Nitric oxide, adsorption catalysts

Piccolo L, Henry CR (2000) Reactivity of metal nanoclusters nitric oxide adsorption and CO plus NO reaction on Pd/MgO model catalysts. Appl Surf Sci 162 670... 

Reduction of Nitric Oxide with Ammonia. - Control of the emission of NO from stationary sources is possible by selective catalytic reduction, for which up to now NH3 is the only effective reductant in the presence of excess 02. Beside noble metal catalysts Bauerle etal.101 109 and Wu and Nobe108 studied Al2 03-supported vanadium oxide and found this to be highly effective in NO removal which is considerably enhanced by the presence of 02. Alkali metal compounds which are usually added as promoters for S02 oxidation completely inactivate the catalysts for NO reduction. Adsorption kinetic studies indicated first-order dependence on NH3 adsorption. Similar results were obtained for NO on reduced vanadium oxide, but its adsorption on... 

Infrared spectra were recorded on a Perkin-Elmer I80 grating spectrometer. Self-supporting wafers of the catalyst powder were placed in an situ quartz IR cell (19) which allowed pretreatments at various conditions. Before the NO adsorption experiments, N2 (purified by passage through Cu turnings at 523 K and a molecular sieve trap (Linde 5A) kept at 195 K) was passed over the catalyst at 673 K for 16 hr. This was followed by cooling to ambient temperature. Nitric oxide (99% purity) was further purified by freeze-thaw cycles. Further details have been given previously (20). 

In closing, it is important to note that the CO/CO2 adsorption technique effectively titrates the active sites for WGS on magnetite catalysts which differ in activity by over an order of magnitude. Nitric oxide on the other hand titrates all of the surface cation sites and is unaffected by Si-substitution. Indeed, NO is known to chemisorb strongly on iron oxides and may even be able to reconstruct the surface. Thus, the combined use of NO and CO/CO2 adsorption provides information about the total magnetite surface area and fraction of the magnetite surface which is active for the WGS reaction. 

Kapteijn F, Singoredjo L, Vandriel M, Andreini A, Moulijn JA, Ramis G, Busca G (1994) Alumina-Supported Manganese Oxide Catalysts. 2. Surface Characterization and Adsorption of Ammonia and Nitric-Oxide. J Catal 150 (1) 105-116 Kijlstra WS, Brands DS, Poels EK, Bliek A (1997) Mechanism of the Selective Catalytic Reduction of NO by NH3 over Mn0x/Al203. J Catal 171 (1) 208-218... 

Kapteijn, R, Singoredjo, L., van Driel, M., Andreini, A., Moulijn, J.A., Ramis, G., and Busca, G. Alumina-supported manganese oxide catalysts surface characterization and adsorption of ammonia and nitric oxide. J. Catal 1994, 150,105-116. 

Adsorption of nitric and sulfuric acids on ice particles provides the sol of the nitrating mixture. An important catalyst of aromatic nitration, nitrous acid, is typical for polluted atmospheres. Combustion sources contribute to air pollution via soot and NO emissions. The observed formation of HNO2 results from the reduction of nitrogen oxides in the presence of water by C—O and C—H groups in soot (Ammann et al. 1998). As seen, gas-phase nitration is important ecologically. 

Zeolites have also proven applicable for removal of nitrogen oxides (NO ) from wet nitric acid plant tail gas (59) by the UOP PURASIV N process (54). The removal of NO from flue gases can also be accomplished by adsorption. The Unitaka process utilizes activated carbon with a catalyst for reaction of NO, with ammonia, and activated carbon has been used to convert NO to N02, which is removed by scrubbing (58). Mercury is another pollutant that can be removed and recovered by TSA. Activated carbon impregnated with elemental sulfur is effective for removing Hg vapor from air and other gas streams the Hg can be recovered by ex situ thermal oxidation in a retort (60). The UOP PURASIV Hg process recovers Hg from clilor-alkali plant vent streams using more conventional TSA regeneration (54). Mordenite and clinoptilolite zeolites are used to remove HQ from Q2, clilorinated hydrocarbons, and reformer catalyst gas streams (61). Activated aluminas are also used for such applications, and for the adsorption of fluorine and boron—fluorine compounds from alkylation (qv) processes (50). 

First NO is formed and then it is oxidized in the atmosphere to NOj. Since in combustion, the origin of nitrogen is not only from N-rich fuel but also from air supphed for oxidation, in the elimination of NO, postcombustion methods are important. So far the most effective technique has been selective catalytic reduction of NO . on various catalysts. When the activated carbons are used as removal media, the elimination process includes also adsorption combined either with oxidation or reduction. Oxidation usually leads to the formation of nitric acid whereas Nj is the product of NO, reduction. As in the cases of other pollutants addressed in this review, for NO, removal either unmodified or impregnated (caustics, catalytic metals) activated carbons have been used [101-114]. 

H. N. Warren, some nitride as well 0. Schmidt studied the adsorption of nitrogen by chromic oxide, and also of ammonia. J. E. Ashby found that heated chromic oxide favours the combustion of ammonia in air. D. Maneghini studied it as a catalyst in the oxidation of ammonia. F. Ephraim observed that chromic oxide is attacked by SOdium amide. M. Z. Jovitschitsch found that chromic oxide dissolves when digested for 10 hrs. with fuming or cone, nitric acid the calcined oxide does not dissolve in nitric acid R. Weber found that if strongly heated with phosphorus pentachloride chromic oxide furnishes the chloride. C. Lefevre studied the action of alkali arsenates on chromic oxide. 

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