The hydrocarbon in the gas mixture is extremely influential both on the CO and HC oxidation efficiency, and on NO reduction efficiency. There are complex chemical differences between the gasoline fuel and NG and LPG fuels in the reaction mechanisms of the three-way catalytic converters. 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,

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... CO and NO conversion efficiencies of the catalytic converter 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.