| Nitrogen oxides originate mainly from high temperature combustion used for heat and energy generation. Their removal is one of the greatest challenges in environment protection.;The objective of the studies comprising this thesis was to evaluate the performance of several specific perovskites in direct decomposition of nitric oxide under a wide range of experimental conditions and to determine the effect of various reaction parameters in order to contribute to a better understanding of this elusive reaction.;Several new multi-metal compositions were formulated specifically for this study. Three groups of compositions were included, one based on cobalt as principal active element, the second based on nickel and manganese, and the third including copper as an active element.;The first part of the study was carried out in absence of oxygen added to the feed. Majority of the perovskites studied in this work exhibit better activity than the individual component oxides or other perovskite catalysts tested previously in other laboratories.;Three perovskite compositions that exhibited the best activities at high temperatures, La0.87Sr0.13Mn0.2Ni0.8 O3-delta (LSMN-28), La0.8Sr0.2Cu 0.15Fe0.85O3-delta (LSCuF) and La 0.66Sr0.34Ni0.3Co0.7O3-delta (LSNC), were chosen as representative for a complete kinetic study. Oxygen added to the feed reduces the nitric oxide conversion, but the degree of this inhibition depends on temperature and varies with composition and contact time. Over LSNC the inhibition is the strongest, regardless the temperature.;In a complementary study, the effects of water, carbon dioxide and methane on the nitric oxide decomposition were determined. Both water and carbon dioxide inhibit the decomposition. However, the inhibiting effect of water is considerably weaker than that of carbon dioxide. The effect of added CH4 seems to be less influenced by the catalyst composition than the inhibition effects of O2, CO2 and H2O.;The original contribution of the work of this thesis, in which performance of several perovskites was evaluated in the decomposition of nitric oxide under a wide range of experimental conditions, is the following: (1) The results show clearly that the catalytic activity of the tested perovskites is inadequate for practical applications. (2) Covering a wide range of operational parameters, the results demonstrate the great complexity of the reaction, but indicate some useful information, which can help to elucidate the mechanism of nitric oxide decomposition in the presence of a catalytic surface. (Abstract shortened by UMI.). |
