Bench Scale NOX Trap System For Diesel Applications

A NO_X storage and reduction approach addresses NO_X emissions from mobile diesel sources. A bench scale rig system has been constructed, allowing experiments with real diesel exhaust gases under well defined conditions. The system consists of a 50 cm³ NO_X storage and reduction catalyst located in a temperature controlled oven, and has the possibility of adding reducing agents, both gaseous (i.e. propene) and liquid diesel-like (e.g. heptane), into the gas stream upstream of the catalyst to subsequently react with NO_X on the catalyst. A similar laboratory scale system, using a 6 cm³ NO_X storage and reduction catalyst, has been used with synthetic gases of diesel exhaust-like composition, with the possibility to add a gaseous reducing agent.

Factorial NO_X storage and reduction experiments have been performed in the two systems. Results from the investigations and statistical analysis thereof show which parallels can be drawn between laboratory scale and bench scale systems regarding adsorption and reduction of NO_X in a relevant temperature range. Similarities and divergences of results using different reducing agents or catalyst set-ups in the application are discussed. The investigations show the possibility to use the NO_X storage approach for diesel vehicles and the potential principles of operation in full-scale systems. The consequences of these operation principles in terms of NO_X removal efficiency relative to fuel consumption increase are elucidated.