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排序方式: 共有1858条查询结果,搜索用时 15 毫秒
101.
Claude Descorme Patrick Gélin Michel Primet Christine Lécuyer 《Catalysis Letters》1996,41(3-4):133-138
The adsorption of NO at room temperature on a H-ZSM-5 catalyst exchanged with Pd(NH3)
4
2+
complex and activated in oxygen at 773 K has been examined by FTIR spectroscopy. After the oxidizing treatment, the Pd tetrammine complex decomposed into Pd(II) ions and/or Pd(II) hydroxyl complexes dispersed in the zeolite channels. The subsequent adsorption of NO at room temperature led to the reduction of Pd(II) to Pd(I) entities, resulting in the formation and adsorption of NO2 on H-ZSM-5. The Pd(I) entities were shown to adsorb NO and form mononitrosyl complexes dispersed in the zeolite porosity and characterized by a single infrared absorption band at 1881 cm–1. The Pd(I) mononitrosyl complex was shown to reversibly coordinate water and NO2 molecules. The resulting nitrosyl complex was characterized by a single NO vibration band at 1836 cm–1. 相似文献
102.
103.
Giuseppe Spoto Silvia Bordiga Domenica Scarano Adriano Zecchina 《Catalysis Letters》1992,13(1-2):39-44
In this note an exchange procedure of the acidic protons of H-ZSM5 by CuI ions through reaction with CuCl in the gas phase is described. In the so obtained CuI-ZSM5 exchanged zeolite the CuI ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The CuI(NO)2 species are transformed at RT into CuII(NO)X (X=O– and/or NO
2
–
) species which could represent an intermediate in NO decomposition. 相似文献
104.
为了研究MnO_x-CeO_2复合氧化物催化氧化柴油机NO的性能,采用溶胶凝胶法制备了不同Mn/Ce摩尔比的xMn10Ce/γ-Al_2O_3(x=5,6,7,8)催化剂。利用X射线衍射(X-ray diffraction,XRD)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)和H_2程序升温还原(H_2temperature programmed reduction,H_2-TPR)技术分别对其物相结构、元素价态及还原性能进行了表征。结果表明:CeO_2晶粒尺寸随Mn含量增加而逐渐变大,同时添加适量的Mn也有利于提高催化剂中Mn~(4+)的数量,从而促进NO氧化;当x=6时,催化剂的氧化还原性能最好。最后,基于模拟气试验平台考察了不同Mn/Ce比对xMn10Ce/γ-Al_2O_3催化剂氧化NO性能的影响。结果表明:在350℃时,NO浓度达饱和所需时间和反应速率与Mn添加量呈非线性关系;在250~450℃范围内,6Mn10Ce/γ-Al_2O_3的NO氧化性能最好,其NO浓度在350℃时最先达到稳定,仅需4min,但在450℃时则延长至6min,这主要是受热力学平衡及随反应进行活性氧数量及氧空位逐渐饱和共同作用的结果。 相似文献
105.
开展基于可调谐激光吸收光谱(tunable laser absorption spectroscopy,TLAS)的内燃机排放中气体组分浓度检测技术研究。选取NO气体作为试验室静态测试的目标气体,利用可调谐带间级联激光器(interband cascade lasers,ICL)作为探测光源,采用直接探测法及谐波探测法对4种不同浓度的标准NO气体进行测试,结果与标准气真实浓度吻合度较高。直接探测法中,探测相对误差均方根为2.6%,体积浓度的最大绝对误差为18.6×10~(-6),理论探测极限可达2×10~(-6);谐波探测相对误差均方根为1.4%,最大绝对误差为13×10~(-6),理论探测极限可达10~(-7)。数据处理过程中引入温度修正算法,可实现温度波动下的准确测量。同时,对不同流速下的标准气体进行了在线测量,结果表明气体的流动性对测试结果并无影响。本研究表明:TLAS方法动态响应特性好,环境适应性强,可根据瞬态环境参数进行实时修正,可以在复杂的测试环境下实现高精度、高灵敏度瞬态测量。 相似文献
106.
在AVL全流采样(CVS)发动机台架上,对2台国V柴油机进行了ESC、ETC测试循环,并利用FTIR气体分析仪对非常规气体排放进行了测试。通过对比不同技术路线(增压中冷+共轨+EGR+DOC+DPF和增压中冷+共轨+SCR)发动机的NO2、SO2、NH3、HCHO和NOx排放,对它们的排放特性进行了试验研究;同时还分析了两种路线的CO2排放和油耗情况。研究结果表明DOC+DPF可以使NOx中NO2的比例升高,ESC循环达到了24.3%;两种路线都可以使车用柴油机满足国V排放标准要求,但前者THC、CO、HCHO、NH3排放明显低于后者,后者NO2排放及NO2在NOx排放中的比例明显低于前者。SCR路线在油耗和CO2排放方面相对具有优势。 相似文献
107.
108.
The selective catalytic reduction of NO by H2 under strongly oxidizing conditions (H2-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La2O3, MgO, Y2O3, CaO, CeO2, TiO2, SiO2 and MgO-CeO2). The Pt/MgO and Pt/CeO2 solids showed the best catalytic behavior with respect to N2 yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO2 support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N2 production (mols N2/gcat s). High NO conversions (70–95%) and N2 selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h−1 with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H2, 5 vol% O2 and He as balance gas. Addition of 5 vol% H2O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO2 during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO2 in the feed stream following a given support pretreatment. N2 selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO2 catalyst in the 100–200 °C range in the presence of water and SO2 in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO2 catalyst towards a new NOx control technology in the low-temperature range of 100–200 °C using H2 as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NOx species with H2 experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NOx intermediate species, NOx spillover). 相似文献
109.
对多重富集低 NOx 煤粉燃烧器的结构及特点进行了分析 ,初步阐述了这种燃烧器的低负荷稳燃和低 NOx 排放原理 ,并进行了一系列冷态模化实验 ,研究了燃烧器结构和气流等因素对这种燃烧器性能 ,即浓淡风比、阻力系数的影响 .实验结果表明 ,档块间开度对燃烧器阻力损失影响显著 ,开度增加可使燃烧器阻力损失降低 ,浓淡风比减小 ,但双档块开度过多 ,会使加粉时煤粉气流的浓淡分离效果变差 ;浓淡风比受燃烧器浓淡侧阻力平衡决定 ,为此 ,必须在浓侧设置阻力调节器 ,满足阻力特性和风量平衡的多重要求 ,根据实验结果得到了优化的燃烧器结构 . 相似文献
110.
NO removal using CH4 as a reductant in a dual-bed system has been investigated with Co-NaX and Ag-NaX catalysts, which were prepared by Co2+-, Ag+-ion exchange into zeolite NaX, respectively, and activation for 5 h at 500 °C. The experimental result has been compared with that of a Co-NaX-CO catalyst, additionally pre-treated under CO flow for the Co-NaX catalyst. The cobalt crystal structure of a Co-NaX-CO catalyst is Co3O4, which promotes NO oxidation to NO2 by excess O2 at a low temperature (523 K). The mechanical mixture of Co-NaX-CO and Ag-NaX catalysts shows a synergy effect on NO reduction to N2 by CH4 in the presence of excess O2 and H2O, but the NO reduction decreases quickly as time passes. However, the NO reduction to N2 in a deNO bed at 523 K and a deNO2 bed at 423 K, which are relatively lower than the reaction temperatures for common SCR systems, still remained at 67% even in a H2O 10% gas mixture after 160 min. 相似文献