CCD involves three types of experimental runs: 1. Factorial Points: These are experiments conducted at the high and low levels of each factor. 2. Axial Points: These are additional runs that allow the design to be rotatable or orthogonal, helping in estimating curvature. 3. Center Points: These are replicates of the mid-point of all factors and help in measuring the experimental error.
By combining these runs, CCD can provide a robust model that describes the behavior of the catalytic system under study.