Al-MCM-41 type catalysts with different Al content (Si/Al = 10, 20,40 as atomic ratio) have been prepared using cetyltrimethylammonium chloride as the organic surfactant and characterised by XRD, NMR, TGA, N-2 sorption, FT-IR, TPD and pyridine adsorption. Different diluents such as methanol, ethanol, isopropanol and water have been used in different compositions for cyclohexanone-oxime (CEOX) selective conversion to epsilon-caprolactam over these ordered mesostructures, revealing the positive effect of polar diluents and above all of ethanol on conversion and epsilon-caprolactam selectivity. The increase of the weight hourly space velocity (WHSV) decreases the catalyst lifetime, while a better catalytic activity is obtained for a lower SUM ratio. (C) 2004 Elsevier B.V. All rights reserved.