THE DECOMPOSITION OF NITROUS OXIDE ON THE SURFACE OF PLATINUM: II. THE EFFECT OF FOREIGN GASES

1936 ◽  
Vol 14b (3) ◽  
pp. 84-89 ◽  
Author(s):  
E. W. R. Steacie ◽  
J. W. McCubbin
Keyword(s):  
Nitrous Oxide ◽  
Inert Gases ◽  
Previous Conclusion ◽  
Retarding Effect ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide ◽  
Mechanism Of The Reaction

Further experiments have been made on the kinetics of the decomposition of nitrous oxide on the surface of platinum. Observations on the effect of foreign gases confirm the previous conclusion that inert gases may exert a surprisingly large retarding effect by hindering the diffusion of the reactant to the more remote parts of a porous catalyst.Adsorption measurements have also been made, and their bearing on the mechanism of the reaction is discussed.

scholarly journals The catalytic decomposition of nitrous oxide on the surface of gold: a comparison with the homogeneous reaction

1925 ◽  
Vol 108 (745) ◽  
pp. 211-215 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Catalytic Decomposition ◽  
Bimolecular Reaction ◽  
Homogeneous Reaction ◽  
Gaseous Reaction ◽  
Measurable Velocity ◽  
Rare Class ◽  
The Moment ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide

The bimolecular reaction 2N 2 O = 2N 2 + 2N 2 was recently shown to belong to the rather rare class of homogeneous reactions. Decomposition of two molecules of nitrous oxide takes place when a collision of a certain critical degree of violence occurs in the gas. At the moment of collision the two molecules must possess a combined energy of at least 58,000 calories (per 2 gram molecules), and it is probable that most of the collision in which this condition is fulfilled are fruitful. A comparison between the kinetics of this homogeneous decomposition and the corresponding reaction proceeding catalytically at the surface of a solid might be expected to throw light on the mechanism of heterogeneous catalysis. Previous efforts ( loc. cit .) to accelerate the reaction catalytically by the introduction of metals into the bulb in which the homogeneous reaction was going on were fruitless, since the reaction, if any, which took place at the surface of the metal was slow in camparison with the gaseous reaction. This difficulty was overcome by using as a catalyst a fine metal wire heated electrically. This could be raised to a sufficiently high temperature to cause the surface reaction to proceed with measurable velocity while the bulk of the gas was kept cold, thus eliminating the homogeneous reaction. Experiments made with platinum wires in this way were successful. The kinetics of the decomposition of nitrous oxide on the surface of platinum are summarized in the equation – d [N 2 O]/ dt = k [N 2 O]/1 + b [O 2 ]. The reaction is unimolecular, but is complicated by the strong retarding action of the oxygen formed.

The kinetics of the oxidation of ammonia by nitrous oxide

1964 ◽  
Vol 17 (2) ◽  
pp. 202 ◽  
Author(s):  
TN Bell ◽  
JW Hedger
Keyword(s):  
Thermal Decomposition ◽  
Nitrous Oxide ◽  
Free Radical ◽  
Rate Equation ◽  
Radical Mechanism ◽  
15N Isotope ◽  
Free Radical Mechanism ◽  
Products Of Reaction ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide

Ammonia is oxidized by nitrous oxide smoothly and homogeneously at temperatures between 658 and 730� and total pressures up to 250 mm. The products of reaction, nitrogen, water, and hydrazine are accounted for by a free-radical mechanism initiated by oxygen atoms which result from the thermal decomposition of nitrous oxide. Ammonia labelled with the 15N-isotope was used to distinguish between the nitrogen formed from the nitrous oxide and that from the ammonia. The kinetics follow an empirical rate equation, ������������� Rate = k'[N2O]1.56 + k"[N2O]0.61[NH3]. This is of a form which shows the importance of the ammonia molecule participating in the activation of nitrous oxide through bimolecular collision. Assigning a collisional efficiency of unity for like N2O-N2O collisions, the efficiency of ammonia in the process ������������ NH3 + N2O → NH3 + N2O* is determined as 0.85.

THE DECOMPOSITION OF NITROUS OXIDE ON A SILVER CATALYST

1937 ◽  
Vol 15b (6) ◽  
pp. 237-246 ◽  
Author(s):  
E. W. R. Steacie ◽  
H. O. Folkins
Keyword(s):  
Thermal Decomposition ◽  
Nitrous Oxide ◽  
Rate Equation ◽  
Platinum Catalyst ◽  
Silver Catalyst ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide

The kinetics of the thermal decomposition of nitrous oxide on a silver catalyst has been investigated. The rate of the reaction can be expressed by the equation[Formula: see text]It may therefore be concluded that the nitrous oxide is slightly adsorbed by the catalyst, while oxygen is fairly strongly adsorbed and retards the reaction. Added oxygen affects the reaction in the manner predicted by the rate equation, in contrast to its behavior on a platinum catalyst as previously found by Steacie and McCubbin.

The decomposition of nitrous oxide catalysed by palladium-gold alloy wires

1966 ◽  
Vol 294 (1436) ◽  
pp. 1-19 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Fermi Level ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Kcal Mole ◽  
Dissociative Chemisorption ◽  
Retarding Effect ◽  
Effect Of Oxygen ◽  
Decomposition Of Nitrous Oxide

The rate of decomposition of nitrous oxide has been examined by pressure measurements, at temperatures between 500 and 900 °C and pressures between 10 -2 and 1 torr. The reaction is first order, but shows retardation by oxygen, but not nitrogen. Over the range of alloys, from Pd to nearly 40 at. % Pd, the velocity at 650 °C falls by a factor of 104, the apparent activation energy falls from 30 to 13 kcal/mole, and the retarding effect of oxygen falls to zero. Over this range of alloys the Fermi level which lies in the d band hardly changes but the concentration of the d band vacancies falls to zero. Over the range of alloys from 40 at. % Pd to Au the velocity at 650 °C remains constant but the apparent activation energy and frequency factor, which show an abrupt increase at 40 at. % Pd, show a continuous fall. The retarding effect of oxygen remains zero. In this range the Fermi level has entered the s band and increases to Au. A steady state treatment of an irreversible dissociative chemisorption of nitrous oxide, together with an oxygen chemisorption equilibrium, yields an equation for the velocity in quantitative agreement with the results found. It is also possible to account for the increase in apparent activation energy with oxygen coverage of the surface. The heat of adsorption of oxygen is derived as 32-2±2 kcal/mole, and the activation energy for chemisorption of nitrous oxide as 12-7 ±0-5 kcal/mole.

scholarly journals The thermal decomposition of nitrous oxide, and its catalysis by nitric oxide

1932 ◽  
Vol 135 (826) ◽  
pp. 23-39 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Nitrous Oxide ◽  
Initial Pressure ◽  
Low Pressure ◽  
Bimolecular Reaction ◽  
Order Reaction ◽  
Inert Gases ◽  
Unimolecular Reaction ◽  
First Order ◽  
Decomposition Of Nitrous Oxide

When the homogeneous thermal decomposition of nitrous oxide was first studied in connection with the theory of gaseous reactions, the principal problem was to decide whether the activation of the molecules occurred independently of collisions, as would have been required by the radiation theory of activation. The influence of pressure on the rate of reaction showed definitely that the activation depended on a collisional process, in which sense the reaction proved to be bimolecular. The characteristic of an ideal bimolecular reaction is that the time of half change should be inversely proportional to the initial pressure. It was in fact found that the reciprocal of the half change period when plotted against initial pressure gave a straight line, which, however, did not pass through the origin. This meant that at low pressures a reaction of the first order was occurring, as well as the bimolecular change. This first order reaction was not further investigated, as it seemed quite possible that it was a surface reaction, the intrusion of which became relatively more serious as the pressure fell. It was observed, furthermore, that the complete course of a decomposition at a given initial pressure was not represented very well by the usual bimolecular equation; this, however, was capable of explanation in terms of an autocatalytic effect of the by-products of the reaction, since small amounts of the higher oxides of nitrogen were known to be formed in addition to the oxygen and nitrogen constituting the main products. More recently two new observations have been made, rendering desirable a fuller investigation of some of the details about the reaction, which have hitherto been regarded as of less importance than its general interpretation in terms of the collisional mechanism.The first of these is the observation of Volmer and Kummerow that, at low partial pressures of nitrous oxide, inert gases exert an accelerating influence on the decomposition. This suggests that the low pressure unimolecular part of the decomposition is perhaps really homogeneous, and also of the “quas-unimolecular type” which is subject to the influence of foreign gases. The second of the observations referred to is that of Voliner and Nagasako, who state that, between 1 and 10 atmospheres, the whole decomposition becomes of the first order. Thus the second order reaction observed in the earlier experiments, which were not carried out at pressures greater than an atmosphere, would be the low pressure part of a quasi-unimolecular reaction, The difference in mechanism between a true bimolecular reaction and the quasi-unimolecular reaction would be simply that in the former the nitrous oxide reacts at the moment of collision, while in the latter it survives the activating collision for a definite period and then splits up spontaneously into N 2 and an oxygen atom, unless in the meantime it has been deactivated.

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