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

An exploratory study has been carried out to find a satisfactory support for the promising catalytic phase based on eutectic mixtures of Cs2O, V2O5 and MoO3 for the oxidation of diesel soot. High-temperature, high-strength, low-porous ceramics and more conventional porous catalyst supports were investigated as candidate support, i.e. alpha-alumina, gamma-alumina, cordierite, diatomaceous earth, silica, silicon carbide and silicon nitride. The molten salt was deposited at the external surface of the different supports. Synthetic soot was deposited in a loose contact manner on the supported catalysts. 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 were formulated: the molten salt should wet the support, the molten salt should 'anchor' to the support, and the support should not shield the molten salt 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.