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An experimental data base of catalyst conversion efficiency was generated, using a tubular flow reactor which contained either a Pt/Rh (5:1; 40g/ft3) or a Pd/Rh (5:1; 40g/ft3) catalyst sample, for the purpose of updating the kinetic rate constants in the Ford TWC model. Steady-state conversion efficiency of CO, NO, C3H8, C3H6, H2 and O2 through these catalysts were determined for a variety of inlet species concentrations and inlet gas temperatures. These data were obtained for values of redox ratio between 0.5 (excess O2) and 4.0, and inlet gas temperatures between 371°C and 593°C. All experimental details and modeling procedures utilized in obtaining an optimized set of kinetic parameters are included. Results of these experiments show significant improvement in CO and NO conversion efficiency and an increase in NH3 production for both catalyst formulations over previous generation catalyst formulations when redox ratio is greater than unity.

The optimized design of an exhaust emission system in terms of performance, cost, packaging, and engine control strategy will be a key part of competitively meeting future more stringent emission standards. Extensive use of vehicle experiments to evaluate design system tradeoffs is far too time consuming and expensive. Imperative to successfully meeting the challenges of future emission regulations and cost constraints is the development of an exhaust system simulation model which offers the ability to sort through major design alternatives quickly while assisting in the interpretation of experimental data. Previously, detailed catalyst models have been developed which require the specification of intricate kinetic mechanisms to determine overall catalyst performance. While yielding extremely valuable results, these models use complex numerical algorithms to solve multiple partial differential equations which are time consuming and occasionally numerically unstable.