Nitric oxide by carbon monoxide

Roundhill has recently reported the catalytic oxidation of CO to C02 by 02 using noble metal complexes, but no mechanistic details are given (91). Another direct transfer of oxygen to CO may take place in certain homogeneous catalytic systems for the reduction of nitric oxide by carbon monoxide according to (28) when no water is present to serve as the oxygen transfer agent (92,98). The catalyzed reductions of NO by CO are examined in the nitric oxide section of the review. 

The reactions of nitric oxide involve either oxidation or reduction (or both simultaneously in disproportionation and decomposition). Except for oxidation, these reactions of nitric oxide require catalysts for them to proceed at significant rates. An important stimulus to studying these catalyzed reactions lies in the environmental hazards posed by oxides of nitrogen, of which NO is the parent member, as discussed at the beginning of this section. Particular attention in the area of metal complex catalyzed reactions has focused in the last five years on the reduction of nitric oxide by carbon monoxide, (113). 

A third homogeneous catalyst system for the reduction of nitric oxide by carbon monoxide has recently been developed. Kubota et al. (189) find that an aqueous acidic solution of PdCl2 and CuCl2 or CuCl under NO and CO produces various yields of N20 and C02 depending on the relative concentrations of the two metals. Typical conditions are 0.01 M PdCI2, 0.20 M CuCl2, and 2 M HC1 under 1 atm total of NO and CO. Formation of C02 is achieved via (119), and is fast relative to N20 production. 

Ru(NO)2(Pph3)2] catalyzes the reduction of nitric oxide by carbon monoxide (equation 75).3911... 

Reduction of nitric oxide by carbon monoxide was first reported to occur at low temperature (252-369 K) over gold powder (0.86 m2 g-1) 30 the rate was maximal at 314 K, and nitric oxide inhibited the reaction. This paper also provides an early indication of the activity of gold for the oxidation of carbon monoxide near ambient temperature. Nitric oxide reduction occurs in this way in catalytic converters for the treatment of engine exhaust gases 9... 

Reduction of nitric oxide by carbon monoxide is one of the reactions occurring in catalytic converters for the purification of the engine exhaust gases [489] ... 

The Pd +Cu )-catalysed reduction of nitric oxide by carbon monoxide (i.e., C0 + 2N0 C02+N20), which takes place in hydrochloric acid is believed to involve a Cu -Pd -NO species. The catalytic reduction of nitric oxide with ammonia by aqueous [Cu(NH3)4] + has been compared with those in which a Y-type zeolite was employed as a support. ... 

Subbotina IR, Shelimov BN, Kazansky VB, Lisachenko AA, Che M, Coluccia S (1999) Selective photocatalytic reduction of nitric oxide by carbon monoxide over silica-supported molybdenum oxide catalysts. J Catal 184 390-395... 

Synaptic communication between neurons does not only involve the classical neurotransmitter systems reviewed in this chapter. Two other classes of neurotransmitters are also known to affect brain function neuropeptides and atypical neurotransmitters, such as nitric oxide and carbon monoxide. These neurotransmitters are not stored in vesicles, are not released by exocytosis, and do not bind to postsynaptic receptors. We have chosen not to review these neurotransmitters here, since they do not yet have implications for the current practice of neuropsychopharmacology. They are, however, promising targets for the development of new treatment strategies, and the interested reader is referred to other articles for review (Hokfelt, 1991 Snyder and Ferris, 2000). 

The reactor tube was brought to the required temperature under an atmosphere of argon. A mixture of nitric oxide and carbon monoxide or hydrogen, diluted by argon was then introduced into the reacting part of the quartz tube. The gaseous reaction products were intermittently withdrawn from the reactor and analyzed by a chemiluminescent NOx analyzer and a gaschromatograph. Ammonia was measured by detector tube method. The scope of the experiment is shown in Table II. 

In this section the reactivity of metal nitrosyl complexes is discussed and related to the NO coordination mode. A considerable difference between the chemistry of nitric oxide and carbon monoxide complexes has already been noted. The reactivity of nitric oxide coordinated to transition metal centers, and of nitrosyl clusters, were thoroughly reviewed in 1979 by McCleverty (7) and in 1985 by Gladfelter 11), respectively therefore only a summary is presented here. Nucleophilic reactions of linear nitrosyl groups will not be considered. 

The influence of the support is undoubted and spillover was further confirmed by the excess of hydrogen chemisorbed by a mechanical mixture of unsupported alloy and TJ-A1203 above that calculated from the known values for the separate components. It was also observed that the chemisorption was slower on the supported than on the unsupported metal and that the greater part of the adsorbate was held reversibly no comment could be made on the possible mediation by traces of water. On the other hand, spillover from platinum-rhenium onto alumina appears to be inhibited for ratios Re/(Pt Re) > 0.6. In an infrared investigation of isocyanate complexes formed between nitric oxide and carbon monoxide, on the surface of rhodium-titania and rhodium-silica catalysts, it seems that the number of complexes exceeded the number of rhodium surface atoms.The supports have a pronounced effect on the location of the isocyanate bond and on the stability of the complexes, with some suggestion of spillover. 

The analysis of Nox/ nitric acid, or n-propyl nitrate was carried out by reduction to nitric oxide using carbon monoxide and gold catalyst (Bollinger et al. 1983). 

Dumpelmann, R., N.W. Cant and D.L. Trimm, 1995, Enhancement of the reaction of nitric oxide and carbon monoxide by hydrogen and water over platinum and rhodium-containing catalysts, in Catalysis and Automotive Pollution Control III, eds A. Frennet and J.-M. Bastin (Elsevier, Amsterdam) pp. 123-135. 

ENHANCEMENT OF THE REACTION OF NITRIC OXIDE AND CARBON MONOXIDE BY HYDROGEN AND WATER OVER PLATINUM AND RHODIUM-CONTAINING CATALYSTS... 

From the results of other authors should be mentioned the observation of a similar effect, e.g. in the oxidation of olefins on nickel oxide (118), where the retardation of the reaction of 1-butene by cis-2-butene was greater than the effect of 1-butene on the reaction of m-2-butene the ratio of the adsorption coefficients Kcia h/Kwas 1.45. In a study on hydrogenation over C03O4 it was reported (109) that the reactivities of ethylene and propylene were nearly the same (1.17 in favor of propylene), when measured separately, whereas the ratio of adsorption coefficients was 8.4 in favor of ethylene. This led in the competitive arrangement to preferential hydrogenation of ethylene. A similar phenomenon occurs in the catalytic reduction of nitric oxide and sulfur dioxide by carbon monoxide (120a). 

The noncatalytic reduction of nitric oxide by insitu formed char is considered one of the significant reactions which control nitric oxide emission and a detailed kinetic study was carried out. (2, 3, 4) The present authors demonstrated that this reaction proceeded even under an excess air condition and that the rate is enhanced by the coexisting oxygen up to 750°C. (.5,6) Besides the noncatalytic reaction, carbon monoxide may have a significant effect on nitric oxide reduction by char. (2.) Roberts et al.(8) reported that the gas phase reactions in the nitric oxide reduction play a minor role and that the absence of a major gas phase reaction of NO and coal nitrogen into N2 requires the participation of a surface which catalyzes reactions. Char is considered to... 

This indicates that the amount of carbon dioxide formed by this experiment coincided with the amounts of both carbon monoxide and nitric oxide consumed. Thus the use of carbon monoxide reduced the consumption of carbon to approximately zero and the char provided catalytic surfaces for nitric oxide reduction by carbon monoxide as ... 

The reduction of nitric oxide by char in the presence of hydrogen or carbon monoxide was carried out over a temperature range of 500 -900°C. The reaction could be analyzed by assuming first order with respect to nitric oxide. The predominant mechanisms are the catalytic reduction of nitric oxide by hydrogen or carbon monoxide over char surface. The rate obtained under a = 4W7 was approximately equal to the rate of noncatalytic reduction of... 

Studies with gold catalysts have focused on the selective reduction of nitric oxide by propene, carbon monoxide and hydrogen urea,10 methane11 and other hydrocarbons9,11,13 have also been used. NOx removal using the first three of these will now be discussed. 

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