SELECTIVE CATALYTIC REDUCTION OF NOX BY PROPANE ON CO-LOADED ZEOLITES

To ascertain the reason of the superiority of cobalt ion-exchanged BEA (Co-BEA) in the selective catalytic reduction of NOx by hydrocarbons (HC-SCR) using propane, the dependence of the catalytic performance of Go-loaded zeolite (Co-zeolite) in the PIC-SCR reaction using propane on zeolite species was examined using IR and catalytic activity tests. The order of catalysts according to their initial activity in the abs ence of sulfur dioxide (SO2) was BEA > MFI > MOR much greater than FER much greater than FAU. In the presence of SO2, only Co-BEA exhibited stable activity, whereas the activities of Go-MOP and Co-MFI rapidly d ecreased, although no tendency to clogging of micropores nor decrease in dispersion of Co were observed. On the other hand, there was no obv ious difference in the IR spectra of absorbed NOx species between Go-P EA and Co-MFI. Since in the presence of SO2 the crystal size effect on catalytic performance was observed even with Co-BEA, intracrystalline diffusion is considered to control the overall reaction rate under su ch conditions. Thus, it is concluded that the micropore structure of B EA, advantageous to intracrystalline diffusion, is considered to be on e of the reasons for the superiority of Go-PEA in the HC-SCR reaction using propane. (C) 1998 Elsevier Science B.V. All rights reserved.