Limitations of the Microactivity Test for Comparing New Potential Cracking Catalysts with Actual Ultrastable-Y-Based Samples

The gasoil cracking activity of a USY zeolite and a SAPO-37 zeotype, both having the faujasite structure, has been measured at 755 K using an automated MAT unit. MAT experiments performed at conventional (60 s) and less conventional (23 s) TOS showed a higher activity for the SAPO-37 catalyst, despite the USY sample has Brönsted sites of a higher acid strength. However, the kinetic parameters obtained for both catalysts from a complete kinetic study including experiments at very low TOS (5 s - 120 s) demonstrated that USY is more active for cracking gasoil than SAPO-37, but the former decays much faster. It is then concluded that cracking conversions obtained in conventional MAT experiments may be inadequate to compare the activity of catalysts having very different activity-decay behavior.