Effect of fluorine doping on the properties of tin oxide based powders prepared via Pechini’s method

Esteves, Marcos C.; Gouvêa, Douglas; Sumodjo, Paulo Teng An

doi:10.1016/j.apsusc.2004.02.015

Cited by 23 publications

(14 citation statements)

References 8 publications

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“…The presence of dopant did not modify the cassiterite structure when compared the samples obtained at 400°C. The same behaviour was observed by Esteves in fluorine doping [19].…”

Section: Xrd Measurementssupporting

confidence: 76%

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

et al. 2008

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Metallic nanoaggregates deposited on nonconductive oxides powders as catalysts have shown good efficiency in electrocatalytic hydrogenation (ECH). In this process, the polarization of the metallic nanoaggregates is very important. This polarization can be improved when the electrode material is conductive. Thus, the goal of this work was to study the effect of the conduction of the supported material on the ECH process. Tin dioxide was chosen as oxide because it can be obtained in non-conductive or conductive form by doping with fluorine. Palladium supported catalysts powders were prepared by the sol-gel method. These electrocatalysts were characterized by XRD, SEM, TGA/DSC, FTIR and electrical conductivity. The effects of temperature and time of calcination were also investigated. Comparison of nonconductive and conductive catalysts for ECH of phenol shows that conductive F-doped SnO 2 increases the rate of electrohydrogenation.

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“…The presence of dopant did not modify the cassiterite structure when compared the samples obtained at 400°C. The same behaviour was observed by Esteves in fluorine doping [19].…”

Section: Xrd Measurementssupporting

confidence: 76%

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

et al. 2008

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“…A difficulty to overcome in the study of segregation in oxide is the quantification of the surface composition. In situ measurements of the dynamic electrophoretic mobility using the electrokinetic sonic amplitude (ESA) has been successfully used to study segregation on oxide nanopowders considering the changes in the IEP (isoelectric point) and dispersion electrical conductivity during the surface titration …”

Section: Introductionmentioning

confidence: 99%

“…In situ measurements of the dynamic electrophoretic mobility using the electrokinetic sonic amplitude (ESA) has been successfully used to study segregation on oxide nanopowders considering the changes in the IEP (isoelectric point) and dispersion electrical conductivity during the surface titration. 6,31,46 Therefore, this work aims to propose a chemical method by selectively solubilizing the additive to quantify the surface and grain-boundary excess, and the method was applied to the ZnO-doped SnO 2 nanopowders that were prepared using the polymeric precursor method. The chemical compositions of the bulk, grain boundary, and surface were related to the colloidal properties and stabilization of the particle size.…”

Section: Introductionmentioning

confidence: 99%

Surface and grain‐boundary excess of ZnO‐doped SnO₂ nanopowders by the selective lixiviation method

2017

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The primary characteristic of nanopowders is the high surface area and consequently high fraction of atoms on the interfaces, which changes the energy of the system. The additive distribution in the nanopowder interfaces is a fundamental aspect to control the energy, particle size, and final properties of nanopowders. In this work, the surface excess was determined using a selective lixiviation method, where a low‐water‐soluble oxide, SnO2, was used as the matrix, and a high‐water‐soluble oxide, ZnO, was used as the additive. The X‐ray photoelectron spectroscopy (XPS) analysis confirmed that ZnO segregated on SnO2 surfaces. However, after acid lixiviation the same analysis showed an undetectable surface concentration of ZnO. The evaluation of the nanostructure change and surface composition enables us to calculate the heat of segregation for the grain boundary (ΔHsegnormalgb=−47.2kJ·mol−1) and surface (ΔHsegnormals=−36.4kJ·mol−1) and the interface energy reduction because of segregation. At low‐ZnO concentrations, the additive solubilizes in the bulk and promotes particle growth. However, the segregation to the grain boundary and surface determines the relative stability of each interface, which promotes hard agglomeration and particle size stabilization at intermediated ZnO amounts. At high‐ZnO concentrations, the surface segregation stabilizes the solid‐gas interface and decreases the agglomeration and final particle size.

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“…115 The isoelectric point is determined preparing a suspension of the support and by acid-base titration measuring the electrokinetic mobility. 116,117 According to Toebes et al, the approximate IEPs for the common Pd supports are (values in parentheses): 118 SiO 2 (1.0-2.0) < MnO 2 (3.9-4.5) < SnO 2 (5.5) < TiO 2 (6.0) < ZrO 2 (6.7) < CeO 2 (6.8) < α,γ-Al 2 O 3 (7.0-9.0) < ZnO (8.7-9.7) < MgO (12.1-12.7).…”

mentioning

confidence: 99%

Engineering in direct synthesis of hydrogen peroxide: targets, reactors and guidelines for operational conditions

et al. 2014

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The demand for hydrogen peroxide is booming since it is considered as one of the most environmentally friendly and versatile chemical oxidants available and has a wide range of applications. The annual market, close to 3000 kt per year being produced via the auto-oxidation process (with 2-ethyl anthraquinone (traditional) or amyl anthraquinone for mega-plants), is mostly supplied by the company Solvay (30%), followed by Evonik (20%) and Arkema (13%). Nevertheless, the dream of a direct synthesis process is close to a century old and it has gained momentum in research efforts during the last decade with more than 15 groups active in the world. In this review, we focus the discussion on the targets, e.g. plant tonnage, the reactors and the most feasible industrial operational conditions, based on our experience and point of view using the chemical engineering tools available. Thus, direct synthesis can be competitive when on-site production is required and capacities less than 10 kt per year are He has led and participated in 3 EU, 6 national/regional projects and 10+ SME contracts and has published 30+ research papers. Teresa MorenoTeresa Moreno obtained her degree in Chemical Engineering from Complutense University (Madrid, Spain) and later completed her PhD in Chemical Engineering at the University of Valladolid (Spain, 2011) studying the catalytic direct synthesis of hydrogen peroxide in supercritical CO 2 and the online determination of the product using Raman spectroscopy. She is currently a Research Scientist in the Industrial Bioactive Technologies Group at Callaghan Innovation (New Zealand) working on the development of processes for adding value to natural materials toward high value products and applications, including the development of sustainable technologies using supercritical fluids. View Article OnlineView Journal | View Issue and semi-continuous modes of operation. However, at the moment, demonstrations of continuous operations as well as carefully determined kinetics are needed in order to scale up the process. Finally, operational conditions, including the catalyst composition (active metal, oxidation state and support), promoters (halides and acids-pH-isoelectric point), solvents, pressure and temperature need to be carefully analysed. In our opinion, as we try to show here, H 2 O 2 direct synthesis is a competitive process and is ready for larger scale demonstration. Also, more than a hundred patents within the area support this claim, although the barriers of technology demonstration and further licensing are still pending.

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Effect of fluorine doping on the properties of tin oxide based powders prepared via Pechini’s method

Cited by 23 publications

References 8 publications

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

Surface and grain‐boundary excess of ZnO‐doped SnO₂ nanopowders by the selective lixiviation method

Engineering in direct synthesis of hydrogen peroxide: targets, reactors and guidelines for operational conditions

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Effect of fluorine doping on the properties of tin oxide based powders prepared via Pechini’s method

Cited by 23 publications

References 8 publications

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

Effect of support conductivity of catalytic powder on electrocatalytic hydrogenation of phenol

Surface and grain‐boundary excess of ZnO‐doped SnO2 nanopowders by the selective lixiviation method

Engineering in direct synthesis of hydrogen peroxide: targets, reactors and guidelines for operational conditions

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Surface and grain‐boundary excess of ZnO‐doped SnO₂ nanopowders by the selective lixiviation method