Investigation of Effect of Propane and Methane Gases on Commercial Catalytic Converter Activity

Abstract

Reaching the limit values that are necessary for exhaust emissions stemming from motor vehicles is only possible by three-way catalytic converters that make the HC, NOx and CO emissions harmless in spark-ignited engines. The reaction mechanisms of the TWC catalyst is extremely complex. The interactions between the HC, CO and NO change constantly in low and high temperatures. It is observed that especially the hydrocarbon in the gas mixture is extremely influential both on the CO and HC oxidation efficiency, and on NO reduction efficiency. There are more than 200 hydrocarbons in the exhaust gases of the spark-ignited engines. Hydrocarbon types also influence the removal of the CO and NO in three-way catalysts. There are complex chemical differences between the gasoline fuel and NG and LPG fuels in the reaction mechanisms of the three-way catalysts. For this reason, the gas mixture that simules the stoichiometric burning exhaust gases was prepared by choosing propane to represent the LPG fuel, and the methane to represent the NG fuel as hydrocarbon. The HC, CO and NO conversion efficiency of the catalyst were tested by changing the hydrocarbon type used in the gas mixture in 10000/h space velocity and between the temperatures of 150°C and 500°C with 25°C intervals. The propane was oxidized at much lower temperatures than methane, which is consistent with the C-H connection energy. In addition, the propane is a more active reducing agent in reducing the NO, and it is possible to reach the NO conversion efficiency at lower temperatures with propane. Methane or propane existing in the gas mixture as hydrocarbon is not influential on the CO conversion efficiency at a significant level and the T90 temperature of CO is reached at around 200°C in the existence of both gases.