NOx adsorption behavior of LaFeO3 and LaMnO3+δ and its influence on potentiometric sensor response

NO_x adsorption behavior on LaFeO₃ (LFO) and LaMnO_3+δ (LMO) was characterized using temperature controlled methods and mass spectrometry. Temperature program desorption revealed decomposition of complex surface species formation when NO or NO₂ was adsorbed on LFO and LMO. LFO exhibited higher adsorption capacity for NO_x species than LMO and was shown to be more active for NO_x surface conversion. Both effects were attributed to the different B-site cations, with iron in LFO in the 3+ valence state, and manganese in LMO in the 3+ and 4+ valence states. Results from diffuse reflectance infrared spectroscopy were used to identify specific nitrite and nitrate species that are formed on the surfaces of LFO and LMO at room temperature. Temperature programmed reaction revealed a complex NO₂ decomposition mechanism to NO and O₂ for LFO and LMO in which the formation of nitrite and nitrate species serve as intermediates below ∼600 °C. NO_x sensing mechanisms were considered and predicted based on the types and quantities of surface species formed.     

聚苯胺-多壁碳纳米管薄膜SAW NO2传感器

将聚苯胺-多壁碳纳米管聚合物沉积于声表面波(SAW)气体传感器的敏感区,形成敏感薄膜,实现了室温下对不同体积分数NO2的检测.研究表明:这种传感器具有很高的敏感性,良好的重复性和低体积分数检测极限.同时,单一聚苯胺薄膜也做了对比测量,实验结果表明:聚苯胺-多壁碳纳米管聚合物敏感膜比单一聚苯胺薄膜具有更高的敏感性和更短的...     

SCR脱硝系统静态混合器优化布置数值模拟研究

基于CFD数值模拟技术系统地研究了静态混合器对改善SCR脱硝系统首层催化剂入口截面速度/浓度均匀分布特性的作用规律。数值计算结果表明,针对特定的静态混合器型式,优化前后速度/浓度分布偏差最大改善量分别为8.89%、12.26%,系统整体压损最大升高量约为188 Pa。因此认为静态混合器的优化布置可以显著改善截面内的速度/浓度均匀分布特性,但基于系统压损呈现的变化规律,建议在进行静态混合器设计时需综合权衡速度/浓度分布偏差改善性能与系统整体压损变化特性两方面的因素。     

系列无弧交流接触器的研制

介绍所研制的无弧交流接器的工作原理和特点。无弧交流接触器是在普通接触器基础上,在两主触点间并联可控硅,利用可控硅电流过零关断的特性,消除触点间的电弧,实现无弧关断,适用于重负载下频繁启动的电气控制系统。     

NO and N2O emissions from savanna soils following the first simulated rains of the season

Data on the emissions of oxides of nitrogen from the soil during the early part of the wet season are reported for nutrient-rich and nutrient-poor sandy soils at Nylsvley, South Africa. The emissions of NO_x and N₂O following the first wetting event of the season are elevated relative to subsequent events. The observed high emission rates (76 ng N-NO m^-2 s^-1) are partially attributed to the sandiness of the soil, which permits NO to diffuse out of the soil rapidly. The pulse of high emissions following wetting is maintained for approximately 72 hours, thereafter continuing at around 20 ng NO m^-2 s^-1 while the soil remains moist. The initial pulse is suggested to be due to the accumulation of a substrate pool during the dry period, coupled with an inability of plants and microbes to use it effectively during the first few days after wetting. There were no significant differences in the peak or subsequent emission rates for either NO or N₂O between two sites of differing nitrogen mineralisation potentials. N₂O emissions averaged 8% of NO_x emissions. The enhanced emissions of NO_x which follow the first wetting after a prolonged dry period do not make a very large contribution to the annual gaseous N emission budget, but could be a significant contributor to the high tropospheric ozone levels observed over southern Africa in springtime.     

330MW燃煤电厂SCR技术的应用研究

研究选择性催化还原法（SCR）在330MW燃煤电厂上的应用,分析了SCR系统工艺流程、工作原理及影响脱硝效率的因素。经过较长时间稳定运行,系统脱硝效率在80%以上,达到设计参数,为燃煤电厂NOx控制提供参考。     

聚3—己基噻吩及其掺杂TiO2材料对NO2的气敏特性

制作了一种工作于室温下的NO2气体传感器。该传感器以有机聚合物聚3—己基噻吩(P3HT)为敏感材料,以聚对苯二甲酸乙二醇酯(PET)薄膜为柔性衬底。对敏感膜进行了SEM表征。室温下,对不同体积分数的NO2进行了测试,对器件尺寸的影响进行了分析,并对响应规律进行了总结。经实验,对NO2测试下限可达到0.2×10-6。为提高敏感性、减小恢复时间,尝试对敏感膜掺杂TiO2,并同未掺杂的敏感膜进行实验比较,发现对体积分数1.5×10-6的NO2,掺杂TiO2可将敏感性提高8%,恢复性也有明显改善,对周期为1060 s的循环测试表明:掺杂TiO2下阻值基本能完全恢复。     

Role and importance of oxidized nitrogen oxide adspecies on the mechanism and dynamics of reaction over copper-based catalysts

The formation of nitrate and NO₂ adspecies over Cu/MFI and copper-on-alumina catalysts and their role in the mechanism of reaction is discussed on the basis of FT-IR results and catalytic tests in unsteady-state conditions. Three specific cases are discussed: (i) reduction of NO by propane/O₂ over Cu/MFI, (ii) conversion of NO by NH₃/O₂ over copper-on-alumina catalysts and (iii) oxygen-promoted reduction of NO in the absence of reductants over Cu/MFI. The formation of nitrate species leads to self-deactivation, but Cu²⁺-NO₂ like adspecies are suggested to be a key intermediate in the reduction of NO to N₂ in all three cases examined.     

C3H6选择性催化还原NO催化剂Ag／γ—A12O3的研究

采用低负载量的(0～3％)Ag／γ-A12O3体系作为C3H6选择性催化还原(C3H3-SCR)NO的催化剂，考察了银负载量、反应温度、空速对NO转化率的影响．同时对于原料气中氧的作用进行了研究．结果表明：银负载量为1．5％时，催化剂表现出最高的反应活性；在考察的条件范围内，原料气中含氧对NO的还原有促进作用，适宜的氧浓度为0．27％；反应温度的过高会导致还原气中C3H6大幅度转化为CO2。     

基于霍耳效应的气敏传感器的研制

利用霍耳效应成功地研制了WO3半导体气敏传感器.这种新型传感器不仅可以根据需要输出几毫伏至几十毫伏甚至几百毫伏的直流电压,而且具有其它半导体传感器所没有的优点--无需另外加热.在实验中对NO2气体进行检测,结果表明:传感器的输出霍耳电动势在几毫伏到几百毫伏之间,且随待测气体浓度变化而变化.因此,利用霍耳效应制作气敏传感器是一条完全可行的新思路.