碱处理法改性ZSM-5分子筛催化苯与乙醇烷基化制乙苯

用不同浓度的NaOH溶液对ZSM-5分子筛进行改性,以XRD、SEM、NH3-TPD和BET方法对改性前后的催化剂进行表征,并考察了碱处理改性对ZSM-5分子筛孔结构、酸性以及催化苯与乙醇烷基化反应的性能的影响.结果表明,通过调变NaOH溶液浓度可以在保持ZSM-5分子筛的微孔骨架结构的同时,调变介孔分布.随着NaOH溶液浓度升高,ZSM-5分子筛的酸量、介孔孔容、介孔表面积都增加,孔径分布变宽,从而改善了催化剂的催化性能.对ZSM-5分子筛进行碱改性,比较合适的NaOH溶液浓度为0.2mol/L,改性后的ZSM-5分子筛催化剂具有较高的活性和稳定性.但超过0.5mol/L的NaOH溶液会破坏ZSM-5分子筛骨架结构,该浓度的NaOH溶液改性后的ZSM-5分子筛催化活性下降较快.

Study on Surface Acidity and Morphology of Alkaline-treated ZSM-5 Zeolite for Alkylation of Benzene with Ethanol to Ethylbenzene

The alkylation of benzene with ethanol to produce ethylbenzene over ZSM-5 catalyst has been widely investigated.In order to improve the ZSM-5 catalyst performance,the ZSM-5 zeolite catalysts were modified by desilication treatment in alkaline solution with different concentrations for the alkylation of benzene with ethanol to ethylbenzene,and characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),NH3-TPD,and BET techniques.The characterization results show that mesopore size distribution of the catalysts can be controlled by changing NaOH solution concentration without destroying framework of ZSM-5 zeolite.With the increase concentration of NaOH solution,the amount of acid sites,mesopore volume,and specific surface area increased,the pore size distribution became broader.Therefore,the catalytic performance for the reaction was effectively improved.It was found that the optimal concentration of NaOH solution used to treat the ZSM-5 zeolite was 0.2 mol/L.When the NaOH concentration was over 0.5 mol/L the framework of ZSM-5 zeolite was found to be severely destroyed.