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http://www.springerlink.com/content/l247g28vt300417x/?p=698c67b3891a43f3bc064091b415f84b&pi=5
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http://www.springerlink.com/content/l247g28vt300417x/fulltext.pdfJournal Catalysis Letters
Publisher Springer Netherlands
ISSN 1011-372X (Print) 1572-879X (Online)
Subject Chemistry and Materials Science
Issue Volume 45, Numbers 1-2 / April, 1997
DOI 10.1023/A:1018970318628
Pages 65-72
Online Date Monday, November 29, 2004
An alkali-promoted ruthenium catalyst for the synthesis of ammonia, supported on thermally modified active carbon
Z. Kowalczyk, J. Sentek, S. Jodzis, E. Mizera, J. Góralski, T. Paryjczak and R. Diduszko
Abstract
Ruthenium catalysts deposited on active carbon and pre-calcined at 1900°C in He atmosphere were studied. The precursors of the active phase were RuCl3·0.5H2O and Ru3(CO)12. Potassium and cesium (hydroxides or nitrates) were used as promoters. The catalysts were characterized by TEM, WAXS and H2 chemisorption. Activity measurements in NH3 synthesis were performed in a flow integral reactor under a pressure of 10 MPa at 470, 430, and 400°C (H2:N2=3:1). It has been found that the alkali-promoted catalyst deposited on the thermally modified carbon is much more active than that based on untreated carbon. The form of the Ru precursor used in the manufacture of the K-promoted catalyst had no effect on its dispersion or activity. The promoting effect of potassium was comparable to that of cesium. A monotonous increase in the activity of alkali-promoted catalyst vs. Ru content (5--15%) was observed, accompanied by a decrease in dispersion.
This revised version was published online in July 2006 with corrections to the Cover Date.
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http://www.springerlink.com/content/nh661103t26161x2/?p=99013d58dc6c4eaca70f23c1da15458c&pi=4Код: Выделить всё
http://www.springerlink.com/content/nh661103t26161x2/fulltext.pdfJournal Catalysis Letters
Publisher Springer Netherlands
ISSN 1011-372X (Print) 1572-879X (Online)
Subject Chemistry and Materials Science
Issue Volume 76, Numbers 3-4 / October, 2001
DOI 10.1023/A:1012201613791
Pages 193-199
Online Date Tuesday, October 26, 2004
Effect of Methanation of Active Carbon Support on the Barium-Promoted Ruthenium Catalyst for Ammonia Synthesis
Hai Sheng Zeng1, Takashi Hihara1, Koji Inazu1 and Ken-ichi Aika1 Contact Information
(1) Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8502, Japan
Abstract
The effect of the induced methanation of hydrogen-treated active carbon (HTAC) support on the structural change and then catalytic activity over Ba-promoted Ru/HTAC catalysts (Ba(NO3)2 and RuCl3 were precursors) for ammonia synthesis was investigated. It was found that a moderate degree of the methanation of HTAC support increased the catalyst surface area and pore volume significantly rather than destroyed the porous structure. But the methanation of carbon support might accelerate the growth of Ru particles, which finally led to the low activity. We suggested that both the dechlorination temperature (refer to the reductive dechlorination of RuCl3 to form Ru on HTAC) and the hydrogenolysis temperature (refer to the hydrogenolysis of Ba(NO3)2 on Ru/HTAC) have binary effects on the catalytic activity, respectively. On the one hand, the dechlorinating effect and the hydrogenolysis effect increased with the increase of H2 treatment temperature. On the other hand, simultaneously the methanation degree of the support increased too in above both processes. The performance of the catalyst was the combined result of the interaction of the amount of residual chlorine, Ru particle size, and the active promoter component. A respective control of the methanation degree during the catalyst preparation and activation processes was suggested to be necessary for the practical use of the promoted Ru/C catalyst.
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http://www.springerlink.com/content/m446np7v45475147/?p=10fb1bbd902b41bdbd6371f676db955a&pi=3Код: Выделить всё
http://www.springerlink.com/content/m446np7v45475147/fulltext.pdfJournal Catalysis Letters
Publisher Springer Netherlands
ISSN 1011-372X (Print) 1572-879X (Online)
Subject Chemistry and Materials Science
Issue Volume 25, Numbers 1-2 / March, 1994
DOI 10.1007/BF00815416
Pages 61-74
Online Date Tuesday, December 21, 2004
Ruthenium supported on zeolite A: preparation and characterisation of a stable catalyst for ammonia synthesis
J. Wellenbüscher1, M. Muhler1, W. Mahdi1, U. Sauerlandt2, J. Schütze1, G. Ertl1 and R. Schlögl2
(1) Fritz Haber Institut der Max-Planck Gesellschaft, Faradayweg 4, W-1000 Berlin 33, Germany
(2) Institut für Anorganische Chemie der Universität Frankfurt, Marie-Curie Strosse 11, D-60439 Frankfurt, Germany
Received: 20 July 1993 Accepted: 2 December 1993
Abstract Reaction of Ru(NH3)6Cl3 with Na-A and K-A zeolites yielded oligomeric amino-oxo-complexes supported on the zeolite. Controlled thermal activation under hydrogen converted the precursor in a two-step reaction into an active catalyst with good long-term stability and resistance against small doses of oxygen poison. Several nanometers sized Ru metal particles are chemically bonded to the zeolite surface which provides in the K form an alkali promoter at the metal-zeolite interface. Extensive oxidation breaks the metal-support anchoring and re-reduction produces Ru metal particles sintering rapidly into large metal crystals with only small residual catalytic activity.
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