Synthesis Of 2,6-Dimethylnaphthalene On Mesoporous ZSM-5 Catalyst

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.