HREM study of the reoxidation of heavily reduced Ce-La mixed oxides of interest in environmental catalysis.

2022 ◽  
pp. 387-390
Author(s):  
G Blanco ◽  
J J Calvino ◽  
C López-Cartes ◽  
J A Pérez-Omil ◽  
J M Pintado ◽  
...  
Keyword(s):  
Mixed Oxides ◽  
Environmental Catalysis

Well Dispersed Co0 by Reduction of LaCoO3 Perovskite

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Bousselham Echchahed ◽  
Serge Kaliaguine ◽  
Houshang Alamdari
Keyword(s):  
Systematic Study ◽  
Mixed Oxides ◽  
High Surface ◽  
High Surface Area ◽  
Cobalt Metal ◽  
Environmental Catalysis ◽  
Perovskite Crystal ◽  
Reactive Grinding ◽  
Lower Temperature ◽  
Metal Sintering

A well dispersed Co0 supported on deficient LaCo1-xO3-delta perovskite was formed after reduction of LaCoO3 by hydrogen. The formation of some metal cobalt was achieved at the first step of reduction corresponding to reduction of bulk Co3+ to Co2+. The LaCoO3 perovskites were synthesized by reactive grinding, a technique which allows the preparation of nanocrystalline mixed oxides. The H2 reduction of Co is easier in the perovskites prepared this way, due to high surface area and small perovskite crystal domains. The reduction thus happens at lower temperature which helps avoiding metal sintering. This work is a systematic study of the cobalt metal masses generated in strictly controlled reduction conditions. It shows that the perovskites made by reactive grinding are potentially significant for the preparation of supported transition metals with possible applications in several environmental catalysis processes.

Heterogeneous environmental catalysis – a gentle art: CeO2–ZrO2 mixed oxides as a case history

2005 ◽  
Vol 100 (1-2) ◽  
pp. 27-35 ◽  
Author(s):  
Roberta Di Monte ◽  
Jan Kašpar
Keyword(s):  
Case History ◽  
Mixed Oxides ◽  
Environmental Catalysis

scholarly journals Template Synthesis of Porous Ceria-Based Catalysts for Environmental Application

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4242
Author(s):  
Igor Yu. Kaplin ◽  
Ekaterina S. Lokteva ◽  
Elena V. Golubina ◽  
Valery V. Lunin
Keyword(s):  
Active Sites ◽  
Mixed Oxides ◽  
Oxide Catalysts ◽  
Synthetic Methods ◽  
Oxygen Storage ◽  
Environmental Catalysis ◽  
Active Components ◽  
Environmental Application ◽  
Mixed Oxide Catalysts ◽  
Porous Oxide

Porous oxide materials are widely used in environmental catalysis owing to their outstanding properties such as high specific surface area, enhanced mass transport and diffusion, and accessibility of active sites. Oxides of metals with variable oxidation state such as ceria and double oxides based on ceria also provide high oxygen storage capacity which is important in a huge number of oxidation processes. The outstanding progress in the development of hierarchically organized porous oxide catalysts relates to the use of template synthetic methods. Single and mixed oxides with enhanced porous structure can serve both as supports for the catalysts of different nature and active components for catalytic oxidation of volatile organic compounds, soot particles and other environmentally dangerous components of exhaust gases, in hydrocarbons reforming, water gas shift reaction and photocatalytic transformations. This review highlights the recent progress in synthetic strategies using different types of templates (artificial and biological, hard and soft), including combined ones, in the preparation of single and mixed oxide catalysts based on ceria, and provides examples of their application in the main areas of environmental catalysis.

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

Correction: Small Batch Synthesis of Mixed Oxides of Nitrogen

2020 ◽  
Author(s):  
Philip M. Piper ◽  
Taylor B. Groom ◽  
Jeremy W. Marcum ◽  
Timothee L. Pourpoint
Keyword(s):  
Mixed Oxides ◽  
Oxides Of Nitrogen

In infrared study of sulphated ZrO2-TiO2 mixed oxides

2005 ◽  
Vol 30 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Abdelaziz Sahibed-Dine ◽  
Mhamed Sadiq ◽  
Naima Aderdour ◽  
Mohamed Bensitel
Keyword(s):  
Mixed Oxides ◽  
Infrared Study

Study of nickel-molybdenum catalysts for methanation of carbon monoxide

1980 ◽  
Vol 45 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Petr Taras ◽  
Milan Pospíšil
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Mixed Oxides ◽  
Minor Component ◽  
Fast Neutrons ◽  
Scanning Calorimetry ◽  
Low Concentrations ◽  
Γ Rays ◽  
Molybdenum Catalysts ◽  
Kinetics Of

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.

The effect of origin and physico-chemical properties on the kinetics of reduction of mixed NiO-Fe2O3 oxides with hydrogen

1986 ◽  
Vol 51 (10) ◽  
pp. 2098-2108 ◽  
Author(s):  
Milan Pospíšil ◽  
Jan Topinka
Keyword(s):  
Mixed Oxides ◽  
Mutual Influence ◽  
Spinel Phase ◽  
Chemical Properties ◽  
Inhibitory Effect ◽  
Chemical Parameters ◽  
Physico Chemical ◽  
Preliminary Annealing ◽  
Kinetics Of ◽  
Kinetics Of Reduction

We investigated the effect of origin and some physico-chemical parameters on the kinetics of reduction with hydrogen of two series of mixed NiO-Fe2O3 oxides differing by their composition, the character of their precursors (mixed crystalline nitrates and coprecipitated hydroxides) and their decomposition temperature.This effect manifested itself by different magnitudes of specific surfaces of the mixed oxides and coherent regions of present phases as well as by different oxidizing abilities of the surface and differences in morphology and phase composition of corresponding samples in both series investigated. Nonlinear or nonmonotonous composition dependences of physico-chemical parameters investigated point to a mutual influence of individual components, which is also a function of the system origin and which modifies its reactivity during its reduction with hydrogen. The kinetics of the reduction was studied thermogravimetrically at 320-410 °C. The reduction of oxides of the hydroxide origin is catalytically accelerated by primarily reduced nickel, whereas in corresponding samples of the nitrate series, the total NiO is bound to the spinel phase and the reduction is delayed. Experimental IR spectra, the effect of preliminary annealing and DTA of the mixed oxides point to an inhibitory effect of water, which is constitutionally bound in trace admixtures of the goethite phase, on the kinetics of reduction of samples in the hydroxide series.

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