Estimation of nox conversion into oxide, platinum and combined oxide - platinum SCR catalyst

The paper contains the results of the tests of the oxide, platinum and combined oxide-platinum catalytic reactor model used in the NH3-SCR system. As regards the combined oxide-platinum catalyst the first reactor block was extracted from the oxide catalyst used in trucks. As the second module of the reactor a block with platinum acting as a catalyst was used with 2.5g/dm3 platinum load. The only differences between the combined reactor system and the single platinum and oxide catalysts were connected with the reactors volume which in the case of the single reactors was two times higher than the volume of the corresponding blocks of the combined system. During the tests the ammonia concentration in the engine exhaust gases at the inlet of the reactors was set to 400 ppm. The article contains the results of the physical and chemical active surface structure tests of the reactors with their active surface chemical microanalysis and its topographic pictures performed and taken with the Scanning Electron Microscope. The results obtained from the tests of the influence of the reactor type on the NOX and NO conversion and the content of NO2 in NOX are presented in this article in the form of the function of their operating temperature. Additionally, the results of measured ammonia slip at the outlet of the reactors are presented. The obtained results have shown that the usage of the combined oxide-platinum reactor allows for widening the SCR system effective operating temperature range with a low ammonia slip at its outlet. This was achieved by use of the platinum reactor block which features a high nitric oxides conversion efficiency at the operating temperatures which are lower than those of the oxide catalyst and which can also provide the high ammonia spices conversion rangeto lower the ammonia slip at system outlet.