High-temperature catalytic applications

Lutecki, M and Glaser, R. (2011) Nickel-loaded zirconia catalysts with large specific surface area for high-temperature catalytic applications. ChemCatChem, 3 (3),... 

Coke is another problem associated with metal when an initially defect-free Pd-based composite membrane is used in high temperature catalytic applications. The further diffusion of these deposited carbonaceous impurities into the bulk phase of the membrane can lead to defects in the membrane (Lu et al., 2007). Lin (2001) has conducted some systematic investigations into this. Figure 2.24 shows the permeance and separation results of a thin Pd/Ag membrane prepared by sputter deposition before and after being exposed to a graphite ring (surrounding the membrane disk) at 600°C... 

Considering the case of crystalline complex salts and the amorphous precursor method, both chemical com-plexation methods have found important and innovative applications in recent years for the preparation of a wide variety of catalysts and of various perovskite-type catalysts and barium hexaaluminates, as required for high-temperature (>1500K) applications such as catalytic combustion. It is therefore worthwhile describing some applications, in the next two subsections. 

Alloy 602 CA a modification of other 600 alloys is used in heat-treating, annealing furnaces, furnace rolls, high-temperature calcination application, catalytic support systems, and glow plugs in automobiles, vitrification of nuclear waste 800, 45 TM Have high creep and rupture strength and oxidation resistance used... 

Materials such as aluminum titanate and silicon carbide appear to be promising for high-temperature catalytic combustion. However, problems such as extrudability, the application of washcoats, and reaction with deposited washcoats are not solved yet. For instance, when hexa-aluminate, presented in the introduction to this section, was applied to silicon carbide monoliths, solid-state reactions occurred at 1200-1400 C [76], causing exfoliation of the coating and the formation of new phases. The application of an intermediate mullite layer was suggested as an approach to hinder these solid-state reactions. 

The introduction of solid catalysts into a traditionally non-catalytic free-radical process like combustion occurred in recent years under the influence of two pressures, the energy crisis and the increased awareness of atmospheric emissions. The major applications of catalytic combustion are twofold at low temperatures to eliminate VOC s and at high temperatures (>1000 C) to reduce NOx emission from gas turbines, jet motors, etc. Both these applications are briefly reviewed here. Some recent developments in high-temperature catalytic combustion are trend-setters in catalysis and hence of particular interest. For instance, novel materials are being developed for catalytic applications above 1000 C for sustained operation for over one year. Where material/catalyst developments are still inadequate, systems engineering is coming to the rescue by developing multiple-monolith catalyst systems and the so-called hybrid reactors. 

The most commonly utilized catalytic membrane reactor is the PBMR, in which the membrane provides only the separation function. The reaction function is provided (in catalytic applications) by a packed-bed of catalyst particles placed in the interior or exterior membrane volumes. In the CMR configuration the membrane provides simultaneously the separation and reaction functions. To accomplish this, one could use either an intrinsically catalytic membrane (e.g., zeolite or metallic membrane) or a membrane that has been made catalytic through activation, by introducing catalytic sites by either impregnation or ion exchange. This process concept is finding wider acceptance in the membrane bioreactor area, rather than with the high temperature catalytic reactors. In the latter case, the potential for the catalytic membrane to deactivate and, as a result, to require sub-... 

Despite the significant recent interest in these types of membranes, there are relatively few reports of the application of such membranes in high temperature catalytic membrane reactor applications. Dalmon and coworkers (Casanave et al. [2.29, 2.30], Ciavarella... 

Pd/AligB4033 Synthesis and application in the high temperature catalytic combustion of methane... 

The use of supported mixed oxides in both catalytic combustion and NO reduction are challenging applications. In the case of high-temperature catalytic combustion there is an unsatisfied need to obtain solids able to maintain high combustion activity during extended operation, i.e., high-surface-area structurally stable solids. Another hot subject that deserves exploration is the use of washcoated highly dispersed mixed oxides for the selective reduction of NO with CO and hydrocarbons. These studies should be conducted in the presence of both SO2 and H2O to evaluate the potential practical application of these catalysts. 

Spetz, A. L., Tobias, E, Uneus, L., Svenningstorp, H., Ekedahl, L. G. and Lundstrom, L. (2000) High temperature catalytic metal field effect transistors for industrial applications . Sensors and Actuators B-Chemical, 70(1-3), 67-76. 

Aral, H. and Machida, M. Thermal stahilization of catalyst snpports and their application to high-temperature catalytic combustion, ylpp/. Catal. A Gen. 1996, 138, 161-176. 

Ceramic hollow fiber membranes represent a relatively recent development due to their high specific area per volume. However, they are mechanically too weak to withstand the kind of environments one expects to encounter in high-temperature catalytic reaction applications. Another major problem still to be solved is the creation of the connection between the ceramic material and the steel tubing of the rest of the reactor [14]. 

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