Synthesis of hierarchical ZSM-11 and its catalytic performances during methanol to propylene.

To solve the easy deactivation of zeolite catalyst in methanol to propylene (MTP) reaction, hierarchical ZSM-11 zeolite composed of loosely aggregating ultra-small nanocrystals (∼10 nm) were prepared using vinyltrimethoxysilane-methyl methacrylate (VTMS-MMA) copolymer latex as a "bond blocker". The structure and texture properties of the as-synthesized zeolite were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption desorption, NH 3 -TPD, and thermogravimetric analysis (TG). The results showed that as compared with the parent ZSM-11-0 without adding the latex, the hierarchically porous ZSM-11- x (1 ≤ x ≤ 3) zeolite synthesized with VTMS-MMA copolymer latex had a higher surface area, mesopore volume, and moderate acidity. Due to the nanocrystallization of the primary grain in the polycrystalline aggregates, the micropores channels in the as-synthesized ZSM-11- x (1 ≤ x ≤ 3) were effectively shortened and abundant intercrystalline mesopores resulted from loosely aggregating of the ultrasmall primary crystals were therefore introduced, which offered the optimized ZSM-11-1 catalysts with a longer catalyst life (46 h) and a higher propylene yield (∼40.5 %) in MTP. Active R–Si(OH) 3 species yielded from the hydrolyzation of the vinyl trimethoxysilane copolymer segment of CPMMA-VTMS suffers from polycondensation reaction with the hydroxyl groups of silicon (aluminum) and then form R–Si(OT) 3 (T = Al or Si) on the surface of the primary microcrystals, locally inhibiting the continuous growth of primary microcrystals. [Display omitted] • Polycrystal ZSM-11 aggregates composed of loosely aggregating ultrasmall nanocrystal. • Active R–Si(OH) 3 species acting as a "bond blocker" inhibit the growth of microcrystals. • Increased C 3 = selectivity and catalytic life while suppressed HTI of C 3 and coke deposition. [ABSTRACT FROM AUTHOR]