A series of Al-MCM-41 modified with 1-7% lanthanum were used as supports to prepare the Mo/La-Al-MCM-41 catalysts containing 10 wt.% molybdenum. The supports and catalysts were characterized with XRD, BET, XPS, TPD, TEM and SEM, and their catalytic activities were tested for thiophene hydrodesulfurization. The La addition did not cause any significant collapse of the structure and morphology of Al-MCM-41 samples, and increased the acidity of Al-MCM-41 samples. The Mo/La-Al-MCM-41 catalysts showed higher thiophene HDS activity than nonmodified catalysts. The La-modified catalysts showed an enhanced butene selectivity but a decreased tetrahydrothiophene selectivity, indicating that the La-Al-MCM-41 supports contained a larger amount of acid sites. (c) 2005 Elsevier B.V. All rights reserved.