Effects of solvent on the catalytic isomerization of 1,5-dimethylnaphthalene and the adsorption of 2,6-dimethylnaphthalene

Abstract

2,6-dimethylnaphthalene (DMN) is a precursor to a polyester with enhanced properties, e.g. polyethylene naphthalate (PEN). Limitations of PEN production are the maximum yield and separation of 2,6-DMN. Recently, it was revealed that using toluene as a media can lower the isomerization temperature and provide hiigh purity 2,6-DMN from the adsorptive separation. In this work, the effects of seven solvents on the DMN isomerization and adsorption were investigated; i.e. benzene, toluene, ethylbenzene, m-, o-, p-xylene and p-diethylbenzene. The isomerization experiment using an H-beta catalyst was conducted in a batch reactor. The result indicates that only benzene and toluene facilitate the desired reaction without any side reactions, while the other solvents do not. The adsorptive separation study by using the pulse test technique over NaX and NaY reveals that in order to achieve good separation the adsorptivity of the desorbent has to be balanced with that of DMNs. The acid-base interaction plays an important role by controlling both the DMNs and desorbent adsorptivity. In addition, the Na cations are the major sites creating 1,5-DMN preferential adsorption.