I am currently working in Exxon Flexicracking FCC model. During start-up of the unit, when we establish catalyst circulation, sour water received in the MF O/H drum is acidic. When we introduce feed to the reactor, it becomes neutral. Why is it so? I am interested in the chemistry of the process leading to acidic boot water. Can we reduce the acidity by changing operating conditions of the MF or R-R section?