Exchange Reactions deuterium-ammonia

The log—log plot of the adsorption isotherm, which can possibly be correlated to the pressure-dependency of the catalytic reaction rate, is very flat. The adsorption of ethylene on nickel increases only by 10% for an increase of the equilibrium pressure by a factor of 10, although the surface is still far from being covered by a monolayer. The work of Laidler et al. (3), who studied the ammonia-deuterium exchange reaction on a promoted iron catalyst by means of the microwave method, also throws doubt on the zero-order kinetics with respect to observations made by Farkas (4). 

Analogous parahydrogen conversion and deuterium exchange reactions, catalyzed by NH2, have been observed in liquid ammonia (Wilmarth and Dayton, 61). The kinetics are of the same form as those of the OH -cat-alyzed reaction in water and the mechanism is open to similar interpretations. The NH2 -catalyzed reaction is much faster, its rate constant at —50° being 10 times that of the OH -catalyzed reaction at 100°. The assumption of equal frequency factors for the two reactions leads to a calculated activation energy for the NH2 -catalyzed reaction of about 10 kcal. This low value has been attributed to the much greater base strength of NH2 relative to OH . The results provide some support for the hydride ion mechanism. 

Another process that has been used to extract deuterium from ammonia synthesis gas is the deuterium-exchange reaction between liquid ammonia and gaseous hydrogen ... 

The equilibrium constant for the third, deuterium exchange, reaction is around 2 at the temperature at which the second, water-gas shift, reaction is carried out. Because an excess of water is used to convert CO completely to COj, the deuterium content of hydrogen will be less than that of the methane and water fed, unless the excess water is fully recycled. Because water recycle is usually not practiced at ammonia synthesis plants, the deuterium content of synthesis gas at operating plants is sometimes as low as 0.009 percent [M7]. If the ammonia plant were specifically designed for deuterium recovery from its synthesis gas, the deuterium content could be increased to the average of the methane and water feeds by recycling aU water and preventing losses. 

The deuterium exchange reaction between water and ammonia, water and hydrogen sulfide, or water and the hydrogen halides proceeds rapidly in the liquid phase without catalysis, because of ionic dissociation. In the case of a mixture of water and hydrogen sulfide, for example, the ionic equilibria... 

To cause the deuterium exchange reaction between hydrogen and ammonia to take place at a useful rate, it is necessary to have 1 to 2 m/o (mole percent) of potassium amide, KNH2, dissolved in the liquid phase to serve as a homogenous catalyst [C2]. Presence of potassium amide complicates the process for three reasons ... 

Because of the reduced rate of the deuterium exchange reaction at —50°C, the stages of the cold tower (D) are to be of the type developed by Sulzer [LI ] for the ammonia-hydrogen exchange process and used in the Maangarbe plant. Sec. 9.1. For the methylamine-hydrogen system at —50°C, a stage efficiency of 70 percent has been obtained [W6]. 

Schuit, van Reijen, and Sachtler (470) have also calculated the volcanoshaped curves for other reactions according to the data of a number of authors the ammonia-deuterium exchange [Fig. 64, Kemball (471)], the hydrogenation of ethylene [Fig. 65, Schuit and van Reijen (472)-, Beeck... 

This investigation was undertaken to establish the ionic mechanism responsible for exchange reactions occurring at pressures ranging from 0.85 to 0.98 atm. in irradiated deuterium, hydrocarbon and deuterium, ammonia gaseous mixtures at 25 °C. and lower temperatures. New tech-... 

Deuterio-ammonia was synthesized by means of the reaction between heavy water and magnesium nitride, with subsequent drying by potassium amide (Landsberg et al., 1956). Compounds containing deuterium in a specific position were obtained either by deuterium exchange or by organic synthesis (Shatenshtein and Izrailevich, 1957). 

Hydrogen exchange reactions in liquid ammonia can be used to prepare many organic compounds labelled with tritium or deuterium. 

The power to catalyse certain other reactions, in which dissociation of the molecules of hydrogen or of some other gas must occur at some stage of the reaction, is more certain evidence of chemisorption. One instance, the exchange reaction in which HD, deuterium hydride, is formed from a mixture of hydrogen and deuterium, has already been mentioned. Another is the immensely important synthesis of ammonia the reaction... 

The exchange reaction of deuterium with the hydrogens in ammonia is an excellent test for chemisorption of hydrogen Taylor and Jungers9... 

Proton magnetic resonance techniques have been used for the measurement of rates of hydrogen-deuterium exchange of pyrazine (in CHsOD-CHsONa at 164.6") (591) for a study of protonation of pyrazine (1472) for analysis of the reaction mixture from quatemization of 2-substituted pyrazines with methyl iodide (666) for elucidation or confirmation of the structures of alkylpyrazines obtained by alkylation of pyrazines with aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia, or a suspension of these metals in other solvents (614) for a study of changes in chemical shifts produced on ionization of 2-methyl and 2-amino derivatives of pyrazine in liquid ammonia (665) for characterization of methoxymethylpyrazines (686) for the determination of the position of the A -oxide function in monosubstituted pyrazine V-oxides and the analysis of V-oxidation reactions (838) for a study of the structure of the cations of fV-oxides of monosubstituted pyrazines (1136) and for the determination of the structure of the products of peroxyacetic and peroxysulfuric acid iV-oxidation of phenyl- and chlorophenylpyrazines (733b). 

An objection to this view was made by Laidler (3), who found that the rate of the exchange reaction between deuterium and ammonia on a promoted iron catalyst passed through a maximum with increase of the ammonia pressure, contrary to the zero-order kinetics with respect to ammonia reported by Farkas (4). 

Various reactions appeared to be very useful in this respect. Well-known examples are the hydrogen-deuterium exchange and the hydrogenation of ethylene on metals and oxides. Such studies deepened the understanding of hydrogenation reactions in general, while these reactions could at the same time serve as a means of comparing the activities of different catalysts. Other examples of reactions well suited for use in fundamental catalysis research, are the synthesis and decomposition of ammonia, and the decomposition of NaO. 

Activation Energies for the Exchange Reaction Between Ammonia and Deuterium ... 

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