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Auto exhaust catalysts

Figure 4.10. SIMS spectra obtained from a fresh auto-exhaust catalyst. (Courtesy Vickerman et al. 2000.)... Figure 4.10. SIMS spectra obtained from a fresh auto-exhaust catalyst. (Courtesy Vickerman et al. 2000.)...
Figure 4.11. Cesium ion initiated static SIMS spectra of platinum species on fresh auto-exhaust catalyst. Figure 4.11. Cesium ion initiated static SIMS spectra of platinum species on fresh auto-exhaust catalyst.
The object was an auto exhaust catalyst, a monolith cylinder 25 mm in length and 38 mm in diameter. The outside wall was broken away so that one of the 1 ram-wide channels became accessible to the IR and probe laser beams, and a portion of one channel was studied in the manner shown schematically in the insert of Fig. 8. The sample was examined in air, because a cell large enough to contain the monolith was not available. The spectrum shows the features of cordierite [20], the material from which honeycomb monoliths are usually made, a broad absorption in... [Pg.410]

This completely automated spectrum analysis procedure represents the final element in our effort to reduce to routine practice the quantitative analysis of similarly constituted gaseous samples by FTIR. It has seen wide and successful application within our laboratory, having been the principle analytic method for two extensive hydrocarbon species-specific auto exhaust catalyst efficiency studies, a comprehensive study of the gases emitted by passive-restraint air bag inflators, several controlled furnace atmosphere analyses, several stationary source stack emission checks and several health-related ambient atmosphere checks. [Pg.171]

A variety of metal oxides (e.g. V2O5) have been employed for oxidation reactions, besides noble metals (e.g. Pt and Ag). Auto-exhaust catalysts employ metals such as Rh, Pd and Pt besides Ce02 and other oxides. The use of metal oxide catalysts for oxidation reactions has been discussed quite widely in the literature (Grasselli Brazdil, 1985). Perovskite oxides of the type CaMn03 and Laj A jM03 (A = Ca, Sr M = Co, Mn) are excellent candidates as oxidation catalysts. The 14-electron oxidation of butane to maleic anhydride is effectively carried out over phosphorus vanadium oxide catalysts of the type VOPO4 (Centi et al., 1988). [Pg.523]

Refractory high surface area oxides are deposited from slurries onto the walls of the channels that make up monoliths in order to provide an adequate surface area to support the active catalytic species. Washcoats such as AI2O3 and TiC>2 are commonly used for pollution abatement applications (auto exhaust, stationary NO abatement, etc.) where the monolith is usually a ceramic. Metal monoliths are finding increasing use however, they represent only a small percentage of the total monoliths used. Optical microscopy enables one to see that the catalyzed washcoat follows the contour of the ceramic surface. Figure 7 shows the AI2O3 washcoat-ceramic interface for a typical auto exhaust catalyst. In this case, no evidence of loss of adhesion between washcoat and ceramic can be seen. [Pg.111]

Lanthana is supposed to be superior to ceria as a washcoat stabilizer, but for oxygen storage, ceria is most effective. The market for auto exhaust catalysts is extensive with over several million units being produced each year in the world, but the rare earth content is only of the order of several grams. [Pg.906]

R. D. Shoup, K. E. Hoekstra, and R. J. Farrauto, Thermal Stability of Copper Chromite Auto Exhaust Catalyst , Am. Cer. Soc. Annual Meeting, Chicago, Illinois, April 29, 1974. [Pg.16]

Organic sulphur- and nitrogen-compounds in motor fuels are a source for acid rain and harmful to the environment. Moreover, they are poisonous to the auto exhaust catalysts. To meet new developments in EU regulations on the S-concentration, a commonly applied one-step hydrodesulfurization (HDS), using conventional catalysts, e.g. C0-M0/7-AI2O3, is insufficient. A second HDS step, viz. a deep HDS step, can be more economical to reduce the S-content to the currently allowed European level of 350 ppm. This level will be reduced further to 50 ppm in 2005 [1]. In the first HDS step, often the heavy organic sulfur-containing polyaromatics survived, such as dibenzothiophene (DBT) and (4-, and/or 6-) alkylated DBTs [2,3]. They are the most refractory. In crude oils, there are also aromatic N-compounds, which suppress the performance of the HDS catalysts. Hence, a model feed for representative HDS-activity measurements should contain characteristic S- and N- compounds for practical relevance. [Pg.1019]

The Pt content can be reduced by a factor of at about 15 while maintaining the catalytic performance at the same level as that of a commercial auto exhaust catalyst. [Pg.343]

The spatial distributions of catalytic metals and contaminant poisons in auto exhaust catalysts were delineated by electron probe line scans. Element concentrations were characterized by element sensitivities, i.e. in counts per second (cps). The electron probe microanalyses (EPM) were qualitative or semiqualitative in nature. Accurate correlation between element sensitivity and element concentration requires rather sophisticated instrument calibration. A quantitative evaluation of the EPM findings is beyond the scope of this paper. In general, it can be stated that element concentration is directly proportional to element sensitivity. Furthermore, the proportionality constant between element concentration and element sensitivity varies greatly from element to element. [Pg.92]

Shelef et ah (2) reported the following representative contaminant retention values for monolithic noble metal HC-CO oxidation catalysts lead, 15% phosphorus, 9% zinc, 3% and sulfur, 0.05%. Furthermore, for monolithic noble metal HC-CO catalysts which had been subjected to 30,000 miles of vehicle testing, the ratios of front to rear contaminant poison concentrations were lead, 7 phosphorus, 16 and zinc, 11. Because NO, and HC-CO catalysts are normally operated under different ambient conditions, i.e. net reducing vs. net oxidizing atmosphere, it is expected that the nature, distribution, and retention of contaminant poisons will differ for these two types of auto exhaust catalysts. [Pg.105]

Ceria first, and since the mid 1990s ceria-zirconia mixed oxides, are key components in the formulation of TWCs [18,19]. A variety of functions are attributed to them, those related to their redox properties being particularly relevant [247]. Under the usual TWC operation conditions, the chemical composition of the exhaust gases rapidly oscillates between net reducing and net oxidizing conditions [8]. This implies deviations from the optimum stoichiometric air to fuel (A/F) ratio (A/F = 14.63), and therefore, loss of efficiency in the auto-exhaust catalyst. To attenuate these oscillations, oxygen buffer materials are required, ceria-based oxides constituting the best option at present available [19]. [Pg.31]

The dominant catalyst support for the auto exhaust catalyst is a monolith or honeycomb structure. (For some early history on the use of bead catalyst, see Reference (6).) The monolith can be thought of as a series of parallel tubes, with a cell density ranging from 300 to 1200 cpsi (cells per square inch). Advances in monolith technology, catalyst-mounting methods, flexibility in reactor design, low pressure drop, and high heat transfer and mass transfer rates are the main reasons the monolithic support dominates the entire market as the preferred catalyst support. [Pg.346]

High area supports such as y-alumina, chromia, etc. can be used for catalysts for low-temperature adiabatic reforming, but these supports suffer from substantial sintering and weakening at temperatures above 500°C. The deterioration is strongly accelerated by the high steam partial pressure and stability tests at atmospheric pressure can therefore be misleading. Stabilisation methods applied in, for instance, auto-exhaust catalysts may become ineffective. [Pg.213]

Pedersen, LJt. and Libby, W.F. (1972) Unseparated rare earth cobalt oxides as auto exhaust catalysts. Science, 176 (4041), 1355-1356. [Pg.64]

Since lead can poison auto exhaust catalysts, automobiles equipped with catalytic exhaust-control devices require lead-free gasoline, which has become the standard motor fuel. Sulfur in gasoline is also detrimental to catalyst performance, so sulfur levels in gasoline are kept very low. [Pg.234]

Some catalysts can now be regarded as mini-reactors and are designed that way. For example, the auto exhaust catalyst is supported on a monolith small enough to fit underneath an automobile. On a molecular scale, metallocene compounds are single-site catalysts that are now being used to make polyolefins more selectively. It is probably not necessary to emphasize that the industrial catalysts used in chemical and refining processes are not the same as the catalysts of theory. They all have well-defined features related to the basic demands of the process in order to achieve predictable and economic operation. These are shown in Table 1.3. [Pg.4]


See other pages where Auto exhaust catalysts is mentioned: [Pg.493]    [Pg.82]    [Pg.271]    [Pg.126]    [Pg.129]    [Pg.1420]    [Pg.493]    [Pg.278]    [Pg.44]    [Pg.141]    [Pg.94]    [Pg.493]    [Pg.303]    [Pg.389]    [Pg.451]    [Pg.343]    [Pg.212]    [Pg.325]   
See also in sourсe #XX -- [ Pg.906 ]




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