Dialkylation of naphthalene with isopropanol over [H.sub.3]P[O.sub.4]/MCM-41 catalysts for the environmentally friendly synthesis of 2,6-dialkylnaphthalene

AlMCM-41 materials with Si[O.sub.2]/[Al.sub.2][O.sub.3] molar ratios 20, 70, 110, 150, 200, and Si-MCM-41 were synthesized following standard procedures, and loaded with different amounts of [H.sub.3]P[O.sub.4]. The catalysts were well characterized by powder X-ray diffraction (XRD), nitrogen adsorption studies, and solid state [sup.29]Si, [sup.27]Al, [sup.31]P, [sup.23]Na and ¹H MAS NMR spectroscopy. Acidity measurement by FT-IR spectroscopy monitoring of pyridine adsorption reveals that the incorporation of Al in the framework generates Bronsted and Lewis acidity, which increases with the increase in metal content. By loading [H.sub.3]P[O.sub.4] on the AlMCM-41, Bronsted sites increases substantially, but the Lewis sites decrease to a large extent. Liquid phase isopropylation of naphthalene with isopropanol in n-hexane under autogeneous pressure was performed in the temperature range 473-623 K. The optimum feed molar ratio was found to be 1:2:10 (naphthalene:isopropanol:n-hexane), where the naphthalene conversion reaches to 85.5%. The β-and β,β-selectivities over 30 wt% [H.sub.3]P[O.sub.4]AlMCM-41(200) were 97.0 and 84.8, respectively, at 85.5% conversion. The main products of the reaction, mono and diisopropylnaphthalenes, were analyzed and identified by gas chromatography and confirmed by GC-MS. The conversion and selectivity of the products are discussed from the point of view of catalyst characteristics and reaction conditions.