Journal of Molecular Catalysis A: Chemical 191 (2003) 67–74 Immobilization of aluminum chloride on MCM-41 as a new catalyst system for liquid-phase isopropylation of naphthalene X.S. Zhao a,∗ , Max G.Q. Lu b , C. Song c a Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore b Nanomaterials Center, University of Queensland, Brisbane, Qld 4072, Australia c Applied Catalysis in Energy Laboratory, Department of Energy and Geo-Environmental Engineering, Pennsylvania State University, University Park, PA 16802, USA Received 16 November 2001; received in revised form 20 May 2002; accepted 4 June 2002 Abstract A great deal of effort has been made at searching for alternative catalysts to replace conventional Lewis acid catalyst alu- minum trichloride (AlCl 3 ). In this paper, immobilization of AlCl 3 on mesoporous MCM-41 silica with and without modifica- tion 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. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Aluminum chloride; MCM-41; Isopropylation of naphthalene; Silylation 1. Introduction Liquid-phase Friedel–Crafts isopropylation of naphthalene is a process currently used in the chem- ical industry to produce 2,6-diisopropylnaphthalene (2,6-DIPN), an important chemical intermediate for manufacturing advanced polymers and polyesters [1]. The catalyst used in this process is Lewis acid AlCl 3 [2]. While AlCl 3 is catalytically efficient and readily available commercially, the use of it as a ∗ Corresponding author. Tel.: +65-8744727; fax: +65-7791936. E-mail address: chezxs@nus.edu.sg (X.S. Zhao). catalyst is environmentally problematic [1]: (i) the AlCl 3 catalyst produces the thermodynamic ratio of the desired linear 2,6-DIPN and the undesired nonlinear 2,7-diisoprolylnaphthalene (2,7-DIPN) and other DIPN isomers, requiring a costly sepa- ration step to isolate the 2,6 isomer; (ii) significant quantities of other naphthalene derivatives such as 2-isopropylnaphthalene (2-IPN) are formed, which must also be separated and removed or recycled; (iii) the AlCl 3 catalyst cannot be regenerated and must be hydrolyzed and disposed of, resulting in a large volume of solid waste. Consequently, much research effort has been directed towards zeolite alternatives 1381-1169/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S1381-1169(02)00366-7