Performance comparison between cobalt aluminosilicate and cobalt ion-exchanged MFI catalysts for selective catalytic reduction of nitrogenmonoxide with methane in the presence of excess oxygen

Abstract

Performance for selective NO reduction by methane in excess oxygen of a series of Co, Al-silicates, new synthesis bimetallosilicates, having MFI structure, was investigated with comparison of Co/ZSM-5. NO conversion of H-Co, Al-silicates increases with cobalt content incorporated into the frame work but its Na-form is hardly active in the same condition except at elevated temperature (> 500 ํC). Comparison to Co/ZSM-5 shows that protonated catalysts of both have almost the same conversion activity for No but different effective reaction temperature windows. Co/Na-ZSM-5 exhibits superior NO conversion over that of Na-Co, Al-silicate, although the new synthesis catalysts, both in H-form and Na-form show lower activity for methane conversion. Like Co/H-ZSM-5, the kinds and the concentration of hydrocarbon affect the NO and CH4 conversion of H-Co, Al-silicate. Presence of SO2 poisons the NO removal activities of H-Co, Al-silicate and Co/H-ZSM-5 at moderate temperature (400 ํC) but enhances them at higher temperature (550 ํC) while IR-pyridine spectra indicate the different sites for SO2 adsorption. Data from TPR, CO adsorption and ESR demonstrate the change of cobalt's environment after SCR reaction. Finally, the effect of Co ion-exchanged in Co, Al-silicate was consider in either H- and Na-form.