Skeletal isomerization of tetradecane catalyzed by TON-type zeolites with a fragmented core–shell structure

TON-type zeolites with a core–shell structure were synthesized by crystal overgrowth of an aluminum-free TON-type zeolite on an aluminum-containing TON-type zeolite in the presence of fluoride ion, which was used as a mineralizing reagent to restrain the formation of defects. The core–shell structured zeolite showed greater selectivity for skeletal isomerization in tetradecane hydroisomerization because the acid sites on the external surface of needle-shaped crystals were passivated to inhibit cracking. Breaking the needle-shaped crystals of the core–shell structure to create shorter crystal pieces effectively enhanced the catalytic activity and selectivity for isomerization because new pore entrances were formed.

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► TON-type zeolites with a core–shell structure were synthesized by crystal overgrowth.
► The core–shell zeolite with minimal defects was synthesized in the presence of F ion.
► The shell passivated acid sites on the external surface.
► Breaking the core–shell structure enhanced the catalytic activity and selectivity.