Rh三元触媒のCO+NO表面反応機構の解明

抄録

To meet the emission regulations that are becoming stricter year by year, it is important to reduce emissions from spark-ignition engines, which are expected to continue to account for a certain share of the market in the future. The main emission control method for spark-ignition engines is the use of three-way catalysts for CO, NOx, and HC purification, but there are issues such as inactivity at low temperatures and the high cost of supported precious metals. In this study, a reaction model focusing on CO-NO redox reaction was developed for Rh catalysts to facilitate prediction of catalytic performance. Temperature rise tests were conducted to confirm the CO and NO purification rate behavior, and temperature-steady-state tests were conducted for several gas compositions in the low purification rate temperature range. From the test results, equilibrium constants for the adsorption and desorption reactions of CO and NO on the Rh surface at each steady-state temperature were calculated based on the differences in purification rates caused by the differences in gas composition. Based on the obtained equilibrium constants and the test results, an Arrhenius plot was generated to calculate the reaction rate constants for the CO-NO reaction on the Rh surface. Parameters were adjusted on the model simulation. The reaction of N₂O formation as a byproduct was considered to reproduce the behavior of the temperature rise test in a CO+NO atmosphere.