scholarly journals CO2 Methanation over Rare Earth Doped Ni-Based Mesoporous Ce0.8Zr0.2O2 with Enhanced Low-Temperature Activity

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 463
Author(s):  
Zhenglong Yang ◽  
Yan Cui ◽  
Pengxiang Ge ◽  
Mindong Chen ◽  
Leilei Xu
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Low Temperature ◽  
Impregnation Method ◽  
Co2 Methanation ◽  
X Ray ◽  
Wide Range ◽  
Temperature Programmed ◽  
Rare Earth Doped ◽  
The Rare Earth

The Ni-based catalysts have a wide range of industrial applications due to its low cost, but its activity of CO2 methanation is not comparable to that of precious metal catalysts. In order to solve this problem, Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts doped with rare earth were prepared by the incipient impregnation method and directly used as catalysts for the methanation of CO2. The catalysts were characterized systematically by x-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), energy-dispersed spectroscopy (EDS) mapping, x-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), and so on. The results show that Ni is highly dispersed in the mesoporous skeleton, forming a strong metal–skeleton interaction. Therefore, under the condition of CO2 methanation, the hot sintering of metallic Ni nanoparticles can be effectively inhibited so that these mesoporous catalysts have good stability without obvious deactivation. The rare earth doping can significantly increase the surface alkalinity of catalyst and enhance the chemisorption of CO2. In addition, the rare earth elements also act as electron modifiers to help activate CO2 molecules. Therefore, the rare earth doped Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts are expected to be an efficient catalyst for the methanation of CO2 at low-temperature.

scholarly journals Electronic Structure of the Rare-Earth Nitrides

2021 ◽  
Author(s):  
◽  
A. R. H. Preston
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Band Structure ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
X Ray ◽  
Rare Earth Nitrides ◽  
Wide Range ◽  
X Ray Absorption ◽  
The Rare Earth

<p>The rare-earth nitrides (ReNs) are a class of novel materials with potential for use in spintronics applications. Theoretical studies indicate that among the ReNs there could be half-metals, semimetals and semiconductors, all exhibiting strong magnetic ordering. This is because of the complex interaction between the partially filled rare-earth 4f orbital and the nitrogen 2p valence and rare-earth 5d conduction bands. This thesis uses experimental and theoretical techniques to probe the ReN electronic structure. Thin films of SmN, EuN, GdN, DyN, LuN and HfN have been produced for study. Basic characterization shows that the films are of a high quality. The result of electrical transport, magnetometry, and optical and x-ray spectroscopy are interpreted to provide information on the electronic structure. SmN, GdN, DyN are found to be semiconductors in their ferromagnetic ground state while HfN is a metal. Results are compared with density functional theory (DFT) based calculations. The free parameters resulting from use of the local spin density approximation with Hubbard-U corrections as the exchange-correlation functional are adjusted to reach good agreement with x-ray absorption and emission spectroscopy at the nitrogen K-edge. Resonant x-ray emission is used to experimentally measure valence band dispersion of GdN. No evidence of the rare-earth 4f levels is found in any of the K-edge spectroscopy, which is consistent with the result of M-edge x-ray absorption which show that the 4f wave function of the rare-earths in the ReNs are very similar to those of rare-earth metal. An auxillary resonant x-ray emission study of ZnO is used to map the dispersion of the electronic band structure across a wide range of the Brillouin zone. The data, and calculations based on GW corrections to DFT, together provide a detailed picture of the bulk electronic band structure.</p>

CO2 methanation over rare earth doped Ni based mesoporous catalysts with intensified low-temperature activity

2017 ◽  
Vol 42 (23) ◽  
pp. 15523-15539 ◽  
Author(s):  
Leilei Xu ◽  
Fagen Wang ◽  
Mindong Chen ◽  
Dongyang Nie ◽  
Xinbo Lian ◽  
...  
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Co2 Methanation ◽  
Mesoporous Catalysts ◽  
Rare Earth Doped

scholarly journals Influence of Nickel Loading on Reduced Graphene Oxide-Based Nickel Catalysts for the Hydrogenation of Carbon Dioxide to Methane

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 471
Author(s):  
Nur Diyan Mohd Ridzuan ◽  
Maizatul Shima Shaharun ◽  
Kah Mun Lee ◽  
Israf Ud Din ◽  
Poppy Puspitasari
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
High Surface ◽  
Nickel Catalysts ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Co2 Methanation ◽  
X Ray ◽  
Reduced Graphene ◽  
Temperature Programmed

In this study, a series of novel nickel catalysts supported on reduced graphene oxide nanosheets (Ni/rGO) with Ni loadings of 10, 15 and 20 wt% were successfully synthesized via the incipient wetness impregnation method. The physicochemical properties of the catalysts and rGO support were thoroughly characterized by thermogravimetric analyser, X-ray diffraction, fourier-transform infrared spectroscopy, Raman spectroscopy, N2 adsorption-desorption, temperature programmed reduction, temperature programmed CO2 desorption and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy. The properties of the catalysts are correlated to its catalytic activity for CO2 methanation which were investigated using three-phase slurry reactor at low temperature and pressure of 240 °C and 10 bar, respectively. Among the three catalysts of different Ni loading, Ni15/rGO shows the highest activity of 51% conversion of CO2 with total selectivity towards CH4. N2-physisorption and CO2-TPD analysis suggest that high catalytic performance of Ni15/rGO is attributed to the high surface area, strong basic sites and special support effect of rGO in anchoring the active metal.

Preparation and Properties of Rare Earth-Doped TiO2 Thin Films by Sol-Gel Process

2014 ◽  
Vol 1033-1034 ◽  
pp. 1235-1238
Author(s):  
Tao Bai ◽  
Shi Gen Zhu
Keyword(s):  
Thin Films ◽  
Rare Earth ◽  
Sol Gel ◽  
Rare Earth Doping ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sol Gel Process ◽  
Scanning Electronmicroscopy ◽  
Rare Earth Doped ◽  
The Rare Earth

Rare earth doped titaniumdioxide (TiO2) thin films (rare earth-doped TiO2) have been successfully prepared on a glass substrate by a sol–gel route. After the rare earth-doped TiO2thin films were calcined at 773K for 1h, the effect of rare earth-doping on the properties were investigated using X-ray diffraction (XRD), scanning electronmicroscopy (SEM), ultraviolet–visible spectroscopy and thermogravimetric techniques (TG/DTG). The XRD results showed that rare earth-doped TiO2thin films contained only a single crystalline phase of anatase TiO2after calcining at 773K for 1h. SEM micrographs showed that rare earth-doped TiO2thin films have smooth surfaces containing granular nanocrystallines and are without cracks. The UV–vis absorption spectra showed that the absorption of the rare earth-doped TiO2thin films has a red-shift. From ambient to 1273K, it is about 12% of mass loss because of the volatilizing of water and organic and the phase transformation.

scholarly journals Electronic Structure of the Rare-Earth Nitrides

2021 ◽  
Author(s):  
◽  
A. R. H. Preston
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Band Structure ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
X Ray ◽  
Rare Earth Nitrides ◽  
Wide Range ◽  
X Ray Absorption ◽  
The Rare Earth

<p>The rare-earth nitrides (ReNs) are a class of novel materials with potential for use in spintronics applications. Theoretical studies indicate that among the ReNs there could be half-metals, semimetals and semiconductors, all exhibiting strong magnetic ordering. This is because of the complex interaction between the partially filled rare-earth 4f orbital and the nitrogen 2p valence and rare-earth 5d conduction bands. This thesis uses experimental and theoretical techniques to probe the ReN electronic structure. Thin films of SmN, EuN, GdN, DyN, LuN and HfN have been produced for study. Basic characterization shows that the films are of a high quality. The result of electrical transport, magnetometry, and optical and x-ray spectroscopy are interpreted to provide information on the electronic structure. SmN, GdN, DyN are found to be semiconductors in their ferromagnetic ground state while HfN is a metal. Results are compared with density functional theory (DFT) based calculations. The free parameters resulting from use of the local spin density approximation with Hubbard-U corrections as the exchange-correlation functional are adjusted to reach good agreement with x-ray absorption and emission spectroscopy at the nitrogen K-edge. Resonant x-ray emission is used to experimentally measure valence band dispersion of GdN. No evidence of the rare-earth 4f levels is found in any of the K-edge spectroscopy, which is consistent with the result of M-edge x-ray absorption which show that the 4f wave function of the rare-earths in the ReNs are very similar to those of rare-earth metal. An auxillary resonant x-ray emission study of ZnO is used to map the dispersion of the electronic band structure across a wide range of the Brillouin zone. The data, and calculations based on GW corrections to DFT, together provide a detailed picture of the bulk electronic band structure.</p>

scholarly journals CO2 Methanation: Nickel–Alumina Catalyst Prepared by Solid-State Combustion

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6789
Author(s):  
Olga Netskina ◽  
Svetlana Mucha ◽  
Janna Veselovskaya ◽  
Vasily Bolotov ◽  
Oxana Komova ◽  
...  
Keyword(s):  
Solid State ◽  
Low Temperature ◽  
Photoelectron Spectroscopy ◽  
Combustion Method ◽  
Nickel Aluminum ◽  
Alumina Catalyst ◽  
Co2 Methanation ◽  
X Ray ◽  
Temperature Programmed ◽  
Temperature Activation

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO2 methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H2-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO2. In addition, the synthesized catalyst had higher activity in low-temperature CO2 methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

Comparison Study on Support Effect of Co-Series Compound Oxide Catalysts Supported Rare Earth

2011 ◽  
Vol 356-360 ◽  
pp. 439-444
Author(s):  
Xue Li ◽  
Rui Sheng Hu ◽  
Jia Nan Hu ◽  
Ya Qin Bai
Keyword(s):  
Rare Earth ◽  
Active Component ◽  
Support Effect ◽  
Impregnation Method ◽  
Comparison Study ◽  
Temperature Programmed Reduction ◽  
Active Components ◽  
Rare Earth Compound ◽  
X Ray ◽  
Temperature Programmed

The catalysts were prepared by the impregnation method and characterized thought X-ray powder diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), measurement of surface area, differial thermal and thermogravimetric analysis. Rare-earth compound oxides La0.8Sr0.2CoO3act as active component; Alumina act as carriers. The effects were investigated on loading amounts of active components, calcinations temperature and the addition components on the catalytic oxidation of xylene.

scholarly journals Low Temperature Water-Gas Shift: Enhancing Stability through Optimizing Rb Loading on Pt/ZrO2

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 210
Author(s):  
Caleb Daniel Watson ◽  
Michela Martinelli ◽  
Donald Charles Cronauer ◽  
A. Jeremy Kropf ◽  
Gary Jacobs
Keyword(s):  
Low Temperature ◽  
Hydrogen Transfer ◽  
Water Gas Shift ◽  
Significant Shift ◽  
Catalyst Activation ◽  
X Ray ◽  
Temperature Programmed ◽  
Water Gas ◽  
X Ray Absorption ◽  
Temperature Water

Recent studies have shown that appropriate levels of alkali promotion can significantly improve the rate of low-temperature water gas shift (LT-WGS) on a range of catalysts. At sufficient loadings, the alkali metal can weaken the formate C–H bond and promote formate dehydrogenation, which is the proposed rate determining step in the formate associative mechanism. In a continuation of these studies, the effect of Rb promotion on Pt/ZrO2 is examined herein. Pt/ZrO2 catalysts were prepared with several different Rb loadings and characterized using temperature programmed reduction mass spectrometry (TPR-MS), temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an X-ray absorption near edge spectroscopy (XANES) difference procedure, extended X-ray absorption fine structure spectroscopy (EXAFS) fitting, TPR-EXAFS/XANES, and reactor testing. At loadings of 2.79% Rb or higher, a significant shift was seen in the formate ν(CH) band. The results showed that a Rb loading of 4.65%, significantly improves the rate of formate decomposition in the presence of steam via weakening the formate C–H bond. However, excessive rubidium loading led to the increase in stability of a second intermediate, carbonate and inhibited hydrogen transfer reactions on Pt through surface blocking and accelerated agglomeration during catalyst activation. Optimal catalytic performance was achieved with loadings in the range of 0.55–0.93% Rb, where the catalyst maintained high activity and exhibited higher stability in comparison with the unpromoted catalyst.

scholarly journals High Pressure X-ray Diffraction as a Tool for Designing Doped Ceria Thin Films Electrolytes

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 724
Author(s):  
Sara Massardo ◽  
Alessandro Cingolani ◽  
Cristina Artini
Keyword(s):  
Thin Films ◽  
High Pressure ◽  
Rare Earth ◽  
Ionic Conductivity ◽  
Bulk Material ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rare Earth Doped

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.

scholarly journals High-pressure synthesis of REB5O8(OH)2 (RE = Ho, Er, Tm)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Michael Zoller ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Ir Spectroscopy ◽  
Earth Metal ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Solution ◽  
Pressure Synthesis ◽  
The Rare Earth

AbstractThe rare earth oxoborates REB5O8(OH)2 (RE = Ho, Er, Tm) were synthesized in a Walker-type multianvil apparatus at a pressure of 2.5 GPa and a temperature of 673 K. Single-crystal X-ray diffraction data provided the basis for the structure solution and refinement. The compounds crystallize in the monoclinic space group C2 (no. 5) and are composed of a layer-like structure containing dreier and sechser rings of corner sharing [BO4]5− tetrahedra. The rare earth metal cations are coordinated between two adjacent sechser rings. Further characterization was performed utilizing IR spectroscopy.

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