The immobilization "in situ" of soluble catalyst Tp(Ms)*TiCl3 (1) on MAO-modified silica (4.0 wt.% Al/SiO2) yields active supported catalyst for ethylene polymerization. This supported catalyst showed activities between 132 and 461 kg of PE/mol[Ti] h atm which varies according to the nature of cocatalyst (MAO > TMA > TiBA > IPRA). Upon activation with MAO, no significant impact on the activity has been observed at 30 and 60 degrees C however at higher temperature (90 degrees C) the activity decreases substantially as result of a partial catalyst deactivation. Studies related to the influence of the [Al]/[Ti] molar ratio using TMA as cocatalyst have shown that this supported catalyst presented higher activities using Al concentrations as low as 25:1. The viscosity-average molecular weights ((M) over bar (v)) of the PE's produced with 1/SMAO-4 are strongly influenced by the Al concentration varying from 0.41 to 13.6 x 10(5) g/mol. Resulting polyethylenes can replicate the support morphology. The scanning electron microscopy (SEM) studies revealed that the spherical morphology of the supported catalyst is replicated in the polyethylene particles. (C) 2007 Elsevier B.V. All rights reserved.