Several porous Nb(x)Mo(10-x) mixed oxides prepared from NbCl(5) and MoCl(5) in the presence of block copolymer surfactant Pluronic P-123 were examined as potential solid acid catalysts. Amorphous mesoporous structures were observed in samples with x from 10 to 9, whereas samples with higher Mo concentrations (x = 3-8) formed large pores by inter-particle voids and a non-porous structures with crystallized molybdenum oxide (MoO(3)) were observed in samples with x from 0 to 2. The acid strength increased with increasing the Mo content in Nb(x)Mo(10-x) oxides, which was determined by NH(3) temperature-programmed desorption (NH(3)-TPD) and Fourier transform infrared (FT-IR) spectroscopy using pyridine as a probe molecule. Porous Nb(3)Mo(7) oxide exhibited the highest acid-catalytic activity for the Friedel-Crafts alkylation of anisole due not only to mole ratio of Nb/Mo but also to pore structure. (C) 2010 Elsevier B. V. All rights reserved.