A series of methylaluminoxane (MAO)-modified PQ and EP 12 silicas, calcined at 110, 250, and 450 degrees C, were prepared. The resulting MAO-modified supports were characterized by a set of complementary techniques: Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), small angle X-ray scattering (SAXS), and thermal gravimetric analysis (TGA). The Al/Si ratios of the MAO-modified PQ and EP12 silicas were in the ranges of 0.19-0.27 wt % and 0.17-0.30 wt %, respectively. MAO-modified silicas were used in the polymerization of ethylene using an Et(2)IndZrCl(2) catalyst. The MAO-modified PQ silica showed higher activity in comparison to the MAO-modified EP12. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4568-4575, 2013