Facile fabrication of hierarchical SAPO-34 zeolite with enhanced MTO catalytic performance

SAPO-34 zeolites with excellent selectivity towards to light olefins and highly catalytic stability are highly desirable. In this work, SAPO-34 zeolite (SAPO-34-S-F) featuring both significantly reduced crystal dimension and a hierarchical structure was synthesized for the first time through a seed-assisted strategy employing cost-effective triethylamine (TEA) as the only organic structure-directing agent (OSDA) in the NH₄F-containing medium. The resulting SAPO-34 zeolite demonstrated exceptional catalytic performance in methanol-to-olefin (MTO) reaction, exhibiting a substantially increased catalytic lifetime of 525 min as well as an impressive light olefin selectivity of up to 83.7 %. These results significantly outperform those of conventional SAPO-34 zeolite with larger crystal dimension synthesized using TEA as OSDA, and SAPO-34 zeolite with similar crystal dimension synthesized without fluoride addition. Thermogravimetric analysis (TGA) of the spent catalysts revealed that SAPO-34-S-F possesses enhanced coke tolerance. Furthermore, in situ UV/Vis studies of the organic intermediates generated on zeolites during MTO reaction provided additional evidence for the excellent catalytic activity and stability of the SAPO-34-S-F sample. These findings offer important insights for the rational development of stable and high-efficiency SAPO-34 zeolite for MTO reaction.