Preparation And Investigation Of Ti_1-yMn_yO_x/CH Monolithic Catalysts And Its Tolerance To SO₂ For Low Temperature NH₃-SCR Reaction

Selective catalytic reduction of NOx with NH₃ ?NH₃-SCR? is an important technology for the tail gas denitrification of diesel vehicles.The development of low temperature catalyst is the key to application for NH₃-SCR technology since the temperature of exhaust gas would decrease after the long journey in the exhaust pipe.Although the noble metal catalysts have good low temperature SCR activity, but because of its complex process, high cost, narrow activity window, vulnerable to SO₂ poisoning and other shortcomings,will limit its application. Hence,to prepare a new SCR catalyst with high activity and low cost has its vital practical significance in the application of vehicle exhaust denitration.The Ti_1-yMn_yO_x/CH catalyst was prepared via a simplicity and fast SHS process which using cordierite honeycomb ceramics as carrier and MnO_x as activity components.The effects of preparation parameters and operation conditions on the activity of Ti_1-yMn_yO_x/CH catalyst were investigated. The results indicated that the catalysts ignited once at 350? with Ti/Mn=1:6 in the combustion solution showed the optimal NH₃-SCR activity and GHSV=30000 h-1 and 3% vol O₂ was optimal operation condition,the catalyst showed excellent H2O tolerance when temperature was above 150 ?. The characterization of the catalyst indicated that there is synergistic effect between Ti and Mn. This synergistic effect is beneficial for dispersion of MnO_x,improving Mn⁴⁺/ Mn³⁺ratio and increasing the quantity of acid sites on the surface of catalysts, which are beneficial for the NH₃-SCR activity of the catalysts.Meanwhile, the influence of SO₂ on the activity of the optimal catalyst during NH₃-SCR process has been studied. A series of metal elements were used for the modification of the optimal catalyst to improve its sulfur resistance. The results illustrated that Ti_0.14Mn_0.86O_x/CH catalyst can be easily influenced by SO₂ and its catalytic activity has sharply dropped to around 20% at 250 ?. The sulfur resistance of catalyst can be improved by metal doping modification, which enhanced its catalytic activity under SO₂ condition. Especially the catalytic activity of Ti_0.14Mn_0.34Ce_0.34O_x/CH can approach to 60%. Ammonium sulfate salt and MnSO4 were poisoned products of catalysts which can dope on the surface of the catalysts, resulting the low activity.However, Ammonium sulfate salt on the surface of catalyst can be inhibited after Ce was doped and the activity of the Ti_0.14Mn_0.34Ce_0.34O_x/CH catalyst was improved.