Regulated and Speciated Hydrocarbon Emissions from a Dual Fuel Light Duty Vehicle with and Without a Three-Way Catalyst

The regulated pollutants （CO,HC and NOx） and unregulated pollutants （volatile organic compounds and carbonyl compounds）,emitted from a dual fuel vehicle fueled with gasoline and E10 fuel,are measured under a transient cycle and steady modes.The impacts of a three-way catalyst （TWC） are investigated for the two types of fuels.The measured results show that NOx and acetaldehyde emitted from the E10-fueled car are much more than that from the gasoline-fueled car under the same modes.On the basis of maximum incremental reactivity （MIR） factors and emissions of organic gases,the ozone specific reactivity of the tailpipe gases are evaluated.

Quaternary Oxide of Cerium, Terbium, Praseodymium and Zirconium for Three-Way Catalysts

Oxygen storage-capacity （OSC）, oxygen buffer capacity （OBC）, X-my diffraction and electron diffraction pattern, high resolution electron microscopy were used to study the quaternary oxides, i .e., of Ce, Tb, Pr and Zr. （Ce0.6 Tb0.2Zr0.2O2- δ and Ce0.6Pr0.2Zr0.2O2-δ ）. OSC and OBC data indicate that these oxides have very good oxygen transfer capacity （OTC） and their pseudo-solid solutions exhibit fluorite-type structure. These oxides may act as a good candidate for three-way catalysts （TWC）.

Durability of three-way and close-coupled catalysts for Euro IV regulation

The durability of three-way catalyst （TWC） and corresponding close-coupled catalyst （CCC） for Euro Ⅳ stage regulation was investigated through Vehicle Road Running Mode tests, whereas emissions of regulated pollutants of three car fleet were investigated at every 100,000 km miles. The results showed that HC, NOx, and CO emission values could meet Euro Ⅳ regulation limits at every point. The redox properties of TWC and CCC were measured by CO reduction during each isothermal. It was obvious that both aged TWC and aged CCC behaved a good redox property at 673 and 773 K. Based on XRD and BET measurement results, TWC and CCC washcoat were characterized with good thermal stability.

Influence of Ce_(0.35)Zr_(0.55)Y_(0.10) Solid Solution on Performance of Pt-Rh Three-Way Catalysts

Ce0.35Zr0.55Y0. 10 solid solution was prepared by co-precipitation technique and characterized by specific surface area measurements （BET） and X-ray diffraction （XRD）. Ce0.35Zr0.55Y0.10 was used to prepare low Pt-Rh threeway catalyst （TWC）, and its influence on the performance of TWC was investigated. The results revealed that Ce0.35 Zr0.55Y0.10 had a cubic structure similar to Ce0.50Zr0.50O2 and its specific surface area can maintain higher than Ce0.50 Zr0.50O2 after 1000 ℃ calcination for 5 h. Being hydrothermal aged at 1000 ℃ for 5 h, the catalyst containing Ce0.35 Zr0.55Y0.10 still exhibited higher conversion of C3H8, CO and NO and lower light-off temperature in comparison with Ce0.50Zr0.50O2 TWC.

Influences of (Ce-Zr-La-Pr)O Contents on Three-Way Catalyst Performances

A series of catalysts with (Ce-Zr-La-Pr)O contents range from 0 to 50% in coating and single-palladium loads on substrates were prepared to study effects of (Ce-Zr-La-Pr)O contents on catalytic activities and durability by contrasting the characteristics of light-off, A/F and catalytic conversions of the fresh catalysts with that of the aged catalysts. The results show that (Ce-Zr-La-Pr)O can enhance the catalysts light-off characteristics, widen A/F windows and increase catalytic conversions at a certain extent through optimizing physical structural and chemical property of the mixed coating. However, (Ce-Zr-La-Pr)O contents influence greatly on the catalysts activities and durability, and the catalysts with contents ranging from 10% to 30% exhibited better integrative properties in all samples, and 10% was the optical content to make the catalyst performance highest in this thesis. It is indicated that an suitable content of (Ce-Zr-La-Pr)O plays an important role in assisting catalysis, enhancing durability and increasing oxygen storage capability.

Effect of Sulfur on the Performance of Three-Way Catalysts

Sulfur content is one of the fuel properties to be monitored. Sulfur dioxide, the major product derived from organic sulfur compounds in the exhaust gas emissions, is a poison to the three-way catalysts (TWC). A gas mixture was applied to simulate the exhaust gases used in the TWC aging procedure tests. Two types of the TWC, REX-IIC and REX-IID, were tested in this study. The performance of both TWC's before and after the 100-hour sulfur aging program was compared. It was concluded that the Pt component in the TWC was apt to be poisoned by sulfur much easily than Rh. The performance of the REX-IID catalyst was generally better than that of the REX-IIC catalyst.

电控发动机三元催化转化器(TWC)的检诊维修

汽车尾气排放作为机动车污染的首要来源,已然严重威胁到了人类健康。三元催化转换器作为车辆尾气处理的核心装置,可以有效控制车辆尾气排放,实现预定环保目标。基于电控发动机,本文对三元催化转化器TWC的工作原理以及常见故障做了分析研究,提供了对三元催化转化器TWC使用性能进行综合判断的四种检诊方案,并给出了相应的车辆维修使用策略。

Effect of BaO on Catalytic Activity of Pt-Rh TWC

The effects of BaO doping on the three-way catalytic activity of Pt-Rh catalyst and on water-gas shift were investigated. The results show that the light-off temperatures of hydrocarbon and carbon monoxide and nitrogen oxides of the fresh catalysts slightly differ from those of the aged catalysts, and the catalysts containing CeO2-ZrO2-BaO have lower lightoff temperature and better catalytic activity than these containing BaO and CeO2-ZrO2 after hydrothermal aging for 5 h at 1000 ℃. The catalysts were characterized by means of the temperature-programmed reduction （TPR） in hydrogen and the temperature-programmed desorption （TPD） in oxygen. It is confirmed that the suggested route of CeO2-ZrO2-BaO by coprecipitation can improve the catalytic activity of catalysts.

Effects of CuO-CeO₂Addition on Structure and Catalytic Properties of Three Way Catalysts

The noble metals (Pt, Pd, Rh) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate were investigated as catalytic performance of Three Way Catalysts (TWC) under simulated automotive exhaust feed gas. The structural, morphological features and catalytic activity were observed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and GC-TCD (Varian CP-4900). The catalytic performance of noble metals (Pt, Rh, Pd) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate was be compared with noble metals (Pt, Rh, Pd) supported on Ce-Zr mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate and only γ-Al2O3 washcoat/FeCrAl substrate at various stoichiometric ratio of oxygen. The results showed that the addition of Cu-Ce mixed oxides improved CO oxidation reaction at lower temperature during stable lambda of 1, the highest CO conversion of 99% is observed for the noble metals (Pt, Pd, Rh) support on Cu-Ce with γ-Al2O3 washcoat/FeCrAl substrate. The results also showed that, the addition of Cu-Ce mixed oxides promoted released oxygen, thus it improved strongly CO and C3H8 conversion at lean oxygen stoichiometric operation.

Influences of Platinum Precursors and Solution Acidities on REO-Based Catalysts Performances

Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity.

Recent progress of Rh-based three-way catalysts

Three-way catalysts are widely used to control criterion pollutant emissions fromthe increasing gasoline engines.With the stringent requirements of automotivepollutant emission standards in various countries,Rh has become an irreplaceablecomponent of three-way catalysts due to its superior NOx elimination,high N2selectivity,and simultaneous elimination of CO and hydrocarbons.In this review,we systematically review the recent development of Rh-based three-way catalystsin terms of potential supports and effective active center construction strategies.We further summarize the key role of Rh metal in the three-way catalytic mechanismand reaction kinetics.Finally,we conclude the current challenges and futureopportunities facing Rh-based catalysts.It is believed that based on the deep understandingof Rh-based three-way catalysts,the design of Rh-based catalysts withgood low-temperature catalytic performance and low cost is expected to be realizedin the future.

The structure–activity relationships of Rh/CeO_(2)-ZrO_(2) catalysts based on Rh metal size effect in the three-way catalytic reactions

With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(TWCs).To guide the design of next-generation TWCs,it is essential to further develop our understanding of the relationships between microstructure and catalytic performance.Here,Rh/CeO_(2)–ZrO_(2) catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment.These catalysts included Rh single-atom catalysts,cluster catalysts,and nanoparticle catalysts.The results showed that the Rh nanoparticle catalyst,with an average size of 1.9 nm,exhibited superior three-way catalytic performance compared to the other catalysts.Based on the catalytic activity in a series of simple reaction atmospheres such as CO+O_(2),NO+CO,and hydrocarbons(HCs)+O_(2) and operando infrared spectroscopy,we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.

水热老化对天然气发动机三元催化转化器性能影响的试验研究

利用水热老化试验装置开展了催化剂小样的水热老化试验,分析了催化剂在水热老化前后起燃性能的变化规律,利用X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)、X射线衍射(X-ray diffraction, XRD)、N_2吸脱附与透射电子显微镜(transmission electron microscopy, TEM)等测试方法研究了老化温度和老化气氛(水含量)对催化剂活性、表面化学状态及微观结构的影响。试验结果表明,老化温度对催化剂理化特性的影响较大,随着老化温度的提高,催化剂的氧空位含量减少,储氧能力下降,助剂的粒径变大,比表面积变小,孔径变大,催化剂活性降低;老化气氛中水含量的变化对催化剂理化特性的影响较小,当水含量为10%时,催化剂的活性最高,此时催化剂的储氧能力较高,比表面积最大,表明适宜的水热老化有利于催化剂性能提升。

含铂汽车尾气三效催化剂的研究

研究了不同负载量的含铂三效汽车尾气催化剂的催化活性 ,结果表明铂的负载量对催化剂的起燃温度影响很大 .经 10 5 0℃老化后 ,在高负载量的铂催化剂上 ,丙烷、丙稀和一氧化碳起燃温度 (T50 )分别为 95℃ ,15 5℃和190℃ ;而在低负载量的铂催化剂上 ,对应的值为 180℃ ,2 10℃和 2 6 5℃ .另一方面 ,添加过渡金属可以显著提高铂催化剂对氮氧化物的还原活性 ,在低负载量的铂催化剂上 ,氮氧化物的起燃温度可达 2 5 0℃ ,这将有助于开发研制非铑贵金属汽车催化剂 ,更有效地降低催化剂的成本 。

锆钛复合氧化物的制备及用作Pt三效催化剂载体的性能

用共沉淀法制备了Zr_(0.5)Ti_(0.5)O_2复合氧化物,考察了沉淀时的pH值、温度及焙烧温度对样品织构性能的影响.分别用BET、XRD、NH_3-TPD对样品的织构、结构性能和表面酸性进行了表征.将经过不同温度焙烧后的样品作为载体制备成Pt/Zr_(0.5)Ti_(0.5)O_2催化剂,考察了催化剂对C_3H_8、CO、NO的催化性能,并与传统的以La-Al_2O_3为载体的Pt/La-Al_2O_3汽车尾气三效催化剂进行了比较.结果表明:当沉淀时的pH=11、温度为25℃、焙烧温度为550℃时,所制得的样品具有较好的织构性能(比表面积为195m^2·g^(-1)、孔容为0.28mL·g^(-1))、较强的表面酸性和较宽的酸度分布;用该样品制备的汽车尾气三效催化剂与传统的以La-Al_2O_3作载体的Pt/La-Al_2O_3催化剂相比,具有更好的HC和CO催化性能和优异的NO转化性能.

SO_2对三效催化剂载体的毒化作用研究

根据三效催化剂的工况,分别于400℃和760℃,在不同气氛下对其载体的主要组分γ-Al2O3和CeO2用SO2进行硫化处理,采用红外、XRD、扫描电镜等方法对SO2处理前后的γ-Al2O3和CeO2结构进行表征。结果表明,对于γ-Al2O3而言,在氧化气氛下SO2可与γ-Al2O3反应生成硫酸盐,而还原气氛下则未检测到硫酸盐;与400℃、氧化气氛相比,760℃、氧化气氛下SO2更容易与γ-Al2O3反应生成硫酸盐。SO2与γ-Al2O3反应生成硫酸盐,使γ-Al2O3的比表面积下降,孔结构被破坏。对于CeO2而言,在氧化气氛和还原气氛下SO2均可与CeO2反应生成硫酸盐;氧化气氛下,400℃时SO2比760℃时更容易与CeO2反应生成硫酸盐。CeO2与SO2反应生成硫酸盐后,其催化CO氧化的能力显著下降。

Zr_xTi_xAl_(1-2x)O_2的制备及其在三效催化剂上的应用

Zr0.5Ti0.5O2(ZT) and Zr0.25Ti0.25Al0.5O2(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption,XRD and NH3-TPD. The activity of Pt/Zr0.5Ti0.5O2 and Pt/ Zr0.5Ti0.5Al0.5O2 catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area,larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon,carbon monoxide and nitrogen oxides,especially better conversion for nitrogen oxides (NOx). The addition of Al2O3 into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural,structural,surface acidity and thermal stability.

新一代三效催化剂的关键材料─Ce_xZr_(1-x)O_2固溶体研究进展

汽车尾气排放法规的日趋严格迫切要求开发高性能的三效催化剂。传统三效催化剂中的CeO2 高温下易发生烧结而降低或失去储氧能力。而加入锆所形成的CexZr1 -xO2 固溶体具有良好的抗高温老化性能、低温还原性能和较高的储氧能力 ,可以作为新一代三效催化剂的关键材料。

发动机不同工况下三效催化器的温度场和转化效率试验

在发动机台架上,通过研究在发动机不同工况下催化器内部温度场的分布及由此得到的载体平均温度对转化效率的影响,揭示了催化器的工作机理,并得到如下结论:在催化器工作时,内部由于存在化学反应放热、热质输运等,造成载体内部不同部位存在温差,最大可达82℃;由于决定整个催化进程的因素不同,催化器的转化效率随不同的载体平均温度的变化趋势也显著不同,这些均为催化器的设计及其与发动机的有效匹配提供了试验依据。

HEV电加热能量对三元催化器转化效率、油耗和排放的影响

对混合动力汽车电加热型三元催化器冷起动阶段的催化过程进行了分析,建立了适用于开发整车控制策略的三元催化器动力学模型。在此基础之上,通过对混合动力汽车运行工况的模拟,对影响三元催化器起燃的加热功率和位置等因素进行了研究,分析了电加热能量对电池荷电状态、整车油耗和排放的影响。结果表明,混合动力汽车采用电加热方式不会造成电池过放电,能以微小的燃油消耗为代价,有效加快三元催化器起燃,提高冷起动阶段的HC/CO转化效率。