Fabrication of Ceramic and Metallic Monoliths

Once the ceramic monolith is fabricated and coated with catalyst, it needs to be canned in a metallic reactor body. A mat material is used to bridge the gap between 

An alternative to Fecralloy is aluminium when the operating temperature of the monolith is limited to below about 450 °C. An alumina layer may be formed on the aluminium, for example, by anodic oxidation. 

Ceramic foams are produced from organic precursor foams such as polyurethane or polyolefins. Their pores are then filled with an aqueous slurry of the ceramic typically containing 20 wt.% of ceramic particles in the size range of from 0.1 to 10 pm [461]. Wetting agents, dispersion stabilisers and viscosity modifiers are added to the slurry. Suitable ceramics are alumina, alumina silicates, zirconia, stabilised zirconia and titania, amongst others. The pores ofthe precursor foam may be filled completely or only coated on their surface by the ceramic particles. The foam is then dried and calcined at 1000 °C, which removes the polymer and sinters the ceramic. Metallic foams have similar properties compared with ceramic foams, but superior mechanical stability and improved heat conductivity. 

Plate heat-exchangers are usually made from stainless steel, however, to deal with the demands of high temperature applications, such as hydrocarbon steam reforming and partial oxidation reactions, nickel-based alloys may be considered, despite their higher price. 

Another option are Fecralloys, which are also used for fabrication of metallic monoliths and are mechanically stable up to very high temperatures exceeding 1200 °C. However, the material is britde, which generates practical problems with respect to mechanical stability. 

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