| 초록 |
ZSM-5 catalysts (Si/Al ratio of ~30) with different mesoporosity were synthesized by using a structure directing agent of tetra-n-butylphosphonium hydroxide. The resulting ZSM-5 catalysts were formed via the interconnection of very thin lamellae; H_30 (high mesoporous ZSM-5) and L_30 (low mesoporous ZSM-5). Acid site titration reveals that H_30 had internal Brønsted acid sites similar to those in the commercially available ZSM-5 with a Si/Al ratio of 75 (referred to as C_75), though H_30 contained a large amount of external Brønsted acid sites. The methanol to hydrocarbons (MTH) reaction performance demonstrates that H_30 preferred to produce propene over ethene compared to C_75, while L_30 showed a very poor MTH performance mainly due to the lower amount of internal Brønsted acid sites. The short diffusion length in H_30 disfavored the production of ethene due to suppressed aromatic dealkylation reaction. With this, H_30 allowed for achieving the propene to ethene ratio as high as ~9.1. Furthermore, surface passivation with CeO2 was conducted on H_30. The ceria-doped H_30 not only showed an enhanced stability, but also even higher propene to ethene ratio up to ~15.0. |
