Selective Introduction of Acid Sites in Different Confined Positions in ZSM-5 and Its Catalytic Implications

Controlling the location of acid sites in zeolites can have a great effect on catalysis. In this work we face the objective of directing the location of Al into the 10R channels of ZSM-5 by taking advantage of the structural preference of B to occupy certain positions at the channel intersections, as suggested by theoretical calculations. The synthesis of B-Al-ZSM-5 zeolites with variable Si/Al and Si/B ratios, followed by B removal in a postsynthesis treatment, produces ZSM-5 samples enriched in Al occupying positions at 10R channels. The location of the acid sites is determined on the basis of the product distribution of 1-hexene cracking as a test reaction. The higher selectivity to propene and lower C /C ratio in the samples synthesized with B and subsequently deboronated can be related to a larger concentration of acid sites in 10R channels, where monomolecular cracking occurs. Finally, several ZSM-5 samples have been tested in the methanol to propene reaction, and those synthesized through the B-assisted method show longer catalytic lifetime, higher propene yield, and lower yield of alkanes and aromatics.This work was supported by the European Union through ERC-AdG-2014-671093 (SynCatMatch) and the Spanish Government-MINECO through ‘‘Severo Ochoa” (SEV-2016-0683) and CTQ2015-70126-R. The Electron Microscopy Service of the UPV is acknowledged for their help in sample characterization. Red Española de Supercomputación (RES) and Centre de Càlcul de la Universitat de Valencia are gratefully acknowledged for computational resources and technical support. C.L. acknowledges the China Scholarship Council (CSC) for a Ph.D. fellowship