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High-speed aircraft rely primarily on thermal protection systems (TPS) to withstand extreme thermal loads and safeguard internal structures. Designing TPS requires materials that are both lightweight and capable of providing robust thermal protection. This study developed a surface catalytic reaction model based on the Direct Simulation Monte Carlo (DSMC) method, incorporating adsorption, desorption, Eley-Rideal (E-R), and Langmuir-Hinshelwood (L-H) surface composite reactions. The effects of initial and maximum surface coverage of adsorption sites on the heat flux around a cylindrical flow were analyzed. Results show that higher initial and maximum surface coverage significantly increase the surface heat flux. Moreover, competitive adsorption among multiple gas species was observed during the surface catalytic process. These findings suggest that when selecting TPS materials for aircraft design, it is essential to consider their interactions with gas components in the flow environment and the adsorption behavior of each component on the surface to prevent irreversible heat-induced damage.