以四丙基氢氧化胺为模板剂、聚乙二醇为添加剂,水热合成了粒径在0.1~14μm且分布均一的ZSM-5分子筛,并采用XRD、SEM、BET、Py-IR、NH3-TPD和ICP等技术对其进行了表征,考察了不同粒径分子筛在甲醇转化制碳氢化合物反应中的催化作用。结果表明,通过调变PEG添加量、硅源种类和水含量以及控制陈化和晶化条件,可以在较大范围内调变分子筛晶粒尺寸。随着粒径的减小,ZSM-5晶粒的聚集程度、比表面积和Si/Al比提高,而结晶度、Brnsted酸浓度和总酸量有所下降。在甲醇催化转化制碳氢化合物的反应中,粒径为0.1μm的分子筛催化稳定性最好;随着粒径的增大,其稳定性逐渐下降,粒径为14μm的分子筛催化剂寿命明显降低。同时,粒径对甲醇转化产物分布也有较大影响;小粒径分子筛有利于生成轻质烃类(C1~C4),而大粒径分子筛对C5以上烷烃和芳烃的选择性较高。
ZSM-5 molecular sieves with a uniform particle size from 0.1 to 14μm were hydrothermally synthesized by using tetrapropylammonium hydroxide(TPAOH) as the template and polyethylene glycol(PEG) as a co-template.The ZSM-5 samples were characterized by XRD,SEM,BET,Py-IR,NH3-TPD and ICP and their catalytic performance in the conversion of methanol to hydrocarbons were investigated.The results indicated that the crystal size of ZSM-5 molecular sieves can be regulated by adjusting the quantity of PEG,silica source and water content in the precursor gel as well as controlling the aging and crystallizing conditions.The ZSM-5 molecular sieves with smaller crystal sizes exhibit higher conglomeration degree,Si/Al ratio and surface area than those with large crystal sizes,but lower crystallinity,Brnsted acid density and total acid quantity.When used as the catalysts in methanol conversion to hydrocarbons,the crystal size of ZSM-5 molecular sieves has a significant effect on their catalytic stability and the products distribution.The catalyst with smaller crystal size shows much higher stability and selectivity to the light alkanes of C1~C4;an increase in the crystal size can enhance the formation of C5+ and aromatic products but lead to a significant decline in its stability.