Ultrafast dealumination of *BEA zeolite using a continuous-flow reactor

Abstract

• Ultrafast dealumination of zeolite was performed using continuous-flow reactor. • The dealuminated zeolites were characterized by PXRD, SEM, MAS NMR and ICP-AES. • The dealuminated zeolites exhibited the enhanced hydrothermal stability. Dealumination is an efficient post-synthetic treatment to enhance the catalytic activity and thermal/hydrothermal stabilities of zeolites. Development of fast dealumination process is a critical requirement from a practical perspective. Herein, the ultrafast dealumination of zeolite is performed in a continuous-flow system, where a slurry of commercial *BEA zeolite, as the parent (Si/Al = 12.2) material, in sulfuric acid solution is fed into the flow reactor preheated at 200 °C. The *BEA zeolites obtained after dealumination in the flow reactor for residence times of 1–5 min possesses increased Si/Al ratios of ∼70, while retaining the original crystalline structure and particle morphology. The heat treatment with various residence periods indicates that the removal of Al atoms from the parent zeolite is completed within 1 min in the flow system. Hydrothermal stability of the dealuminated zeolite for 1 min in the flow system is compared with that of the parent and dealuminated zeolites in various reactors, confirming that the dealumination of the *BEA zeolite at 200 °C for 1 min in the flow system is sufficient to enhance its hydrothermal stability. This study demonstrates the potential of a continuous-flow system for application in post-synthetic treatments with a timescale of the order of minutes.