摘要
船舶发动机尾气中的氮氧化物(NO_(x))和碳氢化合物(HC)对大气环境有较大的危害.直接利用HC作为还原剂与NO_(x)发生选择性催化还原脱硝反应(HC-SCR),实现对发动机尾气中的HC和NO_(x)协同催化净化,是非常具有应用前景的船舶尾气净化技术之一,而开发高性能的HC-SCR催化剂是该技术的核心.采用商业伽马型氧化铝(γ-Al_(2)O_(3))作为载体、硝酸银(AgNO_(3))作为前驱体,通过湿浸渍法制备了负载型银基氧化铝(Ag/Al_(2)O_(3))催化剂.经固定床反应器活性测试发现,纯γ-Al_(2)O_(3)载体在甲烷-SCR(CH_(4)-SCR)和丙烷-SCR(C_(3)H_(8)-SCR)中具有一定的催化活性,而负载银(Ag)后得到的催化剂(Ag/Al_(2)O_(3))在反应中的低温催化性能得到进一步提高.利用粉末X射线衍射技术(XRD)、紫外可见分光光谱(UV-Vis)、HC完全氧化、NO_(x)程序升温脱附(NO-O_(2)-TPD)及原位红外光谱(in situ DRIFTS)等表征手段,分析了Ag/Al_(2)O_(3)催化剂的主要物相组成以及Ag物种的状态,并详细阐述了Ag/Al_(2)O_(3)催化剂表面HC-SCR反应的反应路径,即:HC在催化剂表面Ag物种的作用下部分氧化形成活性中间体醋酸类物种;一氧化氮(NO)在催化剂载体表面吸附活化成单齿硝酸盐类物种;HC部分氧化中间体醋酸类物种与NO吸附活化物种单齿硝酸盐物种发生反应,生成氮气(N2)和水(H2O).
Nitrogen oxide(NO_(x))and hydrocarbon(HC)emitted from marine engines have large impact on the environment.Directly using HC as a reductant to selective catalytic reduction reaction with NO_(x)(HC-SCR)under the effect of catalyst is a future promising technology for synergistically catalytic removal of NO_(x) and HC.The catalyst with high performance plays a crucial role in HC-SCR process.A supported Ag/Al_(2)O_(3)catalyst with the commercialγ-Al_(2)O_(3)as support and AgNO_(3)as precursor was prepared by wet impregnation method in this research.Fixed bed activity test results indicate that the pureγ-Al_(2)O_(3)support exhibits catalytic activity for CH_(4)-SCR and C_(3)H_(8)-SCR,and low-temperature catalytic performance is significantly promoted by the Ag addition.Through the characterization methods of X-ray diffraction(XRD),ultraviolet and visible spectrophotometry(UV-Vis),HC catalytic oxidation,NO_(x) temperature programed desorption(NO-O_(2)-TPD)and in situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS),the supported Ag species state and HC-SCR reaction process were investigated in detail.It is found that HC partially oxidizes into acetate promoted by Ag species.NO is activated by catalyst support into monodentate nitrate on the catalyst.The acetate reacts with monodentate and generates N_(2) and H_(2)O.
作者
杨新伟
郭江峰
周伟中
Yang Xinwei;Guo Jiangfeng;Zhou Weizhong(Hudong Heavy Machinery Company Limited,Shanghai 201206,China;CSSC Power(Group)Corporation Limited,Shanghai 201208,China)
出处
《内燃机学报》
EI
CAS
CSCD
北大核心
2024年第2期144-152,共9页
Transactions of Csice
基金
上海市科技计划资助项目(20QB1400400,20dz1204200).
关键词
船舶发动机
氮氧化物
碳氢
选择性催化还原
marine engine
nitrogen oxide
hydrocarbon
selective catalytic reduction
