Nitrogen oxides and carbon monoxide oxidation

2 727 20 torr. Reaction stopped at 1 % conversion of CO. CO2 removed from other products by repeated distillation from —135 °C to liquid N2 temp. Also studied C isotope effect.  

200)/T 45 mm diam., 278 ml vol. NO2 in equilibrium with dissociation products. Zero rate of pressure change initially hence initial rate due to reaction (Ixxvi) alone. d[N02 ]/df measured photometrically. Found —d[N02]/ df oc [CO] 0 -0.02 X [N02]° -°° Rate coefficient in good agreement with ref. 485.  

A more direct study of the reaction between CO and NO2 was made by Brown and Crist [485], who used a KCl coated Pyrex reaction vessel fitted with a greaseless valve to avoid decomposition of the NO2. In order also to avoid complications due to gas phase dissociation of the NO2, its pressure was kept very low ( 0.5 torr), and the reaction times were kept comparatively short. Amounts of reaction were measured by freezing and then analyzing for the product CO2 by vacuum sublimation from the nitrogen oxides. In order to obtain measurable amounts of reaction under the conditions stated, it was necessary to employ high concentrations of CO. Even then the partial pressures of CO2 in the products were less than 30 microns, and often as little as 5 microns, so that good experimental technique was required. It was confirmed that the reaction was second order over some two- to three-fold variation of the partial pressures of CO and NO2. Mean rate coefficients between 500 and 563 K are given in Table 57. 

At higher temperatures and pressures the reaction passes into explosion [489], during which other oxides of nitrogen are also formed and the unimolecular decomposition of the N2O contributes at the higher temperatures involved. Small amounts of added NO inhibit the explosion. 

During a study of the oxidation of carbon at lower temperatures, Strickland-Constable [490], and Madley and Strickland-Constable [491] found in subsidiary experiments that CO and N2O did not react together appreciably in Pyrex or silica vessels at around 620 K. Oxidation of CO did, however, occur in a vessel in which N2O was already reacting with charcoal at 593 K. The latter reaction (without added CO) gave CO2 as the principal gaseous product, with very little CO formed. Thus in the presence of added CO two reactions occur simultaneously 

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