The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Lutz Mädler - One of the best experts on this subject based on the ideXlab platform.

  • phase selective laser induced breakdown spectroscopy in Flame Spray Pyrolysis for iron oxide nanoparticle synthesis
    Proceedings of the Combustion Institute, 2020
    Co-Authors: Udo Fritsching, Lutz Mädler, Malte F B Stodt, Chenyang Liu, Johannes Kiefer
    Abstract:

    Abstract The Flame Spray Pyrolysis of iron oxide nanoparticles using the new reference nozzle SpraySyn is a key step towards the understanding of the coupling of physicochemical steps such as precursor atomization, Spray evaporation, combustion, particle formation and growth. Owing to the countless available solvents and precursors, systematic investigations are necessary to fully understand the impact of precursor formulation on the reaction route and, hence, the particle properties. In this work, the recently developed phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique is applied to an external mixing Spray Flame reactor in order to study iron oxide particle formation along the axial centerline of the Spray under varying precursor solutions. The addition of 2-ethylhexanoic acid (EHA) to precursors is investigated and significant differences in the evolution of the atomic emission spectra are observed, enabling the differentiation between droplet-to-particle and gas-to-particle routes in situ. The observations from PS-LIBS are in good agreement with TEM images and XRD, where haematite (α-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) were observed. Raman spectroscopy (RS) in particle-free Spray-Flames revealed a significant gas-phase temperature difference of about ΔT∼500 K under addition of EHA to the Spray and demonstrated accurate temperature measurements up to droplet rates of 103 Hz. The experimental results allow deep insights into the Spray Flame combustion and particle nucleation kinetics. Moreover, they can be coupled with population balance models and be used for the validation of numerical simulations.

  • asymmetrical double Flame Spray Pyrolysis designed sio2 ce0 7zr0 3o2 for the dry reforming of methane
    ACS Applied Materials & Interfaces, 2019
    Co-Authors: Emma C Lovell, Lutz Mädler, Jonatha Horlyck, Henrike Grosman, Jason Scott, Rose Amal
    Abstract:

    Silica has the potential to enhance the performance of ceria-zirconia as a support for the dry reforming of methane; however, controlling the integration of silica with the ceria-zirconia using Flame Spray Pyrolysis (FSP) is a significant challenge. To address this challenge, an asymmetrically variable double-FSP (DFSP) system was established to control the SiO2 interaction with Ce0.7Zr0.3O2. The engineered materials were then utilized as supports for Ni for the dry reforming of methane. Initially, silica formation during FSP synthesis was examined where it was revealed that, at a low precursor concentration (<1.5 M tetraethyl orthosilicate in xylenes), the physical characteristics of the silica varied differently in relation to what is typically encountered during FSP synthesis. Explicitly, on using a 0.5 M tetraethyl orthosilicate precursor, increasing the FSP feed rate provided an increase in the specific surface area from 217 m2/g at 3 mL/min to 363 m2/g at 7 mL/min. Adopting this knowledge on silica formation under these conditions, the asymmetrical DFSP system was then exploited to regulate the integration of ceria-zirconia with the silica. To restrict the silica from coating the particles during DFSP, the intersection distance along the silica Flame was tuned from 18.5 to 28.5 cm, whereas the distance along the ceria-zirconia Flame was fixed at 5 cm. It was found that at short intersection distances the ceria-zirconia provided sites for silica nucleation and growth, resulting in high surface-area silica encapsulating the ceria-zirconia. At large intersection distances, encapsulation of the ceria-zirconia by silica was suppressed. An enhanced oxygen storage capacity and basicity along with the small Ni sizes facilitated by the longer intersection distances produced the most selective catalyst for the dry reforming of methane.

  • fabrication and performance of li4ti5o12 c li ion battery electrodes using combined double Flame Spray Pyrolysis and pressure based lamination technique
    Journal of Power Sources, 2018
    Co-Authors: Michael Gockeln, Florian Meierhofer, Jens Glenneberg, Suman Pokhrel, Marco Schowalter, Andreas Rosenauer, Udo Fritsching, Matthias Busse, Lutz Mädler
    Abstract:

    Abstract Reduction of lithium-ion battery (LIB) production costs is inevitable to make the use of LIB technology more viable for applications such as electric vehicles or stationary storage. To meet the requirements in today's LIB cost efficiency, our current research focuses on an alternative electrode fabrication method, characterized by a combination of double Flame Spray Pyrolysis and lamination technique (DFSP/lamination). In-situ carbon coated nano-Li4Ti5O12 (LTO/C) was synthesized using versatile DFSP. The as-prepared composite powder was then directly laminated onto a conductive substrate avoiding the use of any solvent or binder for electrode preparation. The influence of lamination pressures on the microstructure and electrochemical performance of the electrodes was also investigated. Enhancements in intrinsic electrical conductivity were found for higher lamination pressures. Capacity retention of highest pressurized DFSP/lamination-prepared electrode was 87.4% after 200 dis-/charge cycles at 1C (vs. Li). In addition, LTO/C material prepared from the double Flame Spray Pyrolysis was also used for fabricating electrodes via doctor blading technique. Laminated electrodes obtained higher specific discharge capacities compared to calendered and non-calendered blade-casted electrodes due to superior microstructural properties. Such a fast and industrially compelling integrative DFSP/lamination tool could be a prosperous, next generation technology for low-cost LIB electrode fabrication.

  • screening precursor solvent combinations for li4ti5o12 energy storage material using Flame Spray Pyrolysis
    ACS Applied Materials & Interfaces, 2017
    Co-Authors: Florian Meierhofer, Michael Gockeln, Andreas Rosenauer, Udo Fritsching, Lutz Mädler, Johannes Birkenstock, Robert Kun, Tim Grieb, Johannes Kiefer, Suman Pokhrel
    Abstract:

    The development and industrial application of advanced lithium based energy-storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor materials. Flame Spray Pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process control, material versatility, and cost. In the present study, phase pure anode material Li4Ti5O12 (LTO) was designed using FSP via extensive systematic screening of lithium and titanium precursors dissolved in five different organic solvents. The effect of precursor and solvent parameters such as chemical reactivity, boiling point, and combustion enthalpy on the particle formation either via gas-to-particle (evaporation/nucleation/growth) or via droplet-to-particle (precipitation/incomplete evaporation) is discussed. The presence of carboxylic acid in the precursor solution resulted in pure (>95 mass %) and homogeneous LTO nanoparticles of size 4–9 nm, attributed to...

  • decrease of the required dopant concentration for δ bi2o3 crystal stabilization through thermal quenching during single step Flame Spray Pyrolysis
    CrystEngComm, 2016
    Co-Authors: Jochen A H Dreyer, Suman Pokhrel, Marco Schowalter, Andreas Rosenauer, Wey Yang Teoh, Johannes Birkenstock, Miguel A G Hevia, Atsushi Urakawa, Lutz Mädler
    Abstract:

    δ-Bi2O3 is one of the best oxygen ion conductors known. However, due to its limited thermal stability and complicated synthesis techniques, its applications are limited. Here, the synthesis of stable nano-sized δ-Bi2O3 using versatile and rapid Flame Spray Pyrolysis (FSP) combined with in situ Ti and/or Mn doping for an enhanced thermal stability is reported for the first time. Exceptionally low Bi replacing cation concentrations (8 at% Ti) were sufficient to obtain phase-pure δ-Bi2O3 which was attributed to the extraordinarily high temperature gradient during FSP. The required cation amount for δ-phase stabilization was even further reduced by introducing mixtures of Mn and Ti (2.5 at% Mn + 2.5 at% Ti). Rietveld analysis revealed that the δ-Bi2O3 structure is best represented by the Fmm space group containing two closely neighbored 8c and 32f Wyckoff positions. Depending on the amount of Mn/Ti cations, about 25% of the possible oxygen positions remain vacant, suggesting high bulk oxygen mobility. The enhanced oxygen mobility was confirmed by temperature programmed reduction (H2-TPR) with bulk reduction for δ-Bi2O3 in contrast to exclusive surface reduction for β-Bi2O3.

Richard M Laine - One of the best experts on this subject based on the ideXlab platform.

  • photocatalytic la4ti3o12 nanoparticles fabricated by liquid feed Flame Spray Pyrolysis
    Ceramics International, 2020
    Co-Authors: Yoshiyuki Abe, Richard M Laine
    Abstract:

    Abstract Hexagonal plate-like nanoparticles (NPs) of the layered perovskite La4Ti3O12 were fabricated using liquid-feed Flame Spray Pyrolysis (LF-FSP) followed by subsequent heat-treatments. Their photocatalytic activity was evaluated using decolorization of methyl orange solutions under Uv irradiation. LF-FSP combusts metalloorganic precursor aerosols to produce mixtures of cubic simple perovskite (ABO3) phase and lanthanum oxycarbonate (La2O4·846C0.846) phase with very low agglomeration and average particle sizes (APSs) of 23 nm (as-produced NPs). Rietveld refinement of synchrotron XRD powder patterns verified that the simple perovskite in the as-produced NPs is LaTiO3 (originally cubic Pm-3m-type space group) and heat-treating gives NPs of the trigonal layered perovskite La4Ti3O12 (R-3-type space group). La4Ti3O12 NPs heat-treated at 1100 °C/3-6h/air exhibits hexagonal plate-like morphology and high crystallinity offering enhanced photocatalytic degradation of methyl orange solutions compared to the as-produced NPs. The LF-FSP approach to obtaining layered perovskite La4Ti3O12 NPs provides a simple route to photocatalytic materials in reasonable quantities.

  • liquid feed Flame Spray Pyrolysis derived nanopowders nps as a route to electrically conducting calcium aluminate 12cao 7al2o3 films
    Journal of The European Ceramic Society, 2019
    Co-Authors: Eleni Temeche, Vazrik Keshishia, Joh Kieffe, Richard M Laine
    Abstract:

    Abstract Traditionally, C12A7 materials have been processed via solid-state reaction followed by pulsed laser deposition (PLD) or floating zone (Fz) crystallization methods at high temperature, high cost approaches to single-phase films. These techniques require a significant number of process steps to generate C12A7:e− materials that have been shown to exhibit exceptional electrical conductivities as high as 1 S/cm. We demonstrate here an effective alternative method using Flame made C12A7 nanopowders (NPs) produced via liquid-feed Flame Spray Pyrolysis (LF-FSP). Nearly fully dense, single phase, and transparent C12A7 films ( ℃ /3 h/O2. Subsequent heat treatments in 20/80 H2/N2 replaces cage trapped O2- ions forming C12A7:H− followed by UV irradiation to generate C12A7:e− with electrical conductivities of 35 mS cm-1. C12A7:e- appears to belong to a new class of transparent conducting oxides (TCOs) that may offer commercial potential on further optimization due to low materials and processing costs, environmental stability, and natural abundance when processed efficiently.

  • synthesis of zn1 xcoxal2o4 spinel nanoparticles by liquid feed Flame Spray Pyrolysis ceramic pigments application
    JOM, 2016
    Co-Authors: Natalia Betancur Granados, Richard M Laine, Oscar Jaime Restrepo Baena
    Abstract:

    Zn1� xCoxAl2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) spinel nanoparticles were synthesized by a liquid-feed Flame Spray Pyrolysis (LF-FSP) method by combusting metallorganic precursor solutions to produce nanopowders with precise composition control. The precursor solutions were aerosolized into a methane/oxygen Flame where it was combusted in an oxygen-rich environment to result in nanopowders at a single step. The nanopowders were analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, colorimetry, field emission scanning electron microscopy, transmission electron microscopy, and BET (Brunauer–Emmett–Teller) N2 adsorption. Results show formation of spherical nanopowders with specific surface areas of 42 m 2 /g to 50 m 2 /g, which correspond to average particle sizes of 26 nm to 31 nm. Single-phase materials were obtained with a high control of composition, which indicates that LF-FSP is an excellent method to produce mixed-metal oxides for applications in which powder homogeneity is crucial. The products were evaluated for ceramic pigment application, where the ratio of Zn to Co was gradually changed to observe the color change in the structure with the increase of cobalt concentration. The resulting pigments were calcined at 1200C, which aimed to identify the color stability after a high-temperature process, whereby the colors were measured using the color space CIE L*a*b* under standardized light, D65. Finally, the powders were tested for ceramic decoration using transparent glazes and ceramic bodies. The application was carried out at 1250C to evaluate the color performance after a decoration process.

  • coal2o4 blue nanopigments prepared by liquid feed Flame Spray Pyrolysis method
    Materia-rio De Janeiro, 2015
    Co-Authors: Natalia Betancur Granados, Richard M Laine, Oscar Jaime Restrepo Baena
    Abstract:

    CoAl2O4 pigments were synthesized through Liquid-Feed Flame Spray Pyrolysis (LF-FSP) method using metallorganic precursors of cobalt propionate and alumatrane. The precursors were dissolved in ethanol and aerosolized into a methane/oxygen Flame where it was combusted to result in nanopowders at a single step. The resulting nanopowders were collected in electrostatic precipitators and analyzed by x-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), colorimetry, Field Emission Scanning Electron Microscopy (FE-SEM) and BET (Brunauer-Emmett-Teller) nitrogen adsorption. Results show formation of single phase blue nanopigments, suggesting that LF-FSP is an excellent method to produce nanoparticles with high quality in a continuous process for new industrial applications. The nanoparticles presented spherical morphology with specific surface area of 50 m2/g, corresponding to average particle size of 27 nm. The pigments were calcined at 500, 600, 800, 1000, 1200 and 1300 °C, aiming to find the color stability whereby the colors were measured using the color space CIE L*a*b* under standardized D65 light. The brightest and bluest was obtained at calcination temperature of 1200°C and its application into a glaze was carried out at 1200 °C to evaluate the color performance and stability after a decoration process. Finally, LF-FSP produced pigments were compared with those produced by solid state reaction. Differences in the color due to the average particle size and process conditions were observed. It is possible to obtain new hues for ceramic applications by LF-FSP method.

  • combinatorial nanopowder synthesis along the zno al2o3 tie line using liquid feed Flame Spray Pyrolysis
    Journal of the American Ceramic Society, 2011
    Co-Authors: Min Kim, Samson Yuxiu Lai, Richard M Laine
    Abstract:

    Liquid-feed Flame Spray Pyrolysis (LF-FSP) of mixtures of alumatrane [Al(OCH2CH2)3N]/zinc acetate dihydrate [Zn(O2CCH3)2·2(H2O)] or zinc propionate [Zn(O2CCH2CH3)2]/aluminum acetylacetonate [Al(Acac)3] dissolved in EtOH in known molar ratios can be used to combinatorially generate nanopowders along the ZnO–Al2O3 tie-line. LF-FSP was used to produce (ZnO)x(Al2O3)1−x powders with x=0–1.0. Powders were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, thermal gravimetric analysis, differential thermal analysis, and BET. The resulting powders had average particle sizes (APSs) <100 nm with the majority being <50 nm. Analytical data suggest that at concentrations of interest for transparent conducting oxides, <10 mol% Al2O3 the particle morphologies are combinations of plates and rods that grow with c/a ratios close to 1. The spinel phase dominates at (ZnO)x(Al2O3)1−x (x=0.5 and 0.3). In the latter case, the currently accepted phase diagram for the ZnO–Al2O3 couple indicates that phase separation should occur to form zinc spinel (ZnAl2O4) and α-alumina. It appears that the rapid quenching during LF-FSP helps to preserve the spinel phase at ambient temperature giving rise to kinetic nanopowder products along the ZnO2–Al2O3 tie-line. Finally, the solubility of ZnO in Al2O3 and vice versa in the materials produced by LF-FSP suggest apparent Flame temperatures reached before quenching are 1700°–1800°C. Efforts to re-pass the spinel phase powders, (ZnO)x(Al2O3)1−x, x=0.5 and 0.3 through the LF-FSP system were made with the hope of generating core shell materials. However, instead the x=0.5 material generated materials closer to the x=0.3 composition and pure ZnO nanoparticles that coat the former materials. These results suggest that at LF-FSP Flame temperatures ZnO remains in the vapor phase for sufficient times that Al3+ oxy-ions generated promote nucleation of finer particles leaving essentially phase pure ZnO still in the vapor phase to condense giving the two distinct particle morphologies observed.

Suman Pokhrel - One of the best experts on this subject based on the ideXlab platform.

  • fabrication and performance of li4ti5o12 c li ion battery electrodes using combined double Flame Spray Pyrolysis and pressure based lamination technique
    Journal of Power Sources, 2018
    Co-Authors: Michael Gockeln, Florian Meierhofer, Jens Glenneberg, Suman Pokhrel, Marco Schowalter, Andreas Rosenauer, Udo Fritsching, Matthias Busse, Lutz Mädler
    Abstract:

    Abstract Reduction of lithium-ion battery (LIB) production costs is inevitable to make the use of LIB technology more viable for applications such as electric vehicles or stationary storage. To meet the requirements in today's LIB cost efficiency, our current research focuses on an alternative electrode fabrication method, characterized by a combination of double Flame Spray Pyrolysis and lamination technique (DFSP/lamination). In-situ carbon coated nano-Li4Ti5O12 (LTO/C) was synthesized using versatile DFSP. The as-prepared composite powder was then directly laminated onto a conductive substrate avoiding the use of any solvent or binder for electrode preparation. The influence of lamination pressures on the microstructure and electrochemical performance of the electrodes was also investigated. Enhancements in intrinsic electrical conductivity were found for higher lamination pressures. Capacity retention of highest pressurized DFSP/lamination-prepared electrode was 87.4% after 200 dis-/charge cycles at 1C (vs. Li). In addition, LTO/C material prepared from the double Flame Spray Pyrolysis was also used for fabricating electrodes via doctor blading technique. Laminated electrodes obtained higher specific discharge capacities compared to calendered and non-calendered blade-casted electrodes due to superior microstructural properties. Such a fast and industrially compelling integrative DFSP/lamination tool could be a prosperous, next generation technology for low-cost LIB electrode fabrication.

  • screening precursor solvent combinations for li4ti5o12 energy storage material using Flame Spray Pyrolysis
    ACS Applied Materials & Interfaces, 2017
    Co-Authors: Florian Meierhofer, Michael Gockeln, Andreas Rosenauer, Udo Fritsching, Lutz Mädler, Johannes Birkenstock, Robert Kun, Tim Grieb, Johannes Kiefer, Suman Pokhrel
    Abstract:

    The development and industrial application of advanced lithium based energy-storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor materials. Flame Spray Pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process control, material versatility, and cost. In the present study, phase pure anode material Li4Ti5O12 (LTO) was designed using FSP via extensive systematic screening of lithium and titanium precursors dissolved in five different organic solvents. The effect of precursor and solvent parameters such as chemical reactivity, boiling point, and combustion enthalpy on the particle formation either via gas-to-particle (evaporation/nucleation/growth) or via droplet-to-particle (precipitation/incomplete evaporation) is discussed. The presence of carboxylic acid in the precursor solution resulted in pure (>95 mass %) and homogeneous LTO nanoparticles of size 4–9 nm, attributed to...

  • decrease of the required dopant concentration for δ bi2o3 crystal stabilization through thermal quenching during single step Flame Spray Pyrolysis
    CrystEngComm, 2016
    Co-Authors: Jochen A H Dreyer, Suman Pokhrel, Marco Schowalter, Andreas Rosenauer, Wey Yang Teoh, Johannes Birkenstock, Miguel A G Hevia, Atsushi Urakawa, Lutz Mädler
    Abstract:

    δ-Bi2O3 is one of the best oxygen ion conductors known. However, due to its limited thermal stability and complicated synthesis techniques, its applications are limited. Here, the synthesis of stable nano-sized δ-Bi2O3 using versatile and rapid Flame Spray Pyrolysis (FSP) combined with in situ Ti and/or Mn doping for an enhanced thermal stability is reported for the first time. Exceptionally low Bi replacing cation concentrations (8 at% Ti) were sufficient to obtain phase-pure δ-Bi2O3 which was attributed to the extraordinarily high temperature gradient during FSP. The required cation amount for δ-phase stabilization was even further reduced by introducing mixtures of Mn and Ti (2.5 at% Mn + 2.5 at% Ti). Rietveld analysis revealed that the δ-Bi2O3 structure is best represented by the Fmm space group containing two closely neighbored 8c and 32f Wyckoff positions. Depending on the amount of Mn/Ti cations, about 25% of the possible oxygen positions remain vacant, suggesting high bulk oxygen mobility. The enhanced oxygen mobility was confirmed by temperature programmed reduction (H2-TPR) with bulk reduction for δ-Bi2O3 in contrast to exclusive surface reduction for β-Bi2O3.

  • tailoring high performance pd catalysts for chemoselective hydrogenation reactions via optimizing the parameters of the double Flame Spray Pyrolysis
    ACS Catalysis, 2016
    Co-Authors: Kyung Duk Kim, Suman Pokhrel, Lutz Mädler, Zichun Wang, Huajuan Ling, Cuifeng Zhou, Zongwen Liu, Michael Hunger, Jun Huang
    Abstract:

    Tuning the chemical composition during the synthesis is a widely used method to control the activity of catalysts. Here, we reported an alternative synthesis strategy to tune the catalytic properties of nanocatalysts without changing their precursors and compositions. We synthesized a series of Pd catalysts on the most popular SiO2-, Al2O3-, and silica–alumina supports using the double-Flame Spray Pyrolysis (FSP) technique. It was observed that various flow rates used for the synthesis of catalysts with the same composition affected the formation of the catalyst particles and their structures to further tune the surface acidity due to the correlation between acidity and structure, but the flow rates did not influence the electronic properties of Pd particles. It was observed that surface OH groups could associate Pd for the hydrogenation, but Lewis acid sites could not, as Pd/SA-30 and Pd/SiO2 showed much higher activity than Pd/Al2O3 for the same Pd size and surface properties. For Pd catalysts with Bron...

  • double Flame Spray Pyrolysis as a novel technique to synthesize alumina supported cobalt fischer tropsch catalysts
    Catalysis Today, 2013
    Co-Authors: M Minnermann, Suman Pokhrel, Henrike K Grossmann, Karsten Thiel, Helena E Hagelinweaver, Marcus Baumer, Lutz Mädler
    Abstract:

    Abstract The controlled deposition of a catalytically active material on a support, resulting in defined particle sizes and shapes, as well as control over the specific surface area of the active material and the support are usually limited when applying conventional catalyst preparation techniques. Flame Spray Pyrolysis offers the potential to overcome this limitation and is tested for the preparation of Fischer–Tropsch catalysts. Conventional single Flame Spray Pyrolysis and, for the first time, double Flame Spray Pyrolysis are compared for the synthesis of alumina supported cobalt catalysts. In the latter process the metal oxide precursors are combusted individually in two opposing nozzles. The key parameter for defining the final material composition is the intersection distance of the Flames, which was systematically varied. The Fischer–Tropsch performance of the Co-based catalysts was studied in a fixed bed reactor at 230 °C and 20 bar. The catalytic results are discussed on the basis of structural characterization of the different catalysts by XRD, BET, TPR, UV–vis and TEM/EF-TEM. While catalysts made by single Flame Spray Pyrolysis were inactive in the Fischer–Tropsch reaction regardless of whether cobalt was subsequently mixed with alumina or the supported catalyst was directly prepared in the Flame reactor, the double Flame Sprayed catalysts showed good catalytic activity. Depending on the intersection distance of the two Flames, the formation of cobalt oxide and alumina occurred separately in each Flame reactor. In spite of the independent particle growth in the two Flames, the double Flame reactor geometry lead to good adhesion of the two oxides resulting in good stabilization of cobalt nanoparticles on the alumina support during the Fischer–Tropsch reaction.

Rose Amal - One of the best experts on this subject based on the ideXlab platform.

  • asymmetrical double Flame Spray Pyrolysis designed sio2 ce0 7zr0 3o2 for the dry reforming of methane
    ACS Applied Materials & Interfaces, 2019
    Co-Authors: Emma C Lovell, Lutz Mädler, Jonatha Horlyck, Henrike Grosman, Jason Scott, Rose Amal
    Abstract:

    Silica has the potential to enhance the performance of ceria-zirconia as a support for the dry reforming of methane; however, controlling the integration of silica with the ceria-zirconia using Flame Spray Pyrolysis (FSP) is a significant challenge. To address this challenge, an asymmetrically variable double-FSP (DFSP) system was established to control the SiO2 interaction with Ce0.7Zr0.3O2. The engineered materials were then utilized as supports for Ni for the dry reforming of methane. Initially, silica formation during FSP synthesis was examined where it was revealed that, at a low precursor concentration (<1.5 M tetraethyl orthosilicate in xylenes), the physical characteristics of the silica varied differently in relation to what is typically encountered during FSP synthesis. Explicitly, on using a 0.5 M tetraethyl orthosilicate precursor, increasing the FSP feed rate provided an increase in the specific surface area from 217 m2/g at 3 mL/min to 363 m2/g at 7 mL/min. Adopting this knowledge on silica formation under these conditions, the asymmetrical DFSP system was then exploited to regulate the integration of ceria-zirconia with the silica. To restrict the silica from coating the particles during DFSP, the intersection distance along the silica Flame was tuned from 18.5 to 28.5 cm, whereas the distance along the ceria-zirconia Flame was fixed at 5 cm. It was found that at short intersection distances the ceria-zirconia provided sites for silica nucleation and growth, resulting in high surface-area silica encapsulating the ceria-zirconia. At large intersection distances, encapsulation of the ceria-zirconia by silica was suppressed. An enhanced oxygen storage capacity and basicity along with the small Ni sizes facilitated by the longer intersection distances produced the most selective catalyst for the dry reforming of methane.

  • Flame Spray Pyrolysis designed silica ceria zirconia supports for the carbon dioxide reforming of methane
    Applied Catalysis A-general, 2017
    Co-Authors: Emma C Lovell, Jonatha Horlyck, Jaso Sco, Rose Amal
    Abstract:

    Abstract Flame Spray Pyrolysis (FSP) was used to design silica/ceria-zirconia particles with assorted structures as Ni catalyst supports for the carbon dioxide reforming of methane. The FSP precursor feed was varied to produce either mixed-oxide or core-shell arrays. The structures exhibited diversity in their properties including surface area and oxygen storage capacity. NiO deposit size decreased with increasing ceria-zirconia content, from 14 nm for the neat SiO 2 to 5 nm for the neat Ce 0.7 Zr 0.3 O 2 . Compared to the neat supports, the co-operative benefits of coupling the silica with the ceria-zirconia were clear. Introducing ceria-zirconia to the silica enabled the mixed supports to outperform the neat silica by supressing methane decomposition and promoting the dry reforming reaction. Introducing silica to the ceria-zirconia enabled the mixed supports to outperform the neat ceria-zirconia by decreasing susceptibility toward the reverse water gas shift reaction and preventing deactivation at 700 °C, attributed to better support thermal stability.

  • ni sio2 catalysts for the carbon dioxide reforming of methane varying support properties by Flame Spray Pyrolysis
    Molecules, 2015
    Co-Authors: Emma C Lovell, Jaso Sco, Rose Amal
    Abstract:

    Silica particles were prepared by Flame Spray Pyrolysis (FSP) as a support for nickel catalysts. The impact of precursor feed rate (3, 5 and 7 mL/min) during FSP on the silica characteristics and the ensuing effect on catalytic performance for the carbon dioxide, or dry, reforming of methane (DRM) was probed. Increasing the precursor feed rate: (i) progressively lowered the silica surface area from ≈340 m2/g to ≈240 m2/g; (ii) altered the silanol groups on the silica surface; and (iii) introduced residual carbon-based surface species to the sample at the highest feed rate. The variations in silica properties altered the (5 wt %) nickel deposit characteristics which in turn impacted on the DRM reaction. As the silica surface area increased, the nickel dispersion increased which improved catalyst performance. The residual carbon-based species also appeared to improve nickel dispersion, and in turn catalyst activity, although not to the same extent as the change in silica surface area. The findings illustrate both the importance of silica support characteristics on the catalytic performance of nickel for the DRM reaction and the capacity for using FSP to control these characteristics.

  • Flame Spray Pyrolysis an enabling technology for nanoparticles design and fabrication
    Nanoscale, 2010
    Co-Authors: Wey Yang Teoh, Rose Amal, Lutz Madle
    Abstract:

    Combustion of appropriate precursor Sprays in a Flame Spray Pyrolysis (FSP) process is a highly promising and versatile technique for the rapid and scalable synthesis of nanostuctural materials with engineered functionalities. The technique was initially derived from the fundamentals of the well-established vapour-fed Flame aerosols reactors that was widely practised for the manufacturing of simple commodity powders such as pigmentary titania, fumed silica, alumina, and even optical fibers. In the last 10 years however, FSP knowledge and technology was developed substantially and a wide range of new and complex products have been synthesised, attracting major industries in a diverse field of applications. Key innovations in FSP reactor engineering and precursor chemistry have enabled flexible designs of nanostructured loosely-agglomerated powders and particulate films of pure or mixed oxides and even pure metals and alloys. Unique material morphologies such as core–shell structures and nanorods are possible using this essentially one step and continuous FSP process. Finally, research challenges are discussed and an outlook on the next generation of engineered combustion-made materials is given.

Okorn Mekasuwandumrong - One of the best experts on this subject based on the ideXlab platform.

  • high temperature Flame Spray Pyrolysis induced stabilization of pt single atom catalysts
    Applied Catalysis B-environmental, 2021
    Co-Authors: Shipeng Ding, Okorn Mekasuwandumrong, Joongjai Panpranot, Hsian Chen, Max J Hulsey, Chiamin Yang, Ning Yan
    Abstract:

    Abstract Obtaining stable single-atom catalysts (SACs) for high-temperature applications remains challenging due to the thermodynamically favourable metal sintering under harsh reaction conditions. Taking advantage of the high-temperature process conditions (> 1000 °C), we hereby report the preparation of thermally stable metal oxide-supported single-atom Pt catalysts by Flame Spray Pyrolysis. Among the four common supports (Al2O3, SiO2, TiO2 and ZrO2) evaluated, single-atom Pt species were identified on Al2O3, TiO2 and ZrO2, among which ZrO2 was the best to stabilize atomically dispersed Pt. Compared to single-atom Pt catalysts prepared through the conventional impregnation method, samples synthesized by Flame Spray Pyrolysis displayed excellent catalytic performance in CO oxidation, methane combustion and methane partial oxidation reactions. Characterization results revealed that Flame Spray Pyrolysis favoured the formation of tetragonal-monoclinic phase of ZrO2 with improved redox property, thus leading to enhanced catalytic activity in high-temperature applications.

  • preparation and characterization of ceo2 tio2 nanoparticles by Flame Spray Pyrolysis
    Ceramics International, 2011
    Co-Authors: Choowong Chaisuk, Artiwan Shotipruk, Anusara Wehatoranawee, Sirichai Preampiyawat, Sirirat Netiphat, Okorn Mekasuwandumrong
    Abstract:

    Abstract Nanocrystalline TiO2, CeO2 and CeO2-doped TiO2 have been successfully prepared by one-step Flame Spray Pyrolysis (FSP). Resulting powders were characterized with X-ray diffraction (XRD), N2-physisorption, Transmission Electron Microscopy (TEM) and UV–Vis spectrophotometry. The TiO2 and CeO2-doped TiO2 nanopowders were composed of single-crystalline spherical particles with as-prepared primary particle size of 10–13 nm for Ce doping concentrations of 5–50 at%, while square-shape particles with average size around 9 nm were only observed from Flame-made CeO2. The adsorption edge of resulting powder was shifted from 388 to 467 nm as the Ce content increased from 0 to 30 at% and there was an optimal Ce content in association with the maximum absorbance. This effect is due to the insertion of Ce3+/4+ in the TiO2 matrix, which generated an n-type impurity band.

  • liquid phase selective hydrogenation of 1 heptyne over pd tio2 catalyst synthesized by one step Flame Spray Pyrolysis
    Catalysis Letters, 2010
    Co-Authors: Okorn Mekasuwandumrong, Songphon Phothakwanpracha, Bunjerd Jongsomjit, Artiwan Shotipruk, Joongjai Panpranot
    Abstract:

    The Pd/TiO2 nanoparticles synthesized by one-step Flame Spray Pyrolysis (FSP) with Pd loadings 0.5–10 wt% showed good catalytic performances in the liquid-phase selective hydrogenation of 1-heptyne. Higher selectivities to 1-heptene at complete conversion of 1-heptyne were obtained on the FSP-derived catalysts compared to the ones prepared by conventional impregnation of palladium on the FSP-synthesized and the commercial P-25 TiO2 supports. Based on the characterization results from X-ray diffraction (XRD), transmission electron microscopy (TEM), CO-pulse chemisorption, and X-ray photoelectron spectroscopy (XPS), the improved catalytic properties of Pd/TiO2 were attributed to a stronger interaction/an intimate contact between the very fine Pd particles and the TiO2 support obtained via one-step FSP synthesis. The very fine Pd particles confined to the TiO2 supports obtained by one-step Flame Spray Pyrolysis (FSP) method showed high catalytic activity in the liquid-phase selective hydrogenation of 1-heptyne with high selectivity towards 1-heptene.

  • characteristics and catalytic properties of pt sn al2o3 nanoparticles synthesized by one step Flame Spray Pyrolysis in the dehydrogenation of propane
    Applied Catalysis A-general, 2009
    Co-Authors: Sukanya Pisduangdaw, Chatthip Methastidsook, Choowong Chaisuk, Kajornsak Faungnawakij, Piyasan Praserthdam, Joongjai Panpranot, Okorn Mekasuwandumrong
    Abstract:

    Abstract The Pt–Sn/Al 2 O 3 catalysts with 0.3 wt% Pt and 0.5–1.5 wt% Sn loading were prepared by one-step Flame Spray Pyrolysis (FSP). Unlike the catalysts prepared by conventional impregnation method, the FSP-derived catalysts were composed of single-crystalline γ-alumina particles with the as-prepared primary particle size of 10–18 nm and contained only large pores. The FSP catalysts exhibited superior catalytic activity and better stability than the ones made by impregnation in the dehydrogenation of propane, while they did not alter the selectivity to propylene (in all cases, propylene selectivity ≥96%). The presence of large pores in the Flame-made catalysts not only facilitated diffusion of the reactants and products but could also lessen the amount of carbon deposited during reactions. As revealed by CO chemisorption, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), the metal particles appeared to be partially covered by the alumina matrix (Al–O) due to the simultaneous formation of particles during FSP synthesis. Such phenomena, however, were shown to result in the formation of active Pt–Sn ensembles for propane dehydrogenation as shown by higher turnover frequencies (TOFs).

  • preparation of nano pd sio2 by one step Flame Spray Pyrolysis and its hydrogenation activities comparison to the conventional impregnation method
    Industrial & Engineering Chemistry Research, 2009
    Co-Authors: Okorn Mekasuwandumrong, Piyasan Praserthdam, Sirima Somboonthanakij, Joongjai Panpranot
    Abstract:

    Characteristics and catalytic properties of the nano-Pd/SiO2 catalysts synthesized in one-step Flame Spray Pyrolysis (FSP) were compared to those prepared on the Flame-made SiO2 supports by convent...