Metal honeycomb substrates used in catalytic converters are made from extremely thin metal foil, typically with a thickness of just 0.05mm. By comparison the walls of a ceramic substrate may be four times thicker. For this reason, metal substrates offer less resistance to gas flow and therefore can accommodate a given flow rate with a lower pressure drop than an equivalent ceramic substrate. The improved flow properties of a metal substrate mean that, for a given level of pressure drop, a metal substrate can be made with a greater cell density than the ceramic alternative.
Since greater cell density results in increased surface area, this means that a metal substrate of a given volume will be more catalytically active than a ceramic one. Most metal substrates used in the cooking and heating sectors have between 100 and 200 cells per square inch (cpsi). Metal substrates can be made in a variety of profiles, with round, square and rectangular being most common. Another variable is the pattern of the corrugations in the foil, which can either be straight through or involve changes of direction. The latter option is known as ‘herringbone’ and gives rise to turbulence which increases the activity of the catalytic converter but at the expense of an increased pressure drop.
There are various ways of making metal substrates but the top-quality versions utilize Fecralloy foil which consists of 74% iron, 21% chromium and 5% aluminium. The main advantage of Fecralloy is that, when heated in air, a layer of aluminium oxide forms on the surface which protects the iron from corrosion and also provides a good key for the catalytic coating. Therefore this type of metal substrate is hygienic enough to use in cooking appliances.
Chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative reaction pathway with a lower activation energy than non-catalyzed reactions. The catalyst is not consumed in the process and can continue to act repeatedly. Hence only very small amounts of catalyst are required to alter the rate of a chemical reaction. We offer a full range of metal catalysts in varying purities and concentrations that includes homogeneous catalysts, supported/unsupported heterogeneous catalysts and fuel cell catalysts for anodes, cathodes, electrodes.
Metal catalysts are extensively used both in the research laboratory and in industrial/manufacturing processes. Indeed, it is hard to find a complex synthetic reaction or an industrial process that does not, at some stage, require a metal catalyst.
Transition metals in particular are the metal of choice for use as catalysts in organic, organometallic and electrochemical reactions owing to their ability to exist in a variety of oxidation states, interchange between oxidation states form complexes with organic ligands, and act as a good source of electrons. Many key transformations in organic synthesis, e.g., cross-coupling reactions that include the Nobel Prize-winning Heck, Suzuki, and Negishi reactions, require the use of such late transition metals as palladium, platinum, gold, ruthenium, rhodium, or iridium.
We offer a wide selection of homogeneous and heterogeneous metal/precious metal catalysts for a broad range of organic synthetic reactions including metal complexes with chiral ligands for asymmetric hydrogenation, novel palladium coupling catalysts, platinum group metal (PGM)-based heterogeneous catalysts as well as Sponge Nickel catalysts. The benefits of using our metal catalysts include:
Sie sind vermutlich noch nicht im Forum angemeldet - Klicken Sie hier um sich kostenlos anzumelden