Insight into the effect of F- on acidity of H-SAPO-18 and its catalytic performance for conversion of methanol to olefins

In this study, F- was added to the synthesis gel to regulate the acid property of SAPO-18 molecular sieve and enhance its catalytic performance for the methanol-to-olefin (MTO) reactions. The results indicate that adding an appropriate amount of F- during synthesis can increase the crystallinity of SAPO-18 molecular sieve and reduce the overall strong acid density and external surface acid content. The H-SAPO-18-I-20-0.0025 molecular sieve exhibits a much higher catalytic lifetime (1000 min) and light olefins selectivity (45.2% to propene and 96.1% to C2-5 = ) in MTO at 400 degrees C than those of the traditional H-SAPO-18-1-0. The results of the isotope labeling experiments, GC-MS, and 13C MAS NMR results provided direct evidence that the aromatic-based cycle contributes more to the conversion of methanol into light olefins, and hexamethylbenzene serves as the most abundant hydrocarbon species that produces propene via the paring route.

Automated summary

F- was added to regulate the acid property of SAPO-18 molecular sieve and enhance its catalytic performance in methanol-to-olefin reactions. The addition of an appropriate amount of F- during synthesis improved the crystallinity of SAPO-18 and reduced strong acid density and external surface acid content. The H-SAPO-18-I-20-0.0025 molecular sieve exhibited a longer catalytic lifetime (1000 min) and higher selectivity towards light olefins (45.2% propene and 96.1% C2-5 =) than the traditional H-SAPO-18-1-0 sieve in MTO at 400°C.