原位同步辐射光电离质谱研究压力对3Mn10Fe/Ni催化剂上N2O形成途径的影响

Effects of pressure on the formation of N_(2)O over 3Mn10Fe/Ni catalyst by in-situ synchrotron radiation photoionization mass spectrometry

为了研究N_(2)O在氨选择性催化还原脱硝(NH_(3)-SCR)过程中的形成途径及其选择性受压力影响的变化规律,采用原位光电离质谱研究方法结合流动管反应器,对3Mn10Fe/Ni催化剂NH_(3)-SCR反应体系中气相物种进行了原位检测并获得了各组分的质谱图,进一步分析了不同工况、温度和压力条件下N_(2)O选择性以及NO_(x)和NH_(3)转化率的变化规律。研究结果表明,N_(2)O形成主要来源于非选择性催化反应(NSCR)和吸附态NH_(3)氧化(NSNO)反应,其中,100−250℃由NSCR占据生成N_(2)O的主导地位,250−400℃两种形成途径贡献相当,400−500℃NSNO成为主要来源。此外,低压降低了催化剂在低温区的脱硝活性,却促进了在高温区通过NSNO反应生成N_(2)O的形成途径。

In order to study the formation pathway of N_(2)O in NH_(3)-mediated selective catalytic reduction(NH_(3)-SCR)of NO_(x)process and the variation of N_(2)O selectivity affected by pressure,in situ synchrotron radiation photoionization mass spectrometry(SR-PIMS)and flow tube reactor were used to detect the gaseous species in the NH_(3)-SCR reaction over 3Mn10Fe/Ni catalyst.The variations of N_(2)O selectivity,NO_(x)conversion and NH_(3)conversion were analyzed under different conditions.The results show that the formation of N_(2)O is mainly from non-selective catalytic reaction(NSCR)and adsorbed NH_(3)oxidation(NSNO).Among them,NSCR plays a dominant role in N_(2)O formation in the temperature range of 100−250℃.The contributions of the two formation pathways in the temperature range of 250−400℃are equivalent,and NSNO is the main source in the temperature range of 400−500℃.In addition,low pressure reduces the denitration activity of the catalyst at low temperature,but promotes the formation of N_(2)O via NSNO reaction at high temperature.