Synthesis of ethyl β-naphthyl ether (neroline) using SO 42−/Al-MCM-41 mesoporous molecular sieves

Abstract

The mesoporous molecular sieves Al-MCM-41 with Si/Al ratio equal to 30, was synthesized under hydrothermal conditions using cetyltrimethylammonium (CTMA +) surfactants as template in the absence of auxiliary organics. The same ratio of Al-MCM-41 materials was impregnated using sulfuric acid, the materials such as sulfated Al-MCM-41 (SO 4 2−/Al-MCM-41). The mesoporous materials, viz. Al-MCM-41 and SO 4 2−/Al-MCM-41 were characterized using several techniques, e.g. inductively coupled plasma-atomic emission spectroscopy (ICP-AES), nephelometer, powder X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FT-IR), thermogravimetric–differential thermal analyzer (TG–DTA) and nitrogen adsorption measurements. ICP-AES studies indicated the content of Al in the mesoporous materials. Nephelometer studies indicated the SO 4 2− content in the SO 4 2−/Al-MCM-41. XRD studies indicated that the calcined materials of Al-MCM-41 and SO 4 2−/Al-MCM-41 had the standard MCM-41 structure. FT-IR studies indicated that Al ions were incorporated on the hexagonal mesoporous of Al-MCM-41 and sulfuric acid was impregnated into hexagonal Al-MCM-41 materials. Thermal stability of the as-synthesized Al-MCM-41 materials and SO 4 2−/Al-MCM-41 materials was studied using TG/DTA. The surface area, pore diameter, and pore volume of the mesoporous materials were calculated by BET and BJH equations, respectively. Crystallinity, surface area, pore diameter and pore volume of SO 4 2−/Al-MCM-41 decreased and expelling the aluminum from the Al-MCM-41 framework increased the Lewis acidity. The catalytic results were compared with those obtained by using sulfuric acid, amorphous silica-alumina, H-β, USY and H-ZSM-5 zeolites. The SO 4 2−/Al-MCM-41 catalysts was found to be more effective in the ethoxylation of hydroxyl biaromatics, for example, in the production of ethyl β-naphthyl ether (neroline) from β-naphthol using ethyl acetate as the ethoxylating reagent. The SO 4 2−/Al-MCM-41 catalyst exclusively forms the product of ethyl β-naphthyl ether and has much higher yields than other catalysts except USY.