Quantitative Characterization of Fe/Al2O3 Catalysts. Part II: Reduction, Sulfidation, and CO/Hydrogenation Activity

1992 ◽  
Vol 46 (3) ◽  
pp. 489-497 ◽  
Author(s):  
Douglas P. Hoffmann ◽  
Marwan Houalla ◽  
Andrew Proctor ◽  
David M. Hercules
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Co Hydrogenation ◽  
Active Phase ◽  
Alumina Support ◽  
Activity Data ◽  
Co Chemisorption ◽  
Hydrogenation Activity ◽  
Sulfided Catalysts ◽  
Two Phases

ESCA, Mössbauer spectroscopy, XRD, and CO chemisorption were used to study the reduction and sulfidation reactions of a series of 1 to 24 wt % Fe/Al2O3 catalysts. The speciation and particle size of the active phase were correlated with CO hydrogenation activity data. Two phases were previously identified in all oxidic catalysts: Fe2O3 and Fe+3 in solid solution with the alumina support. The Fe2O3 phase was found to reduce to Fe0 and sulfide to Fe1- xS. For the reduced and sulfided catalysts, Mössbauer was able to identify two iron species which were detected as a single solid solution species in the oxidic catalysts. The two species were found to differ by their location in the alumina support. One species is incorporated within the alumina matrix [Fe+2(A)] and the other species [Fe+2(B)] is present at the alumina surface. Both ESCA and CO chemisorption indicate that the Fe particle size increases with increasing iron loading. The turnover frequency (TOF) for CO hydrogenation appears to be a function of the extent of reduction and particle size of the metallic iron phase.

Quantitative Characterization of Fe/Al2O3 Catalysts. Part I: Oxidic Precursors

1992 ◽  
Vol 46 (2) ◽  
pp. 208-218 ◽  
Author(s):  
Douglas P. Hoffmann ◽  
Marwan Houalla ◽  
Andrew Proctor ◽  
Martin J. Fay ◽  
David M. Hercules
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Weight Percent ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Gravimetric Analysis ◽  
Iron Loading ◽  
Quantitative Characterization ◽  
Alumina Support

The structure of a series of Fe/Al2O3 catalysts containing from 1 to 24 weight percent iron has been examined by XRD, EXAFS, Mössbauer, ESCA, and gravimetric analysis. Two iron phases, Fe2O3 and Fe+3 in solid solution in the alumina support, are characterized as a function of iron loading. The combination of ESCA H2 titration and gravimetric analysis allows both quantitative and qualitative measurement of the two species. The amount of Fe2O3 phase increases with increasing iron loading for Fe1 to Fe24, whereas the amount of Fe+3 solid-solution phase increases with increasing iron loading for Fe1 to Fe6 and then levels off to approximately 2.2 wt % Fe for Fe8 to Fe24. The particle size of the Fe2O3 phase, determined from ESCA measurements, increases with increasing iron loading.

The effect of Tin additionon on Structural and magnetic properties of the stannoferrite Li0.5+0.5XFe2.5-1.5XSnXO4

2016 ◽  
Vol 12 (3) ◽  
pp. 4307-4321 ◽  
Author(s):  
Ahmed Hassan Ibrahim ◽  
Yehia Abbas
Keyword(s):  
Particle Size ◽  
Fine Particles ◽  
Magnetic Moments ◽  
Lithium Ferrite ◽  
Tem Analysis ◽  
Weiss Temperature ◽  
X Ray ◽  
Two Phases ◽  
Nanocrystalline Ferrite ◽  
20 Nm

The physical properties of ferrites are verysensitive to microstructure, which in turn critically dependson the manufacturing process.Nanocrystalline Lithium Stannoferrite system Li0.5+0.5XFe2.5-1.5XSnXO4,X= (0, 0.2, 0.4, 0.6, 0.8 and 1.0) fine particles were successfully prepared by double sintering ceramic technique at pre-sintering temperature of 500oC for 3 h andthepre-sintered material was crushed and sintered finally in air at 1000oC.The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction (XRD) and the Rietveld method.The refinement results showed that the nanocrystalline ferrite has a two phases of ordered and disordered phases for polymorphous lithium Stannoferrite.The particle size of as obtained samples were found to be ~20 nm through TEM that increases up to ~ 85 nmand isdependent on the annealing temperature. TEM micrograph reveals that the grains of sample are spherical in shape. (TEM) analysis confirmed the X-ray results.The particle size of stannic substituted lithium ferrite fine particle obtained from the XRD using Scherrer equation.Magneticmeasurements obtained from lake shore’s vibrating sample magnetometer (VSM), saturation magnetization ofordered LiFe5O8 was found to be (57.829 emu/g) which was lower than disordered LiFe5O8(62.848 emu/g).Theinterplay between superexchange interactions of Fe3+ ions at A and B sublattices gives rise to ferrimagnetic ordering of magnetic moments,with a high Curie-Weiss temperature (TCW ~ 900 K).

PHASE EQUILIBRIUM IN THE AS2TE3-TM2TE3 SYSTEM.

2020 ◽  
Vol 5 (8(77)) ◽  
pp. 65-68
Author(s):  
Teymur Mammad Ilyasly ◽  
Rahman Hasanaga Fatullazade ◽  
Zakir Islam Ismailov ◽  
Nigar Nadir Jafarova
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Differential Thermal Analysis ◽  
Phase Equilibrium ◽  
Physicochemical Properties ◽  
Thermal Effects ◽  
Isothermal Annealing ◽  
Intermediate Phase ◽  
Physicochemical Analysis ◽  
Two Phases

The synthesis of alloys of the system was carried out stepwise in rotary furnaces. The synthesis mode was selected based on the physicochemical properties of the elementary components. For homogenization, the alloys were subjected to isothermal annealing at 750 and 1275 K, depending on the Tm2Te3 concentration, for 250 h after homogenization of the alloys, they were subjected to physicochemical analysis. The results of differential thermal analysis showed that reversible thermal effects are observed in the alloys of the system. In alloys in a 1: 1 ratio, a new intermediate phase is formed with a composition corresponding to the TmAsTe3 compound. The homogeneity area is observed in the concentration range 52.5-47.5. It was found that in the concentration range 98.5-52.5 Tm2Te3 there are two phases - a mixture of β and of the solid solution, and in the concentration range of 47.51 mol% Tm2Te3 phases and α are in equilibrium. ) 66 The eutectic has coordinates of 11.5 mol Tm2Te3 at a temperature of 575 K.

scholarly journals Optimization of Yb2O3-Gd2O3-Y2O3 Co-Doped ZrO2 Agglomerated and Calcined Powders for Air Plasma Spraying

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 373
Author(s):  
Zheng Yan ◽  
Haoran Peng ◽  
Kang Yuan ◽  
Xin Zhang
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Plasma Spraying ◽  
Cubic Phase ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Barrier Coating ◽  
Controllable Preparation ◽  
Co Doped

Yb2O3-Gd2O3-Y2O3 co-doped ZrO2 (YGYZ) is considered to be a promising material in thermal barrier coating (TBC) applications. In this study, 2Yb2O3–2Gd2O3–6Y2O3–90ZrO2 (mol.%) (10YGYZ) feedstock candidates for air plasma spraying (APS) were prepared by calcination of agglomerated powders at 1100, 1200, 1300, 1400, and 1500 °C for 3 h, respectively. Incomplete solid solution was observed in calcined powders at 1100, 1200 and 1300 °C, and the 1500 °C calcined powder exhibited poor flowability due to intense sintering effect. The 1400 °C calcined powders were eventually determined to be the optimized feedstock for proper phase structure (cubic phase), great flowability, suitable apparent density and particle size distribution, etc. 10YGYZ TBCs with the optimized feedstock were prepared by APS, exhibiting pure c phase and good chemical uniformity. Controllable preparation of coatings with different porosity (i.e., 7%–9% and 12%–14%) was realized by stand-off distance adjustment.

A Simple Dissolved Metals Mixing Route to Prepare Nanostructured Mg0.8Zn0.2TiO3 Solid Solution

2015 ◽  
Vol 1112 ◽  
pp. 47-52 ◽  
Author(s):  
Frida Ulfah Ermawati ◽  
Suasmoro Suasmoro ◽  
Suminar Pratapa
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Rietveld Analysis ◽  
Dissolved Metals ◽  
Intermediate Phases ◽  
Particle Size Analyzer ◽  
Ft Ir ◽  
Xrd Patterns ◽  
Zn Ions

A study of liquid mixing route to synthesize high purity Mg0.8Zn0.2TiO3 nanopowder, a candidate dielectric ceramics, has been successfully performed. Formation of the phases on the dried powder was studied using TG/DTA, XRD and FT-IR data. Rietveld analysis on the collected XRD patterns confirmed the formation of solid solution in the system. Such solid solution can be obtained from the powder calcined at 500 °C, but calcination at 550 °C gave rise to the most optimum molar purity up to 98.5% without intermediate phases. The role of Zn ions on the formation of solid solution was also discussed. Homogeneity of particle size distribution and nano-crystallinity of the system was verified from the particle size analyzer data, TEM image and the Rietveld analysis output.

scholarly journals Preparation of Ceria-Zirconia Mixed Oxide by Hydrothermal Synthesis

2015 ◽  
Vol 9 (7) ◽  
pp. 134 ◽  
Author(s):  
Siti Machmudah ◽  
M. Akmal Hadian ◽  
Lenno Samodro K. ◽  
Sugeng Winardi ◽  
Wahyudiono Wahyudiono ◽  
...  
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Hydrothermal Synthesis ◽  
Mixed Oxides ◽  
Synthesis Process ◽  
Growth Morphology ◽  
Mixed Powder ◽  
Xrd Pattern ◽  
Tube Reactor ◽  
Internal Volume

Ceria-zirconia mixed oxides have been synthesized by hydrothermal synthesis process. Under hydrothermalconditions, water potential to control the direction of crystal growth, morphology, particle size and sizedistribution, because of the controllability of thermodynamics and transport properties by pressure andtemperature. The synthesis was carried out at temperatures of 150 − 200 oC and pressure of 5 MPa in a batchreactor. The reactor made of SUS 304 tube reactor with internal volume of 8.8 ml. The synthesized productswere calcined and characterized using SEM, XRD and FTIR. The results showed that the particles formed weresphere shaped particles with smooth morphology and the size of particle diameters were 35, 61, and 31 nm onaverage for reactions temperatures of 150, 180, and 200oC, respectively. The XRD pattern indicated thatceria-zirconia mixed powder was uniformly distributed in the structure to form a homogeneous solid solution.

Fabrication and Microstructure of ZnO-TiO2 Composite Membranes by a Reverse Micelle and Sol-Gel Processing

2006 ◽  
Vol 510-511 ◽  
pp. 786-789 ◽  
Author(s):  
Dong Sik Bae ◽  
Byung Ik Kim ◽  
Kyong Sop Han
Keyword(s):  
Particle Size ◽  
Reverse Micelle ◽  
Porous Alumina ◽  
Sol Gel ◽  
Average Particle Size ◽  
Composite Membranes ◽  
Dip Coating ◽  
Narrow Particle Size Distribution ◽  
Average Particle ◽  
Alumina Support

ZnO-TiO2 nanoparticles were synthesized by a reverse micelle and sol-gel process. The average particle size of the colloid was below 30 nm and well dispersed in the solution. ZnOTiO2 composite membranes were fabricated by using the dip-coating method on a porous alumina support. ZnO-TiO2 composite membranes showed a crack-free microstructure and narrow particle size distribution even after the heat treatment up to 600°C. The average particle size of the membrane was 30-40nm, and the pore size of ZnO-TiO2 composite membrane was below 10 nm.

scholarly journals Carbon-supported Platinum Electrocatalysts probed in a Gas Diffusion Setup with Alkaline Environment: how Particle Size and Mesoscopic Environment influence the Degradation Mechanism

2020 ◽  
Author(s):  
Shima Alinejad ◽  
Jonathan Quinson ◽  
Johanna Schröder ◽  
Jacob J. K. Kirkensgaard ◽  
Matthias Arenz
Keyword(s):  
Particle Size ◽  
Degradation Mechanism ◽  
Active Phase ◽  
Active Surface ◽  
Carbon Support ◽  
Gas Diffusion ◽  
Active Surface Area ◽  
Electrochemical Cells ◽  
Co Stripping ◽  
Large Particles

In this work, we investigate the stability of four different types of Pt/C fuel cell catalysts upon applying accelerated degradation tests (ADTs) in a gas diffusion electrode (GDE) setup equipped with an anion exchange membrane (AEM). In contrast to previous investigations exposing the catalysts to liquid electrolyte, the GDE setup provides a realistic three-phase boundary of the reactant gas, catalyst and ionomer which enables reactant transport rates close to real fuel cells. Therefore, the GDE setup mimics the degradation of the catalyst under more realistic reaction conditions as compared to conventional electrochemical cells. Combining the determination of the loss in electrochemically active surface area (ECSA) of the Pt/C catalysts via CO stripping measurements with the change in particle size distribution determined by small-angle X-ray scattering (SAXS) measurements, we demonstrate that i) the degradation mechanism depends on the investigated Pt/C catalyst and might indeed be different to the one observed in conventional electrochemical cells, ii) degradation is increased in an oxygen gas atmosphere (as compared to an inert atmosphere), and iii) the observed degradation mechanism depends on the mesoscopic environment of the active phase. The measurements indicate an increased particle growth if small and large particles are immobilized next to each other on the same carbon support flakes as compared to a simple mix of two catalysts with small and large particles, respectively.

scholarly journals Effects of feed properties in spray drying formulation of prototype industrial cracking catalysts

2021 ◽  
Vol 63 (6) ◽  
pp. 41-44
Author(s):  
Duc Hoan Truong ◽  
◽  
Thuy Phuong Ngo- ◽  
Duc Manh Dinh ◽  
Thanh Tung Dang ◽  
...  
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Spray Drying ◽  
Ph Value ◽  
Catalyst Particle ◽  
Active Phase ◽  
Solid Content ◽  
Medium Ph ◽  
Hy Zeolite ◽  
Cracking Catalysts

This paper studied the effects of feed properties in spray drying formulation of prototype industrial cracking catalysts at the laboratory scale. The results showed that the pH of the drying feed mainly affected the active phase HY zeolite. At a high pH value, a strongly alkaline medium (pH 14), the HY zeolite structure was completely destroyed, resulting in the cracking catalyst with a low surface area. Hence, the pH of the drying feed should be adjusted to a low value, preferably a slightly acidic medium (pH 3). The solid content mainly affected the particle size of the cracking catalyst. As increasing the solid content in the drying feed, the particle size of the cracking catalysts increased and reached the maximum average value at about 40 μm which corresponded to the solid content of 15 wt.%. At a higher solid content (20 wt.%), the catalyst particle size and surface area tended to decrease. Thus, the solid content of 15 wt.% was considered to be optimal.

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