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A particulate trap with additive supported regeneration is a very effective way of reducing soot emissions of diesel exhaust gas. Particulate traps presently available on the market clearly show that the regeneration process is the most important detail in particulate trap technology. In this specific case of particulate traps, active rare earth oxides are added into the fuel to produce an initial and almost continuous regeneration without external burners, resistance heating, etc., as is well known from other systems. It should not be forgotten that an externally initiated regeneration will always produce a temperature peak inside the soot collecting filter media which may destroy them. Such damage can be avoided by catalytically supported regeneration of particulate traps. In the presence of an active catalyst, an inorganic cerium compound, regeneration temperature will decrease from 550 to 600 deg. C normally to about 350 to 400 deg. C.

The paper reports on the results of a joint research program performed at Rhône-Poulenc and AVL concerning a passive trap system with Cerium (Ce) as a new patented fuel additive in conjunction with an engine management control system to increase the exhaust gas temperature for initiating regeneration under practically all engine application conditions. Investigations were carried out on a 12L DI/TCI HD diesel engine which meets the US94 emission standards. From the work done the most effective combination of the engine control measures has been established as an apprepriate solution to increase the exhaust gas temperature up to 400 deg. C. at minimum penalty with respect to emissions and fuel consumption. Furthemore, the influence of Cerium on engine-out emissions and fuel consumption has been investigated. It could be shown that by using Cerium, the fuel consumption improves on average by about 2 percent.

In the past, concentrated efforts were directed at developing a cost effective and reliable particulate trap, assisted by mechanical (burners) or electrical (heating elements) regeneration means. Although ceramic monolith filter developments have been straightforward, regeneration systems have proven to be problematic and costly. Therefore, these development efforts led to disappointing results. Using catalytic fuel additives to promote regeneration in a trap through lowering the incineration temperature of collected soot is an attractive alternative. This passive form of regeneration could be technically and economically advantageous for diesel applications by eliminating complex sensors and controllers required for regeneration systems in new installations as well as retrofitting older vehicles. A cerium based fuel additive was used to assist in regenerating particulate traps in diesel exhaust aftertreatment.