ZSM-22 zeolites were synthesized using different structure-directing
agents (SDAs) with varying alkyl chain lengths, including n-alkyldiamines (DAB, DAH, DAO, and DAD) and lauryl amine
(LA). The characteristics of the resulting samples (denoted as “Z-SDA”)
revealed that optimal elongation of SDA alkyl chains brought about
a decrease in crystallization time while retaining ZSM-22 crystal
phase stability. The morphology and acidity of the samples varied
as the alkyl chain length of the SDAs increased. The average crystal
length ranged from 13 μm to 250 nm, and the total acid content
showed a downward trend, while each sample possessed nonlinear acid
site distributions. Additionally, ZSM-22-supported Pt catalysts were
obtained and probed using the n-hexadecane hydroisomerization
process. It was found that the activity and i-hexadecane
selectivity gradually increased with the alkyl chain length of the
SDAs (C4–C10). Notably, Pt/Z-DAD achieved
>70% yield under specific reaction conditions, which could be attributed
to the abundant mesopore network and high proportion of weak Brønsted
acid site distributions.
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