Preparation, scale-up and application of meso-ZSM-5 zeolite by sequential desilication–dealumination

Abstract

Meso-ZSM-5 zeolites with unique catalytic cracking properties have been prepared from commercial ZSM-5 using sequential desilication–dealumination strategy. Desilication and dealumination conditions, including concentration, temperature, dissolution time and liquid–solid ratio were systematically studied and optimized. Characterization results revealed that mesoporosity can be effectively introduced into commercial ZSM-5 crystals by desilication. The introduction of mesopores enables the well interconnectivity of micropores. Concomitant dealumination by removing Al-rich debris from desilicated samples shows superiority in micro- and mesopore network, remedying the limitation of desilication. The removal of the debris preserves intrinsic microporosity and improves the acid site accessibility in zeolites. Based on optimized parameters of porosity tuning tests at 0.25 L scale, the preparation route was scaled up to a pilot scale (50 L). In the heavy oil catalytic cracking test, compared with P-ZSM-5-contained catalyst, A-ZSM-5-contained and ACP-ZSM-5-contained FCC catalyst display increased heavy oil conversion (from 67.68 to 68.25 and 68.33 wt%, respectively), improved light olefin yield including propylene (from 5.67 to 5.87 and 6.11 wt%, respectively) and promoted yields of both gasoline and diesel.