The potential of supported molten salts in the removal of soot from dieselexhaust gas

An exploratory study has been carried out to find a satisfactory support fo r the promising catalytic phase based on eutectic mixtures of Cs2O, V2O5 an d MoO3 for the oxidation of diesel soot. High-temperature, high-strength, l ow-porous ceramics and more conventional porous catalyst supports were inve stigated as candidate support, i.e. alpha-alumina, gamma-alumina, cordierit e, diatomaceous earth, silica, silicon carbide and silicon nitride. The mol ten salt was deposited at the external surface of the different supports. S ynthetic soot was deposited in a loose contact manner on the supported cata lysts. Oxidation rates of 15 mu g(soot) g(soot,initial)(-1) s(-1) at 650 K were observed. These rates are in the same order of magnitude as found for the best catalytic fuel additives, and, therefore, the molten salt catalyst is promising. Basic requirements for the support-molten salt interaction w ere formulated: the molten salt should wet the support, the molten salt sho uld 'anchor' to the support, and the support should not shield the molten s alt from the soot. Low-porous, high-temperature, high-strength ceramics are promising candidate supports for the molten salt soot oxidation catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.