catalysts: Effects of the Metal Loading on the Catalytic Activity

Mesoporous Cu(Fe)/SBA-15 catalysts were prepared with distinct metal loadings of ca. 2–10 wt.%. A detailed set of characterizations using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS), Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy was performed to correlate the relationship among structure, electronic properties and catalytic performances. All solids were evaluated in the selective catalytic reduction of NOx in the presence of CO (CO-SCR). The influence of the metal loadings on the overall activity indicated that introducing high amounts of Fe or Cu on the catalysts was beneficial to form either CuO or α-Fe2O3 clusters. Cux/SBA-15 series exhibited more efficient activity and poison-tolerant ability during CO-SCR reaction, in contrast to Fex/SBA-15. In spite of the Fe species introduced on SBA-15 having structural features similar to those of Cu ones, low interactions among Fe nanoparticles, silica and clusters impeded the high performances of Fe10/SBA-15. XPS revealed the Fe species in a more oxidized state, indicating the stability of the solid after the catalytic tests, in agreement with EPR and Raman spectroscopy. Cu8/SBA-15 worked better, being recyclable due to the interaction of the Cu2+ ions with SBA-15, avoiding the deactivation of the catalyst.The authors acknowledge the financial support by the Funcap (Grant PS1-0186-00346.01.00/21). A.C.O. and ERC thank to Ministerio de Ciencia e Innovación (Spain) projects PID2021-126235OB-C32 and TED2021-130756B-C31, and FEDER funds. Partial funding for open access charge: Universidad de Málag

Effect of Basic Promoters on Porous Supported Alumina Catalysts for Acetins Production

A facile strategy for the design of porous supports was obtained by modifying the sol-gel method followed by the wet impregnation technique. In this respect, herein, the acidity of the γ-Al2O3 phase was modulated by adding basic MgO, La2O3 or ZnO promoters to form binary supported catalysts. The Ni and Co dispersion on the supports associated with their tunable acidity and morphologies resulted in highly porous supported alumina-based catalysts. The physicochemical properties of the solids were comprehensively investigated by XRD, textural properties, Raman and FTIR spectroscopy, SEM-EDS, TEM, EPR and XPS analyses. The catalytic performances in the esterification of glycerol in the presence of acetic acid (EG) for the acetins production were evaluated. The highly dispersed NiO and Co3O4 active species on binary porous supports produced synergistic effects appearing to be the reason for the activity of the solids in the EG reaction. Under the optimized reaction conditions, NiCo/MgO-Al2O3 was found to be a robust solid with superior catalytic performance and improved stability in four reaction cycles with 65.0% of glycerol conversion with an exclusive selectivity of 53% for triacetin. The presence of Co2+/Co3+ and Ni2+ strongly interacting with the spinel γ-Al2O3 and MgAl2O4 phases, the latter having a large number of lattice oxygen species, was considered another active component besides those of Ni and Co in the esterification of glycerol.This work is supported by Funcap (Grant n° PS1-0186-00346.01.00/21). Financial assistance received from Ministerio de Ciencia e Innovación, Junta de Andalucía and FEDER is also thankfully acknowledged for funding project n° PID2021-126235OB-C32, UMA18-FEDERJA-126 and P20_00375. Partial funding for open access charge: Universidad de Málag

Characterizations of nanostructured nickel aluminates as catalysts for conversion of glycerol: Influence of the preparation methods

Three different preparation methods were applied to prepare nickel aluminates (i.e. nanocasting (NiAlN), coprecipitation (NiAlC) and wet impregnation (NiAlW) methods). All catalysts exhibited the NiAl2O4 phase besides that of NiO and γ-Al2O3. The NiAlN catalyst showed nanoparticles of the aforesaid oxides whereas NiAlxOy was the predominant phase found over NiAlW catalyst. The performances of the nickel aluminate-based catalysts were evaluated in glycerol dehydration to produce valuable chemical compounds through the dehydration of glycerol. The sintering effects were responsible for the decreased performance of NiAlC in glycerol dehydration. On the contrary, NiAlN is found to be deactivated due to the lesser stability of its supported nanoparticles, being the glycerol conversion of ca. 3.3% at the end of the reaction. Besides, the reaction efficiently proceeded on NiAlW, which had a high catalytic performance with 19.7% glycerol conversion to acetol and others products and no deactivation along of the time for 25 h of time on stream was observed. This was due to the stability of the NiAlxOy phase, which impeded phase transformation and was resistant to heavy coking.Fil: Neto, Antonio S. B.. Universidade Federal do Ceará; BrasilFil: Oliveira, Alcemira C.. Universidade Federal do Ceará; BrasilFil: Mendes Filho, Josué. Universidade Federal do Ceará; BrasilFil: Amadeo, Norma Elvira. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles; ArgentinaFil: Dieuzeide, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles; ArgentinaFil: de Sousa, Francisco F.. Universidade Federal do Pará; BrasilFil: Oliveira, Alcineia C.. Universidade Federal do Ceará; Brasi

CeFe-Based Bead Nanocomposites as Catalysts for Oxidation of Ethylbenzene Reaction

Oxides with good catalytic performances and more selectivity to valuable chemicals attract numerous research interests for the oxidation of hydrocarbon fuels. Taking advantage of the nanocasting route, CeFe-based nanocomposites were prepared and characterized to achieve superior stability in the oxidation of cyclic compounds. Adding a third metal (Me = Ni2+, Mn2+/Mn3+ or Co2+/Co3+) to the CeFe-based oxide helped the formation of Ce3+/Ce4+, Fe2+/Fe3+ and active couples in the ternary nanocomposites. The solids having a spherical morphology and good textural properties enabled the formation of promising ternary oxide catalysts for the oxidation of ethylbenzene compared with those of binary and single monoxide nanocomposites. The close contact among the Ce3+/Ce4+ and Fe2+/Fe3+ pairs with Ni2+ species provided the formation of a highly stable CeFeNi catalyst with enhanced performance in the oxidation of cyclic compounds such as ethylbenzene, styrene and benzyl alcohol substrates

Applied catalysis a-general

Acesso restrito: Texto completo. p. 50-62.Catalytic performance of binary nanostructured oxides has been evaluated in the gasphase dehydration of glycerol, an environmental friendly reaction. SnO2–Mn2O3, SnO2–ZrO2, SnO2–TiO2, ZrO2–Mn2O3 nanocasted oxides, and a reference, NiO–Co3O4, were characterised by XRD, Raman spectroscopy, acid–base measurements, SEM–EDX, TPR, HTEM and XPS. Correlations among the catalyst’s activity and the surface, textural, and acid–base properties of the nanocasted oxides were tentatively conducted in attempts to justify the catalytic results. Influences of nanoparticle or nanostructure structural properties on the catalytic activity have been investigated. The better activity of SnO2–TiO2 at 250 ◦C and a glycerol/ water molar ratio of 0.25 was due to cooperativity of Sn4+ and Ti4+. The most important finding was that nanostructure features of the solid enhanced nanoparticle stability through the redox ability of the binary solid compared to conventional binary catalysts

Applied catalysis a-general

Acesso restrito: Texto completo. p. 50-62.Catalytic performance of binary nanostructured oxides has been evaluated in the gasphase dehydration of glycerol, an environmental friendly reaction. SnO2–Mn2O3, SnO2–ZrO2, SnO2–TiO2, ZrO2–Mn2O3 nanocasted oxides, and a reference, NiO–Co3O4, were characterised by XRD, Raman spectroscopy, acid–base measurements, SEM–EDX, TPR, HTEM and XPS. Correlations among the catalyst’s activity and the surface, textural, and acid–base properties of the nanocasted oxides were tentatively conducted in attempts to justify the catalytic results. Influences of nanoparticle or nanostructure structural properties on the catalytic activity have been investigated. The better activity of SnO2–TiO2 at 250 ◦C and a glycerol/ water molar ratio of 0.25 was due to cooperativity of Sn4+ and Ti4+. The most important finding was that nanostructure features of the solid enhanced nanoparticle stability through the redox ability of the binary solid compared to conventional binary catalysts

Selective Catalytic Reduction of NOx by CO over Doubly Promoted MeMo/Nb2O5 Catalysts (Me = Pt, Ni, or Co)

Doubly promoted MeMo/Nb2O5 catalysts, in which Me = Pt, Ni, or Co oxides were prepared for the selective catalytic reduction of NOx by CO reaction (CO-SCR). Comparable chemical, textural, and structural analyses revealed similarities between NiMo and CoMo impregnated on Nb2O5, in contrast to PtMo sites, which were not homogeneously dispersed on the support surface. Both the acid function and metal dispersion gave a synergistic effect for CO-SCR at moderate temperatures. The reactivity of PtMo catalysts towards NOx and CO chemisorption was at low reaction temperatures, whereas the NOx conversion over CoMo was greatly improved at relatively high temperatures. Careful XPS, NH3-TPD, and HRTEM analyses confirmed that the large amounts of strong and moderate acid sites from PtOx entrapped on MoO3 sites induced high NOx conversions. NiMo/Nb2O5 showed poor performance in all conditions. Poisoning of the MeMo sites with water vapor or SO2 (or both) provoked the decline of the NOx conversions over NiMo and PtMo sites, whereas the structure of CoMo ones remained very active with a maximum NOx conversion of 70% at 350 °C for 24 h of reaction. This was due to the interaction of the Co3+/Co2+ and Mo6+ actives sites and the weak strength Lewis acid Nb5+ ones, as well