Improving the dehydrogenation function and stability of Zn-modified ZSM-5 catalyst in methanol-to-aromatics reaction by Ca addition

• Published in: Applied catalysis. A, General General, 2024-08, Vol.683, p.119854, Article 119854
• Main Authors: Vicente, Héctor, Liu, Chuncheng, Gayubo, Ana G., Castaño, Pedro, Pidko, Evgeny A.
• Format: Article
• Language: English
• Subjects: Catalyst deactivation; Dual-cycle mechanism; Ethane dehydrogenation; Methanol-to-aromatics; ZSM-5
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2024.119854

Adding Zn to the ZSM-5 zeolite effectively increases the aromatic selectivity in the methanol-to-aromatics (MTA) process. The formation of metal-derived Lewis acid sites promotes the dehydrogenation but at the cost of a rapid deactivation of the catalyst by coke, due to the increased aromatic formation. In this work, we impregnated a Zn-modified catalyst (2 wt%) with variable contents of Ca (0.02 and 0.5 wt%) and evaluated their kinetic behavior in the MTA and ethane dehydrogenation reactions. The results proved the superior performance of the Zn(2)Ca(0.02) catalyst due to a synergistic effect between the two metals. The Ca ions limit coke formation from excessive aromatization, increasing catalyst stability and removing Zn clusters, resulting in a recovery of Brønsted acid sites (BAS) active for the formation of light aromatics. Combining these effects results in a more efficient and viable catalyst for aromatic production from methanol. [Display omitted] •Ca addition to 2 wt% Zn/ZSM-5 catalyst improves its performance for methanol-to-aromatics conversion.•Synergy between Zn and Ca improves aromatics yield and catalyst lifetime.•Zn promotes the dehydrogenation pathways verified by ethane dehydrogenation.•Ca influences Zn speciation and inhibits coke formation.•Minor Ca addition to Zn/ZSM-5 recovers active Brønsted acid sites of the zeolite.