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排序方式: 共有60条查询结果,搜索用时 31 毫秒
1.
Granados M. López Galisteo F. Cabello Lambrou P. S. Alifanti M. Mariscal R. Gurbani A. Sanz J. Sobrados I. Efstathiou A. M. Fierro J. L. G. 《Topics in Catalysis》2007,42(1-4):443-447
The chemical nature of P-containing species of varying concentration present in CeO2 after impregnation with (NH4)2HPO4 and calcination at 1273 K, and their effects on the oxygen storage and release (OSR) properties of ceria are reported for
the first time. The samples were characterized by different techniques and the results were compared with those recently reported
on the same samples but calcined at 873 K. When P-containing ceria solids were calcined at 1273 K, CePO4 (monazite) was the predominant P-containing species on the surface of ceria, confirming previous studies that showed that
monazite exists for those samples in which the surface P loading (P atoms per nm−2) is larger than 5.5. For lower surface P concentrations, isolated orthophosphate units are present at the surface and within
the subsurface region of the solid. Severe sintering of CeO2 after calcination at 1273 K resulted in P concentrations >5.5 P atoms·nm−2 in all samples. Isolated PO4 units that could initially be present in the samples calcined at 873 K nucleated and CePO4 was formed when samples were calcined at 1273 K. OSR properties of CeO2 deteriorated progressively when P loading increased due to the presence of larger crystals of the very stable Ce(III) phase
of CePO4 at the surface of the P-containing ceria solids. 相似文献
2.
Mejía-Centeno Isidro Martínez-Hernández Angel Fuentes Gustavo A. 《Topics in Catalysis》2007,42(1-4):381-385
The use of low-sulfur fuel is known to improve the performance of the three-way catalytic converter (TWC). However, in this
work we report how low-sulfur operation of commercial TWC also favors formation of N2O and NH3 as by products. We found that low-sulfur rich operation above 300 °C increases the production of NH3, inhibiting the formation of N2O characteristic of high-sulfur operation. During lean operation, the production of N2O near the stoichiometric point is not significantly affected by the sulfur level. The large production of N2O observed during light-off is not affected by SO2 when the operation is lean, but under rich conditions N2O is produced up to 575 °C. The increased production of NH3 and N2O in TWC as a result of the introduction of low-sulfur gasoline is an area that requires further analysis because of its implication
upon public health in large urban settings. 相似文献
3.
作者在汽车的机外排放控制装置———三元催化器的失效原理的基础上 ,提出了汽车三元催化器故障诊断系统。该方案主要是检测发动机排气的参数和催化器的转化效率 ,通过这些特征参数诊断催化器故障。同时 ,对本系统采集的数据进行了分析 ,证实了该方法的可行性 相似文献
4.
随着三元催化器在乘用车上的广泛使用,三元催化器引起的车辆后处理系统故障并不鲜见。本文通过与整车厂合作,批量分析了售后市场返回的135件三元催化器故障件,对故障类型进行分类后,有针对性的对部分故障零件进行了实验室分析。证明了三元催化器的损坏主要来自催化器封装缺陷、中毒和高温失火。其中催化器中毒和高温失火烧熔在前级催化剂较容易发生,而后级催化器的损坏大多来自封装缺陷造成的机械损坏。 相似文献
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7.
采用溶胶-凝胶法制备一系列CexZr1-xO2(x=0~1)复合氧化物,并以该复合氧化物为载体制备负载贵金属的PdO/CexZr1-xO2(x=0~1)催化剂,选择NO-CO反应和CO以及CH4氧化反应为模型反应对催化剂的三效催化性能进行评价,并通过XRD、H2-TPR等手段对载体和催化剂进行初步表征。结果表明:Ce/Zr比对CexZr1-xO2载体及负载PdO催化剂三效催化性能均存在重要影响,不同Ce/Zr比的CexZr1-xO2复合氧化物载体具有不同的晶相结构及还原性能,由其负载的PdO催化剂的三效催化性能也各不相同。同时,催化剂的NO还原活性与CO氧化活性与α还原峰存在一定的对应关系。 相似文献
8.
Juan R. Gonzlez-Velasco Miguel A. Gutirrez-Ortiz Jean-Louis Marc M. Pilar Gonzlez-Marcos Gilbert Blanchard 《Applied catalysis. B, Environmental》2001,33(4):452-314
A number of experiments were carried out with fresh and aged high surface area Ce0.68Zr0.32O2 mixed oxide samples with complex feed-streams in order to determine their performance as three way catalyst (TWC). The results confirmed the oxygen storage capacity (OSC) of these samples, which favour NO conversion in cycled versus stationary stoichiometric operation. Several experiments carried out with different feed-streams have shown that a pre-reducing treatment can significantly improve both NO reduction at low-temperature and selectivity to N2, which can be very useful to reduce the emission of nitrogen oxides immediately after starting the automobile. Although a significant reduction of the specific surface area of the mixed oxide takes place during ageing at 1173 K, it has been shown that the performance of the sample remains similar or even better than when fresh, due to an increased OSC. Thus, the reduction of CO and hydrocarbon emissions during start could be achieved by situating the catalytic converter nearer the exhaust to the engine, where the catalyst will be heated faster. 相似文献
9.
Juan R. Gonz lez-Velasco Juan A. Botas Raquel Ferret M. Pilar Gonz lez-Marcos Jean-Louis Marc Miguel A. Guti rrez-Ortiz 《Catalysis Today》2000,59(3-4):395-402
Mono- and multi-metallic (bi- and tri-) Pt, Pd and Rh supported on cerium-promoted alumina (La Roche, SAS-1/16) catalysts were tested for activity as TWC, both fresh [G.C. Koltsakis, and A.M. Stamatelos, Progr. Energy Combust. Sci. 23 (1997) 1] and after accelerated aging. Aging consisted of a treatment at 900°C for 5 h during which an oxidizing (2.5% O2, 10% H2O, in N2) and a reducing (5.0% CO, 10% H2O, in N2) feedstream were cycled at 0.017 Hz through the catalyst. Activity tests were carried out by increasing temperature from 100 to 600°C at 3°C min−1, while two oxidizing and reducing (±0.5 A/F) feedstreams were alternately (1 Hz) fed through the reactor at 125 000 h−1 (STP). Conversion was continuously analyzed. Light-off temperature, T50, conversion at 500°C (normal running temperature), X500, and the stoichiometric window (A/F from 14.13 to 15.13) for stationary feedstreams, were determined. 相似文献
10.
Oxygen storage capacity (OSC) of TW catalysts has a strong impact on their performances under oscillatory conditions. This paper reviews the different methods developed for OSC measurements, the effects of catalyst composition on OSC as well as the impact of OSC on TW catalysis, concentrating on the results obtained in our laboratory. Use of OSC measurements for catalysts control (on-board diagnostic) is also examined. The role of superoxide species as intermediates in the oxygen storage process will be emphasized. Finally, we shall review the recent developments on CeZr-based oxides. 相似文献