Application of photocatalyst-plasma-honeycomb system for cold-start emission of gasoline vehicles

摘要

The more stringent emission regulations become, the more important it becomes to reduce light-off time of a catalytic converter especially for elimination of cold-start THCs (total hydrocarbons). In this paper, an innovative exhaust emission aftertreatment system to cut light-off time effectively to zero is proposed. One of the key components in this system is the photocatalytic material, titanium dioxide, which is coated on a honeycomb monolith of a converter and is acting as a non-thermal catalyst in reduction of cold-start THCs. In addition, non-thermal plasma is used for ultraviolet (UV) light generation source to activate the photocatalyst on the surface of honeycomb cells. Since photocatalysts are activated by UV irradiation not by thermal energy and non-thermal plasma is immediately generated with the electric power-on, catalytic reactions in this system start with the ignition of an engine, therefore unlike conventional thermal catalysts, no light-off time is needed. A newly developed photocatalyst-plasma-honeycomb system (PPH) has been tested in an ULEV vehicle (2.0 DOHC, A/T) to check the feasibility for automotive application. It is shown that the PPH system could achieve about 50% reduction of cold start THCs compared with the conventional three-way catalyst for the first 40 seconds running after engine start. The electric power consumption is less than 200 watts during this running time.