Structure Sensitivity of NO Reduction over Iridium Catalysts in HC–SCR

2002 ◽  
Vol 205 (1) ◽  
pp. 157-167 ◽  
Author(s):  
C. Wögerbauer ◽  
M. Maciejewski ◽  
A. Baiker
Keyword(s):  
No Reduction ◽  
Structure Sensitivity ◽  
Iridium Catalysts

Positive effect of coexisting SO2 on the activity of supported iridium catalysts for NO reduction in the presence of oxygen

2003 ◽  
Vol 41 (1-2) ◽  
pp. 157-169 ◽  
Author(s):  
Tomohiro Yoshinari ◽  
Kazuhito Sato ◽  
Masaaki Haneda ◽  
Yoshiaki Kintaichi ◽  
Hideaki Hamada
Keyword(s):  
No Reduction ◽  
Iridium Catalysts ◽  
Catalysts For No Reduction ◽  
Positive Effect

NO reduction with CO over HY zeolite-supported rhodium dicarbonyl complexes: giving insight into the structure sensitivity

2019 ◽  
Vol 4 (2) ◽  
pp. 418-426 ◽  
Author(s):  
Artem D. Vityuk ◽  
Shuguo Ma ◽  
Oleg S. Alexeev ◽  
Michael D. Amiridis
Keyword(s):  
No Reduction ◽  
Structure Sensitivity ◽  
Hy Zeolite ◽  
Catalytic Transformations ◽  
Insight Into

Mononuclear zeolite-anchored Rh(CO)2 complexes do not facilitate NO reduction with CO and groups of rhodium atoms are required to initiate and sustain NO/CO catalytic transformations.

scholarly journals NO Reactions Over Ir-Based Catalysts in the Presence of O2

2011 ◽  
Vol 8 (s1) ◽  
pp. S349-S357 ◽  
Author(s):  
Mingxin Guo ◽  
Rongshu Zhu ◽  
Minhua Dong ◽  
Feng Ouyang
Keyword(s):  
Catalytic Activity ◽  
No Reduction ◽  
Active Phase ◽  
No Oxidation ◽  
Impregnation Method ◽  
Iridium Catalysts ◽  
Support Materials ◽  
Surface Active ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

The behaviour of a series of Ir-based catalysts supported on SiO2, ZSM-5 and γ-Al2O3 with various Ir loadings prepared by impregnation method was conducted by temperature programmed reaction (TPR) technique. The result implies that NO is oxidized to NO2while simultaneously being reduced to N2or N2O in the NO reactions over iridium catalysts. The surface active phase over iridium catalysts that promote the NO reactions is IrO2. The catalytic activity increases with the increase of the Ir loading and support materials have a little effect on the catalytic activity. When the loading is less than 0.1%, the catalytic activity was found to be dependent on the nature of support materials and in order: Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2. When the loading is higher than 0.1%, the catalytic activity for NO oxidation is in order: Ir/ZSM-5>Ir/SiO2>Ir/γ -Al2O3, which is correlated with Ir dispersion on the surface of support materials and the catalytic activity for NO reduction is in sequence: Ir/γ -Al2O3>Ir/SiO2>Ir/ZSM-5, which is attributed to the adsorbed-dissociation of NO2. Compared to Pt/γ-Al2O3, Ir/γ-Al2O3catalyst is more benefit for the NO reduction.

A High Resolution Study of Alumina Supported Iridium Catalysts

1980 ◽  
Vol 38 ◽  
pp. 202-203
Author(s):  
C. Stoeckert ◽  
B. Etherton ◽  
M. Beer ◽  
J. Gryder
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Metal Particles ◽  
Optical Transfer Function ◽  
Particle Sizes ◽  
Iridium Catalysts ◽  
Transmission Electron ◽  
Optical Transfer ◽  
Conventional Transmission Electron Microscope ◽  
Resolution Study

The interpretation of the activity of catalysts requires information about the sizes of the metal particles, since this has implications for the number of surface atoms available for reaction. To determine the particle dimensions we used a high resolution STEM1. Such an instrument with its simple optical transfer function is far more suitable than a conventional transmission electron microscope for the establishment of particle sizes. We report here our study on the size and number distribution of Ir particles supported on Al2O3 and also examine simple geometric models for the shape of Ir particles.

Pilot Scale Testing of a New Radium-226 Removal Process

1985 ◽  
Vol 20 (2) ◽  
pp. 55-67
Author(s):  
W.B. Anderson ◽  
P.M. Huck ◽  
T.M.R. Meadley ◽  
T.P. Hynes
Keyword(s):  
Treatment Process ◽  
No Reduction ◽  
High Surface ◽  
High Surface Area ◽  
Barium Chloride ◽  
Pilot Scale ◽  
Activity Levels ◽  
New Process ◽  
Removal Efficiencies ◽  
New Treatment

Abstract This paper describes the on-going pilot scale development of a new treatment process designed to remove radium-226 from uranium milling effluents. Presently, decants from Canadian uranium mining and milling tailings areas are treated with barium chloride to remove radium-226 prior to discharge into the environment. This is usually accomplished in large natural or man-made ponds which provide an opportunity for a (Ba,Ra)SO4 precipitate to form and subsequently settle. Sand filtration is sometimes used as a polishing step. This new process differs from conventional and other experimental processes in that it involves the use of a fluidized bed to facilitate the deposition of a (Ba,Ra)SO4 precipitate on a granular medium of high surface area. As a stand-alone treatment process, the new process is consistently able to reduce incoming radium-226 activity levels by 90-99%. Effluent levels of 10 pCi/L (0.370 Bq/L) or less have been achieved, depending on the influent activity levels. Recent testing of the process as a polishing step has demonstrated radium removal efficiencies up to 60% when the process influent was already less than 5 pCi/L (0.185 Bq/L). The process has been operated at temperatures ranging from 26°C down to 0.3°C with no reduction in efficiency. In contrast to treatment times in the order of days for conventional settling pond systems and hours for mechanical stirred tank/filtration systems, the new process is able to achieve these radium removal efficiencies in times on the order of one minute.

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