Abstract
Immobilized aluminum chloride catalyst on surface-modified mesoporous MCM-41 silica displays a similar catalytic activity to that of homogeneous aluminum chloride catalyst while offers the advantages of high selectivity towards 2,6-DIPN. This new catalyst system can be easily recovered from the reaction mixture, regenerated and reused without significant loss in catalytic performance, showing that it is a very promising alternative for replacing environmentally unfriendly AlCl
3 catalyst.
A great deal of effort has been made at searching for alternative catalysts to replace conventional Lewis acid catalyst aluminum trichloride (AlCl
3). In this paper, immobilization of AlCl
3 on mesoporous MCM-41 silica with and without modification was carried out. The catalytic properties of the immobilized catalyst systems for liquid-phase isopropylation of naphthalene were studied and compared with those of H/MCM-41 and H/mordenite. The structures of the surface-immobilized aluminum chloride catalysts were studied and identified by using solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption, and X-ray diffraction (XRD) techniques. The catalytic activity of the immobilized catalysts was found to be similar to that of acidic mordenite zeolite. A significant enhancement in the selectivity of 2,6-diisopropylnaphthalene (2,6-DIPN) was observed over the immobilized aluminum chloride catalysts. Immobilization of aluminum chloride on mesoporous silica coupled with surface silylation is a promising way of developing alternative catalyst system for liquid-phase Friedel–Crafts alkylation reactions.