Catalytic Abatement

Catalytic decomposition can be considered the simplest removal method for N2O because it does not need any additional chemical compounds. The catalytic decomposition of nitrous oxide is highly exothermic (—19.6kcalmol )  

The reaction of N2O with the active site of the catalyst is envisaged as a donation of electronic charge from the catalyst to the antibonding molecular orbital of N2O, thus destabilizing the N—O bond and leading to scission. 

The various processes for the catalytic reaction are similar. The factor that makes the difference is the choice of catalyst, which in turn affects the temperature regime needed to trigger the decomposition of nitrous oxide. In the literature, numerous works illustrate the several classes of catalysts appropriate for this reaction [9a, k] noble metals (Pt, Au), pure or mixed metal oxides (spinels, perovskite-types, oxides from hydrotalcites), supported systems (metal or metal oxides on alumina, silica, zirconia) and zeolites. 

Zeolitic systems are very active at low temperatures but they also have disadvantages related to their hydrothermal stability and the possibility of inhibition or poisoning by different compounds. These drawbacks drastically limit the industrial applications of these catalysts. Rhodium-supported systems are also active at low temperatures and low N2O concentration, but at high temperatures and in the presence of O2 the noble metal is oxidized. Furthermore, the high cost of Rh may prove to be a limit for industrial applications. 

Owing to their crystal structure, which can contain various metal ions and can stabilize unusual and mixed valence states of active ions, mixed oxide catalysts have been thoroughly investigated, and have been found to be better catalytic materials than other systems. 

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Oxides of nitrogen, NO, can also form. These are generally at low levels and too low an oxidation state to consider water scmbbing. A basic reagent picks up the NO2, but not the lower oxidation states the principal oxide is usually NO, not NO2. Generally, control of NO is achieved by control of the combustion process to minimize NO, ie, avoidance of high temperatures in combination with high oxidant concentrations, and if abatement is required, various approaches specific to NO have been employed. Examples are NH injection and catalytic abatement (43). 

Nitrogen monoxide, catalytic abatement, 39 201-203 Nitrogen oxides... 

Regardless of the techniques used to purify the KA oil, several waste streams are generated during the overall oxidation —separation processes and must be disposed of. The spent oxidation gas stream must be scrubbed to remove residual cyclohexane, but afterwards will still contain CO, CO 2, and volatile hydrocarbons (especially propane, butane, and pentane). This gas stream is either burned and the energy recovered, or it is catalytically abated. 

High dust separation efficiency Dust should not markedly penetrate the filter struc> ture since this would lead to pore obstruction and/or to catalyst deactivation. High catalytic activity so as to attain nearly complete catalytic abatement for conveniently high superficial velocities, i.e., those employed industrially for dust filtration 10-80 m/hr. 

Camo J., Berg M. and J iis S., Catalytic abatement of emissions from small-scale combustion of wood. A comparison of the catalytic effect in model and real flue gases, Fuel 75 959 (1996). 

Berg, M., Berge, N. (1999) Development of domestic wood fired boilers with catalytic abatement of emissions, Proc. of 2 Olle Lindstrdm Symposium on Renewable Energy - Bioenergy, Stockholm, Sweden... 

Figure 7.4 Schematic diagram of the catalytic abatement of nitrous oxide.

Pettersson, L.J. and Jaras, S.G. (1993). Catalytic abatement of emissions from alcohol-flieled diesel engines. Final Report, Phase 1. Swedish National Board for Industrial and Teclmical Development, Stockliohn, NUTEK Report No U823-91-02088. In Swedish. 

Djinovic, P., Batista, J., Pintar, A. (2012). Efficient catalytic abatement of greenhouse gases methane reforming with CO2 using a novel and thermally stable Rh—Ce02 catalyst. International Journal of Hydrogen Energy, 57(3), 2699—2101. 

Matatov-Meytel Y.I., Sheintuch M. Catalytic abatement of water pollutants. Ind. Eng. Chem. Res.,... 

Busca G, Larrubia M A, Arrighi L, Ramis G (2005) Catalytic abatement of NOx Chemical and mechanistic aspects. Catal Today 107-108 139-148. 

Catalytic Abatement of N2O from Stationary Sources Table 27.1 Estimated amount of N2O and characteristic of typical composition of off-gases. 

Many attempts at the lab scale were devoted to the catalytic abatement of N2O, and the technology is now available at the industrial scale even if some problems persist related to the catalyst stability at high temperature inside the ammonia burner. In the particular case of nitric acid plant, the simultaneous removal of low concentration of N2O and NO, is still of interest, since no technology is viable especially end-of-pipe systems for which the low temperatures of the exhaust gas do not allow the simultaneous conversion of N2O and NO. The implementation of a process running at medium temperatures is technologically... 

Wu, Y., Dujardin, C., Lancelot C., Dacquin, J.P., Parvulescu, V.I., Cabid, M., Henry, C.R., Neisius, T., and Granger, P. (2015) Catalytic abatement of NO and N2O from nitric acid plant a novel approach using noble metal-modified perovskites. /. Catal, 328, 236-247. 

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