Ammonia-Steam Treatment of ZSM-5 for the efficient conversion of ethylenediamine to triethylenediamine

Conventional ZSM-5 zeolites face significant challenges in achieving high product selectivity and avoiding rapid catalyst deactivation due to coke deposition during the condensation of ethylenediamine (EDA) to triethylenediamine (TEDA). Based on the characteristic of ammonia generation during the synthesis of TEDA from EDA, this study treats ZSM-5 with high-temperature ammonia-steam to investigate its effect on the catalytic synthesis of TEDA. The results show that ZSM-5 sample treated with 5   wt% ammonia-steam at 600 ℃ exhibited higher crystallinity and more mesoporous structure. A large amount of framework aluminum  in the catalyst was removed, resulting in significant decrease of acid strength and a high L/B ratio. The modified catalyst achieved complete EDA conversion during the reaction, with 64% TEDA selectivity—a 17% improvement over that of unmodified catalyst. It also exhibited a significant reduction in coke deposition from 6% to 2.3% and a 15-days continuous fixed-bed reaction test confirmed the high stability of the modified catalyst without noticeable deactivation. Compared to acid-base treated and metal ion treated ZSM-5, ammonia-steam treated ZSM-5 demonstrates superior selectivity and stability, and it has been verified that the TEDA yield is higher than that of TS-1. This study provides a novel strategy for designing efficient catalysts for amine cyclization reactions.