Ammonia synthesis catalysis

Ammonia concentration calculated from microkinetic model versus longitudinal distance from reactor inlet. (Figure adapted from Kinetic Simulation of Ammonia Synthesis Catalysis by J. A. Dumesic and A. A. Trevino, in Journal of Catalysis, Volume 116 119, copyright 1989 by Academic Press, reproduced by permission of the publisher and the authors.)... 

P. Stolze, In Ammonia Synthesis Catalysis and Manufacture, A.E. Nielsen, ed. Springer-Verlag, Berlin (1995) p 21. 

J.U. Nwalor, Isotopic Transient Kinetic Analysis of Ammonia Synthesis Catalysis. Ph.D. Dissertation, University of Pittsburgh, Pittsburgh, 1988. 

The results of the present study show clearly that Fe( 111) is by far the most active and Fe(llO) the least active plane in ammonia synthesis catalysis, Fe(lOO) having in-... 

ErtI G 1991 Catalytic Ammonia Synthesis Fundamentals and Practice, Fundamentals and Applied Catalysis ed J R Jennings (New York Plenum)... 

Throughout the book we use the terms catalysis, catalyst and catalytic reaction referring to processes which do not involve any net charge transfer, such as e.g. the oxidation of CO on Pt or the ammonia synthesis on Fe ... 

The development of ammonia synthesis represents a landmark in chemical engineering, as it was the start of large-scale, continuous high-pressure operation in flow reactors, and in catalysis, because the numerous tests of Mittasch provided a systematic overview of the catalytic activity of many substances. 

The studies of ammonia synthesis over Fe and Re and the hydrodesulfurization of thiophene over Mo, described above, illustrate the importance and success of our approach of studying catalysis over single crystal samples at high pressures. The use of surfaces having a variety of orientations allows the study of reactions that are surface structure sensitive 6Uid provides insight into the nature of the catalytic site. Here we have shown that the ammonia synthesis... 

The range of reactions which have been examined is wide (248) and includes hydrogenations (256), ammonia synthesis (257), polymerizations (257), and oxidations (258). Little activity has occurred in this area during the past few years. Recent reports of the effects of sonication on heterogeneous catalysis include the liquefaction of coal by hydrogenation with Cu/Zn (259), the hydrogenation of olefins by formic acid with Pd on carbon (260), and the hydrosilation of 1-alkenes by Pt on carbon (261). 

As catalysis proceeds at the surface, a catalyst should preferably consist of small particles with a high fraction of surface atoms. This is often achieved by dispersing particles on porous supports such as silica, alumina, titania or carbon (see Fig. 1.2). Unsupported catalysts are also in use. The iron catalysts for ammonia synthesis and CO hydrogenation (the Fischer-Tropsch synthesis) or the mixed metal oxide catalysts for production of acrylonitrile from propylene and ammonia form examples. 

Mossbauer spectroscopy is one of the techniques that is relatively little used in catalysis. Nevertheless, it has yielded very useful information on a number of important catalysts, such as the iron catalyst for Fischer-Tropsch and ammonia synthesis, and the cobalt-molybdenum catalyst for hydrodesulfurization reactions. The technique is limited to those elements that exhibit the Mossbauer effect. Iron, tin, iridium, ruthenium, antimony, platinum and gold are the ones relevant for catalysis. Through the Mossbauer effect in iron, one can also obtain information on the state of cobalt. Mossbauer spectroscopy provides valuable information on oxidation states, magnetic fields, lattice symmetry and lattice vibrations. Several books on Mossbauer spectroscopy [1-3] and reviews on the application of the technique on catalysts [4—8] are available. 

In comparison to most other methods in surface science, STM offers two important advantages STM gives local information on the atomic scale and it can do so in situ [51]. As STM works best on flat surfaces, applications of the technique in catalysis concern models for catalysts, with the emphasis on metal single crystals. A review by Besenbacher gives an excellent overview of the possibilities [52], Nevertheless, a few investigations on real catalysts have been reported also, for example on the iron ammonia synthesis catalyst, on which... 

The reasoning which led the author to make this first shot in the dark regarding the usefulness of combinations of solid compounds as ammonia catalysts was as follows If we assume that a labile iron nitride is an interminate in the catalytic ammonia synthesis, every addition to the iron which favors the formation of the iron nitride ought to be of advantage. In other words, the hypothesis was used that surface catalysis acts via the formation of intermediate compounds between the catalyst and one or more of the reactants. An experimental support for this theory was the fact that a stepwise synthesis via the formation and successive hydrogen reduction of nitrides had been carried out with calcium nitrides (Haber), and cerium nitrides (Lipski). Later, the author found molybdenum nitride as being the best intermediate for such a stepwise synthesis. 

M. V. Twigg and M. S. Spencer (series eds.), Fundamental and Applied Catalysis. Plenum, New York. This series includes J. T. Richardson, Principles of Catalyst Development, 1989 V. P. Zhdanov, Elementary Physicochemical Processes on Solid Surfaces, 1991 J. R. Jennings (ed.), Catalytic Ammonia Synthesis, 1991. 

It is currently used in ammonia synthesis as a means of removing CO (89), and its employment as a hydrogen source is expected to increase in the future (67). We shall discuss catalysis of the water gas shift reaction more extensively later in this section. 

Catalysis by enzymes the biological ammonia synthesis. Top. Catal., 37, 55. 

Hinnemann B. Norskov J. K. Catalysis by enzymes The biological ammonia synthesis. 

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