(532az) Effects of Hierarchically Structured ZSM-5 Zeolite on Methanol to Hydrocarbons Reactions

To synthesize two different types of ZSM-5 (Si/Al = 30) catalysts, we changed the molar composition of ethanol and water in the synthesis solution. One of the ZSM-5 catalysts had a high mesoporous with a 6 nm thickness (named H_30) and another ZSM-5 catalyst had a low mesoporous with a 13 nm thickness (named L_30). Two types of ZSM-5 catalysts are composed of interconnection with thin pillars and lamellae. We measured pyridine-adsorbed FT-IR spectra to know the acid site of ZSM-5 catalysts. As a result of acid site titration, the internal BrØnsted acid sites of H_30 are similar to those of commercial ZSM-5 (Si/Al = 75, named by C_75). But the external BrØnsted acid sites of H_30 are larger than C_75. In the methanol to hydrocarbon (MTH) reaction, H_30 was found to be preferable to ethene in the formation of propene than C_75. However, L_30 showed poor MTH performance because of the lower amounts of BrØnsted acid sites. Also, H_30 had a very short diffusional length that dislikes aromatic dealkylation, which mainly produces ethene. So, H_30 was able to obtain highest ratio of ethene to propene. In addition, ceria-impregnated H_30 improved the stability of the MTH reaction as well as propene to ethene ratio.

Research Interests : Catalysis, Acid site titration, Methanol-to-hydrocarbons reaction