Monolithic metal composite

MEE magnetic field eflect MMC monolithic metal composite... 

The precious metal composition is typically uniform in the radial and axial directions of the monolith structure, although different designs have been described in the patent literature and have even been used in some selected applications. However, much more common is a nonuniform distribution of the precious metals within the washcoat layer. One - macroscopic - example of nonuniform distribution is that the amount of one precious metal component decreases from the part of the washcoat that is in contact with the gas phase towards the part of the washcoat that is in contact with the monolith wall and eventually vice-versa for the second precious metal component. Another - microscopic - example of nonuniform distribution within the washcoat is that each precious metal component is selectively deposited on different washcoat components. These nonuniformities are intentional and are desirable for kinetic reasons or because of specific beneficial interactions between the precious metals and the washcoat oxides. The type of nonuniformity that can be achieved depends strongly on the production procedure of the catalyst. 

Although the same basic curves of performance vs. noble metal composition were obtained for both spherical and monolithic catalyst at each... 

Catalysts were prepared by incipient wetness impregnations using nickel nitrate and tetraamine-platinum (II) nitrate separate impregnations were made with air calcination at 593°C to decompose the nickel salts before platinum was added. After a second calcination, the powders were ball-milled with water to form a coating slurry which was used to coat Poramic (from W. R. Grace) monoliths slurry compositions were adjusted to give 10% solids pickup. The metal levels did not depend on support density. See Table II for final compositions. 

The technical feasibility of an almost entirely polymeric composite airframe has been demonstrated by the Beech Corp. Starship I business aircraft, but some factors discourage the total-composite concept. The costs of raw materials, tooling, production, quality control, in-service maintenance and repairing can run several times higher than those for aluminium. The most likely way ahead will be the application-driven employment of both traditional monolithic metals and advanced composites. 

Emerging potential applications for UHTCs require complex shapes and/or functionalized surfaces. In this chapter, recent achievements in the development of monolithic and composites based on Hf and Zr borides and carbides are presented and discussed, especially with reference to the effects of shaping and sintering technologies. Novel UHTC structures and architectures, dense and porous, open new potential fields of applications for UHTCs not only in aerospace applications, but also in energy sectors (such as solar energy), hot gases and molten metal filtration and catalysis. 

GP 8[ [R 7[ Syngas generation with commercial Pt-Rh gauzes, metal-coated foam monoliths and extruded monoliths has been reported. For similar process pressure, process temperature, and reaction mixture composition, methane conversions are considerably lower in the conventional reactors (CH4/O2 2.0 22 vol.-% methane, 11 vol.-% oxygen, 66 vol.-% inert species 0.14—0.155 MPa 1100 °C) [3]. They amount to about 60%, whereas 90% was reached with the rhodium micro reactor. A much higher H2 selectivity is reached in the micro reactor the CO selectivity was comparable. The micro channels outlet temperatures dropped on increasing the amount of inert gas. 

The replacement of vanadia-based catalysts in the reduction of NOx with ammonia is of interest due to the toxicity of vanadium. Tentative investigations on the use of noble metals in the NO + NH3 reaction have been nicely reviewed by Bosch and Janssen [85], More recently, Seker et al. [86] did not completely succeed on Pt/Al203 with a significant formation of N20 according to the temperature and the water composition. Moreover, 25 ppm S02 has a detrimental effect on the selectivity with selectivity towards the oxidation of NH3 into NO enhanced above 300°C. Supported copper-based catalysts have shown to exhibit excellent activity for NOx abatement. Recently Suarez et al and Blanco et al. [87,88] reported high performances of Cu0/Ni0-Al203 monolithic catalysts with NO/NOz = 1 at low temperature. Different oxidic copper species have been previously identified in those catalytic systems with Cu2+, copper aluminate and CuO species [89], Subsequent additions of Ni2+ in octahedral sites of subsurface layers induce a redistribution of Cu2+ with a surface copper enrichment. Such redistribution... 

Figure 7-16 A highly simplified sketch of an automohile engine and catalytic converter with typical gas compositions indicated before and after the automotive catalytic converter. The catalytic converter is a tube wall reactor in which a noble-metal-impregnated wash coat on an extruded ceramic monolith creates surface on which reactions occur.

Weiland et al observed that a small amount of Pt metal present in the Rh-based catalyst could significantly improve the catalyst activity for ATR of gasoline range fuels. They claimed that the role of Pt is to enhance oxidation activity, whereas Rh provides high SR activity. The Rh-Pt/alumina catalyst used in the study was supported on monolithic honeycombs and had a Rh to Pt ratio of 3-10 by weight. The geometry (metal monolith, ceramic monolith, or ceramic foam) of the support did not affect the product composition. ... 

The differences in reactions at different reactor positions was studied by Springmann et al. who reported product compositions for ATR of model compounds as a function of reactor length in a metal monolith coated with a proprietary noble metal containing Rh. As expected, the oxidation reactions take place at the reactor inlet, followed by the SR, shift, and methanation reactions. Figure 32 shows the product concentration profiles for a 1-hexene feed, which are typical results for all the fuels tested. These results show that steam, formed from the oxidation reactions, reaches a maximum shortly after the reactor inlet, after which it is consumed in the shift and reforming reactions. H2, CO and CO2 concentrations increase with reactor length and temperature. In this reactor, shift equilibrium is not reached, and the increase in CO with distance from the inlet is the net result of the shift and SR reactions. Methane is... 

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