Catalytic Reduction of S I Engine Emissions using Cu-ION Exchange ZSM-5 2001-26-0013
The growing pollution from automobiles and increasing awareness of harmful effects of the air due to pollution has resulted in more stringent emission control norms. Consequently earlier techniques of emission control such as combustion modification, water injection and exhaust gas recirculation have to be supplemented by advance exhaust gas after treatment to meet stringent regulations.
The most efficient exhaust gas after treatment system envisages the use of a Catalytic Converter for oxidizing the Carbon monoxide (CO), and un-brunt Hydrocarbon(UBHC) to Carbon-dioxide (CO2) and water, and reducing the oxides of Nitrogen (NOx). The exhaust gas is made to pass through a catalytic bed which catalyses the conversion reactions for the different exhaust gas components.
Three way catalysts (TWC) are, extensively used for simultaneous control of the three principal automotive pollutants, namely, carbon monoxide (CO), Hydrocarbon (HC) and Oxides of Nitrogen (NOx).
Unlike noble metals, the Cu-ion exchanged ZSM-5 zeolite catalysts in a pellet form of 1.5-mm dia are placed in a catalytic converter for the reductions of CO, HC and NOx, studied here, and tested in a commercial Maruti (800cc) SI engine and some encouraging results for reduction of NOx, CO and HCs have been obtained. Maximum conversion efficiencies achieved with Cu-ZSM-5 catalysts are 85% of NOx at 490° and 71% of CO at 495° and 72% of HC at 500°C.
The design and fabrication of the converter is such that it consists of two parts, namely, casing and catalyst cartridge.
The ion exchanged ZSM-5 Zeolite with Cu studied here exhibits significant NOx reduction for a lean A/F ratio of 17.5. Back pressure developed across the catalytic bed is found to be well within the acceptable limits and power loss due to the back pressure is only 0.2%. During 300 hours of testing of the catalyst no significant deactivation of any catalyst was observed.