高硅铝比B-NaY分子筛合成及催化二乙苯烷基转移性能

为了得到性能良好的B-NaY分子筛,采用直接水热合成法合成杂原子B-NaY分子筛,研究了未处理硅源以及分别用草酸、硫酸、硫酸铝预处理硅源方法所合成B-NaY分子筛物化性能。结果表明,当采用草酸对硅源进行预处理时,可以得到相对结晶度为97%,骨架硅铝比为6.3的高硅B-NaY分子筛,且晶化速率较快。采用草酸对硅源进行预处理,不仅可以增大硅源中硅酸根离子的聚合度,而且在晶化过程中草酸作为一种络合剂能通过与OH-一起和Al3+配位形成四配位活性铝物种,促进凝胶溶解,使得溶液中活性铝物种含量增加,有利于加速晶化。考察了所合成分子筛在二乙苯与苯烷基转移制备乙苯的反应中的催化性能,在反应温度175℃、反应压力3 MPa、苯与二乙苯质量比2、质量空速为3.3 h-1条件下,二乙苯转化率达50%以上,乙苯选择性达99.3%。草酸预处理硅源合成B-NaY分子筛的方法操作简单、快捷,所合成B-NaY分子筛性能优异,有良好的工业应用前景。

Synthesis of High SiO2/Al2O3 Ratio B-NaY Zeolite and its Catalytic Performance in the Diethylbenzene Transalkylation

To obtain a well-behaved B-NaY zeolite,a series of heteroatom B-NaY zeolites were synthesized by direct hydrothermal method using the untreated silicon source and that pretreated with oxalic acid,sulfuric acid and aluminum sulfate,respectively.The physical and chemical properties of the synthesized B-NaY zeolites were studied.The results showed that when the silicon source was pretreated by oxalic acid,the well-crystallized B-NaY zeolites with the relative crystallinity 97％ and the SiO2/Al2O3 ratio 6.3 were obtained,and the crystallization rate was faster.The pretreatment of silicon source with oxalic acid can not only increase the degree of polymerization of silicate ion in the silicon source,but also increase the active aluminum species in the process of crystallization,because oxalic acid as a complexing agent can form four coordination active aluminum with OH-and Al3+ to promote the dissolution of the gel,making the solution of active aluminum species content increased,which was conducive to accelerated crystallization.The catalytic performance of the synthesized catalysts in the reaction of diethylbenzene with phenylalkyl transfer to ethylbenzene was studied.Under the experimental conditions of the reaction temperature 175 ℃,reaction pressure 3 MPa,mass ratio of benzene to diethylbenzene 2 and mass space velocity of 3.3 h-1,the diethylbenzene conversion was over 50％,and the selectivity of ethylbenzene was up to 99.3％.The method for the B-NaY zeolites synthesis using oxalic acid pretreated silicon source was simple and fast,and the synthesized B-NaY zeolites had excellent performance.There would be a good industrial application prospect in the future.