Catalysts based on tungstophosphoric and molybdophosphoric acids supported on SiMCM-41 and amine-functionalized SiMCM-41 were obtained. They were characterized by FF-IR and P-31 NMR spectroscopies, and their acidity was determined by potentiometric titration with n-butylamine. The undegraded Keggin structure was observed when the heteropolyacids (HPA) are supported on SiMCM-41, and there was a partial degradation to a lacunar species on the amine-functionalized carrier. Also, the acidity of the latter catalysts was lower. The supported Keggin heteropolyacid catalysts are used for the preparation of different substituted ethyl beta-arylaminocrotonates, intermediates in the synthesis of 4-quinolones, from substituted anilines and ethyl acetoacetate. The products were obtained with high selectivity. The effect of the different nature of the aniline substitutes was observed. For this Conrad-Limpach reaction, the activity of the prepared catalysts agrees with the different characteristics of the supported heteropolyacids, the yield being higher for the SiMCM-41 supported catalysts. (c) 2006 Elsevier B.V. All rights reserved.