Impact of external surface passivation of nano-ZSM-5 zeolites in the methanol-to-olefins reaction

[Display omitted] •Complete passivation of ZSM-5 zeolites external surface through silylation.•High selectivity toward light olefins obtained over silylated zeolites, up to 65%.•Above 45g of C2–C4 olefins produced per gram of catalyst.•ZSM-5nano-French fries (Si/Al=27) behave as a conventional ZSM-5 with (Si/Al=52). Surfaces of nano-sized ZSM-5 zeolites have been passivated by a chemical liquid deposition (CLD) technique using tetraethylorthosilicate (TEOS). The impact of this post-synthesis treatment has been evaluated in the methanol-to-olefins (MTO) reaction. A two-step surface passivation led to enhanced selectivity towards C2–C4 light olefins, between 10 and 30% in relative, at nearly complete methanol conversion when compared with pristine zeolites. However, these post-treated zeolites exhibited a significant loss in stability. To rationalize these results and establish structure-activity relationships, zeolite catalysts have been thoroughly characterized by nitrogen adsorption–desorption, SEM, XRF, XRD and FTIR techniques. ZSM-5 zeolite (Si/Al=27) in the form of well-arranged rectangular nanocrystals behave in MTO after silylation as a commercial ZSM-5 zeolite having a Si/Al=52.