scholarly journals Ce- and Y-Modified Double-Layered Hydroxides as Catalysts for Dry Reforming of Methane: On the Effect of Yttrium Promotion

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 56 ◽  
Author(s):  
Katarzyna Świrk ◽  
Magnus Rønning ◽  
Monika Motak ◽  
Patricia Beaunier ◽  
Patrick Da Costa ◽  
...  
Keyword(s):  
Textural Properties ◽  
Dry Reforming ◽  
Dry Reforming Of Methane ◽  
Side Reactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Nickel Species

Ce- and Y-promoted double-layered hydroxides were synthesized and tested in dry reforming of methane (CH4/CO2 = 1/1). The characterization of the catalysts was performed using X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 sorption, temperature-programmed reduction in H2 (TPR-H2), temperature-programmed desorption of CO2 (TPD-CO2), H2 chemisorption, thermogravimetric analysis coupled by mass spectrometry (TGA/MS), Raman, and high-resolution transmission electron microscopy (HRTEM). The promotion with cerium influences textural properties, improves the Ni dispersion, decreases the number of total basic sites, and increases the reduction temperature of nickel species. After promotion with yttrium, the increase in basicity is not directly correlated with the increasing Y loading on the contrary of Ni dispersion. Dry reforming of methane (DRM) was performed as a function of temperature and in isothermal conditions at 700 °C for 5 h. For catalytic tests, a slight increase of the activity is observed for both Y and Ce doped catalysts. This improvement can of course be explained by Ni dispersion, which was found higher for both Y and Ce promoted catalysts. During DRM, the H2/CO ratio was found below unity, which can be explained by side reactions occurrence. These side reactions are linked with the increase of CO2 conversion and led to carbon deposition. By HRTEM, only multi-walled and helical-shaped carbon nanotubes were identified on Y and Ce promoted catalysts. Finally, from Raman spectroscopy, it was found that on Y and Ce promoted catalysts, the formed C is less graphitic as compared to only Ce-based catalyst.

scholarly journals Influence of synthesis parameters of mesocellular silica foams doped by nickel on methane reforming by CO2

2018 ◽  
Vol 171 ◽  
pp. 03002 ◽  
Author(s):  
O. Daoura ◽  
M. Boutros ◽  
O. Daoura ◽  
F. Launay ◽  
P. Massiani ◽  
...  
Keyword(s):  
Textural Properties ◽  
Dry Reforming Of Methane ◽  
Synthesis Methods ◽  
Methane Reforming ◽  
X Ray Diffraction ◽  
Synthesis Parameters ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Mesocellular Silica Foams ◽  
Catalytic Performances

New catalysts based on Ni(0) dispersed onto mesocellular silica foams (MCF) were prepared for Dry Reforming of Methane (DRM). Different synthesis methods of MCF supports (with and without using NH4F or n-butanol) were tested in order to study the influence of the textural properties of the support on the catalytic performances of the catalysts. In all cases, nickel was incorporated using the double solvents method. The resulting calcined materials were characterized by N2 sorption, X-Ray diffraction (XRD) and transmission electron microscopy. Their reducibility was tested by temperature-programmed reduction (TPR). Interestingly, particularly large specific surfaces, pores diameters and pores volumes were observed when NH4F was added to the synthesis gel (MCF(N) materials). The corresponding Ni-MCF(N) catalysts were shown to be the most attractive among other prepared samples with respect to their performances in DRM.

Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM)

2014 ◽  
Vol 68 (9) ◽  
Author(s):  
Ted Johansson ◽  
Devendra Pakhare ◽  
Daniel Haynes ◽  
Victor Abdelsayed ◽  
Dushyant Shekhawat ◽  
...  
Keyword(s):  
Dry Reforming ◽  
Broad Peak ◽  
Dry Reforming Of Methane ◽  
Single Type ◽  
Side Reactions ◽  
Boudouard Reaction ◽  
Co2 Reforming ◽  
Xrd Pattern ◽  
Temperature Programmed

AbstractThis work reports on the characterization of LaRhO3 perovskite as a catalyst for dry reforming of methane. The catalyst was studied using CH4-temperature programmed reduction (TPR), H2-TPR, and temperature programmed surface reaction (TPSR), and the changes in the crystal structure of the catalyst due to these treatments were studied by X-ray diffraction (XRD). XRD pattern of the freshly calcined perovskites showed the formation of highly crystalline LaRhO3 and La2O3 phases. H2-TPR of the fresh calcined catalyst showed a shoulder at 342°C and a broad peak at 448°C, suggesting that the reduction of Rh in perovskite occurs in multiple steps. XRD pattern of the reduced catalyst suggests complete reduction of the LaRhO3 phase and the formation of metallic Rh and minor amounts of La(OH)3. The CH4-TPR data show qualitatively similar results as H2-TPR, with a shoulder and a broad peak in the same temperature range. Following the H2-TPR up to 950°C, the same batch of catalyst was oxidized by flowing 5 vol. % O2/He up to 500°C and a second H2-TPR (also up to 950°C) was conducted. This second H2-TPR differed significantly from that of the fresh calcined catalyst. The single sharp peak at 163°C in the second H2-TPR suggests a significant change in the catalyst, probably causedby the transformation of about 90 % of the perovskite into Rh/La2O3. This was confirmed by the XRD studies of the catalyst reduced after the oxidation at 500°C. TPSR of the dry reforming reaction on the fresh calcined catalyst showed CO and H2 formation starting at 400°C, with complete consumption of the reactants at 650°C. The uneven consumption of reactants between 400°C and 650°C suggests that reactions other than DRM occur, including reverse water gas shift (RWGS) and the Boudouard reaction (BR), probably as a result of in-situ changes in the catalyst, consistent with the H2-TPR results. TPSR, after a H2-TPR up to 950°C, showed that the dry reforming reaction did not light off until 570°C, which is much higher temperature than the one observed using fresh calcined catalyst. This shows that the uniform sites produced during the 950°C H2-TPR are catalytically less active than those of the fresh calcined catalyst, and that no significant side reactions such as RWGS or the Boudouard reaction occur. This suggests that reduction leads to the formation of a single type of sites which do not catalyze simultaneous side reactions.

scholarly journals Catalytic Dry Reforming and Cracking of Ethylene for Carbon Nanofilaments and Hydrogen Production Using a Catalyst Derived from a Mining Residue

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1069 ◽  
Author(s):  
Abir Azara ◽  
El-Hadi Benyoussef ◽  
Faroudja Mohellebi ◽  
Mostafa Chamoumi ◽  
François Gitzhofer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fixed Bed ◽  
Dry Reforming ◽  
Fixed Bed Reactor ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Spent Catalysts ◽  
Temperature Programmed

In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based catalyst via a solid-state reaction protocol. Ni-UGSO with different Ni weight percentages wt.% (5, 10, and 13) were tested for C2H4 dry reforming (DR) and catalytic cracking (CC) after activation with H2. The reactions were conducted in a differential fixed-bed reactor at 550–750 °C and standard atmospheric pressure, using 0.5 g of catalyst. Pure gases were fed at a molar ratio of C2H4/CO2 = 3 for the DR reaction and C2H4/Ar = 3 for the CC reaction. The flow rate is defined by a GHSV = 4800 mLSTP/h.gcat. The catalyst performance is evaluated by calculating the C2H4 conversion as well as carbon and H2 yields. All fresh, activated, and spent catalysts, as well as deposited carbon, were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), temperature programmed reduction (TPR), and thermogravimetric analysis (TGA). The results so far show that the highest carbon and H2 yields are obtained with Ni-UGSO 13% at 750 °C for the CC reaction and at 650 °C for the DR reaction. The deposited carbon was found to be filamentous and of various sizes (i.e., diameters and lengths). The analyses of the results show that iron is responsible for the growth of carbon nanofilaments (CNF) and nickel is responsible for the split of C–C bonds. In terms of conversion and yield efficiencies, the performance of the catalytic formulations tested is proven at least equivalent to other Ni-based catalyst performances described by the literature.

scholarly journals Characterization of Highly Dispersed Rod- and Particle-Shaped CuFe19Ox Catalysts and Their Shape Effects on WGS

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 635
Author(s):  
Lingjuan Ma ◽  
Dawei Han ◽  
Hongbin Ma ◽  
Longgang Liu ◽  
Huichao Guo
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
In Situ Xrd ◽  
Transmission Electron ◽  
Highly Dispersed ◽  
Shape Effects ◽  
Temperature Programmed ◽  
Water Gas

Highly dispersed CuFe19Ox catalysts with different shapes were prepared and further characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and in-situ XRD. XRD and TEM results showed that the synthesized CuFe19Ox nanoparticles consisted of CuO and Fe2O3, while CuFe19Ox nanorods consisted of CuFe2O4 and Fe2O3. The reduction properties of CuFe19Ox samples were finely studied by H2-TPR, and the phase composition was identified by in-situ XPS, HR-TEM, and surface TPR (s-TPR). In-situ X-ray photoelectroscopy (XPS) indicated that the metallic Cu and Fe3O4 were the main species after reduction. Moreover, s-TPR studies showed that the reduction performance of copper was significantly affected by the shapes of the Fe3O4 supports. Low-temperature water gas shift (LT-WGS) was chosen to characterize the Cu species on the surface. It was found that reduced CuFe19Ox nanorods had no activity. On the contrary, reduced CuFe19Ox particles showed higher initial WGS activity, where the active Cu0 should originate from the reduction of Cu2O at lower temperatures, as confirmed by the s-TPR profiles.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Detonation Synthesis of Nano-Size Materials

1995 ◽  
Vol 418 ◽  
Author(s):  
J. Forbes ◽  
J. Davis ◽  
C. Wong
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Nucleation And Growth ◽  
Detonation Synthesis ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray ◽  
Transmission Electron ◽  
Nano Size

AbstractThe detonation of explosives typically creates 100's of kbar pressures and 1000's K temperatures. These pressures and temperatures last for only a fraction of a microsecond as the products expand. Nucleation and growth of crystalline materials can occur under these conditions. Recovery of these materials is difficult but can occur in some circumstances. This paper describes the detonation synthesis facility, recovery of nano-size diamond, and plans to synthesize other nano-size materials by modifying the chemical composition of explosive compounds. The characterization of nano-size diamonds by transmission electron microscopy and electron diffraction, X-ray diffraction and Raman spectroscopy will also be reported.

One Step Synthesis and Characterization of Zirconia-Graphene Composites

2012 ◽  
Vol 600 ◽  
pp. 174-177 ◽  
Author(s):  
Jian Fei Xia ◽  
Zong Hua Wang ◽  
Yan Zhi Xia ◽  
Fei Fei Zhang ◽  
Fu Qiang Zhu ◽  
...  
Keyword(s):  
Synthesis And Characterization ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Graphene Composite ◽  
Transmission Electron ◽  
One Step ◽  
Ft Ir ◽  
Xrd Techniques

Zirconia-graphene composite (ZrO2-G) has been successfully synthesized via decomposition of ZrOCl2•6H2O in a water-isopropanol system with dispersed graphene oxide (GO) utilizing Na2S as a precursor could enable the occurrence of the deposition of Zr4+ and the deoxygenation of GO at the same time. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the samples. It was found that graphene were fully coated with ZrO2, and the ZrO2 existing in tetragonal phase, which resulted in the formation of two-dimensional composite.

Hydrothermal Synthesis and Characterization of BiFeO3 Polyhedral Crystallites

2012 ◽  
Vol 174-177 ◽  
pp. 508-511
Author(s):  
Lin Lin Yang ◽  
Yong Gang Wang ◽  
Yu Jiang Wang ◽  
Xiao Feng Wang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

BiFeO3 polyhedrons had been successfully synthesized via a hydrothermal method. The as-prepared products were characterized by power X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The possible mechanisms for the formation of BiFeO3 polyhedrons were discussed. Though comparison experiments, it was found that the kind of precursor played a key role on the morphology control of BiFeO3 crystals.

scholarly journals Characterization of ferrite nanoparticles for preparation of biocomposites

2017 ◽  
Vol 8 ◽  
pp. 1257-1265 ◽  
Author(s):  
Urszula Klekotka ◽  
Magdalena Rogowska ◽  
Dariusz Satuła ◽  
Beata Kalska-Szostko
Keyword(s):  
Chemical Method ◽  
Ferrite Nanoparticles ◽  
Chemical Activity ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Wet Chemical Method ◽  
X Ray ◽  
Transmission Electron ◽  
Wet Chemical

Ferrite nanoparticles with nominal composition Me0.5Fe2.5O4 (Me = Co, Fe, Ni or Mn) have been successfully prepared by the wet chemical method. The obtained particles have a mean diameter of 11–16 ± 2 nm and were modified to improve their magnetic properties and chemical activity. The surface of the pristine nanoparticles was functionalized afterwards with –COOH and –NH2 groups to obtain a bioactive layer. To achieve our goal, two different modification approaches were realized. In the first one, glutaraldehyde was attached to the nanoparticles as a linker. In the second one, direct bonding of such nanoparticles with a bioparticle was studied. In subsequent steps, the nanoparticles were immobilized with enzymes such as albumin, glucose oxidase, lipase and trypsin as a test bioparticles. The characterization of the nanoparticles was acheived by transmission electron microscopy, X-ray diffraction, energy dispersive X-ray and Mössbauer spectroscopy. The effect of the obtained biocomposites was monitored by Fourier transform infrared spectroscopy. The obtained results show that in some cases the use of glutaraldehyde was crucial (albumin).

Solvothermal synthesis and characterization of well-dispersed cerium-doped Y2SiO5 phosphor particles

2021 ◽  
Vol 112 (10) ◽  
pp. 812-816
Author(s):  
Xianxue Li
Keyword(s):  
Solvothermal Method ◽  
Luminescence Decay ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fluorescence Spectrophotometry ◽  
Decay Properties ◽  
Transmission Electron ◽  
Water As Solvent ◽  
Pure Phase

Abstract Well-dispersed cerium-doped Y2SiO5 (Ce:YSO) phosphor particles with spherical morphology and good luminescence intensity have been achieved by a solvothermal method with ethanol and water as solvent media. X-ray diffraction, Fourier transform infrared spectroscopy, fluorescence spectrophotometry and transmission electron microscopy were employed to characterize the as-synthesized Ce:YSO precursor and powders. The results showed that pure-phase Ce:YSO powders with a mean particle size of about 162 nm were accurately available at 310°C and above. The fluorescence ability and persistent luminescence decay properties of the Ce:YSO powders were also studied, and the excellent fluorescence properties could be attributed to the homogeneous Ce:YSO particles obtained through the solvothermal method.

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