Study Of CH₄-SCR To Remove NOx On Pd-supported Metal Catalyst

Methane is the main components of natural gas and the nature reserves are rich. So the selective catalytic reduction of NOx using methane as reducing agent has wide application prospects. But methane is difficult to be activated for stable chemical properties; the activity of CH4-SCR reaction obtained with the present catalyst is low. This paper mainly studies the catalyst preparation methods and catalytic reaction conditions, such as oxygen concentration, the ratio NO:CH4, which influence the catalyst activity, and mainly studies the internal relation between surface structure characteristics of Pd/SO42--Al2O3 solid acid catalyst and the catalytic reaction activity.With the XRD,BET,TG-DTG,H2-TPR,FT-IR,NH3-TPD,NO-TPD,UV-Vis, we have researched the structural feature of catalyst. The results show that:Best CH4-SCR performances under the conditions 500 ppm NO; 1000 ppm CH4; 5 vol.% O2 were achieved using Pd loadings in 0.2%; [H2SO4]=1.5M with 33-40% NO conversion to N2 around 550℃.However, the conversion rate reduced with increasing Pd loading due to the production of PdO. it was proposed that PdO particles rather catalyze the non-selective methane oxidation.When [H2SO4]<2.5M, the amount and strength of acid increased with increasing concentration of H2SO4, and some Bronsted acidity,which played an important role in CH4-SCR for NOx, were created in the support. While [H2SO4]>2.5M,the formation of neutral crystallized A12(SO4)3 which was non activity and also could inhibit the access of the reactant gases to the active sites within the mesoporous led to a corresponding decrease in the amount of acid consequently suppressed the catalytic performances. In addition, acid treatment of the catalyst can promote NO was oxidized to NO2. According to existing mechanism, it is considered that the process further promoted the CH4-SCR reaction.