||The research program is to develop a high performance of ZSM-5 supported palladium-cobalt catalysts for the selective catalytic reduction of NOX with hydrocarbons. Recently, selective catalytic reduction (SCR) of NOX with hydrocarbons was studied over ZSM-5 based palladium catalysts. However, ZSM-5 supported palladium-cobalt catalysts deactivated immediate in the presence of H2O in feed. The related articles mentioned about that ZSM-5 supported palladium catalysts with cobalt promoter showed better durability of H2O, and the ZSM-5 supported palladium catalysts have good activity and selectivity for the SCR reaction. The sodium could be as the promoter to increase the stability of the catalysts. Tungsten and manganses could be as the promoter to broaden the suitable temperature range of SCR reaction.
In this research, all the promoted ZSM-5 supported Pd catalysts will be prepared by added each promoter such as cobalt, sodium, tungsten or manganses. Their catalytic surface area, temperature programmed reduction (TPR) spectra, X-ray diffraction (XRD) spectra, inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), catalytic activity of NOX selective of catalytic reduction, and catalytic stability will be characterized respectively. The optimum composition of catalysts will be found by comparing catalytic characterizations of all kind of catalysts. Besides, the relationship between the catalytic activity of NOX selective catalytic reduction (SCR) and the characterizations of prepared catalysts will be investigated and discussed.
The experimental result showed that Na as the promoter to Pd-Co/H-ZSM-5 catalysts didn’t influence the reaction activity obviously, but actually can effectively increase the stability of the catalyst. And at the sample of 7 wt.% Na, NO conversion could keep at 62.8% after 20 hr reaction. While the addition of W as a promoter, it known that the addition quantities of W won’t affect the stability of catalysts. But, NO conversion was higher than Pd-Co/H-ZSM-5. And at the sample of 9 wt.% W, NO conversion could keep at 43.4% after 20 hr reaction. While the addition of Na as a promoter, it could observe that the addition of Mn would made catalysts declined within 4 hr, and lost activity after 8 hr. This phenomenon would effect deeply with the addition quantities of Mn.