Stable co-production of olefins and aromatics from ethane over Co 2+ -exchanged HZSM-5 zeolite

• Published in: Catalysis science & technology 2022-06, Vol.12 (11), p.3716-3726
• Main Authors: Hu, Wenjin, Xu, Yuebing, Xin, Jian, Liu, Bing, Jiang, Feng, Liu, Xiaohao
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/D2CY00664B

Catalytic conversion of ethane into olefins and aromatics is an effective approach for the utilization of low-cost light paraffins. In this study, with the ion-exchange method, Co-exchanged HZSM-5 catalysts were prepared in which Co 2+ ions were stably anchored at exchangeable sites, i.e. , the Brønsted acid sites (–Al F –O(H)–Si F –), to form isolated extra-framework Co( ii ) species (–Al F –O–Co( ii )–O–Al F –) in the zeolite. In comparison to the CoO x clusters mainly formed in an impregnated catalyst, the isolated Co( ii ) species can withstand the reduction by H 2 even at a high temperature, and are only active for C–H bond dissociation but almost inactive for the C–C bond scission, ensuring a high selectivity to the primary ethylene product without serious coke and CH 4 formation. Further with appropriate acidity and right pore size of the employed HZSM-5 zeolite, the formed olefins can be partly converted into aromatics with a total selectivity to olefins and aromatics up to 83% under reaction conditions of 600 °C, 0.1 MPa, 3000 mL g −1 h −1 and 90%C 2 H 6 /10%N 2 . Fortunately, at a moderate temperature, the Co( ii ) species did not suffer a significant de-anchoring from the zeolite framework to form sintered Co 0 clusters, ensuring good catalyst stability.