| The emission of nitrogen oxides and small molecule hydrocarbon from ship and vehicle is the main form of mobile pollution sources.The use of hydrocarbons as a substitute for NH3 in the SCR of NOx is seen as a promising solution for abatement of NOx and low molecular weight organic matter. This technology used the hydrocarbon represented by CH4 exhausted from diesel as reduction and NOx through selective catalytic reduction reaction （CH4-SCR） generated N2% CO2 and H2O, it has a promising application. This article used the unreactable honeycomb cordierite （CC） as structure matrix,palygorskite （PG） and ZrO2 were selected as coating materials, manganese nitrate solution was chosen as precursor to obtain Mnx/PG-CC or Mnx/ZrO2-CC catalysts as research subjects, the effects of the preparation parameters, operation conditions and structural characteristics on performance of the monolith catalysts for the CH4-SCR were also investigated. Catalysts structure and morphology were characterized by BET, XRD, FE-SEM and Adsorption and TPD profiles, several conclusions were gained as following:When PG was used as carrier, the Mnx/PG-CC catalyst prepared by manganese nitrate solution as precursor has the best low temperature CH4-SCR activity. It was observed that the catalyst calcined at 300 ℃ with 11wt% of manganese （Mnll/PG-CC（300 ℃）） showed the best CH4-SCR activity when tested at 300 ℃ with a CH4/NO ratio at 1 and 5 vol% O2 presented. Manganese oxide active specie was observed to be highly dispersed on the catalyst’s surface, which was beneficial for the CH4-SCR activity of the catalyst mainly due to the adsorption of NO was enhanced and surface nitrate was formation as active mediate for SCR.When ZrO2 was used as carrier, the factor of coating process had remarkable influence on the activity of catalysts, ZrO2-CC carrier prepared by a suspension slurry method could do better than the carrier that preparation by using in-situ synthesis method. It was observed that the catalyst with 10 wt% of manganese （Mn10/ZrO2-CC（300 ℃）） showed the best CH4-SCR activity when tested at 250 ℃ with 5 vol% O2 presented, and were higher than the carrier itself. The active material Mn species in the catalyst were MnO2 and Mn2O3. MnO2 played a main role for the activity. O2 adsorption on the catalyst surface in the form of O", they can reaction with NO, NO can be oxidized to N2O. CH4 as gas phase take part in the reaction.Ce was added to modify Mn10/ZrO2-CC catalyst. Ce can help improve the activity of catalyst in low temperature by changing the surface property and appearance. |
