ZSM-22分子筛合成及其正十二烷烃临氢异构化性能:模板剂和动态晶化的影响

Synthesis of ZSM-22 molecular sieve and its n-dodecane hydroisomerization performance:Effect of template agent and dynamic crystallization

以二乙胺(DEA)或1,6-己二胺(DAH)为模板剂,分别在静态或动态条件下合成具有不同形貌和聚集状态的ZSM-22分子筛,采用XRD、SEM、EDS、TEM、NH3-TPD及N2吸附/脱附表征手段对其进行表征分析。并负载Pt在Al2O3上和ZSM-22机械混合制备双功能催化剂,考察其正十二烷的临氢异构化反应性能。结果表明,模板剂和动态晶化会改变ZSM-22分子筛的形貌及聚集状态,并且会影响其酸性、比表面积和临氢异构活性。其中,以二乙胺为模板剂,静态晶化72h合成的ZSM-22具有最优的催化性能,在310℃反应温度下,正十二烷异构化转化率为66%时,异构十二烷的选择性达到90%。但是,模板剂及动态晶化条件对单支链异构体的产物分布影响较小,异构体产物以支链靠近端位的2-甲基十一烷为主,且随着反应温度升高,2-甲基异构体选择性明显降低。

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.