Preparation of ZSM-5 zeolites by sodium-free method in rotating packed bed

Abstract

In industry, H-type zeolites are usually synthesized under hydrothermal conditions in the sodium-containing system, in which great deal of ammonia nitrogen wastewater will be produced during the transformation of zeolites from Na-type to H-type. In this work, we prepared ZSM-5 zeolites in the sodium-free system using organic amines in a rotating packed bed (RPB), which can greatly reduce the amount of wastewater. It was found that the ZSM-5 zeolites synthesized by isopropanolamine (MIPA) had the highest acid amount with a value of 2.331 mmol/g compared to that by other three amines, and exhibits the highest conversion of benzaldehyde with a value of 77.63% in the acetal reaction of benzaldehyde and ethylene glycol. More importantly, RPB premixing can improve the transfer of Al into the framework of ZSM-5 zeolites relative to conventional stirring technique. This work provided a new route to prepare ZSM-5 zeolites with high acid amount in sodium-free system.