【作者】 周小江；

【导师】 胡浩权； 靳立军；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 硕士

【摘要】 2,6-二甲基萘（2,6-DMN）是合成高性能聚酯材料的重要中间体,目前倍受关注。沸石催化2-甲基萘（2-MN）与甲醇烷基化合成2,6-DMN具有工艺路线短、原料来源广、价格便宜等优点,是一种具有开发潜力的工艺路线。本论文以获得高活性、高稳定性、高2,6-DMN选择性和收率以及2,6-/2,7-DMN比为目标,考察了以MFI系列中,HZSM-5催化剂的制备、改性过程中引入介孔和杂原子对催化效果的影响。对硅铝比为65的微米级HZSM-5进行碱处理脱硅,之后进行Zr同晶取代,并与硅铝比为28纳米沸石进行比较。发现尽管所使用的纳米ZSM-5催化剂有着较低的硅铝比和较小的颗粒尺寸,但其催化活性却没有碱处理后的微米ZSM-5催化剂高,由N₂吸附等温线和XRF可知,碱处理脱硅产生了介孔,能够有效地降低反应物在沸石孔道中的扩散阻力,更容易接近活性位从而提高2-MN的转化率。另外,介孔也容易使结炭前驱体扩散出孔道,从而使催化剂寿命得到提高。以硅铝比为28的纳米级HZSM-5进行碱处理脱硅,随后进行Zr同晶取代,考察在纳米级沸石上引入介孔和杂原子改性对催化效果的影响。发现经过碱处理之后,催化剂的活性和寿命的都得到提高,分析其原因为,在碱处理脱硅过程中产生了介孔,增大了反应物和产物在沸石孔道中的扩散性,既有利于反应物接触到催化活性位,又有利于产物扩散出孔道,抑制了结炭前驱体的生成。我们在对纳米ZSM-5以0.025 mol/L的NaOH溶液处理4 h,并以Zr/Al比为0.5的（NH₄）₂ZrF₆进行改性所得的MFI沸石为催化剂进行烷基化反应,在反应进行0.75 h,得到最高9.9%的2,6-DMN收率。以炭气凝胶为硬模板合成多级孔道Fe-MFI沸石,并考察不同含量炭气凝胶对合成的沸石介孔孔容的影响。我们发现,由于炭气凝胶加入所产生的介孔同样有助于沸石催化剂活性和寿命的提高。更多还原

【Abstract】 Selective synthesis of 2,6-dimethylnaphthalene（2,6-DMN）,a preferred intermediate of high performance polymeric materials,has been widely studied.Methylation of 2-methylnaphthalene（2-MN） with methanol is a more promising route to produce 2,6-DMN owing to the simple technologic process,cheap and wide source of raw materials.In this work, we investigatived the effect of preparation,introduce mesoporous and extra-atom into HZSM-5 by modificating to the catalyst reaction,and try to get the catalysts with high activitation and stability,high 2,6-/2,7-DMN ratio and high 2,6-DMN selectivity and yield.The micrometer-scale HZSM-5 with a 65 SiO₂/Al₂O₃ was selected as parent catalyst to be alkali-treated by NaOH solution,and to be modified with（NH₄）₂ZrF₆,the samples were compared the nano-scale HZSM-5.It shows that,the catalyst activity of nano-scale HZSM-5 is lower than the alkali-treated micrometer-scale HZSM-5,although,it has a lower ratio of SiO₂/Al₂O₃ and a smaller crystal-scale.The Nitrogen adsorption isotherms and the XRF show that it is the step of alkali-treatment had introduced some mesoporous into micrometer-scale HZSM-5 by desilication reaction.The mesoporous reduced the resistence of reactants diffusing to catalyst active sites,and the mesoporous made the coking percusor more easliy left catalyst,the lifetime of catalyst improved.The nano-scale HZSM-5 with a 28 SiO₂/Al₂O₃ was selected as parent catalyst to be alkali-treated by NaOH solution,and modified with（NH₄）₂ZrF₆,the effect of the introducing of mesoporous and modified by Zr on methylation reaction was investagated.We found that the activity and life of catalyst were both improved.We considered that the mesoporous had the reactants and reaction products easily diffusing in and out pores,both reactants proned to reach the active sites and reaction products slope off the zeolite internal.When we used the sample prepared by 0.025 mol/L NaOH solution treated for 4 h and then modified by （NH₄）₂ZrF₆ solution with a 0.5 Zr /Al to be modified for 10 h as catalyst to perform the methylation reaction.We got a 9.9%yield of 2,6-DMN when the reaction carried on for 0.75 h.Carbon aerogel as hard template was used to synthesize Fe-MFI zeolite which has some mesoporous,and the effect of carbon aerogel content on the pore volume.We found that the use of carbon aerogel is also helpful to improve the activity and lifetime of the zeolite catalyst.更多还原