Ammonia on platinum

The decomposition of ammonia on platinum has a rate expression of this form. The reaction is first order in ammonia and inverse first order in hydrogen. 

Thus if we insert the values m = 1 and w = 2 in the first case and m = 2, K = 1 in the second, so that the hydrogen atom is held on by one elementary space and the hydrogen molecule by two elementary spaces, the conception of a uni- and divalent union is readily realised. In this way a valency of two for carbon monoxide, sulphur trioxide and ammonia on platinum two for the oxygen molecule and one for carbon monoxide on quartz can be established. 

The kinetics of the electrochemical oxidation of ammonia on platinum to dinitrogen in basic electrolytes has been extensively studied. In the widely supported mechanism originally suggested by Gerischer and Mauerer[ll], the active intermediate in the selective oxidation to N2 is a partly dehydrogenated ammonia adsorbate, NH2 ads or NHaatomic nitrogen adsorbate N ag, which is apparently formed at more positive potentials, is inactive toward N2 production at room temperature. Generally, only platinum and iridium electrodes exhibit steady-state N2 production at potentials at which no sur-... 

The equation expressing the retarding action of the products is not always of such a simple form. While the decomposition of ammonia on platinum is well enough represented by the simple equation... 

Ohmic heating of catalyst is often used as a simple method of igniting the chemical reaction during reactor startup, for instance, in the oxidation of ammonia on platinum-rhodium gauze catalysts. Another application is the prevention of cold-start emissions from automotive catalysts responsible for much of the residual pollution still produced from this source (21). The startup times needed for the catalyst to attain its operating temperature can be cut by a factor of 5 or more by installing an electrically heated catalyst element with a metallic support upstream of the main catalyst unit. Direct electrical catalyst heating permits facile temperature control but requires a well-defined catalyst structure to function effectively. 

Rate of Oxidation of Ammonia on Platinum Wires, Ribbons, and Gauzes... 

The manufacture of nitric acid by the oxidation of ammonia on platinum-type metal gauzes uses a technology which has change little since its first introduction in 1902. Although the conversion proceeds with an efficiency in excess of 90%, the loss of... 

Nutt.C.W. Kapur,S Nature. 224, 160, 1969. "Oxidation of Armenia on Platinum". Also Nature. 220, 697, 1968. "Mechanism of Oxidation of Ammonia on Platinum". 

Kapur,S PhD Thesis, Univ. of Birmingham 1969. "Oxidation of Ammonia on Platinum". 

Figure 1 schematically represents an oxidizer-absorption tower used in nitric acid production. In this tower the nitric oxides generated by high-temperature air oxidation of ammonia on platinum gauze are oxidized and absorbed to yield nitric acid. Koukolik and Marek [49] simulated the behavior of the tower on a digital computer. The following reaction scheme was used ... 

Hydrogen cyanide is produced industrially by thermolysis of formamide, or from methane and ammonia on platinum-rhodium catalysts (following a process developed by Leonid Andrussow (1896-1988) in 1927 at BASF in Ludwigs-hafen) (Fig. 5.196). 

Kane proposed that ammonia and ammonium are compounds of a radical NH2, amidogene, with hydrogen. The compounds formed by the action of ammonia on platinum, palladium, and mercury salts contain this radical united with the metal. He says ... 

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