Preparation of 2,6-diisopropylnaphthalene with recycled process of isomers

2,6-Diisopropylnaphthalene (2,6-DIPN), as the precursor of important monomer 2,6-naphthalene dicarboxylic acid, was prepared by hydroisopropylation of refined naphthalene with propene over shape-selective catalyst. Naphthalene conversion of 92% and 2,6-DIPN selectivity of 64% were obtained. Static melt crystallization was applied to separate and purify 2,6-DIPN from its isomers, resulted in a product purity of ≥99%. The other isomers were converted into monoisopropylnaphthalene, which also reacted with propene to form 2,6-DIPN. A recycled process including hydroisopropylation, separation and transalkylation was established, the yield of 2,6-DIPN based on naphthalene could be doubled by one cycle operation.