Catalytic reactors are devices used in chemical processes to accelerate reactions by using a catalyst. A catalyst is a substance that increases the rate of a reaction without being consumed in the process. These reactors are commonly used in industries such as petroleum refining and chemical manufacturing to produce fuels, chemicals, and other products more efficiently. In a catalytic reactor, reactants flow over the catalyst, which facilitates the transformation into desired products. The design of these reactors can vary, including fixed-bed, fluidized-bed, and packed-bed configurations, each suited for different types of reactions and operational conditions.