A reactor suitable for a reaction containing an exothermic reaction is provided. The reactor includes the following components. A reaction channel has an inlet and an outlet, and has a front-end reaction zone, middle-end reaction zones, and a back-end reaction zone from the inlet to the outlet. A front-end catalyst support and a front-end catalyst are located in the front-end reaction zone, a middle-end catalyst support and a middle-end catalyst are respectively located in the middle-end reaction zones, and a back-end catalyst support and a back-end catalyst are located in the back-end reaction zone. The concentration of the front-end catalyst is less than the concentration of the back-end catalyst, and the concentration of the middle-end catalyst is decided via a computer simulation of reaction parameters. The reaction parameters include size and geometric shape of the reaction channel. |