Ethylation of isopropylbenzene (IPB) with diethyl carbonate (DEC) was studied using Al-MCM-41 molecular sieves with Si/Al ratios of 33, 52, 75 and 114 at temperatures ranging from 200 to 350 degrees C. Both mono-ethylated and diethylated isomers were obtained. The products obtained were 2-ethyl-isopropylbenzene (2-EIPB), 3-ethyl-isopropylbenzene (3-EIPB), 4-ethyl-isopropylbenzene (4-EIPB), 2,4-diethylisopropylbenzene (2,4-DEIPB), 2,6-diethyl-isopropylbenzene (2,6-DEIPB) and ethylbenzene (EB). The Al-MCM-41 mesoporous materials were characterized using powder X-ray diffraction (XRD), nitrogen adsorption measurements (BET) and thermogravimetric-differential thermogravimetric analysis (TGA-DTG). XRD studies indicated that the calcined and as-synthesized materials had the standard MCM-41 structure. Nitrogen adsorption was used to determine specific surface area, pore volume, and pore size distribution in the Al-MCM-41 (33), Al-MCM-41 (52), Al-MCM-41 (75) and Al-MCM-41 (114) mesoporous molecular sieves. FT-IR studies showed that Al ions were incorporated into the hexagonal mesoporous structures of Al-MCM-41. The thermal stability of the as-synthesized materials was studied using TGA-DTG. The effects of reaction temperature, WHSV and feed ratios on the selectivity of 4-EIPB were studied. (c) 2005 Elsevier B.V. All rights reserved.