Monolith aluminum oxide

Starting with a ceramic and depositing an aluminum oxide coating. The aluminum oxide makes the ceramic, which is fairly smooth, have a number of bumps. On those bumps a noble metal catalyst, such as platinum, palladium, or rubidium, is deposited. The active site, wherever the noble metal is deposited, is where the conversion will actually take place. An alternate to the ceramic substrate is a metallic substrate. In this process, the aluminum oxide is deposited on the metallic substrate to give the wavy contour. The precious metal is then deposited onto the aluminum oxide. Both forms of catalyst are called monoliths. 

An alternate form of catalyst is pellets. The pellets are available in various diameters or extruded forms. The pellets can have an aluminum oxide coating with a noble metal deposited as the catalyst. The beads are placed in a tray or bed and have a depth of anywhere from 6 to 10 inches. The larger the bead (1/4 inch versus 1/8 inch) the less the pressure drop through the catalyst bed. However, the larger the bead, the less surface area is present in the same volume which translates to less destruction efficiency. Higher pressure drop translates into higher horsepower required for the oxidation system. The noble metal monoliths have a relatively low pressure drop and are typically more expensive than the pellets for the same application. 

Although few applications have so far been found for ceramic matrix composites, they have shown considerable promise for certain military applications, especially in the manufacture of armor for personnel protection and military vehicles. Historically, monolithic ("pure") ceramics such as aluminum oxide (Al203), boron carbide (B4C), silicon carbide (SiC), tungsten carbide (WC), and titanium diboride (TiB2) have been used as basic components of armor systems. Research has now shown that embedding some type of reinforcement, such as silicon boride (SiBg) or silicon carbide (SiC), can improve the mechanical properties of any of these ceramics. 

The work presented in this paper is the first part of a project aiming at the development of tailor-made oxidation catalysts for diesel engines fuelled by alcohol fuels, ethanol or methanol. The investigation is focused on the influence of support material on the low temperature oxidation of ethanol and acetaldehyde. The study presents results from an experimental investigation with precious metal catalysts applied on monolithic cordierite substrates. Platinum or palladium were applied onto a support consisting of either aluminum oxide, cerium dioxide, silicon dioxide or titanium dioxide. 

The catalysts were prepared by using the following support materials aluminum oxide (Condea PX 140), cerium dioxide (Molycorp HSA 5315), silicon dioxide (EKA Nobel Bindzil 50/80), and titanium dioxide (Thann et Mulhouse OT 51). According to the manufacturers specifications, the BET surface areas were 140, 145, 80 and 80-100 m /g, respectively. TTie monolithic catalyst samples were prepared according to standard techniques at Svenska Emissionsteknik AB. The preparation of the platimun and palladium catalysts was made on an equimolar basis and they contained 9.5 mmol/dm3 monolith, which corresponds to 1.8 g Pt/dm3 and 1.0 g Pd/dm3. 

Metal monoliths were obtained from Emitec (Germany). They were subjected to high-temperature treatment by the supplier. The cell density of the monoliths used is approximately 4(X) cpsi. The monoliths consist of an iron-chrome-aluminum alloy which provides the surface with a textured whisker structure after suitable treatment. These whiskers, shown in Figure 8, act as anchors for the washcoat when deposited onto the substrate. Tbe whiskers consist of aluminum oxide, completely covering the metal surface. This is shown by the data in Table 2, giving the results of EDX and XPS analyses of the whiskers-covered metal surface. 

In general, both cordierite and metallic monoliths are unsuitable as catalytic supports. To process a monolith into an active monolithic catalyst, a layer of porous catalytic support must be deposited on the walls between channels. y-Alumina appeared to be the most effective support for automotive catalysts. The alumina layer is deposited by sol-gel technique (so called washcoating). Adherence of 7-alumina to cordierite is relatively strong. However, to form the stable 7-alumina layer on a metallic surface, we need to use an appropriate alloy that is appropriately processed before the layer is deposited. Stainless steel containing chromium, aluminum, and yttrium subjected to thermal treatment under oxidizing conditions meets requirements of automotive converters. Aluminum in the steel is oxidized to form 7-alumina needles (whiskers) protruding above the metal... 

Thin metallic sheets or strips can lie corrugated or rolled to form metallic monoliths. Often the sheets or strips are made of erric alloys, e.g., stainless steel, and/or contain a small amount of aluminum [39,44], wlich after oxidation forms a layer of alumina that is helpful in bonding to an extra oxidi c layer later on, for supporting the active phase when the sheets or strips are used to piepare monolithic catalysts [43,48-54]. 

Monoliths made of metal foils can also be used as substrates in combustion catalysts [19, 20]. The metal is generally an iron- or nickel-based steel containing small amounts of aluminum. The aluminum diffuses to the surface on heating and oxidizes to form an adherent alumina layer. This alumina layer gives the alloy high oxidation resistance and is essentially self-healing as it arises from diffusion from the bulk material. It also provides good adhesion for the alumina washcoat. 

The present investigation was conducted to identify and determine the degree of Rh-base metal oxide interaction, using unsupported rhodium oxides and bulk aluminum and rare earth metal rhodates. Catalytic activities were determined using monolithic catalysts containing various bulk rhodium species exposed to a simulated stoichiometric auto exhaust composition. The activities were correlated with information obtained from CO chemisorption measurements, temperature-programmed reduction,... 

Chromium oxide-containing catalysts are promising for partial oxidation of methane to synthesis gas (POM). TTie known preparation procedure of the foam monoliths from chromium oxide includes the use of gels prepared from alkoxides of metals forming matrix for the monolith catalysts [1]. In the present work, the preparation procedure of ceramometal monoliths from the metallic chromium and aluminum alloy blend has been described. The main stages of the preparation procedure and properties of the porous monolith have been studied. The catalysts performmce in the POM has been tested. 

The rudimentary IC that Kilby made contained one bipolar transistor, three resistors, and one capacitor, all made in germanium and coimected by wire bonding. For his invention of the IC, Jack Kilby was awarded the Nobel Prize in physics in 2000." The monolithic (monolith means single stone ) IC that Noyce proposed in 1959 was a flip-flop circuit containing six devices, in which the aluminum interconnection lines were obtained by etching an evaporated aluminum layer over the entire oxide surface using a lithographic technique. ... 

Figure 25.2. Photographs of a monolith aerogel iron (III) oxide/nanometric aluminum energetic composite that is shown with a penny for scale.

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