Extruded Zeolite Based Honeycomb Catalyst for NOx Removal from Diesel Exhaust 2008-01-1024
The most promising technique to reduce the NOx emissions from diesel engines is the SCR-technology. This technique is well known since several years and derived from the exhaust gas treatment of power plants and stationary engines. These SCR catalysts are now available in mass production for heavy duty vehicles in Europe. This technology uses urea and a so called SCR catalyst to convert NOx to harmless substances water and nitrogen. Honeycomb shaped catalysts based on titanium dioxide containing vanadium oxides as active component are used predominantly. The SCR active material can either be applied as a coating on an inert carrier honeycomb or be worked up to a homogeneous honeycomb by extrusion. The homogeneously extruded catalysts have the advantage that they contain 100 % of active material. Especially in the lower temperature range higher NOx-conversions can be achieved compared to coated systems. Anymore they feature a superior resistance against poisoning (e.g. by sulfur).
To establish this technology for new US 2010 and EURO 6 systems containing a particulate filter and to meet the demands of the U.S. market for a catalyst that is not containing Vanadium, Argillon recently invented a new catalyst presented on SAE 2007 World Congress. The reason not to use vanadium in these future systems is that filter regeneration demands high temperature stability of the SCR catalyst and that there are concerns about vanadia loss during operation.
Recent data on this homogeneous catalyst honeycomb consisting of 100 % active material based on Zeolite and containing no Vanadium is presented.
The catalyst features superior low temperature activity and provides high-temperature stability to withstand particulate filter regenerations upstream in the exhaust. Additionally the low bulk-density helps to reduce efforts in canning and system design.
Information on the manufacturing process, NOx-removal efficiency and thermal stability in comparison to a commercial V/TiO2 homogeneous catalyst are presented to prove the high performance of the new Zeolite-based catalyst.