The heterogeneous decomposition of hydrazine.

The heterogeneous decomposition of liquid hydrazine on supported platinum group metal catalysts has been found to follow one, or both of the reactions. On rhodium, palladium and platinum catalysts reaction (2) occurs while on the ruthenium catalyst both reactions occur. Reaction (2) occurs following the dissociative chemisorption of hydrazine molecules in the form of amide radicals followed by a Langmuir-Rideal reaction between adsorbed radicals and a solution phase hydrazine molecule to form the products. Reaction (1) occurs following the associative adsorption of hydrazine molecules to form an activated complex which then breaks down to yield the products. These mechanisms are consistent with the dual plane theory postulated by Cosser and Tompkins to explain the decomposition of hydrazine on tungsten films. The decomposition of hydrazine on the supported iridium catalyst was observed to follow reaction (1) but the kinetics were found to be complex. For concentrations of hydrazine up to 3 mole dm-3 the reaction was observed to be first order with an activation energy of 35 kJ mole-1. Increasing the concentration of hydrazine results in a change in kinetics to a reaction having an activation energy of 65 kJ mole-1 and although the rate is a linear function of hydrazine concentration the reaction is not true first order. The hydrazine concentration at which the change in kinetics occurred was found to increase with increasing oxide content of the catalyst. It has been postulated that at low concentrations of hydrazine the associative adsorption of hydrazine molecules occurs on the sites of higher oxidation state as these are energetically favoured. Only when these sites have been saturated does adsorption and decomposition of hydrazine occur on the sites of lower oxidation state

Vorträge des 129. PTB-Seminars am 19./20.3.1996

Am 19./20.03.1996 fand in Braunschweig das 129. PTB-Seminar „Brennwertbestimmung von Gasen im geschäftlichen Verkehr“ statt. 145 Teilnehmer dokumentierten das große Interesse seitens der Gasversorgungsindustrie, der Eichämter und der Gasverbraucher. In 16 Vorträgen wurde der Bogen gespannt von den zur Brennwertbestimmung verwendeten Verfahren (Gaskalorimetrie, Gaschromatographie, Brennwertverfolgungssysteme, digitale Datenübertragung), über deren metrologische Grundlagen (Rückführung von Gasanalysen, Metrologie in der Chemie, primäre Methoden zur Messung der Stoffmenge), die gesetzlichen und normativen Grundlagen und deren zukünftige Entwicklung in der Bundesrepublik bis hin zu einer Vorstellung der in einigen benachbarten europäischen Ländern angewandten Regeln und Gesetze mit einem Überblick über die zukünftige Arbeit der OIML auf diesem Gebiet.PTB-Bericht PTB-ThEx-1, ISBN 3-89701-013-5, ISSN 1434-2391.Vorträge des 129. PTB-Seminars am 19./20.3.199