柴油机尾气净化催化剂的最新研究进展

柴油机尾气排放的污染物已经引起了严重的环境污染问题,催化净化技术是柴油机尾气污染治理必不可少和最有效的处理技术之一,而高效催化剂的研制和开发是催化净化技术的核心.本文以柴油机尾气中最难处理的两种污染物NOx和碳烟颗粒(PM)的催化处理技术为主线,综述了NOx的催化还原(选择性催化还原(SCR)和贮存还原(NSR))催化剂、碳烟的催化燃烧催化剂、NOx和碳烟颗粒同时消除的催化剂及柴油机尾气四效催化剂的最新研究进展,并总结性地提出了目前该研究方向存在的主要问题和发展方向.     

稀土在机动车尾气催化净化中的应用与研究进展

随着我国机动车尾气排放法规日趋严格,对机动车尾气净化催化剂性能提出了更高的要求.稀土元素由于独特的4f电子层结构和储放氧性能等特性,在机动车尾气催化剂中得到广泛应用.本文综述了稀土元素在机动车尾气催化剂中的应用及相关机理研究现状,并依据京V排放法规要求探讨了最新排放限值对尾气净化催化剂性能的要求,分析了稀土在开发高性能催化剂中的作用,并对稀土在机动车尾气净化催化剂中的应用前景进行了展望.     

多段微通道负载型钯催化剂上天然气预混催化燃烧的研究

制备了一系列用钡、镧、铈等氧化物进行改性的Pd／RExOγ·γ-Al2O3,堇青石蜂窝催化剂,在自行设计的催化燃烧实验平台上进行了天然气催化燃烧实验。研究了钯含量、催化剂床层数、功率对天然气催化燃烧特性的影响。结果表明,当钯含量为0.5％时催化剂具有最好的催化燃烧性能。在空燃比为12-16范围内,燃烧器尾气中NOx含量低于5×10^-6V/V,CO,Hc排放低于10×10^-6V/V。催化剂床层数对催化燃烧的温度峰值以及尾气中NOx含量影响不大,但明显利于降低HE,CO的排放。     

金属-ZSM-5/堇青石整体式催化剂上稀燃汽车尾气的净化

 在原位合成的ZSM-5/堇青石整体式样品基础上制备了几种金属(Cu, In或Ag)改性的ZSM-5/堇青石催化剂,并将其应用于稀燃发动机尾气的净化. 结果表明, Cu-ZSM-5/堇青石催化性能最好,尾气中的三种主要污染物NOx, CO和HC可以同时得到净化. 用微量(0.02%)贵金属(Pd, Rh或Ir)对Cu-ZSM-5/堇青石进一步改性,所得催化剂对CO的净化能力大大增强,保持高NOx转化率的温度窗口也大大加宽,因而该催化剂在稀燃汽车尾气净化方面具有潜在的应用前景. 微量贵金属对Cu-ZSM-5/堇青石催化剂的改性作用也在文中进行了讨论.     

城市公交车用稀土催化净化反应器的开发与试验

采用稀土元素作催化剂、蜂窝陶瓷作载体, 针对城市公交汽油车设计制造了尾气净化装置, 进行了发动机的性能试验, 测试了净化装置的净化转化率和消声量频率特性. 结果表明, 对于试验用稀土催化净化反应器, 实际消声量在各个频率段上均大于必需消声量; 净化转化效果明显, 例如当发动机怠速运转、补氧量充足时, CO和HC的净化转化率可达90%以上; 同普通消声器相比, 压降稍大, 从而导致发动机输出功率有所下降, 燃油消耗率有所上升.     

掺钾对氧化锰催化剂在深度氧化丁酮反应中催化活性的影响

随着控制大气污染要求的提高,催化燃烧技术日益广泛应用于有害尾气的净化.如何改善一般贱金属氧化物催化剂的性能受到重视.提高催化剂表面的碱性,有利于有机物深度氧化.掺入适量氢氧化钾可促进氧化铁催化剂表面的积炭烧失;过量钾则起相反的作用.钠和理盐使担载的五氧化二钒催化氨还原氮氧化物的活性增高,而钾盐则相反.     

稀土在汽油车尾气净化中的应用

截至2021年底，中国的汽车保有量超过3亿辆，其中汽油车占比90%以上，是中国最重要的汽车类型。为了应对汽油车尾气中的氮氧化物(NO_x)、碳氢化合物(HC)和一氧化碳(CO)等典型污染物，“三效催化剂”这一具有里程碑意义的汽油车尾气后处理技术被开发、应用并不断完善。新近流行的汽油缸内直喷(GDI)技术会导致显著的颗粒污染物(PM)排放，由此又催生了汽油车颗粒物过滤器(GPF)技术。上述技术的实施或多或少都需要依赖中国战略资源——稀土的参与。本文首先对各类汽油车尾气净化技术的发展进行了回顾，之后重点分析了(以CeO₂为主的)稀土材料在三效催化剂储氧材料、催化剂载体/贵金属稳定剂和汽油车颗粒物过滤器中的具体应用方式和效果。可以看出，随着新型稀土材料的开发和技术迭代，现代汽油车尾气净化技术正在变得越来越高效、越来越便宜。最后，本文对汽油车尾气净化用稀土材料的发展趋势进行了展望，分析了相关产业未来升级的重点和难点所在。     

含金属分子筛上Nox选择性催化还原研究进展 I 含非贵金属分子筛体系

贫燃发动机车(包括柴油机),因其能提高燃料的利用、减少温室气体CO2的排放,从而引起了广泛关注.由于贫燃发动机的尾气富含氧,传统的三效催化剂不能有效地控制和转化其中的NOx,因此开发新的催化剂已经引起了世界各国的重视.     

Pt-Rh密偶催化剂的制备及其催化控制汽车尾气排放的性能

 采用一种新型的、耐高温和具有大比表面积的氧化铝为载体,制备了Pt-Rh密偶催化剂,并用其催化控制汽车冷启动期间的尾气排放. 实验结果表明,该催化剂对汽车尾气(特别是尾气中的烷烃)具有较高的催化活性,同时催化剂还具有很好的抗高温老化性能,完全能够满足高性能密偶催化剂的要求.     

掺烧MTBE对电喷汽油机排放特性的影响

将增氧剂甲基叔丁基醚（MTBE）按一定比例添加到90#无铅汽油中，在汽油机台架上，考查了不同掺混比的MTBE/ 汽油混合燃料对电喷汽油机排放特性的影响及三效催化器的净化性能。 实验结果表明, 电喷汽油机掺烧MTBE后，只是在负荷很小时对CO排放有明显改善，而在其他工况下，CO排放改善效果不明显，甚至有所恶化；低速时对碳氢化合物（THC）和 NOx 排放有所改善;中速和高速时的改善效果不明显。催化转化器对CO和THC转化率均能达到70%~99%，对 NOx 的催化转化率相对低一些，为12%~55%。三效催化器的转化率与燃料中MTBE的体积分数、汽油机转速和负荷有关。     

Rhenium- and ruthenium-containing catalysts for neutralization of automobile exhaust

The rhenium- and ruthenium-containing catalysts are active in the oxidation of CH _x and CO and in the reduction of NO _x . Comparative testing of catalyst samples under laboratory conditions and on an engine stand demonstrated that these catalysts outperform the known commercial catalysts in the neutralization of exhaust gas from automotive gasoline engines. It is, therefore, possible to completely replace expensive Rh and partially replace Pt and Pd with cheaper components—Re and Rh—in the manufacturing of catalytic converters.     

Quantitative determination of sulfur compounds in FCC gasolines by AED. A study of the effect of catalyst type and catalytic conditions on sulfur distribution

The identification and quantification of sulfur-containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound-independent and element-specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response. Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline. The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (>C₁₃) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.     

Property and structure of various platinum catalysts for low-temperature carbon monoxide oxidations

The oxidation of carbon monoxide (CO) has received more attention in the last two to three decades owing to its importance in different fields. To control this CO pollution, catalytic converters have been investigated. Different types of catalysts have been used in a catalytic converter for CO emission control purposes. Platinum (Pt)-based noble metal catalysts show great potential for CO oxidation in catalytic converters with high thermal stability and tailoring flexibility. Pt metal catalysts modified with promoters such as alkali metals and reducible metal oxides have received great attention for their superior catalytic activities in CO oxidation. Temperature, close environment of the catalyst, and chemical composition in the surface layer of the catalyst have a huge effect on the active phase dispersion and O₂ adsorption capacity of the Pt metal catalysts. The main difference in activities of Pt metal catalyst for CO oxidation in O₂ or H₂ atmosphere has found. The addition of supports in Pt metal catalysts has improved their performances and reduced their cost. These improvement strongly depends on the surface structure, morphology, number of active sites, and various Pt-O interactions. Many research articles have already been published in CO oxidation over Pt metal catalysts, but no review article dedicated to CO oxidation is available in the literature.     

Aberration-corrected STEM imaging of Ag on gamma-Al2O3.

Ag on gamma-alumina is a promising catalyst for hydrocarbon selective catalytic reduction in lean-burn gasoline and diesel engines for transportation applications. Although much is known about the mechanism of NOx reduction and the various intermediates, little agreement exists on the nature of the active silver species. In the present work, aberration-corrected STEM has provided new information about the nature of Ag on alumina both as impregnated and following treatments at various temperatures with exposure to simulated exhaust gas. Ex situ techniques have provided new insights into the evolution of Ag on alumina following exposure to temperature and simulated exhaust gas.     

Determination of polycyclic aromatic sulfur heterocycles in diesel particulate matter and diesel fuel by gas chromatography with atomic emission detection

The sulfur content of diesel fuel is of environmental concern because sulfur can facilitate the formation of diesel particulate matter (DPM) and sulfur dioxide (SO2) in the exhaust can poison catalytic converters. The US Environmental Protection Agency (EPA) has established more stringent regulations to reduce the sulfur content of diesel fuels in the near future. In this study, various types of organosulfur compounds in DPM extracts and the corresponding fuels have been determined by gas chromatography with atomic emission detection. The diesel fuels used have sulfur contents of 2284 and 433 ppm, respectively, and are labeled as high-sulfur and low-sulfur diesel fuels. The compounds identified are mainly polycyclic aromatic sulfur heterocycles (PASHs). In the fuels tested, trimethylbenzothiophenes (TMBTs), dibenzothiophenes (DBTs), and 4-methyldibenzothiophene (4-MDBT) were the most abundant sulfur compounds, while larger PASH compounds were more abundant in DPM extracts. The high-sulfur diesel fuel contained a larger proportion of PASHs with one or two rings (lighter PASHs). In DPM, the concentrations of total organic sulfur and individual PASHs are higher for the high-sulfur diesel fuel, and the relative percentage of one or two-ring PASHs is higher as well. The influence of engine load on the DPM composition was also examined. With increasing load, the PASH concentration in DPM decreased for lighter PASHs, increased for heavier PASHs, and had a bell-shaped distribution for PASHs in between.     

Identification of Methyl Bromide in Urban Air

Abstract

The presence of methyl bromide at sub-part-per-billion concentration levels in urban air is reported. The major source of methyl bromide in urban areas is believed to be automobile exhaust, rather than of biogenic or agriculturally related origins. Engines operating on “leaded” gasoline contribute a much larger amount of methyl bromide to urban atmospheres than do engines with catalytic converters burning “on-leaded” fuel.     

多酸基深度加氢脱硫催化剂的原位表征和反应性能

采用浸渍法合成了镍盐复合的磷钨酸(HPW)/纳米晶HZSM-5固体酸催化剂,其在催化裂化(FCC)汽油加氢改质反应中显示出了良好地深度加氢脱硫活性。 原位电子自旋共振和原位吡啶吸附红外光谱表征手段的研究结果表明,纳米晶HZSM-5沸石上Ni(Ⅱ)结合3电子还原态的HPW(Ⅲ)是FCC汽油深度加氢脱硫反应的活性中心。 探讨了多酸基催化剂在FCC汽油深度加氢脱硫反应中活性改善的原因。     

Hydrogen Production by Catalytic Reforming of Liquid Hydrocarbons

In this review, we are reporting the catalytic reforming of liquid hydrocarbon fuels carried out in our research group, covering the catalytic reforming of iso-octane and toluene as surrogate of gasoline, gasoline fuel processor system and steam reforming of n-hexadecane and decahydronaphthalene, main constituents of diesel. The commercial ICI reforming catalyst is prone to be poisoned by sulfur contained in iso-octane. We investigated various supported transition metal formulations and developed Ni/Fe/MgO/Al₂O₃ (KIST-5) catalyst with prolonged catalytic stability (>760 h), higher activity and sulfur tolerance ability over commercial ICI and HT catalysts for ATR reaction of iso-octane. We found that the concentration of CO can be reduced to <1,800 ppm by the gasoline fuel processor system charged with KIST-5 reforming catalyst, commercial HTS catalyst and KIST Pt–Ni/CeO₂ LTS catalyst. The addition of Rh metal to spc-Ni/MgAl catalyst as promoter was found to be very effective in inhibiting the deactivation of spc-Ni/MgAl catalyst by sintering of reduced Ni metal at high temperature during steam reforming of n-hexadecane. A 0.3 wt% Rh loading on spc-Ni/MgAl catalyst was optimized to have the best performance for steam reforming of n-hexadecane among the prepared catalysts. The addition of Rh to spc-Ni/MgAl catalyst also restricted the deactivation of the catalyst due to carbon formation at high reaction temperature. In view point of prolonged stability and higher activity, these developed reforming catalysts have a good scope in the reforming process of gasoline and diesel for hydrogen station and fuel processor system applications.     

乙醇/柴油混合燃料的相溶性及对发动机性能影响的研究

利用助溶剂解决乙醇/柴油的相溶性问题，讨论了混合燃料中乙醇和助溶剂添加量对相溶性的影响，并使用助溶剂体积分数为1.5%、乙醇体积分数分别为5%、10%、15%的混合燃料及 20号纯柴油（分别表示为E5、E10、E15和 E0）在发动机台架上进行了性能和排放试验。研究结果表明，柴油的烃组成是决定相分离温度的决定性因素；对全部测试油品，乙醇体积分数在10%、助溶剂添加体积分数为1.5%时，混合燃料相溶性较好。台架试验显示，随着混合燃料中乙醇掺烧比例的增加，发动机的燃油消耗率逐渐增加，而发动机的额定功率和最大扭矩逐渐降低，但最大扭矩降低的幅度较小；此外，随着乙醇掺烧比例的增加，CO比排放量减少，HC、NOx和PM的比排放量逐渐增加，但NOx和PM的比排放量增加幅度不大。10%体积分数的乙醇添加量是乙醇/柴油的最佳掺烧比。