Novel metal oxide catalysts for low temperature selective catalytic reduction of NO with ammonia
Special Symposium - Environmental Protection & Sustainability
Environmental Protection & Sustainability (EPS - Poster)
Keywords: SCR, Metal oxide-based catalysts, NOx
Common sources of NOX are motor vehicles, electric utilities and other industrial, commercial and residential sources that burn fuels. NOx reacts with different compounds to form substances, e.g. smog, that cause respiratory deseases, damage the vegetation and deteriorates building and monuments. Several solutions have been developed to comply with the environmental emission standards.
Selective Catalytic Reduction (SCR) is one of the prevailing technologies in reducing NOX from stationary sources. The main reaction occuring in this process is the reduction of NOX with ammonia over a catalyst to elemental nitrogen and water vapor. A variety of different catalysts have been reported to be effective in SCR of NOX but only few of them are applied. The prominent catalyst used under industrial conditons is V2O5/TiO2 promoted by WO3 and/or MoO3 at 350-400°C [1, 2]. However, the existence of compounds like K2O, CaO and As2O3 in the flue gas reduces the performance and the durability of this catalyst [3]. Particularly, ash from biomass fuels tend to have inorganic constituents that deactivate the catalyst, rendering the SCR setup inoperable. Consequently, placement of the SCR unit downstream of the desulfurizer and electrostatic precipitators, where ashes have been removed, is an attractive solution. This, on the other hand demands the development of low temperature SCR catalysts, since the temperature downstream is below 200°C. Various metal oxide based catalysts have already showed promising SCR activities at low temperatures. Fe-Mn based transition metal oxides exhibit a superior SCR activity related to their high activities for the intermediate step, NO oxidation to NO2, at lower temperatures [4]. Ce-Mn catalysts have also revealed a good potential for the SCR of NO, but the catalytic performance depends critically both on the cerium/manganese ratio as well as the calcination temperature [5]. Also using H2 as a reductant has made possible to achieve de-NOX at 140°C under lean oxygen with Pt based oxide catalyst [6].
The interest in alternative low temperature SCR catalysts could be extended to other mixed oxides. Indeed, the combination of the different properties of several metal oxide-based catalysts can lead to better knowledge of the SCR performance at low temperatures.
Thus, in this work we have prepared and characterized various new combinations of metal oxide-based catalysts, in an effort to find candidates which allow a good NH3- SCR catalysts activity in combination with a high degree of selectivity towards nitrogen and water.
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Presented Monday 17, 13:30 to 15:00, in session Environmental Protection & Sustainability (EPS - Poster) S-7P.
