scholarly journals Na-β-Al2O3 stabilized Fe2O3 oxygen carriers for chemical looping water splitting: correlating structure with redox stability

2021 ◽  
Author(s):  
Nur Sena Yüzbasi ◽  
Andac Armutlulu ◽  
Thomas Huthwelker ◽  
Paula Abdala ◽  
Christoph Müller
Keyword(s):  
Fossil Fuels ◽  
Oxygen Carrier ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Cycle Number ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Edx Analyses ◽  
H2 Yield

Chemical looping is an emerging technology to produce high purity hydrogen from fossil fuels or biomass with the simultaneous capture of the CO2 produced at the distributed scale. This process requires the availability of stable Fe2O3-based oxygen carriers. Fe2O3-Al2O3 based oxygen carriers exhibit a decay in the H2 yield with cycle number due to the formation of FeAl2O4 that cannot be re-oxidized. In this study, the addition of sodium (via a sodium salt) in the synthesis of Fe2O3-Al2O3 oxygen carriers was assessed as a means to counteract the cyclic deactivation of the oxygen carrier. Detailed insight into the oxygen carrier’s structure was gained by combined X-ray powder diffraction (XRD), X-ray absorption spectroscopy (XAS) at the Al, Na and Fe K-edges and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDX) analyses. The addition of sodium prevented the formation of FeAl2O4 and stabilized the oxygen carrier via the formation of a layered structure, Na-β-Al2O3 phase. The resulting material, Na-β-Al2O3 stabilized Fe2O3, showed a very high H2 yield of ca. 13.3 mmol/g during 15 cycles.

scholarly journals Na-β-Al2O3 stabilized Fe2O3 oxygen carriers for chemical looping water splitting: correlating structure with redox stability

2021 ◽  
Author(s):  
Nur Sena Yüzbasi ◽  
Andac Armutlulu ◽  
Thomas Huthwelker ◽  
Paula Abdala ◽  
Christoph Müller
Keyword(s):  
Fossil Fuels ◽  
Oxygen Carrier ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Cycle Number ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Edx Analyses ◽  
H2 Yield

Chemical looping is an emerging technology to produce high purity hydrogen from fossil fuels or biomass with the simultaneous capture of the CO2 produced at the distributed scale. This process requires the availability of stable Fe2O3-based oxygen carriers. Fe2O3-Al2O3 based oxygen carriers exhibit a decay in the H2 yield with cycle number due to the formation of FeAl2O4 that cannot be re-oxidized. In this study, the addition of sodium (via a sodium salt) in the synthesis of Fe2O3-Al2O3 oxygen carriers was assessed as a means to counteract the cyclic deactivation of the oxygen carrier. Detailed insight into the oxygen carrier’s structure was gained by combined X-ray powder diffraction (XRD), X-ray absorption spectroscopy (XAS) at the Al, Na and Fe K-edges and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDX) analyses. The addition of sodium prevented the formation of FeAl2O4 and stabilized the oxygen carrier via the formation of a layered structure, Na-β-Al2O3 phase. The resulting material, Na-β-Al2O3 stabilized Fe2O3, showed a very high H2 yield of ca. 13.3 mmol/g during 15 cycles.

scholarly journals LaFe1-xNix as a Robust Catalytic Oxygen Carrier for Chemical Looping Conversion of Toluene

2021 ◽  
Vol 12 (1) ◽  
pp. 391
Author(s):  
Haiming Gu ◽  
Juan Yang ◽  
Guohui Song ◽  
Xiaobo Cui ◽  
Miaomiao Niu ◽  
...  
Keyword(s):  
Oxygen Carrier ◽  
Fixed Bed ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Carbon Gasification ◽  
Syngas Production ◽  
Toluene Conversion ◽  
Substituted Ferrite ◽  
Tar Model Compound ◽  
H2 Yield

Chemical looping biomass gasification is a novel technology converting biomass into syngas, and the selection of oxygen carrier is key for efficient tar conversion. The performance of LaFe1-xNix as a robust catalytic oxygen carrier was investigated in the chemical looping conversion of toluene (tar model compound) into syngas in a fixed bed. LaM (M = Fe, Ni, Mn, Co, and Cu) was initially compared to evaluate the effect of transition metal on toluene conversion. LaFe (partial oxidation) and LaNi (catalytic pyrolysis) exhibited better performance in promoting syngas production than other oxygen carriers. Therefore, Ni-substituted ferrite LaFe1-xNix (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) was further developed. The effects of Ni-substitution, steam/carbon ratio (S/C), and temperature on toluene conversion into C1 and H2 were evaluated. Results showed that the synergistic effect of Fe and Ni promoted toluene conversion, improving H2 yield yet with serious carbon deposition. Steam addition promoted toluene steam reforming and carbon gasification. With S/C increasing from 0.8 to 2.0, the C1 and H2 yield increased from 73.9% to 97.5% and from 197.7% to 269.6%, respectively. The elevated temperature favored toluene conversion and C1 yield. LaFe0.6Ni0.4 exhibited strong reactivity stability during toluene conversion at S/C = 1.6 and 900 °C.

scholarly journals Comparison of oxygen carriers for chemical-looping combustion

2006 ◽  
Vol 10 (3) ◽  
pp. 93-107 ◽  
Author(s):  
Marcus Johansson ◽  
Tobias Mattisson ◽  
Anders Lyngfelt
Keyword(s):  
Fossil Fuels ◽  
Oxygen Carrier ◽  
High Reactivity ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Reducing Conditions ◽  
Different Temperatures ◽  
Combustion Technology ◽  
Separation Of Co2

Chemical-looping combustion is a combustion technology with inherent separation of the greenhouse gas CO2. This technique involves combustion of fossil fuels by means of an oxygen carrier which transfers oxygen from the air to the fuel. In this manner a decrease in efficiency is avoided for the energy demanding separation of CO2 from the rest of the flue gases. Results from fifty oxygen carriers based on iron-, manganese- and nickel oxides on different inert materials are compared. The particles were prepared using freeze granulation, sintered at different temperatures and sieved to a size 125-180 mm. To simulate the environment the particles would be exposed to in a chemical-looping combustor, reactivity tests under alternating oxidizing and reducing conditions were performed in a laboratory fluidized bed-reactor of quartz. Reduction was performed in 50% CH4/50% H2O while the oxidation was carried out in 5% O2 in nitrogen. In general nickel particles are the most reactive, followed by manganese. Iron particles are harder but have a lower reactivity. An increase in sintering temperatures normally leads to an increase in strength and decrease in reactivity. Several particles investigated display a combination of high reactivity and strength as well as good fluidization behavior, and are feasible for use as oxygen carriers in chemical-looping combustion.

Experimental Investigation of Chemical Looping Combustion of CO with Fe-Based Oxygen Carrier

2014 ◽  
Vol 986-987 ◽  
pp. 72-75
Author(s):  
Qu Li ◽  
Chang Feng Lin ◽  
Jun Jiao Zhang ◽  
Wei Liang Cheng ◽  
Wu Qin
Keyword(s):  
Experimental Investigation ◽  
Oxygen Carrier ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Thermo Gravimetric ◽  
Cu Doping ◽  
X Ray

Reaction activities of Ni-doped and Cu-doped Fe2O3 oxygen carriers (OCs) with CO were investigated using thermo gravimetric (TG-DTG).The structures of the prepared OC were characterized by X-ray diffract meter (XRD).TG-DTG investigations indicated that rational Ni and Cu doping could efficiently enhance the reactivity of Fe-base oxygen carrier for oxidizing CO under different conditions. And Fe-based OC doped with 20 wt. % Ni can realize the highest reactivity.

Efforts to improve the quantification of EDX analyses, particularly for the light elements

1991 ◽  
Vol 49 ◽  
pp. 716-717
Author(s):  
G. L'Espérance
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Light Elements ◽  
Thin Specimen ◽  
Complementary Technique ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Edx Analyses ◽  
Electron Energy Loss ◽  
Detection And Quantification

The attachment of a Si(Li) energy dispersive X-ray (EDX) detector to a (scanning) transmission electron microscope ((S)TEM) is widely used to carry out quantitative determinations of elemental composition of a localized region of a thin specimen. Although the principles of the technique first proposed by Cliff and Lorimer have been established for some time, there are still a large number of sources of errors. In addition, EDX analyses have been generally restricted until recently to elements with an atomic number (Z) larger than that of sodium (Z > 10) so that electron energy loss spectroscopy (EELS) was the preferred technique for the detection of light elements in an AEM. The relatively recent advent of ultra-thin window (UTW) detectors has offered an alternative (and often complementary) technique to EELS for the analysis of light elements with additional difficulties in the detection and quantification. This paper presents some results of investigations made to improve the quantification of EDX data. Particular attention is given to the detection and quantification of data from light elements on a routine and reproducible basis.

scholarly journals Development of CuO-based oxygen carriers supported on diatomite and kaolin for chemical looping combustion

2021 ◽  
Vol 10 (4) ◽  
pp. e15110412831
Author(s):  
Romário Cezar Pereira da Costa ◽  
Rebecca Araújo Barros do Nascimento ◽  
Dulce Maria de Araújo Melo ◽  
Dener Silva Albuquerque ◽  
Rodolfo Luiz Bezerra de Araújo Medeiros ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Direct Reduction ◽  
Oxygen Carrier ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Impregnation Method ◽  
Oxygen Carriers ◽  
Fuel Gas ◽  
Promising Alternative ◽  
X Ray

Chemical Looping Combustion (CLC) technology has emerged as a promising alternative capable of restricting the effects of global warming due to anthropogenic gas emissions, especially CO2, through its inherent capture. This study aims to synthesize and evaluate Cu-based oxygen carriers supported on natural materials such as diatomite and kaolin, through the incipient wet impregnation method for CLC process applications. Oxygen carriers were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy with surface energy dispersive x-ray spectroscopy (SEM-EDS). The mechanical strength of the two oxygen carrier particles was determined after the sintering procedure resulting in high crushing force. Reactivity of oxygen carriers was evaluated in a thermobalance with CH4 and H2 gases. Different reaction pathways were attempted when undergoing the redox cycles: total direct reduction of CuO to Cu0 for Cu-K and partial reduction of CuO to Cu2O and CuO to Cu-D. However, the highest reactivity and reaction rate was achieved in Cu-D due to the pore structure of diatomite, the chemical composition and the resulting interaction between CuO and the support. H2 gas reactivity tests showed a higher conversion rate and greater stability between cycles for both oxygen carriers. Thus, the reducible CuO content present in Cu-Diatomite during the reactivity test with H2 as the fuel gas was ideal for achieving high solids conversion, tendency for greater stability and a higher reaction rate.

scholarly journals Evaluating the reactivity of CuO-TiO2 oxygen carrier for energy production technology with CO2 capture

2021 ◽  
Vol 10 (12) ◽  
pp. e514101220596
Author(s):  
Dener da Silva Albuquerque ◽  
Dulce Maria de Araújo Melo ◽  
Rodolfo Luiz Bezerra de Araújo Medeiros ◽  
Romário Cezar Pereira da Costa ◽  
Fernando Velcic Maziviero ◽  
...  
Keyword(s):  
Titanium Oxide ◽  
Structural Characteristics ◽  
Oxygen Carrier ◽  
Co2 Production ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solid Oxygen

Chemical looping combustion (CLC) processes have been shown to be promising and effective in reducing CO2 production from the combustion of various fuels associated with the growing global demand for energy, as it promotes indirect fuel combustion through solid oxygen carriers (SOC). Thus, this study aims to synthesize, characterize and evaluate mixed copper and titanium oxide as a solid oxygen carrier for use in combustion processes with chemical looping. The SOC was synthesized based on stoichiometric calculations by the polymeric precursor method and characterized by: X-ray fluorescence (XRF), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-FEG) with EDS, and Programmed Temperature Reduction (PTR). The oxygen carrying capacity (ROC) and the speed index of the reduction and oxidation cycles were evaluated by Thermogravimetric Reactivity (TGA). The main reactive phase identified was: The CuO phase for the mixed copper and titanium oxide were identified and confirmed by X-ray diffraction using the Rietveld refinement method. The reactivity of the CuO-TiO2 system was high, obtaining a CH4 conversion rate above 90% and a speed index of 40%/min. Due to the structural characteristics and the reactivity tests of this material, it is concluded that mixed copper and titanium oxide have the necessary requirements to be used in chemical looping combustion (CLC) processes.

High-resolution x-ray imaging of small copper-rich precipitates in steels

1988 ◽  
Vol 46 ◽  
pp. 528-529
Author(s):  
J. R. Michael ◽  
K. A. Taylor
Keyword(s):  
Electron Microscopy ◽  
Thermomechanical Processing ◽  
Atom Probe ◽  
Ferrite Matrix ◽  
Scanning Transmission Electron Microscope ◽  
Probe Field ◽  
X Ray ◽  
Subsequent Transformation ◽  
Transmission Electron ◽  
Scanning Transmission

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.

Techniques for cryoultramicrotomy of propane jet frozen biological samples

1986 ◽  
Vol 44 ◽  
pp. 260-261
Author(s):  
B. Craig ◽  
L. Hawkey ◽  
A. LeFurgey
Keyword(s):  
Freeze Fracture ◽  
Freeze Substitution ◽  
Heart Cells ◽  
Crystal Formation ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
A New Technique

Ultra-rapid freezing followed by cryoultramicrotomy is essential for the preservation of diffusible elements in situ within cells prior to scanning transmission electron microscopy and quantitative energy dispersive x-ray microanalysis. For cells or tissue fragments in suspension and for monolayer cell cultures, propane jet freezing provides cooling rates greater than 30,000°C/sec with regions up to 40μm in thickness free of significant ice crystal formation. While this method of freezing has frequently been applied prior to freeze fracture or freeze substitution, it has not been widely utilized prior to cryoultramicrotomy and subsequent x-ray microanalytical studies. This report describes methods devised in our laboratory for cryosectioning of propane jet frozen kidney proximal tubule suspensions and cultured embryonic chick heart cells, in particular a new technique for mounting frozen suspension specimens for sectioning. The techniques utilize the same specimen supports and sample holders as those used for freeze fracture and freeze substitution and should be generally applicable to any cell suspension or culture preparation.

Magnesium and sulfur in mast cell and basophil granules of lower vertebrates in relation with histamine

1992 ◽  
Vol 50 (2) ◽  
pp. 1596-1597
Author(s):  
Kenichi Takaya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Mast Cell ◽  
Mast Cells ◽  
Tree Frog ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Fresh Frozen ◽  
Ultrathin Sections

Mast cell and basophil granules of the vertebrate contain heparin or related sulfated proteoglycans. Histamine is also present in mammalian mast cells and basophils. However, no histamine is detected in mast cell granules of the amphibian or fish, while it is shown in those of reptiles and birds A quantitative x-ray microanalysis of mast cell granules of fresh frozen dried ultrathin sections of the tongue of Wistar rats and tree frogs disclosed high concentrations of sulfur in rat mast cell granules and those of sulfur and magnesium in the tree frog granules. Their concentrations in tree frog mast cell granules were closely correlated (r=0.94).Fresh frozen dried ultrathin sections and fresh air-dried prints of the tree frog tongue and spleen and young red-eared turtle (ca. 6 g) spleen and heart blood were examined by a quantitative energy-dispersive x-ray microanalysis (X-650, Kevex-7000) for the element constituents of the granules of mast cells and basophils. The specimens were observed by transmission electron microscopy (TEM) (80-200 kV) and followed by scanning transmission electron microscopy (STEM) under an analytical electron microscope (X-650) at an acceleration voltage of 40 kV and a specimen current of 0.2 nA. A spot analysis was performed in a STEM mode for 100 s at a specimen current of 2 nA on the mast cell and basophil granules and other areas of the cells. Histamine was examined by the o-phthalaldehyde method.

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