CO2-Assisted in situ hydrogen extraction for highly selective aromatization of n-Hexane over Zn modified HZSM-5 catalyst

We successfully realized the highly selective aromatization of n-hexane by the assistance of CO2 over Zn modified HZSM-5 catalyst. The in situ H originated from the C-H activation of n-hexane and cyclohexane could be timely removed through the dynamic evolution between CO2 and Lewis acid site, thus inhibiting the hydrogen transfer side reaction and promoting the desorption of BTEX. Therefore, the Zn/ZSM-5-CO2 catalyst exhibits as high as 49.7% BTEX yield, which is nearly 10% higher than that of the Zn/ZSM-5-N2 catalyst (40.3%). [Display omitted] •The introduction of CO2 could timely remove the in situ H.•Hydrogen transfer between olefins and aromatics is effectively inhibited.•The binding of hydrogen proton to π electrons is weakened.•The loss of medium strength Lewis acid is significantly reduced.•The Zn/ZSM-5-CO2 catalyst exhibits as high as 49.7% BTEX yield and superior catalytic stability. Controlling the evolution of H species in CO2-assisted alkane activation represents an opportunity for simultaneously upgrading light alkanes and greenhouse gas CO2. Herein, we successfully realized the highly selective aromatization of n-hexane by the assistance of CO2 over Zn modified HZSM-5 catalyst. Multi-characterizations demonstrated that the introduction of CO2 could timely remove the in situ H originated from the C-H activation of n-hexane and cyclohexane through the dynamic evolution of the pentagonal coordination Zn-OH+-(CO)-O-Zn structure. On this basis, hydrogen transfer between olefins and aromatics is effectively inhibited, and the binding between π electrons of benzene ring and hydrogen proton is weakened, accelerating the generation and desorption of BTEX. Therefore, the Zn/ZSM-5-CO2 displays a record high 49.7% BTEX yield, which is nearly 10% higher than that of the Zn/ZSM-5-N2 (40.3%). In addition, the loss of medium strength Lewis acid caused by in situ H reduction of Si(Al)-O-Zn structure is significantly reduced, ensuring its superior catalytic stability under long-term conditions. These results may provide some insights for the profitable utilization of petrochemical resources to aromatics over zeolites.