The Isopropylation of Naphthalene over H-MCM22 (MWW): The Formation of Triisopropylnaphthalenes

Abstract

Abstract The isopropylation of naphthalene (NP) was carried out over H-MCM-22 (MWW), and the isomer distribution of the isopropylates: isopropylnaphthalene (IPN) diisopropylnaphthalene (DIPN), triisopropylnaphthalene (TriIPN), and tetraisopropyl-naphthalene (TetIPN) was investigated. The catalytic results revealed that MWW is very active for their formation of the isopropylates at the reaction temperatures of 175–300 °C. This rapid formation of DIPN, TriIPN, and TetIPN isomers is considered to occur by multi-step isopropylation of NP during one stay on the catalytic site cooperating with the neighbor propene adsorbed sites. TriIPN isomers were the predominant products. Among them, α,β,β-TriIPN (1,3,6- and 1,3,7-) was obtained as major isomers, which are principally formed from α,β- and β,β-DIPN by α- and β-attacks, and α,α,β-TriIPN (1,4,6- and 1,3,5-) were formed as minor isomers. The selectivities for α,β,β-TriIPN isomers were governed by the steric configuration of the side-pockets of MWW: the pockets favored slim and stable 1,3,6- and 1,3,7-TriIPN from α,β- and β,β-DIPN, and bulky and less stable 1,3,5- and 1,4,6-TriIPN from α,α- and α,β-DIPN are disfavored by their steric restriction with side-pockets. The selectivities for TriIPN isomers were almost constant with the change of reaction factors: temperature, period, and catalyst amount. TetIPN isomers also formed in high yield, particularly, by using large amounts of the catalyst. The comparison of H-MCM-22 (MWW) with H-Y (FAU) and H-AlSBA-1 clarified the roles of the side-pockets in the isopropylation of NP.