After the ninth step, the n-propanol purity at the upper side stream does not return to the desired specification. The side stream composition indicates that S1 is contaminated with i-butanol and S2 is contaminated with n-propanol. At around 32 h, the start-up process is terminated, as there is no noticeable change in the compositions of the side streams in the following 6 h after the last n-propanol withdrawal.