Methane nitrogen oxide reduction with

Since the pioneer work of Li and Armor (1,2,3), y ho found that methane could be used as a selective reductant of nitrogen oxide over Co-ZSM5, several sohds have been used with the same purpose (4,5,6,7). Metals such as Co, Rh and Pt, exchanged in ZSMS (8), were similarly studied. In the absence of the three metals have a high selectivity but when 25% of oxygen is added to the feed,... 

Armor, J.N. (1995) Catalytic reduction of nitrogen oxides with methane in the presence of excess oxygen A review, Catal. Today, 26, 147. 

An original method was proposed by Kulin and Tikhonenko [16], Tliey suggested the reduction of nitrogen oxides escaping from the denitration column with methane, for example ... 

Postformation nitrogen oxide emission control measures include selective catalytic and noncatalytic reduction with ammonia, which between them are used by some 900 power station installations worldwide [51]. The catalytic removal methods are 70-90% efficient at NOx removal, but are more expensive to operate than the noncatalytic methods which are 30-80% efficient. Ammonia or methane noncatalytic reduction of NOx to elemental nitrogen is also an effective method which is cost-effective for high concentration sources such as nitric acid plants (Chap. 11). NOx capture in packed beds is less expensive, but this method is not particularly effective [23]. It is also not a very practical method either for utilities or for transportation sources. Two-stage scrubbing has also been proposed as an effective end-of-pipe NOx control measure. The first stage uses water alone and the second uses aqueous urea. 

Table 1 shows activity of catalysts obtained from ZSM-5 zeolite modified with copper at which the ion exchange level of the copper varied from 55% to 126% in the reduction reaction of NOx with methane. The catalysts with a 100-126% degree of ion exchange of the copper have been found to show a higher conversion of the nitrogen oxide to nitrogen, especially at lower temperatures (300-400°C). 

With the object of stressing the possibility of an oxygenated compound as intermediate of the selective NO reduction with methane, metlianol was used as reducing agent. Figure 3.b shows tlie results of metlianol and nitric oxide conversion at different temperatiues for reactions A and B over CoMordenite. It can be observed that the conversion of nitric oxide to nitrogen begins to occiu at temperatures similar to those for the selective reduction with methane. Tliis fact clearly supports the... 

Misono M., Hirao Y., Yokokawa C. Reduction of nitrogen oxides with hydrocarbons catalyzed by bifunctional catalysts. Catal. Today. 1997 38 157-162 Mizushima T, Tohji K., Udagawa Y., Harada M., Ishikawa M., Ueno A. Characterization of silica-supported bimetallic iron-nickel catalysts by EXAFS. J. Catal. 1988 112 282-289 Mizushima Y., Hori M. Alumina aa-ogel for support of a methane combustion catalyst. Appl. Catal. A Gen. 1992 88 137-148... 

If the irradiated water was, however, saturated with hydrogen or carbon monoxide instead of oxygen then no oxides were formed [35]. Under these conditions reduction of nitrogen occurred to afford ammonia [36]. Interestingly, HCN is also observed when carbon monoxide is replaced by methane [37].Thus the result of a sonochemical reaction, in water, depends largely on the nature of the dissolved gases and their concentration. 

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