Synthesis, characterization, thermal stability and redox behavior of In3+2Ti4+1–xTm3+xO5–δ, (Tm = Fe3+ and Cr3+, 0.0 ≤ x ≤ 0.2) mixed-oxide catalysts

2007 ◽  
Vol 22 (7) ◽  
pp. 1787-1796 ◽  
Author(s):  
M.R. Pai ◽  
A.M. Banerjee ◽  
S.R. Bharadwaj ◽  
S.K. Kulshreshtha
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Oxide Catalysts ◽  
Maximum Temperature ◽  
Mixed Metal Oxide ◽  
Redox Behavior ◽  
X Ray ◽  
Temperature Programmed Oxidation ◽  
Mixed Oxide Catalysts ◽  
Temperature Programmed

Mixed metal oxide catalysts with nominal compositions of In2Ti1–xFexO5–δ, In2Ti1–xCrxO5–δ, where 0.0 ≤ x ≤ 0.2, have been synthesized by the ceramic route and characterized using the powder x-ray diffraction technique. The In2Ti1–xFexO5–δ samples were single-phase compositions, isomorphic with In2TiO5 phase. The particle size of the In2Ti1–xFexO5–δ samples was lower compared to the parent In2TiO5 oxide. Thermal stability (by thermogravimetry-differential thermal analysis) in varying atmospheres, and temperature-programmed reduction (TPR)/temperature-programmed oxidation cycles have been recorded to investigate their redox behavior as a function of the value of x in this study. The amount of H2 consumed under TPR curves was correlated with the nonstoichiometry generated in the In2Ti1–xFexO5–δ samples. Fe substitution induced ease in the reducibility (i.e., maximum temperature) of the substituted oxides compared to that in In2TiO5. X-ray photoelectron spectroscopy has been used to confirm the oxidation states of indium and other metal ions in fresh and reduced samples.

scholarly journals Synthesis, Modification, and Characterization of CuO/ZnO/ZrO2 Mixed Metal Oxide Catalysts for CO2/H2 Conversion

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1037 ◽  
Author(s):  
Ekaterina S. Borovinskaya ◽  
Sebastian Trebbin ◽  
Felix Alscher ◽  
Cornelia Breitkopf
Keyword(s):  
Metal Oxide ◽  
Acid Sites ◽  
Oxide Catalysts ◽  
Mixed Metal Oxide ◽  
One Pot ◽  
Wet Impregnation ◽  
Porous Texture ◽  
Mixed Oxide Catalysts ◽  
One Pot Synthesis ◽  
Temperature Programmed

CuO/ZnO/ZrO2 catalyst systems were synthesized in different ways and comprehensively characterized in order to study synthesis-to-property relations. A series of catalyst samples was prepared by coprecipitation, one-pot synthesis, and wet impregnation. The coprecipitation of multicomponent precipitates is usually a preliminary stage for preparation of mixed oxide catalysts. Cetyltrimethylammonium bromide (CTAB) was used in the surfactant-supported coprecipitation to improve the structural or textural characteristics of the catalytic samples. In the one-pot synthesis, all necessary components are simultaneously converted by evaporation from solutions into solids. During the wet impregnation, zirconium hydroxide is loaded with metal salts. After thermal treatment, all samples formed pure metal oxide forms, which was confirmed by XRD. The specific surface area of the investigated samples and their porous texture were determined by nitrogen adsorption. The reducibility of metal oxides and the kind of CuO phase was characterized by temperature-programmed reduction (TPR), and the surface acid properties by temperature-programmed ammonia desorption (TPAD). The CuO/ZnO/ZrO2 sample with the highest amount of strong acid sites is characterized by the formation of large CuO particles combined with the worst reducibility so that potentially catalytic active Cu/CuO pairs can be formed. One catalyst system was further characterized by in situ diffuse reflection Fourier transform infrared spectroscopy (DRIFTS) to identify surface intermediate species, which may occur during the conversion of CO2/H2 to methanol.

scholarly journals Zn-Al Mixed Oxides Decorated with Potassium as Catalysts for HT-WGS: Preparation and Properties

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1094 ◽  
Author(s):  
Katarzyna Antoniak-Jurak ◽  
Paweł Kowalik ◽  
Kamila Michalska ◽  
Wiesław Próchniak ◽  
Robert Bicki
Keyword(s):  
Photoelectron Spectroscopy ◽  
Mixed Oxides ◽  
Catalyst Activity ◽  
Molar Ratio ◽  
X Ray ◽  
Molar Ratios ◽  
Mixed Oxide Catalysts ◽  
Wgs Reaction ◽  
Temperature Programmed ◽  
Co Precipitation

A set of ex-ZnAl-LDHs catalysts with a molar ratio of Zn/Al in the range of 0.3–1.0 was prepared using co-precipitation and thermal treatment. The samples were characterized using various methods, including X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy FT-IR, N2 adsorption, Temperature-programmed desorption of CO2 (TPD-CO2) as well as Scanning electron microscopy (SEM-EDS). Catalyst activity and long-term stability measurements were carried out in a high-temperature water–gas shift (HT-WGS) reaction. Mixed oxide catalysts with various Zn/Al molar ratios decorated with potassium showed high activity in the HT-WGS reaction within the temperature range of 330–400 °C. The highest activity was found for the Zn/Al molar ratio of 0.5 corresponding to spinel stoichiometry. However, the catalyst with a stoichiometric spinel molar ratio of Zn/Al (ZnAl_0.5_K) revealed a higher tendency for surface migration and/or vaporization of potassium during overheating at 450 °C. The correlation of the activity results and TPD-CO2 data show that medium basic sites enhance the progress of the HT-WGS reaction.

scholarly journals High Dispersion of CeO2 on CeO2/MgO Prepared under Dry Conditions and Its Improved Redox Properties

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7922
Author(s):  
Kenji Taira ◽  
Reiko Murao
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ambient Air ◽  
Ceo2 Nanoparticles ◽  
High Dispersion ◽  
Impregnation Method ◽  
X Ray ◽  
Temperature Programmed Oxidation ◽  
Dry Conditions ◽  
Common Technique ◽  
Temperature Programmed

Suppressing the usage of rare-earth elements is crucial for making the catalysts sustainable. Preparing CeO2 nanoparticles is a common technique to reduce CeO2 consumption, but such nanoparticles are prone to sinter or react with the supports when subjected to heat treatments. This study demonstrated that stable CeO2 nanoparticles were deposited on MgO by the simple impregnation method. When CeO2/MgO was prepared under the dry atmosphere, the CeO2 nanoparticles remained ~3 nm in diameter even after being heated at 800 °C, which is much smaller than ~5 nm of CeO2/MgO prepared under ambient air. Temperature-programmed reduction, temperature-programmed oxidation, X-ray photoelectron spectroscopy, and in situ X-ray diffraction studies showed that CeO2/MgO exhibited higher oxygen mobility when prepared under the dry atmosphere. Dry reforming reaction demonstrated that CeO2/MgO prepared under the dry atmosphere exhibited higher activity than that prepared under ambient air and pure CeO2.

scholarly journals Zeolite Beta Doped with La, Fe, and Pd as a Hydrocarbon Trap

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 173
Author(s):  
Rasmus Jonsson ◽  
Jungwon Woo ◽  
Magnus Skoglundh ◽  
Louise Olsson
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Zeolite Beta ◽  
Substantial Part ◽  
Catalyst Characterization ◽  
Incipient Wetness Impregnation ◽  
X Ray ◽  
Temperature Programmed Oxidation ◽  
Temperature Programmed

Hydrocarbon trapping is a technique of great relevance, since a substantial part of hydrocarbon emissions from engines are released from engines before the catalyst has reached the temperature for efficient conversion of the hydrocarbons. In this work, the influence of doping zeolite beta (BEA) with Fe, Pd, and La on the storage and release of propene and toluene is studied. Five monolith samples were prepared; Fe/BEA, La/BEA, Pd/BEA, Pd/Fe/BEA, and Pd/La/BEA using incipient wetness impregnation, and the corresponding powder samples were used for catalyst characterization by Inductively coupled plasma sector field mass spectrometry (ICP-SFMS), Temperature-programmed oxidation (TPO), X-ray photoelectron spectroscopy (XPS) and Scanning transmission electron microscopy with Energy dispersive X-ray analysis (STEM-EDX). The hydrocarbon trapping ability of the samples was quantified using Temperature-programmed desorption (TPD) of propene and toluene, and in situ Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results from the TPD experiments show that the addition of Pd and La to the zeolite affected the release patterns of the stored hydrocarbons on the trapping material in a positive way. The in situ DRIFTS results indicate that these elements provide H-BEA with additional sites for the storage of hydrocarbons. Furthermore, EDX-mapping showed that the La and Pd are located in close connection.

scholarly journals Characteristics of High Surface Area Molybdenum Nitride and Its Activity for the Catalytic Decomposition of Ammonia

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 192
Author(s):  
Seo-Hyeon Baek ◽  
Kyunghee Yun ◽  
Dong-Chang Kang ◽  
Hyejin An ◽  
Min Bum Park ◽  
...  
Keyword(s):  
Surface Area ◽  
Photoelectron Spectroscopy ◽  
High Surface ◽  
High Surface Area ◽  
Catalytic Decomposition ◽  
Molybdenum Nitride ◽  
X Ray ◽  
Temperature Programmed Oxidation ◽  
Oxidation Reduction ◽  
Temperature Programmed

High surface area (>170 m2 g−1) molybdenum nitride was prepared by the temperature-programmed nitridation of α-MoO3 with pure ammonia. The process was optimized by adjusting the experimental variables: the reaction temperature, heating rate, and molar flow rate of ammonia. The physicochemical properties of the as-formed molybdenum nitride were characterized by X-ray diffraction, N2 sorption, transmission electron microscopy, temperature-programmed oxidation/reduction, and X-ray photoelectron spectroscopy. Of the experimental variables, the nitridation temperature was found to be the most critical parameter determining the surface area of the molybdenum nitride. When the prepared molybdenum nitride was exposed to air, the specific surface area rapidly decreased because of the partial oxidation of molybdenum nitride to molybdenum oxynitride. However, the surface area recovered to 90% the initial value after H2 treatment. The catalyst with the highest degree of nitridation showed the best catalytic activity, superior to that of unmodified α-MoO3, for the decomposition of ammonia because of its high surface area.

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