Platinum nitrogen oxide decomposition

Complex oxides of the perovskite structure containing rare earths like lanthanum have proved effective for oxidation of CO and hydrocarbons and for the decomposition of nitrogen oxides. These catalysts are cheaper alternatives than noble metals like platinum and rhodium which are used in automotive catalytic converters. The most effective catalysts are systems of the type Lai vSrvM03, where M = cobalt, manganese, iron, chromium, copper. Further, perovskites used as active phases in catalytic converters have to be stabilized on the rare earth containing washcoat layers. This then leads to an increase in rare earth content of a catalytic converter unit by factors up to ten compared to the three way catalyst. 

T. Scheerer found that when heated to a yellow heat (c.1000°), in a closed platinum crucible, potassium carbonate loses about 0 5 per cent, in weight owing to the loss of carbon dioxide which is taken up again at lower temp. W. Dittmar could detect no change when heated to redness in an atm. of carbon dioxide, but it is partially converted into oxide in an atm. of nitrogen, and still more so in an atm. of hydrogen. P. Lebeau found that rubidium and caesium carbonates lose carbon dioxide when heated in vacuo, and, if the vacuum be maintained, decomposition is complete. P. Lebeau also found that the dissociation press, of rubidium carbonate is ... 

Thus, copper and platinum give similar results the nitrite formation is greater with iron, nickel, and cobalt, and the nitrate formation less. The gases were mainly nitrous oxide and nitrogen with a small proportion of oxygen. N. D. Zelinsky and S. G. Krapiwin showed that the decomposition of hydroxylamine into acid and base does not occur in soln. with methyl alcohol as solvent. J. Tafel showed that an aq. soln. of hydroxylamine sulphate in presence of 20-50 per cent, of sulphuric acid is not reduced at a copper cathode. O. Flaschner observed some reduction in dil. sulphuric acid soln. J. Tafel and H. Hahl found that reduction always takes place when the sulphuric acid cone, in the layer of electrolyte in contact with the cathode is reduced beyond a certain point, and when there is no excess of acid in other words, when hydroxylamine sulphate itself is electrolyzed, the reduction is quantitative. These results are most readily accounted for on the view that only free hydroxylamine (produced in this case by partial hydrolysis of the sulphate), but not the hydroxylammonium ion, NH3OH, is reduced at a copper... 

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