Tailoring structure and acidity of ZSM-5 zeolite by algae carbon modification: Promoting effect in the MTO reaction

Abstract

A biochar obtained from algae (Trachydiscus minutus, TRA) with rich surface functional groups and metal ions was used as a hard template to efficiently synthesize modified ZSM-5 zeolites with high external surface area (ESA) and mild acidity. Compared with pristine ZSM-5, which exhibited an ESA of 121 m2/g, TRA/ZSM-5 modified with algal carbon yielded an ESA of 171 m2/g. In addition, the catalytic lifetime of TRA/ZSM-5 zeolite in the methanol-to-hydrocarbons (MTH) reaction was also greatly improved compared with H-ZSM-5: TRA/ZSM-5 maintained a methanol conversion >95% during 16 h (at 400 °C, WHSV = 8 h−1), whilst H-ZSM-5 could only last for 10 h. After further optimization, the lifespan of TRA/ZSM-5 could be further enhanced to 24 h. Finally, it could be shown that the presence of hydrophilic functional groups and heteroelements were the key parameters to enhance the ESA of the zeolite and reduce its Brønsted acidity.