碱处理法制备微介孔ZSM-5及其加氢脱硫性能的研究

以不同浓度Na2CO3和NaOH溶液对ZSM-5分子筛进行脱硅处理,采用XRD,SEM,BET,NH3-TPD手段对处理前后的分子筛进行表征,并考察不同浓度碱液处理并负载Co、Mo金属的催化剂对加氢脱硫性能的影响。结果表明:碱处理可以得到微介孔结构的ZSM-5分子筛,并可调变分子筛的酸性,提高脱硫效果与烯烃芳构化活性;NaOH溶液对ZSM-5分子筛的晶体结构影响较大,经低浓度的NaOH溶液(0.5mol/L)处理后,ZSM-5分子筛的相对结晶度下降至90.8%;NaOH溶液浓度为1.0mol/L时,ZSM-5分子筛的结晶度仅为78.3%,比表面积、孔体积和孔径均下降;采用Na2CO3溶液处理时,在得到微介孔结构ZSM-5分子筛的同时对ZSM-5分子筛的晶体结构影响较小,当Na2CO3溶液浓度为4.0mol/L时,得到的Co-Mo/ZSM-5催化剂在FCC汽油加氢脱硫及芳构化反应中,脱硫率高达94.2%,汽油中芳烃体积分数增加20.7百分点。

STUDY ON PREPARATION OF MICRO-MESOPOROUS ZSM-5 ZEOLITE BY ALKALI TREATMENT AND PROFORMANCE IN HYDRODESULFURIZATION OF FCC GASOLINE

ZSM-5 zeolites were treated by different concentrations of Na2CO3 and NaOH solution. The zeolites before and after alkali treatment were characterized by XRD, BET, SEM and NH3-TPD techniques. The hydrodesulfurization and aromatization performance of the catalysts loaded with Co-Mo based on zeolites before and after treated by different concentrations of alkali solution was investigated. The results show that ZSM-5 zeolite is apt to form micro-mesoporous structure after alkali-treatment. The alkali treatment could modulate the acidity and significantly improve the activity of desulfurization and olefins aromatization. The low concentration NaOH solution (0.5 mol/L) impacts on the crystal structure of ZSM-5 zeolite and the relative crystallization declines to 90.8%. When the concentration of NaOH solution is 1.0 mol/L, the crystallinity of ZSM-5 zeolite is only 78.3%, the BET surface area, pore size and pore volume are all reduced. However, the Na2CO3 solution treatment for desilication, micro- mesoporous ZSM-5 zeolite can be obtained with the crystal structure hardly affected. The Co-Mo catalyst based on the zeolite treated with Na2CO3 solution (4.0 mol/L) displays a higher FCCG hydrodesulfurization and aromatization activity. The desulfurization rate reaches 94.2% and the aromatics increase 20.7 percentage points.