Hydrogen separation ammonia decomposition

The phenomenon in each decomposition is determined as follows first by the affinity of the components with the conductors, in so far as they can form new compounds, e.g. oxygen with the metal of the positive wire. Secondly by the mutual affinity of the components when several are deposited together, as in the hydrogen separated from the water in a solution of saltpetre and the nitrogen of the acid separated, which combine to form ammonia. Thirdly by the cohesion of the new compounds which, for example, acts in such a way that the hydrogen set free passes off in the gaseous form, the alkalis dissolve in the liquid, and the earths and metals deposit in the solid form. 

Based on thermodynamic data, temperatures above 673 K are needed to reach complete ammonia decomposition (>99%). Coupling NHj decomposition with Pd-membrane separation can be an ideal way to provide high-purity CO -free H2 with improved yield at low temperatures [62]. Although NH3 may inhibit hydrogen permeation slightly, the permeability of the membrane used can be recovered by air and subsequent H2 treatments. However, the combination of an NH3 cracker with a Pd-membrane separator is more preferable for on-site H2 generation [63]. 

The iodine compound is more stable and separates as so-called nitrogen trHodide monoammoniate [14014-86-9], NI NH, an insoluble brownish-black soHd, which decomposes when exposed to light in the presence of ammonia. In reactions of the halogens with the respective ammonium salts, however, the action is different. Chlorine replaces hydrogen and nitrogen chloride [10025-85-1], NCl, separates as oily, yeUow droplets capable of spontaneous explosive decomposition. 

Preparation of 2-Hydroxy-4,4 -Diamidinostilbene Dihydrochloride 10 grams of 2-hydroxy-4,4 -dicyanostilbene were suspended in 250 cc of absolute ethyl alcohol and the mixture saturated with dry hydrogen chloride at 0°C. The whole was left for eight days at room temperature. The imino-ether hydrochloride formed was filtered off, washed with dry ether and dried in the air for a short time. It was then added to 250 cc of 10% ethyl alcoholic ammonia and the whole heated for 5 hours at 45°C. The 2-hydroxy-4,4 -diamidino-stilbene dihydrochloride which separated was crystallized from 10% hydrochloric acid. It forms pale yellow needles, MP 357°C (decomposition). 

Burk f has laid much stress on the possibility that a molecule might be attached to a surface at more than one point, whereby a distortion, or partial separation of its atoms, is produced. Ammonia, for example, might be held to the surface of a metal by a hydrogen atom and a nitrogen atom simultaneously. Such a distortion is thought of as lowering the heat of activation and facilitating decomposition. 

Ten grams of carbonatopentamminecobalt(III) nitrate (0.036 mol) is suspended in 25 ml. of water, and 4.5 g. of ammonium hydrogen fluoride (0.079 mol) and 15 g. of ammonium fluoride (0.405 mol) are added. The reaction mixture is kept at approximately 90° in a water bath for 1 hour, with occasional stirring. During this digestion some decomposition takes place, and noticeable quantities of ammonia are evolved. The mixture is then cooled to room temperature, 75 ml. of water being added to keep the products in solution. This solution is filtered, and 20 g. of solid ammonium nitrate (0.25 mol) is added to the filtrate. Pink crystals separate immediately after the mixture is cooled in an ice-salt bath. The product is collected on a filter, washed with 10 ml. of ice-cold water, followed by alcohol and ether, and then dried at 90°. Yield, 6 g. (58%). 

Figure 11.8 Comparison of co-current and counter-current porous membrane reactors decomposition of ammonia with a high hydrogen/nitrogen separation factor (= 50 627 C[ColUns etal., 1993)...

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