机动车尾气净化催化剂的研究进展

随着社会经济的快速发展,汽车使用量与日俱增,国家对尾气污染物排放标准的不断提高,机动车尾气净化催化剂也取得了日新月异发展。文章介绍了贵金属催化剂、金属氧化物催化剂、分子筛催化剂、纳米催化剂的研究进展,以及稀土元素在催化剂研究中的重要性。     

国际资讯

正巴斯夫建新装置助力汽车尾气净化巴斯夫工业用贵金属精炼、盐类及溶液生产装置近日在沪落成,这套占地2,200平方米、代表当今最高技术水平的装置将生产车用催化剂配方的重要成分,主要为巴斯夫在上海的机动车排放催化剂生产设施提供支持。车用催化剂是目前最重要的汽车、卡车和巴士尾气净化解决方案。巴斯夫(包括在日本和韩国的合资公司)是亚洲机动车排放催化剂市场的领军企业,也是全球机动车排放催化剂的领军生产商。未来几年内,巴斯夫将进一步扩大在中国的贵金属生产,包括从废弃的车用催化     

催化剂制备工艺对机动车尾气净化效果的影响

制备了以贱金属氧化物,稀土及少量贵金属Pd为活性组分,以蜂窝陶瓷为载体的机动车尾气净化催化剂。研究了其制备工艺及活性组分的负载量对机动车尾气净化效果的影响。     

机动车尾气净化催化剂的研究与展望

随着经济的快速发展,机动车尾气污染已成为空气污染的重要来源,概述了机动车尾气净化催化剂的研究现状并对其未来发展进行了展望。     

巴斯夫在沪建新装置助力汽车尾气净化

巴斯夫工业用贵金属精炼、盐类及溶液生产装置最近在沪落成,这套占地2200m2、代表当今最高技术水平的装置将生产车用催化剂配方的重要成分,主要为巴斯夫在上海的机动车排放催化剂生产设施提供支持。车用催化剂是目前最重要的汽车、卡车和巴士尾气净化解决方案。     

巴斯夫建新装置助力汽车尾气净化

巴斯夫工业用贵金属精炼、盐类及溶液生产装置近日在沪落成,这套占地2,200平方米、代表当今最高技术水平的装置将生产车用催化剂配方的重要成分,主要为巴斯夫在上海的机动车排放催化剂生产设施提供支持。车用催化剂是目前最重要的汽车、卡车和巴士尾气净化解决方案。     

柴油车尾气中烃类物质净化研究进展

随着全球机动车柴油化的发展,柴油车尾气有效可控排放提上日程。柴油车尾气中的碳氢化合物是柴油车在贫燃烧条件下工作时产生的未完全燃烧的碳氢物质。这些烃类物质对健康和环境有害,导致大气污染、臭氧形成和粉尘生成。本文介绍了通过油质改进、机内装置性能优化技术来减少尾气的排放,但这种技术成本昂贵、改善能力有限,所以必须与机外净化后处理技术相结合。现阶段柴油车尾气主流后处理装置有柴油车颗粒过滤器和氧化性催化转换器,它们虽一定程度上减缓了尾气的排放,但过滤筒易堵塞,柴油车排气温度更低,催化剂在温度低的环境下能力不足,因此引进了低温等离子体协同催化净化技术来处理柴油车尾气中的HC。     

控制形貌可提高催化剂性能

中科院大连化学物理研究所通过控制金属氧化物纳米粒子尺寸和形貌,首次实现了金属氧化物催化一氧化碳低温氧化的高活性和高稳定性,该成果将在降低机动车尾气排放和空气净化环保应用等方面发挥作用。科研人员将该催化剂用于汽车尾气净化过程。一氧化碳是汽车冷启动阶段排放尾气中的主要污染物之一,低温催化氧化一氧化碳是目前消除它的有效方法。传统催化剂虽然能够在低温下有效消除一氧化碳,但是在常温下活性不高,而且在微量水汽存在下快速失活。贵金属催化剂使用温度则需要在100℃以上。     

三效基催化剂GYM工艺实现产业化

天津化工研究设计院承担的机动车尾气净化催化剂中试技术开发及总成产品研制取得重要成果。该院开发的具有自主知识产权的三效基催化剂GYM制备技术、三效催化剂用稀土储氧材料技术已完成中试和产业化建设，汽车、摩托车尾气净化催化剂制备及稀土储氧材料的发明等3项成果已申报国家发明专利。     

机动车尾气对环境的影响及其污染控制

介绍了机动车尾气排放对空气的污染以及对人体的危害,分析了我国机动车尾气排放的现状,提出了从加强技术攻关、完善管理体制、机动车总量控制、利用经济调控手段等角度控制机动车尾气排放建设绿色交通的措施和建议。     

Adsorption characteristics of HCA(Hydrocarbon Adsorber) catalysts for hydrocarbon and NOx, removals under cold-start engine conditions

To meet the SULEV (Super Ultra Low Emission Vehicle) regulations, we have focused on the utilization of HCA (Hydrocarbon Adsorber) in order to adsorb the excess hydrocarbons emitted during a period of engine cold-start. As main recipes of HCA materials, many types of zeolite as well as a combination of alumina and precious metals were used. Representative physico-chemical factors of zeolite such as acidic and hydrophobic properties have been characterized and tried to find the optimum recipe of HCA materials. Among the acid properties of zeolites, the Si/ Al ratio has been found to be the most important factor to achieve higher hydrocarbon adsorption capacity.     

Cerium–terbium mixed oxides as alternative components for three-way catalysts: a comparative study of Pt/CeTbOx and Pt/CeO2 model systems

By using a combination of oxygen buffering capacity (OBC) and oxygen storage capacity (OSC) measurements, the redox behaviour of a Pt/CeTbO_x catalyst is compared to that of a classic model TWC system: Pt/CeO₂. The results reported here show that the redox efficiency of the Pt/CeTbO_x catalyst is much better, especially at low temperature operation conditions such as those occurring during the cold start of engines. The catalyst containing terbium also shows lower ‘light-off’ temperatures for both methane and carbon monoxide oxidation.     

Recent advances in automobile exhaust catalysts

Catalysts, which were recently developed by Toyota for the control of automobile exhaust, are reviewed. (1) For use in low emission vehicles, a CeO₂-ZrO₂ solid solution (CZ) with both high oxygen storage capacity and high heat resistance was developed as a support for a high performance three-way catalyst (TWC). (2) A novel three-way catalyst named the NO_x storage-reduction catalyst (NSR) was developed for automotive lean-burn engines. The NSR catalyst can store NO_x in an oxidizing atmosphere and then reduce stored NO_x at stoichiometric or reducing conditions. Also, it has high tolerance to sulfur poisoning which is the most stringent problem for the NSR catalyst.     

Why Rhodium in Automotive Three-Way Catalysts?

The catalytic treatment of motor vehicle exhaust gas has been a feature of all passenger cars in the USA since the 1975 model year. It has since been adopted in all the developed countries as the principal means of con-trolling the emissions from vehicles powered by Otto-cycle internal com-bustion engines. These include passenger cars, light trucks, and heavy-duty trucks. Catalysts have been developed for motorcycles and even smaller power plants. The so-called three-way catalyst (TWC) has been in use since the 1979 model year. The name reflects the simultaneous treatment by this catalyst of the two reducing pollutants, carbon monoxide and uncombusted hydrocarbons, and the oxidizing pollutant, oxides of nitrogen.     

低含氯量高溴环氧树脂的制备

将四澳双酚地环氧氯丙烷依次投入附有冷凝装置的三日烧瓶，使溶解。55～80℃加碱（一），反应四小时。加入适量溶剂，投入催化剂，加碱（二），加毕反应l～2小时，然后进行水洗脱本等后处理最后得成品。产品有机氯含量可降低到0．00022当量／100克，而且由于闭环反应完全，环氧值也略有提高（＞0．254当量／100克）。在较温和的条件下，加入低浓度的碱，很少有副反应产生，后处理也很容易进行。采用添加催化剂进行二次加碱以降低有机氯含量的方法是提高高澳环氧树脂品质的行之有效的方法。这种方法的优点在于成本低、工艺简单、效率高，产品…     

Why Rhodium in Automotive Three-Way Catalysts?

The catalytic treatment of motor vehicle exhaust gas has been a feature of all passenger cars in the USA since the 1975 model year. It has since been adopted in all the developed countries as the principal means of con-trolling the emissions from vehicles powered by Otto-cycle internal com-bustion engines. These include passenger cars, light trucks, and heavy-duty trucks. Catalysts have been developed for motorcycles and even smaller power plants. The so-called three-way catalyst (TWC) has been in use since the 1979 model year. The name reflects the simultaneous treatment by this catalyst of the two reducing pollutants, carbon monoxide and uncombusted hydrocarbons, and the oxidizing pollutant, oxides of nitrogen.     

The effect of Fe on the catalytic behavior of model Pd-Rh/CeO2-Al2O3 three-way catalyst

The present work attempts to address the issue whether iron (Fe) which is accumulated on the surface of “three-way” catalysts (TWCs) used in gasoline-driven cars is a true chemical poison of their catalytic activity. This important issue from a scientific and technological point of view is addressed via catalytic activity, temperature-programmed surface reaction (TPSR), and X-ray photoelectron spectroscopy (XPS) measurements over a model TWC (1 wt% Pd–Rh/20 wt% CeO₂–Al₂O₃). It was found that deposition of Fe up to the level of 0.4 wt% (an average concentration found in aged commercial TWCs) on the model TWC does not deteriorate its activity towards CO and C₃H₆ oxidation, and reduction of NO by H₂. Instead it was found that iron improves significantly the T₅₀ parameter in the activity versus temperature profile. Small Fe clusters in contact with the noble metal (Pd and Rh) particles due to the lower work function of Fe compared to Pd and Rh act likely as a source of electron flow towards the noble metals (as evidenced by XPS measurements), thus altering their surface work function and adsorption energetics of reaction intermediates. The latter have increased significantly the activity of the model TWC towards oxidation of CO and propylene, and to a lesser extent the activity towards the reduction of NO by H₂. The presence of Fe on the surface of the model TWC provided and/or created also new active catalytic sites for the reactions investigated. According to previous work from this laboratory, iron up to the level of 0.4 wt% was shown not to deteriorate the oxygen storage capacity (OSC) of the same model TWC used in the present work. Thus, it could be concluded that Fe when deposited on a commercial TWC at least up to the level of 0.4 wt% acts likely as a promoter than a poison of its catalytic activity.     

汽车尾气净化三效催化剂研究进展

三效催化剂是汽车尾气净化最主要的方法,目前已发展到第四代。开发金属合金载体,以及新型单钯催化剂、过渡金属型或稀土钙钛矿型催化剂是今后三效催化剂研究的热点。     

Effect of basic metal additives on NOx reduction property of Pd-based three-way catalyst

The three-way catalytic (TWC) performance, especially CO and NO_x conversion, of a Pd-only catalyst was improved by the addition of basic elements, and the activity increased as the electronegativity of the additive cations decreased (Ba>Sr>La), indicating that the basicity or electron-donating ability of the additives played a significant role in the improvement of the TWC performance. Thermal decomposition temperature of PdO in promoted catalysts became higher with decreasing the ionic electronegativity of the promoters. XPS analysis proved that the electron density around Pd^(II) in the Ba-promoted catalyst was higher than that of Pd-only catalyst. The improvement of the TWC performance by the addition of basic promoters is discussed in terms of the stabilization of PdO, which may suppress the sintering, as well as of electron enrichment, which endows palladium with the Rh-like catalytic behavior.     

Dynamics of oxygen storage and release on commercial aged Pd-Rh three-way catalysts and their characterization by transient experiments

The present work has provided new fundamental information on the effects of aging (mileage, km) of a commercial Pd-Rh (9:1, w/w) three-way catalyst (TWC) on (a) the H₂ chemisorption, (b) the redox properties of washcoat material, and (c) the dynamic oxygen storage and release properties of TWC. Hydrogen chemisorption in the 25–400 °C range was found to decrease with increasing aging of TWC. On the other hand, H₂ chemisorption performed at 200 and 400 °C resulted in a significantly larger amount of chemisorbed hydrogen (exceeding the monolayer value based on the noble metals) compared to that obtained after chemisorption at 25 °C. This is due to the onset of a hydrogen spill over process in the 200–400 °C range. The features of H₂-TPD spectra were found to strongly depend on the aging of TWC. Hydrogen chemisorption at 25 °C followed by TPD after a given pre-treatment of the catalyst surface might be considered as a procedure for a good estimate of the metal dispersion of a commercial Pd-Rh TWC. The redox properties of the oxygen storage components of the washcoat of a commercial Pd-Rh TWC were found to drastically change with increasing aging of TWC. It was found that the oxygen storage capacity (OSC) of the TWC investigated decreases significantly with catalyst aging in the 0–56,000 km range and in the temperature range of 500–750 °C. In the case of fresh TWC, the presence of 20 ppm SO₂ or 10% CO₂ in a 1.5% O₂/He gas mixture used for oxygen storage (oxidizing gas) was found to result in a large decrease in the amount of dynamic OSC measured by alternating switches between oxidizing and reducing feed gas compositions. The shift in time of the peak maximum of the transient response of CO₂ obtained during the switch O₂/He → He → CO/He (t) can be ascribed to the alteration of the kinetics of the oxygen back-spillover process and not to the kinetics of CO oxidation on the metal surface.