Synthesis of ZSM-34 and Its Catalytic Properties in Methanol-to-Olefins Reaction

ZSM-34 (OFF/ERI intergrowth) was synthesized using choline chloride as the template in a shorter crystallization time under hydrothermal conditions. Many factors that may influence the synthesis were investigated. The ERI content in ZSM-34 could be adjusted by selecting different synthesis conditions. The synthesized products were characterized by X-ray diffraction, scanning electron micros-copy, and X-ray fluorescence spectroscopy. Adsorption experiments showed that ZSM-34 possessed high pore volume, and the adsorption amount of n-hexane reached 11.4%. In the methanol-to-olefins reaction, HZSM-34 exhibited high selectivity for ethylene. The maximum selectivity for total olefins (C2H4 + C3H6) over HZSM-34 was 86.0%, and it nearly did not change even when the methanol conversion decreased. High-temperature steam treatment caused the increase of the framework Si/Al ratio and thus decreased the acidity of HZSM-34, which led to the obvious decrease in propane selectivity and the increase in initial olefins selectivity.