Influence of different templates on the acidity of ZSM-22 zeolite and its catalytic performance for hydroisomerization of n-decane

ZSM-22 zeolites with different SiO₂/Al₂O₃ ratio were synthesized under static conditions by using 1,6-diaminohexane and 1-ethylpyridinium bromide as template, respectively.The structure and acidic properties were characterized by X-ray diffraction (XRD), X Ray Fluorescence (XRF), N₂ adsorption, Scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH₃-TPD) and FT-IR spectroscopy of pyridine adsorbed (Py-IR). The 0.5%Pd/ZSM-22 bifunctional catalysts were prepared, and the dispersions of metal Pd over bifunctional catalysts were characterized by H₂ chemical adsorption, and their catalytic performance for hydroisomerization of n-decane were investigated in the fixed reactor. The results showed that different templates have great influence on the structure and acidity of ZSM-22 zeolites. ZSM-22 zeolite synthesized with 1,6-diaminohexane as template has smaller crystallite size, and isomerization product has shorter spread distance within the molecular sieve channel. It also has high B acid/L acid ratio, medium acidity, and synergetic effect between metal site and acid site. The conversion and isomerization selectivity of n-decane were high over the bifunctional catalysts Pd/ZSM-22.