Reduction of nitric oxide by carbon

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... 

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... 

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. 

Matzer, S. and Boehm, H.-P. (1998). Influence of nitrogen doping on the adsorption and reduction of nitric oxide by activated carbons. Carbon, 36, 1697-709. 

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 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). 

Platinum is an effective oxidation catalyst for carbon monoxide and the complete oxidation of hydrocarbons. Palladium also promotes the oxidation of carbon monoxide and hydrocarbons but is more sensitive to poisoning than platinum in the exhaust environment. Both platinum and palladium promote the reduction of nitric oxide but are less effective than rhodium. In addition to the noble metals, three-way catalysts contain the base metal cerium and possibly other additives such as lanthanum, nickel or iron. These base metal additives are believed to improve catalyst performance by extending conversion during the rapid air-fuel ratio perturbations and help to stabilize the alumina support against thermal degradation. 

Qi G, Yang R T, Thompson L T (2004) Catalytic reduction of nitric oxide with hydrogen and carbon monoxide in the presence of excess oxygen by Pd supported on pillared clay. Appl. Catal. A 259 261-267. 

When automobile emission regulations were first introduced, only platinum and palladium catalysts were used for the oxidation of carbon monoxide and residual hydrocarbons. Both metals were active oxidation catalysts although palladium was more temperature resistant than platinum but was more readily poisoned by sulfur. Rhodium became an important part of the three-way autocatalysts because it had high activity for the reduction of nitric oxide. Three-way catalysts were used in all cars from 1981 because of US Federal regulations although they had been introduced by California for 1978 model cars. 

Bollinger, M.J., R.E. Sievers, D.W. Fahey, and F.C. Fehsenfeld. 1983. Conversion of nitrogen dioxide, nitric acid, and w-propyl nitrate to nitric oxide by gold-catalyzed reduction with carbon monoxide. Anal. Chem. 55 1980-1986. 

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