摘要
合成了不同粒度的ZSM-5分子筛,并通过改性得到两个系列的HZSM-5样品:(1)酸度相近,粒度不同;(2)粒度相同,酸度不同。用扫描电镜和NH_3-TPD方法对粒度和酸度进行了测定,并与单片扩散反应器(SPDR)测定的反应和扩散的结果相关联。结果表明,在邻二甲苯异构化反应中,反应的对位选择性不但受分子筛粒度的影响,也受分子筛表面酸性的影响。大晶粒和高酸度都有利于对位异构体的生成,但两个因素影响的动态性质有所不同。
ZSM-5 samples with different crystallite sizes have been synthesized by conventional method and two series of ZSM-5 sample which are obtained by further modification have been studied. They are samples with similar acidity and different crystallite sizes and samples with similar crystallite size and different acidities. The crystallite size and acidity of ZSM-5 are determined by SEM and NH3-TPD methods respectively, and the results are correlated with the results of isomerization and diffusion of o-xylene obtained by using the single pellet diffusion reactor technique. It Is found that both the crystallite size and the surf ace acidity of ZSM-5 play an important role in isomerization reaction. Either the large crystallite or the high acidity favors the para-selectivity, but these two factors assume different extent of influence on pa r a -selectivity as reaction time goes on.
基金
国家自然科学基金
