scholarly journals Characterization of Mixed-Metal Oxides Using Synchrotron-Based Time-Resolved x-ray Diffraction and x-ray Absorption Spectroscopy

1999 ◽  
Vol 590 ◽  
Author(s):  
José A. Rodriguez ◽  
Jonathan C. Hanson ◽  
Joaquín L. Brito ◽  
Amitesh Maiti
Keyword(s):  
Metal Oxides ◽  
Density Functional ◽  
Chemical Properties ◽  
Local Symmetry ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Mixed Metal ◽  
X Ray Absorption

ABSTRACTExperiments are described showing the utility of synchrotron-based time-resolved x-ray diffraction (TR-XRD) and x-ray absorption near-edge spectroscopy (XANES) for characterizing the physical and chemical properties of mixed-metal oxides that contain Mo and a second transition metal (Fe, Co or Ni). TR-XRD was used to study the transformations that occur during the heating of a FeMoO4/Fe2(MoO4)3 mixture and the α⇒β phase transitions in CoMoO4 and NiMoO4. The Mo LII- and O K-edges in XANES are very useful for probing the local symmetry of Mo atoms in mixed-metal oxides. The results of XANES and density-functional calculations (DMo13, DFT-GGA) show large changes in the splitting of the empty Mo 4d levels when going from tetrahedral to octahedral coordinations. XANES is very useful for studying the reaction of H2, H2S and SO2 with the mixed-metal oxides. Measurements at the S K-edge allow a clear identification of S, SO2, SO3 or SO4 on the oxide surfaces. Changes in the oxidation state of molybdenum produce substantial shifts in the position of the Mo LII- and MIII-edges.

SYNTHESIS OF NOVEL NANOSTRUCTURED LANTHANUM COBALT FERRITE MIXED METAL OXIDES BY SOL–GEL

2013 ◽  
Vol 12 (01) ◽  
pp. 1350007
Author(s):  
V. MARY TERESITA ◽  
V. JESEENTHARANI ◽  
B. AVILA JOSEPHINE ◽  
S. ARUL ANTONY
Keyword(s):  
Metal Oxides ◽  
Sol Gel ◽  
Chemical Properties ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Size Dependent ◽  
Ft Ir ◽  
And Chemical Properties

Properties of nanoscale materials are very interesting and these are either comparable to or superior to those of bulk. These materials are interesting due to their exciting size dependent optical, electronic, magnetic, thermal, mechanical and chemical properties. Different mole ratios of nanostructured mixed metal oxides of LaCo x Fe 1-x O 3-δ (x = 0 to 1) were prepared by the sol–gel method by varying the mole ratios of iron and cobalt substrates. The compounds were sintered for 700°C in the tubular furnace for 8 h. The purity of the compounds was analyzed by TG-DTA. The compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) studies were employed to study the structural phases, vibrational frequencies, surface morphology of the highest humidity sensing compounds.

Properties of CeO2and Ce1-xZrxO2Nanoparticles:  X-ray Absorption Near-Edge Spectroscopy, Density Functional, and Time-Resolved X-ray Diffraction Studies

2003 ◽  
Vol 107 (15) ◽  
pp. 3535-3543 ◽  
Author(s):  
José A. Rodriguez ◽  
Jonathan C. Hanson ◽  
Jae-Yong Kim ◽  
Gang Liu ◽  
Ana Iglesias-Juez ◽  
...  
Keyword(s):  
Density Functional ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Absorption

Novel SrO-CaO Mixed Metal Oxides Catalyst for Ultrasonic-Assisted Transesterification of Jatropha Oil into Biodiesel

2017 ◽  
Vol 70 (3) ◽  
pp. 258 ◽  
Author(s):  
Syed Danish Ali ◽  
Isma Noreen Javed ◽  
Usman Ali Rana ◽  
Muhammad Faizan Nazar ◽  
Waqas Ahmed ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Mixed Metal Oxides ◽  
Jatropha Oil ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Acid Methyl ◽  
Ultrasonic Assisted

The transesterification of edible and non-edible oils to produce biodiesel is traditionally carried out using homogeneous catalysts (such as NaOH, KOH, and H2SO4). However, these homogenous catalysts often suffer from multiple drawbacks including their corrosive nature and solubility in the reaction mixture, and high costs associated with their recovery. Recent studies have shown that heterogeneous catalysts based on mixed metal oxides have the potential to address the issues associated with conventional homogeneous catalysts, thereby emerging as an efficient class of catalyst materials for biodiesel production. In this study, we describe a heterogeneous strontium oxide/calcium oxide (SrO-CaO) mixed metal oxides catalyst, which displays remarkable efficiency towards the ultrasonic-assisted transesterification of Jatropha oil into biodiesel. The SrO-CaO heterogeneous catalyst was prepared by the wet impregnation method, and the structural morphology of the as-synthesized catalyst was revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nitrogen sorption technique coupled with the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. The X-ray diffraction analysis confirmed the cubic structure of the SrO-CaO catalyst. The catalytic activity of this newly developed catalyst showed a high percentage conversion of triglyceride into the corresponding fatty acid methyl esters (98.19 %) as confirmed by 1H NMR spectroscopy. The chemical composition of the prepared biodiesel by this ultrasonic-assisted transesterification process was determined by the gas chromatography–mass spectrometry. Five major fatty acid methyl esters were identified, of which 9-octadecenoic acid methyl ester was obtained with the highest percentage ~38.22 %. Hence, the study reveals that the SrO-CaO catalyst exhibits high efficiency towards converting Jatropha oil into biodiesel by ultrasonic-assisted transesterification.

Structure and Thermo-Chemical Stability of Sr-Fe-Co-O Mixed Metal Oxides

2012 ◽  
Vol 549 ◽  
pp. 193-197
Author(s):  
Xiang Hong Huang ◽  
Jun Qiao ◽  
Qian Feng Zhang
Keyword(s):  
High Temperature ◽  
Metal Oxides ◽  
Chemical Stability ◽  
Elevated Temperatures ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray ◽  
Mixed Metal ◽  
Two Samples

SrFexCo0.5Oδ(x=0.5, 0.75, 1.0, 1.25) mixed metal oxides were synthesized by the citrate method. The structure and thermo-chemical stability of the obtained SrFexCo0.5Oδpowders were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that the SrFexCo0.5Oδpowders are composed of perovskite-type cubic structure at both room temperature and high temperature. The crystalline phases of the SrFexCo0.5Oδpowders are dependent on the content of Fe and SrFe0.5Co0.5O3, SrFe0.19Co081O2.78are the main crystalline phases. The powders have good thermo-chemical stability at elevated temperatures in helium, which is confirmed by an in-situ high-temperature X-ray diffraction. The SEM images show that the product of the SrFexCo0.5Oδ(x=0.5, 1.0) is composed of single grain, while other two samples consist of layer structures and some open porosities.

scholarly journals Synthesis of Mg-Fe layered double hydroxides and its application as catalyst for Friedel-Crafts benzoylation

2016 ◽  
Vol 19 (4) ◽  
pp. 185-193
Author(s):  
Phuong Thi Minh Nguyen ◽  
Phuong Hoang Tran ◽  
Chinh Quoc Nguyen
Keyword(s):  
Metal Oxides ◽  
Layered Double Hydroxides ◽  
Coprecipitation Method ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Before And After ◽  
Double Hydroxides

Mg-Fe layered double hydroxides were synthesized by the coprecipitation method with different of Mg/Fe ratio (2/1, 3/1 and 4/1) and then were thermally transformed into mixed metal oxides. The obtained materials before and after the calcination at 450 oC were characterized by X-ray diffraction (XRD), SEM, BET, TGA, ICP. The samples were used as a catalyst for Friedel-Crafts benzoylation reactions. The catalyst can be easily separated and recycled compared to the traditional one.

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