Three-step Recations for Selective Production of 2,6-Rich-DMN from 2,7-Rich-DMN

摘要

Due to the strong demand and high value of monomer for manufacturing the functional engineering plastic and liquid crystalline polymers, the selective synthesis for 2,6-dimethylnaphthalene (DMN) from its isomers has become an important subject. However, in fact, there are ten different isomers in DMN mixture and of these, nine of them can be grouped into three different triads based on the relative ease of isomerization within each certain triad. Such an intra-triad isomerization can be achieved by using various solid acid catalysts. It is generally accepted that a methyl group on naphthalene shifts relatively easily from an alpha position to a beta position or vice versa on the same ring of naphthalene but does not shift easily from a beta position to another beta position on the same ring or from an alpha position to another alpha position. Inui et al have investigated on the relationship between the particle diameters of crystals and catalytic performance, in the correlation between the distribution of acid centres present on the internal or external surfaces of crystals and shape selectivity, and in the shape-selective isomerization of DMNs. Santilli and Chen have developed a method of selective synthesis of 2,6-DMN using a two-step hydroisomerization/dehydrogenation process. But in both case, the reactant feed by them are pure 2,7-DMN, and there is no reported on the selective production of 2,6-DMN directly from the mixture of ten isomers of DMN.