[Show abstract][Hide abstract] ABSTRACT: The simulation of catalytic converter system is necessary to characterise the catalyst and to optimise the design of a monolithic reactor for NO x abatement. The objective of this study is to obtain a quantitative description of NO x abatement in three-way catalytic converter system of natural gas powered automobile exhaust gas. This work presents a finite element calculation to predict and to evaluate the NO x abatement in three way catalytic converter. A numerical simulation is carried out using a commercial Finite Element Method (FEM) code, FEMLAB. In this work simulation is done on transient isothermal operation of catalytic converter at temperature of 750 K. The results have shown that the maximum reduction of 99% of NO x can be achieved using a monolithic reactor with channel dimensions of 1mm radius and 0.4 m length. Specifically, results obtained from the computer modelling exercise have demonstrated that finite element method is capable of modelling the NO x abatement in TWCC.