Synthesis of ZSM-22 molecular sieve and its n-dodecane hydroisomerization performance:Effect of template agent and dynamic crystallization
ZSM-22 zeolites with different morphologies and aggregation states were synthesized by using diethylamine(DEA)or 1,6-hexadiamine(DAH)as templates under static or dynamic conditions,respectively,and characterized by XRD,SEM,EDS,TEM,NH3-TPD and N2 adsorption/desorption.The bifunctional catalyst was prepared by mechanical mixing Pt loaded Al2O3 with ZSM-22,and its n-dodecane hydroisomerization performance was investigated.The results showed that template agent and dynamic crystallization could change the morphology and aggregation state of ZSM-22 molecular sieve,and affect its acidity,specific surface area and hydroisomerization activity.ZSM-22 synthesized with diethylamine as template and after 72h of static crystallization had the best catalytic performance.At 310℃,the selectivity of isomerization of n-dodecane reached 90%when the conversion of isomerization was 66%.However,the template agent and the dynamic crystallization conditions had little effect on the distribution of the single branched isomer in product.The isomer products were dominated by 2-methylundecane with the branched chain near the end,and the selectivity of 2-methyl isomer decreased with the increase of reaction temperature.
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