2 - Methylnaphthalene Shape-selective Alkylation Synthesis Of 2,6 - Dimethyl Naphthalene

The compound 2,6-dimethylnaphthalene(2,6-DMN) is used as a precursor of 2, 6-naphthalene dicarboxylic acid in the manufacture of high performance polyester resins such as polyethylene naphthalate polymer(PEN).Compared with polyethylene terephthalate(PET) , PEN has improved thermal, gas barrier and mechanical properties that will lead to new and innovative applications. There have been many expected PEN' s applications to film and bottle uses, such as long time recording type video film, Advanced Photo System, hot fill containers, refiliable bottles and ire codes. However, PEN have heretofore been too expensive to expand its market complete because of few effective processes for the 2, 6-DMN commercialization. Therefore, it has become an important subject to find an efficient process which is able to produce 2, 6-DMN in high yield.In this article the process for preparing 2, 6-DMN by methylation of methylnaphthalene over zeolite catalysts is employed and the effects of catalyst type, reaction conditions, modification and the size of alkylating agent on the alkylation of 2-methylnaphthalene were investigated.1) Compared with the reaction capability of alkylation of methylnaphthalene over HZSM-5 HMCM-22, HB and HM zeolite catalyst, the results showed that the pore channel structure and size is the main factor affecting the reaction capability except for the acidic properties. The order of the activity of these zeolites is HM >HB >HMCM-22 >HZSM-5. The HZSM-5 maked with organic amine (ammonia) as template excelled the one maked with inorganic amine (ethylenediamine) in reaction capability and the micron class HZSM-5 is better than nanometer class HZSM-5.2) We studied these factors of reaction temperature, feed velocity, flux of carrier gas and material ratio in the methylation over HZSM-5 zeolite.We get the following suitable conditions:the reaction temperature is 400C ;the prepared weight ratio of 2-MN to 1, 3, 5-trimethylbenzene to methanol is 1:1:0.25;the flux of carrier gas N2 is 20ml/min;the feed velocity is 2 ml/gcat. h.3) The modified HZSM-5 zeolite can decrease the isomerization of the alkylation reaction of methylnaphthalene, increase the selectivity of2,6-DMN. This paper studied the reaction capability of methylnaphthalene over all the modified HZSM-5 zeolites, and found the modified HZSM-5 with Ethyl Silicate, Zn(N03)2, Mg(N03)2, Rare-earth and NH