scholarly journals Highly-Ordered PdIn Intermetallic Nanostructures Obtained from Heterobimetallic Acetate Complex: Formation and Catalytic Properties in Diphenylacetylene Hydrogenation

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 769 ◽  
Author(s):  
Igor Mashkovsky ◽  
Pavel Markov ◽  
Galina Bragina ◽  
Galina Baeva ◽  
Alexander Rassolov ◽  
...  
Keyword(s):  
Intermetallic Phase ◽  
Catalytic Performance ◽  
Minor Amount ◽  
Intimate Contact ◽  
Acetate Complex ◽  
Transmission Electron ◽  
Alkene Hydrogenation ◽  
Temperature Programmed ◽  
Α Al2o3 ◽  
A Minor

Formation of PdIn intermetallic nanoparticles supported on α-Al2O3 was investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and hydrogen temperature-programmed desorption (H2-TPD) methods. The metals were loaded as heterobimetallic Pd(μ-O2CMe)4In(O2CMe) complex to ensure intimate contact between Pd and In. Reduction in H2 at 200 °C resulted in Pd-rich PdIn alloy as evidenced by XRD and the disappearance of Pd hydride. A minor amount of Pd1In1 intermetallic phase appeared after reduction at 200 °C and its formation was accomplished at 400 °C. Neither monometallic Pd or in nor other intermetallic structures were found after reduction at 400–600 °C. Catalytic performance of Pd1In1/α-Al2O3 was studied in the selective liquid-phase diphenylacetylene (DPA) hydrogenation. It was found that the reaction rate of undesired alkene hydrogenation is strongly reduced on Pd1In1 nanoparticles enabling effective kinetic control of the hydrogenation, and the catalyst demonstrated excellent selectivity to alkene.

Polymer-Derived Silicon Carbide Fibers with Near-Stoichiometric Composition and Low Oxygen Content

1994 ◽  
Vol 365 ◽  
Author(s):  
Michael D. Sacks ◽  
Gary W. Scheiffele ◽  
Mohamed Saleem ◽  
Gregory A. Staab ◽  
Augusto A. Morrone ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Oxygen Content ◽  
Stoichiometric Composition ◽  
Alpha Phase ◽  
Minor Amount ◽  
Low Oxygen ◽  
Silicon Carbide Fibers ◽  
Fine Grain ◽  
Transmission Electron ◽  
A Minor

ABSTRACTFine-diameter (∼ 10–15 µm), polymer-derived SiC fibers were characterized. The average tensile strength of the fibers was ∼ 2.8 GPa, although some lots had average strengths exceeding 3.5 GPa. Microstructure observations showed that fibers had fine grain sizes (mostly ∼0.05–0.2 µm), high densities (∼3.1–3.2 g'cm3), and small residual pore sizes (≤0.1 µm). Elemental analysis showed that fibers had near-stoichiometric composition. Electron and X-ray diffraction analyses indicated that fibers were primarily beta silicon carbide, with a minor amount of the alpha phase. A small amount of graphitic carbon was detected in some samples using high resolution transmission electron microscopy. The residual oxygen content in the fibers was ≤0.1 wt%. Fibers exhibited good thermomechanical stability, as heat treatment at 1800°C for 4h in argon resulted in only an ∼ 8% decrease in strength.

Catalytic Performance of Supported Bimetallic Catalysts for Complete Oxidation of Toluene

2021 ◽  
Vol 21 (7) ◽  
pp. 4060-4066
Author(s):  
Sang-Chul Jung ◽  
Young-Kwon Park ◽  
Ho-Young Jung ◽  
Sang Chai Kim
Keyword(s):  
Catalytic Activity ◽  
Transition Metal ◽  
Bimetallic Catalysts ◽  
Xrd Analysis ◽  
Catalytic Performance ◽  
Bet Surface Area ◽  
Complete Oxidation ◽  
Transmission Electron ◽  
The Difference ◽  
Temperature Programmed

The complete oxidation of toluene (as a model volatile organic compound) was studied to determine the influence of adding a transition metal (Mn, Cr, Fe, Co, and Ni) to the 5 Cu/Al catalyst. The physcochemical properties of the catalysts were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD) analysis, field emission transmission electron microscopy (FE/TEM), and hydrogen temperature programmed reduction (H2-TPR). The catalytic activity of the supported bimetallic catalysts followed the order: 5Cu-5Mn/Al > 5Cu-5Cr/Al > 5Cu-5Fe/Al > 5Cu-5Co/Al > 5Cu > 5Cu-5Ni/Al, based on the temperature for T90 of toluene conversion (T90). Two different reaction mechanisms (mixing and the synergistic effect) were operative in the supported bimetallic catalysts except for the 5Cu–5Mn/Al and 5Cu–5Ni/Al catalysts, on the basis of the reaction temperature. The difference between the electronegativity of copper and the added transition metal was associated with the catalytic activity.

Nanoparticles of Ni-Co Alloy Derived from Layered Double Hydroxides and Their Catalytic Performance for CO Methanation

NANO ◽  
2016 ◽  
Vol 11 (10) ◽  
pp. 1650118 ◽  
Author(s):  
Jingge Liu ◽  
Ang Cao ◽  
Jing Si ◽  
Lihong Zhang ◽  
Qinglan Hao ◽  
...  
Keyword(s):  
Metallic Nanoparticles ◽  
Carbon Deposition ◽  
Catalytic Performance ◽  
X Ray Diffraction ◽  
Co Methanation ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
The Stability ◽  
Double Hydroxides ◽  
Adsorption Desorption

Sintering of the active metallic nanoparticles and carbon deposition are the key problems faced for CO methanation catalysts. For overcoming those problems, bimetallic nanocatalyst is a promising route. In this work, a series of Al2O3 supported Ni-Co alloy catalysts were prepared by reducing NiCoAl layered double hydrotalcite (LDHs), and characterized with X-ray diffraction (XRD), temperature programmed reduction TPR, N2 adsorption-desorption, transmission electron microscopy (TEM) and temperature programed oxidation (TPO) techniques. The resultant catalysts were mesoporous with nanoparticles of Ni-Co alloy ranging from 7.9[Formula: see text]nm to 9.2[Formula: see text]nm which were highly dispersed in alumina matrix. The sample Ni7Co3-Al2O3 catalysts showed very good catalytic performance during the stability test at 500/600[Formula: see text]C for 300[Formula: see text]h, meanwhile exhibited excellent anti-sintering ability and anti-carbon deposition ability, owing to the formation of Ni-Co alloy and the feature of LDHs. This strategy for improving anti-sintering and anti-carbon deposition should be extendable for catalysts of other reactions.

scholarly journals Three-Dimensional Mesoporous Ni-CeO2 Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 523 ◽  
Author(s):  
Luhui Wang ◽  
Junang Hu ◽  
Hui Liu ◽  
Qinhong Wei ◽  
Dandan Gong ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Nitrogen Adsorption ◽  
Combustion Method ◽  
Catalytic Performance ◽  
Oxide Interface ◽  
Solution Combustion ◽  
Co2 Methanation ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Adsorption Desorption

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.

scholarly journals Preferential Oxidation of CO over CoFe2O4 and M/CoFe2O4 (M = Ce, Co, Cu or Zr) Catalysts

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 15
Author(s):  
Mehdi Béjaoui ◽  
Abdelhakim Elmhamdi ◽  
Laura Pascual ◽  
Patricia Pérez-Bailac ◽  
Kais Nahdi ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Preferential Oxidation Of Co ◽  
Transmission Electron ◽  
Low Temperature Co Oxidation ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared

CoFe2O4 prepared by sol-gel has been examined with respect to its catalytic performance for preferential CO oxidation in a H2-rich stream. In turn, the promoting effects of incorporation of Ce, Co, Cu, and Zr by impregnation on the surface of CoFe2O4 on the process are examined as well. The catalysts have been characterized by N2 adsorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR), and X-ray photoelectron spectra (XPS), as well as diffuse reflectance infrared DRIFTS under reaction conditions with the aim of establishing structure/activity relationships for the mentioned catalyst/process. It is shown that while the presence of the various metals on CoFe2O4 hinders a low temperature CO oxidation process, it appreciably enhances the activity above 125 °C. This is basically attributed to the surface modifications, i.e. cobalt oxidation, induced in CoFe2O4 upon introduction of the metals. In turn, no methanation activity is observed in any case except for the copper-containing catalyst, in which achievement of reduced states of cobalt appears most favored.

scholarly journals Characteristics and activity of Ni/CeO2 catalyst modified by Cr2O3 in combined steam and CO2 reforming of CH4

2021 ◽  
Vol 10 (1) ◽  
pp. 104-108
Author(s):  
Phuong Phan Hong ◽  
Anh Nguyen Phung ◽  
Huy Tran Anh ◽  
Tri Nguyen ◽  
Loc Luu Cam
Keyword(s):  
Chemical Properties ◽  
Catalytic Performance ◽  
Molar Ratio ◽  
Impregnation Method ◽  
Co2 Reforming ◽  
X Ray ◽  
Co2 Reforming Of Ch4 ◽  
Transmission Electron ◽  
Physico Chemical ◽  
Temperature Programmed

A series of 10%wtNiO/CeO2-nanorod catalyst without and with Cr2O3 additive was prepared by simultaneous impregnation method. Several techniques, including N2 physisorption measurements, X-ray powder diffraction (XRD), temperature-programmed reduction using H2 (H2-TPR), CO2 temperature-programmed desorption (CO2-TPD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) were used to investigate catalysts’ physico-chemical properties. The activity of the catalysts in combined steam and CO2 reforming of CH4 (BRM) was investigated at temperature range of 550-800 °C. The results showed that 10%NiO0.1%Cr2O3/CeO2 catalyst had the best catalytic performance due to a better reducibility and basicity. At 700 °C and CH4:CO2:H2O molar ratio in feed stream of 3:1.2:2.4, both conversion of CH4 and CO2 on this catalyst reached 98.5%.

scholarly journals High Temperature Adsorption of SO2 on Mixed Oxides Derived from CaAl Hydrotalcite-Like Compounds

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 325
Author(s):  
Hailin Wang ◽  
Run Hao ◽  
Meiping Gao ◽  
Zhongshen Zhang ◽  
Zhengping Hao
Keyword(s):  
High Temperature ◽  
Air Pollutants ◽  
High Efficiency ◽  
Mixed Oxides ◽  
Low Cost ◽  
Minor Amount ◽  
So2 Adsorption ◽  
Temperature Programmed ◽  
Calcination Method ◽  
A Minor

SO2 which is usually emitted at high temperature is one of the most important air pollutants. It is of great significance to develop high temperature SO2 adsorbent with high efficiency and low cost. In this work, a series of hydrotalcite-like compound-derived CaAlO and CaXAlO(X = Ce, Co) were prepared by coprecipitation and calcination method, and were employed as adsorbents for SO2 adsorption at high temperature (700 °C). The structure and surface properties of these adsorbents were characterized by XRD, Brunauer–Emmett–Teller (BET), Derivative thermogravimetric analysis (DTG) and CO2-TPD (temperature programmed desorption) measurement. Addition of a minor amount of Ce, Co (5 wt%) could significantly increase the number of weak alkalinity sites. CaO in CaCeAlO showed the best SO2 adsorption capacity of 1.34 g/g, which is two times higher than that of CaO in CaAlO (0.58 g/g).

scholarly journals Synthesis and Catalytic Performance of Ni/SiO2for Hydrogenation of 2-Methylfuran to 2-Methyltetrahydrofuran

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Fu Ding ◽  
Yajing Zhang ◽  
Guijin Yuan ◽  
Kangjun Wang ◽  
Ileana Dragutan ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ni Content ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Ni Species

A series of Ni/SiO2catalysts with different Ni content were prepared by sol-gel method for application in the synthesis of 2-methyltetrahydrofuran (2-MTHF) by hydrogenation of 2-methylfuran (2-MF). The catalyst structure was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR). It is found that structures and catalytic performance of the catalysts were highly affected by the Ni content. The catalyst with a 25% Ni content had an appropriate size of the Ni species and larger BET surface area and produced a higher 2-MF conversion with enhanced selectivity in 2-MTHF.

scholarly journals Phase Composition of Ni/Mg1−xNixO as a Catalyst Prepared for Selective Methanation of CO in H2-Rich Gas

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Mengmeng Zhang ◽  
Hongwei Ma ◽  
Zhiming Gao
Keyword(s):  
Phase Composition ◽  
Calcination Temperature ◽  
Rietveld Method ◽  
Minor Amount ◽  
X Ray Diffraction ◽  
Co Conversion ◽  
Method Effects ◽  
Temperature Programmed ◽  
A Minor ◽  
Supported Ni

Supported Ni catalysts Ni/Mg1−xNixO were prepared by reducing samples NiO-MgO in H2/N2mixture gas at 500°C~800°C for selective methanation of CO in H2-rich gas (CO-SMET). The samples NiO-MgO were obtained by heating water slurry of MgO and Ni(NO3)2in a rotary evaporator at 80°C and a final calcination in air at 400°C~800°C. X-ray diffraction (XRD) and temperature programmed reduction (TPR) measurements demonstrate that the samples NiO-MgO were composed of solid solution Mg1−yNiyO as the main phase and a minor amount of NiO at calcination temperature of 400°C, and amount of the NiO was decreased as calcination temperature increased. Phase composition of the catalysts Ni/Mg1−xNixO was estimated by the Rietveld method. Effects of reduction temperature, feed Ni/Mg ratio, and calcination temperature on phase composition and catalytic activity of the catalysts were investigated. It is clear that CO conversion was generally enhanced by an increased amount of metallic Ni of the catalysts.

Phase Equilibria and Dielectric Properties in Perovskite-like (1 − x)LaCa0.5Zr0.5O3–xATiO3 (A = Ca, Sr) Ceramics

2002 ◽  
Vol 17 (7) ◽  
pp. 1729-1734 ◽  
Author(s):  
Igor Levin ◽  
Terrell A. Vanderah ◽  
Rachel Coutts ◽  
Steven M. Bell
Keyword(s):  
Dielectric Properties ◽  
Phase Equilibria ◽  
Perovskite Phase ◽  
Minor Amount ◽  
Two Phase ◽  
Microwave Frequencies ◽  
Transmission Electron ◽  
Octahedral Tilting ◽  
Ct System ◽  
A Minor

Phase equilibria and dielectric properties were analyzed for selected compositions in both LaCa0.5Zr0.5O3–CaTiO3 (LCZ-CT) and LaCa0.5Zr0.5O3–SrTiO3 (LCZ–ST) systems using x-ray powder diffraction and transmission electron microscopy. The end-member LaCa0.5Zr0.5O3 does not occur as a single phase but rather as a mixture of a perovskite-type phase with approximate composition La0.94Ca0.53Zr0.53O3 plus a minor amount of La2O3. This perovskite phase exhibited a combination of 1:1 ordering of Ca and Zr on the B-sites and octahedral tilting. In the (1 – x)LCZ– xCT system, the compositions x = 1/3 and x = 1/2 yielded single phases with perovskite-like structures featuring similar 1:1 B-site ordering superimposed onto octahedral tilting. The x = 1/2 composition in the LCZ–ST system resides in a two-phase field and contains a major perovskite phase and La2O3; the B-cations in the perovskite phase remain disordered at all temperatures. The approximate boundaries of perovskite-like phase fields in the La2O3–ATiO3–CaZrO3 (A = Ca, Sr) systems were outlined, as well as a schematic diagram for perovskite B-cation ordering transitions in the LCZ–CT system. The dielectric properties of the compositions investigated were measured at microwave frequencies and were correlated with the observed structural behavior.

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