Manipulate the acidity of gallium doped Silicalite-1 to optimize methanol to propene performance

Optimising the balance between propene selectivity, propene/ethene (P/E) ratio and catalytic stability and unravelling the relationship between the acidity of MFI-zeolites and those performances are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the acidity of MFI-zeolites by incorporating gallium(III) centres into Silicalite-1 (S-1), obtain an optimal GaS-1(1.3) zeolite through optimizing the gallium content by hydrothermal method·NH3-TPD and pyridine-IR reveal that the ratios of Weak/Strong acid sites (W/S ratios) dominates P/E ratios, while the ratios of Lewis/Brönsted acid sites (L/B ratios) determines lifetime of MFI-zeolites during MTP process. The resultant GaS-1(1.3) zeolite exhibits simultaneously remarkable propene selectivity (45.3 %), P/E ratio (14.6) and catalytic stability (>180 h) at full methanol conversion. Compared with HZSM-5 zeolite, the acidity could be weakened by Ga substitution and the optimization of Ga coordination structure creates an optimal acidity for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.