Particle analysis of car exhaust by ETV-ICP-MS

Particulates of platinum group elements (Pt, Rh, Pd, Ir) emitted in automotive catalyst exhaust were measured down to the pg/m³ level. Samples were taken from a standard type three-way catalyst equipped gasoline engine, running on a computer controlled dynamometer. Particulates in catalyzed car exhaust were sampled fractionated according to size by using the cascade impactor with separate targets mounted underneath each nozzle. The targets, small flat discs made of pure graphite, were subsequently analyzed by ETV-ICP-MS without any preparatory steps.     

What News in the Surface Chemistry of Bulk and Supported Vanadia Based SCR‐Catalysts: Improvements in their Resistance to Poisoning and Thermal Sintering

This paper reports a short review on the impact of poisoning effects and thermal aging on the reactivity of surface vanadate species on benchmark V₂O₅?WO₃/TiO₂ Selective‐Catalytic‐Reduction catalysts. A renewed interest of this SCR technology is related to its diversification notably as after‐treatment systems to treat the exhaust from Diesel engines with higher running temperature especially when SCR catalysts are coated on Diesel Particulates Filters. Particular attention is also paid to poisoning effects in conjunction with the progressive replacement of fossil fuels by bio‐fuels containing alkaline contaminants which drastically deactivate the catalyst through neutralization of strong acid sites. Most of the investigations show that better insight into the mechanisms of poisoning and aging processes is needed especially to understand the relative sensibility of various vanadate species. This could provide original guidelines to catalyst preparation and or the developments of more stable bulk systems as exemplified.     

Low‐Temperature CO Oxidation over a Ternary Oxide Catalyst with High Resistance to Hydrocarbon Inhibition

Platinum group metal (PGM) catalysts are the current standard for control of pollutants in automotive exhaust streams. Aside from their high cost, PGM catalysts struggle with CO oxidation at low temperatures (<200 °C) due to inhibition by hydrocarbons in exhaust streams. Here we present a ternary mixed oxide catalyst composed of copper oxide, cobalt oxide, and ceria (dubbed CCC) that outperforms synthesized and commercial PGM catalysts for CO oxidation in simulated exhaust streams while showing no signs of inhibition by propene. Diffuse reflectance IR (DRIFTS) and light‐off data both indicate low interaction between propene and the CO oxidation active site on this catalyst, and a separation of adsorption sites is proposed as the cause of this inhibition resistance. This catalyst shows great potential as a low‐cost component for low temperature exhaust streams that are expected to be a characteristic of future automotive systems.     

Recent advances in automobile exhaust catalyst

Catalysts that were recently developed by Toyota for the control of automobile exhaust are reviewed. (1) A system combining a close-coupled catalyst with high heat resistance and an under-floor catalyst with high oxygen storage capacity were developed for low emission vehicles. (2) Based on a new concept, a three-way catalyst having the ability to store NOx at oxidizing atmosphere and to reduce stored NOx at stoichiometric or reducing atmosphere was developed for automotive lean burn engines. (3) A thin wall ceramic substrate was developed for better catalyst performance.     

载体焙烧温度对稀燃天然气汽车尾气净化Pd/Zr0.5Al0.5O1.75催化剂性能的影响

以不同温度焙烧得到的Zr0.5Al0.5O1.75复合氧化物为载体,制备了系列1.5%Pd/Zr0.5Al0.5O1.75催化剂样品.采用N2吸附-脱附、X射线衍射、H2程序升温还原、O2程序升温脱附及CO化学吸附等手段对催化剂进行了表征,并测试了催化剂在模拟稀燃天然气汽车尾气中的活性和抗H2O中毒性能.结果表明,载体...     

Controlling carbon monoxide emissions from automobile vehicle exhaust using copper oxide catalysts in a catalytic converter

Carbon monoxide (CO) is a very poisonous gas present in the atmosphere. It has significant effects on human beings, animals, plants and the climate. Automobile vehicle exhaust contributes 64% of the CO pollution in urban areas. To control this exhaust pollution, various types of catalysts in catalytic converters have been investigated. Increasing costs of noble metals as a catalyst in automobile vehicles motivates the investigation of material that can be substituted for noble metals. Among the non-noble metals, copper (Cu) is found to be the most capable and highly active catalyst for CO oxidation, compared to precious metal catalysts. Lower cost, easy availability and advance preparation conditions with stabilizers, promoters and so on, make Cu a good choice as an auto exhaust purification catalyst. The oxidation of CO proceeds very quickly over Cu°, followed by Cu⁺ and Cu²⁺. The Cu₂O catalyst is more active in an O₂-rich atmosphere than in O₂-lean conditions. The reduced species of copper (Cu⁰, Cu⁺) are essential for better CO oxidation but smaller Cu particles could be less active than the higher ones. There is a great deal of research available on the Cu catalyst for CO oxidation, but there is a gap in the literature for a review article individually applied to the Cu catalyst for CO oxidation. To fill this gap, the present review updates information on Cu catalysts in the purification of exhaust gases.     

催化氧化处理工业废气中高浓度甲醛

制备了用于温和条件下催化氧化去除工业废气中高浓度甲醛(HCHO)的1%Pt-4%CeO₂/AC催化剂. 将高浓度甲醛的催化氧化过程与双甘膦氧化制备草甘膦的反应过程集成在一起,使草甘膦合成过程中产生和排放出来的甲醛(100-300 mg/m³)在通过催化剂床层时被完全除去. 系统研究了温度、空速和甲醛含量对甲醛去除率的影响. 在气体空速(GHSV)低于20000 h^-1时废气中几乎所有的甲醛都被氧化,处理后的废气中的甲醛含量低于0.1 mg/m³,甲醛的转化率为99.1%-100%. 当GHSV为30000- h^-1,催化剂床层温度为12℃时,生产废气通过催化剂床层后的甲醛含量小于1.5 mg/m³,甲醛的转化率为97.56%-99.99%. 1%Pt-4%CeO₂/AC催化剂的中试试验结果表明,处理后最终尾气中甲醛含量小于10 mg/m³,有效地防止了甲醛对人们健康的危害,具有良好的产业化前景.     

Internal energy deposition and ion fragmentation in atmospheric-pressure mid-infrared laser ablation electrospray ionization

Mid-infrared laser ablation of water-rich targets at the maximum of the 2.94 μm absorption band is a two-step process initiated by phase explosion followed by recoil pressure induced material ejection. Particulates and/or droplets ejected by this high temperature high pressure process can be ionized for mass spectrometry by charged droplets from an electrospray. In order to gauge the internal energy introduced in this laser ablation electrospray ionization (LAESI?) process, we apply the survival yield method and compare the results with electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). The results indicate that LAESI yields ions with internal energies indistinguishable from those produced by ESI. This finding is consistent with the recoil pressure induced ejection of low micrometre droplets that does not significantly change the internal energy of solute molecules.     

整体式Pd/La_2O_3-Al_2O_3和Pd/CeO_2-ZrO_2-Y_2O_3催化剂上汽油车尾气净化性能的比较

采用共沉淀法制备了耐高温高比表面积的La2O3-Al2O3(LA)材料和CeO2-ZrO2-Y2O3(CZY)储氧材料,并用浸渍法制备了整体式Pd/LA和Pd/CZY汽油车尾气净化三效催化剂,考察了它们的三效催化性能和空燃比性能,并单独通过水煤气变换和CO氧化反应性能的考察,探讨了两种催化剂空燃比窗口扩大的原因.结果表明,Pd/CZY催化剂三效窗口明显较宽,且催化氧化CO的性能明显更优;对于CO+NO反应,Pd/CZY催化剂的活性较高.当反应中逐步通入O2后,抑制了该反应的进行,但CO氧化的转化率升高,而NO转化率降低,直至CO+NO反应完全被抑制,表明CO氧化反应对于抑制催化剂在NO贫燃方向的窗口具有一定的作用.另外,Pd/CZY催化剂上对于水煤气变换反应性能明显优于Pd/LA催化剂,在一定温度下逐步通入O2后,不会抑制水煤气变换反应的发生;当逐步通入NO时,可以促进水煤气变换反应的进行,表明Pd/CZY催化剂在富燃时对扩展CO转化窗口的性能明显优于Pd/LA催化剂.     

燃油种类对汽车尾气净化催化剂性能的影响

 分别对燃用普通汽油和10%乙醇/汽油(E10)混合燃料的CG125型摩托车进行了 10000 km路试,比较了不同种类燃油的排放特性,并采用X射线光电子能谱,扫描电镜和电子探针考察了催化剂的积炭物种与积炭分布. 结果表明,安装催化转化器后,燃用这两种燃料的摩托车尾气排放均能达到欧盟第二阶段排放标准,但催化转化器对E10尾气的净化效果明显低于普通汽油. 燃用这两种燃料的摩托车尾气净化催化剂表面均存在积炭,径向不同部位积炭量顺序为中心层＞过渡层＞边缘层. 燃用普通汽油时,催化剂表面积炭的碳物种主要是CHx,而燃用E10时的碳物种是(CH)xO. 这说明要合理地设计催化转化器才能使尾气均匀地径向分布,而且必须针对燃油种类匹配适宜的催化剂.     

Effect of cobalt oxide on performance of Pd catalysts for lean-burn natural gas vehicles in the presence and absence of water vapor

Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N_2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spec-troscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust gas from lean-burn natural gas vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al_2O_3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl_2O_4 and Co_3O_4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl_2O_4/Co_3O_4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co_3O_4 played an important role in improving water-resistant performance.     

净化汽车尾气非贵金属催化剂的研究

运用 X-射线衍射分析、DTA 和 DSC 考察了非贵金属催化剂(C-50)的比表面、孔容、制备温度、空速、吸附氧(TPD)等与催化剂表面结构、制备时的固相反应之间的关系.经102.5h 寿命试验,证明 C-50的孔结构稳定,有一定的抗中毒能力。     

Current developments in CO2 hydrogenation towards methanol: A review related to industrial application

Regarding the still increasing CO₂ emissions and the accompanied imminent climate change, utilization of CO₂-containing exhaust gases is one of the major opportunities to lower CO₂ emissions while obtaining valuable products in parallel. Methanol as one of today's key platform chemicals can be industrially produced from these exhaust gases by heterogeneously catalyzed CO₂ hydrogenation. This review elaborates why the Cu/ZnO/Al₂O₃ catalyst is still the most promising candidate to catalyze CO₂ hydrogenation from exhaust gases to reduce CO₂ emissions in the short term. It emphasizes catalyst lifetime and deactivation as well as catalyst poisoning, which are significant factors considering the use of impurity-containing exhaust gases. Besides modifications of the Cu/ZnO system, completely different catalysts are discussed regarding their usability and comparability to the conventional Cu/ZnO/Al₂O₃ catalyst.     

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.     

WO3/CeO2-ZrO2, a promising catalyst for selective catalytic reduction (SCR) of NOx with NH3 in diesel exhaust

A WO3/CeO2-ZrO2 catalyst system was discovered for selective catalytic reduction of NOx with NH3; the catalyst (10 wt% WO3 loading) showed nearly 100% NOx conversion in a temperature range of 200-500 degrees C, at a space velocity of 90 000 h(-1) in a simulated diesel exhaust containing 550 ppm NOx (NO : NO2 feed ratio at 1.0), 10 vol% H2O and 10 vol% CO2; the catalyst also exhibited high temperature stability.     

一种具有低SO2氧化活性并满足欧V排放标准的柴油车氧化型催化剂

制备了具有高性能的稀土储氧材料Ce_0.75Zr_0.25O₂-Al₂O₃,Ti_0.9Zr_0.1O₂复合材料和Cr改性的β分子筛(Cr-β分子筛),并以此制备了单Pt型柴油车尾气净化氧化型催化剂.低温N₂吸附-脱附、储氧量测试结果表明,Ce_0.75Zr_0.25O₂-Al₂O₃样品具有较大的比表面积和优异的储氧性能,Ti_0.9Zr_0.1O₂复合材料也具有优越的织构性能.催化剂对HC和CO具有较高的催化活性,可使SOF在140℃开始转化,且具有较低的SO₂氧化活性.在YC4F国Ⅳ柴油机的测试结果表明,经该催化剂处理后的尾气排放能够满足欧Ⅴ排放标准对HC和CO排放要求.     

(CeO_2-ZrO_2-Al_2O_3)-(La_2O_3-Al_2O_3)复合氧化物负载的Pd密偶催化剂:载体焙烧温度的影响

采用同时共沉淀法制备了(CeO2-ZrO2-Al2O3)-(La2O3-Al2O3)新型复合氧化物(CZA-LA),考察了焙烧温度对CZA-LA负载的Pd密偶催化剂的影响,并采用N2吸附-脱附法和X射线衍射对其进行了表征.结果表明,随着焙烧温度的升高,尽管CZA-LA样品的比表面积降低,但即使在1000°C焙烧5h后,其比表面积仍能保持在122m2/g左右;另外,CZA-LA样品的孔体积降低幅度不大,当在700℃及更高温度下焙烧后基本上保持稳定.以不同温度焙烧5h后的样品为载体,采用等体积浸渍法制备了一系列整体式Pd/CZA-LA密偶催化剂(Pd含量2.0g/L).催化剂对消除模拟汽油车尾气中C3H8活性测试结果表明,各新鲜催化剂的活性相差不大,均具有较低的起燃温度T50和完全转化温度T90.当催化剂经老化处理后,以1000°C焙烧的载体负载的Pd催化剂活性最高,T50和T90分别为310和341℃,ΔT仅为31℃,仅比新鲜催化剂的高7℃.可见,该催化剂表现出优异的催化活性和抗老化性能,可以满足欧Ⅳ及更高标准的用于汽油车尾气净化的密偶催化剂的性能要求.     

Sensitivity improvement of ammonia determination based on flow-injection indophenol spectrophotometry with manganese(II) ion as a catalyst and analysis of exhaust gas of thermal power plant.

The sensitivity improvement of a flow-injection spectrophotometric method for the determination of ammonia was examined based on an indophenol blue coloration reaction with salicylate and hypochlorite in the presence of manganese(II) as a reaction promotion catalyst. The optimal conditions for achieving higher sensitivity of ammonia determination were examined using a three-line flow system. The limit of detection corresponding to a signal-to-noise ratio (S/N) of 3 was 0.005 mg l(-1) (approximately equal to 5 ppb) of NH4+. A calibration graph was linear in the range from 5 ppb to 1,000 ppb of ammonium ion. The relative standard deviations (n = 9) for 50 ppb and 100 ppb of ammonium ion were 6.4% and 2.2%, respectively. The proposed method was applied to the determination of ammonia in the exhaust gas of a thermal power plant. Prior to the FIA determination, ammonia in the exhaust gas was absorbed into a boric acid solution; the absorption solution was then analyzed by the proposed FIA.     

Supercritical fluid clean-up of environmental samples for the analysis of polycyclic aromatic hydrocarbons using time-of-flight secondary ion mass spectrometry.

A novel sample-pretreatment method for time-of-flight secondary ion mass spectrometry (TOF-SIMS) was developed using supercritical fluid extraction (SFE). In SFE, the extraction efficiency of a certain organic matter is controlled by the pressure and temperature of supercritical CO2. Two-step SFE (1st step at 10 Mpa, 40 degrees C; 2nd step at 30 MPa, 120 degrees C) was applied to diesel exhaust particles containing many kinds of n-alkanes and aromatic species. n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) were extracted in the 1st and 2nd steps, respectively. This selectivity was utilized for the sample preparation of TOF-SIMS analysis. Diesel exhaust particles after the 1st step of extraction were analyzed with TOF-SIMS, aiming at PAHs as analytical targets. The obtained spectrum was simplified, and mass peaks of individual PAHs were easily assigned, because unwanted compounds, like n-alkanes, were selectively removed by SFE. Furthermore, a simple calculation elucidated the outline of the spectrum.     

Synthesis of a Copper-Containing Catalyst for Electrocatalytic Oxidation of Volatile Organic Compounds

The synthesis of a copper-containing catalyst for electrocatalytic oxidation of acetone in exhaust gases was studied. Data on the electrocatalytic oxidation of acetone were analyzed in relation to the CuO content.