摘要
为考察MnO_(x)/MWCNTs催化剂抗水效果,实验研究了水蒸气对其低温NH_(3)-SCR脱硝性能的影响,并通过比表面积(BET),程序升温还原(TPR)和热重(TG)等多种手段对催化剂的结构进行了表征。结果表明,水蒸气存在下,催化剂低温活性明显受到抑制,NO_(x)最高转化率温度向高温方向偏移约30℃。随着水蒸气体积分数的增加和反应温度的降低,NO_(x)转化率下降幅度变大。240℃下通入5%、8%和10%H_(2)O,脱硝率由94.5%分别下降至83%,75%和64%。水蒸气在催化剂毛细孔中凝聚,受热膨胀后孔隙结构发生变化,导致平均孔径增大,比表面积减少。通入水蒸气后,催化剂的氧化还原能力和活性Mn物种状态未发生改变,催化剂表面有更多的水分子吸附和表面羟基形成。水蒸气抑制催化剂活性主要是由于分子结合水占据催化剂活性位点,阻碍了SCR反应物在催化剂表面的吸附,从而导致催化活性下降。
To investigate the water resistance of MnO_(x)/MWCNTs catalyst,the influence of water vapor on its performance for low-temperature selective catalytic reduction of NO_(x)with NH_(3) was studied.Furthermore,the structural properties of the catalyst was characterized by a suite of analytical methods such as Brunauer-Emmett-Teller(BET),temperature programmed reduction(TPR)and thermogravimetric analysis(TG).The results show that the low-temperature activity of the catalyst is obviously inhibited in the presence of H_(2)O,the highest NO_(x)conversion temperature shifts upward by about 30℃.With the increase of water vapor volume fraction and the decrease of reaction temperature,the NO_(x)conversion declines more significantly.When 5%,8%and 10% H_(2)O are added at 240℃,the denitration rate drops from 94.5%to 83%,75%and 64%,respectively.The pore structure is changed after capillary condensation H_(2)O thermal expansion,resulting in an increase of average pore diameter and a decrease of specific surface area.The redox property and active Mn species are barely altered by H_(2)O.There are more water molecules adsorption and hydroxyls forming on catalyst after reaction in the presence of H_(2)O.The inhibition of catalyst activity by water vapor is mainly attributed to the fact that the molecular bound water occupies the active site of the catalyst,hindering the adsorption of the SCR reactants,resulting in a decrease in catalytic activity.
作者
罗红成
廖琪
容誉
LUO Hong-cheng;LIAO Qi;RONG Yu(Hubei Provincial Academy of Eco-environmental Sciences(Provincial Appraisal Center for Ecological and Environmental Engineering),Wuhan 430072,Hubei Province,China)
出处
《化学工程》
CAS
CSCD
北大核心
2022年第1期14-18,29,共6页
Chemical Engineering(China)