Matrix Acidity Determination: A Bench Scale Method for Predicting Resid Cracking of FCC Catalysts

Novel methods for determination of matrix acidity of cracking catalysts are discussed. Virgin matrix acidity is determined after complete destruction of the zeolite phase by acid treating the catalyst at pH 2. Properties of acid-treated catalyst closely approximate those of pure matrix. However, the virgin matrix acidity does not correlate with resid cracking performance of the catalyst under commercial or pilot plant conditions. A second method has been developed that facilitates the measurement of matrix acidity on a laboratory deactivated sample with properties similar to that in the commercial cracking unit. The approach is based on total destruction of the zeolite by steaming at 870 C for 5 h. Acidity of the steamed catalyst closely resembles that of steamed pure matrix and has a good correlation with the resid cracking activity in the pilot plant testing. Preservation of matrix acid sites during hydrothermal deactivation was shown to be an important requirement for achieving high resid cracking activity.