Characteristics and roles of surface species in C[subscript 3]H[subscript 6]-SCR of no over a Ag/Al[subscript 2]O[subscript 3] catalyst by temperature programmed technique

Abstract

In this thesis, the behavior of surface species which occur in the selective catalytic reduction of nitric oxide by hydrocarbon over Ag/Al[subscript 2]O[subscript 3] catalyst under excess oxygen was investigated through the Temperature Programmed Technique. With propene as a model reductant, and experimental set of three continuous steps containing reaction step, temperature programmed desorption step and temperature programmed oxidation step shows that there are at least five types of surface species occurred on Ag/Al[subscript 2]O[subscript 3] both TPD and TPO step. From the reactivity tests of surface species on Ag/Al[subscript 2]O[subscript 3] and Ag/SiO[subscript 2] indicate that only two surface species, (S[subscript TPDL]) and (S[subscript TPDL]), play an important role in the production of N[subscript 2]. Hence, the reaction mechanisms consist of two pathways including the decomposition of (S[subscript TPDL]) species and the NO reduction of STPOH species. Moreover, the results show that the STPOH species first occurred on silver active site after expose to the reactant gases and then move to the alumina active site. In addition, some of STPOH species can react with NO+O[subscript 2] to form the other surface species (S[subscript TPDL]). Therefore, the Temperature Programmed Techniques do not use only to characterize the behavior of surface species but also apply to investigate the appeared position of surface species.