OSDA-free synthesis of FeZSM-22 zeolite from natural minerals for n-octane hydroisomerization

A seed-directed approach to synthesizing FeZSM-22 zeolite without organic structure directing agent (OSDA) was developed by using Fe-rich diatomite as all aluminum and iron sources. The FeZSM-22 zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions. Characterizations show that FeZSM-22 zeolite synthesized with OSDA-free owns high crystallinity, obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio. Significantly, when used for n-octane hydroisomerization reaction, its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C-8 isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals, respectively. This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance. (c) 2023 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.