A series of amorphous silica-alumina catalysts with similar surface area has been prepared by sol-gel chemistry, We report the results of a study of the role of catalyst acidity on the distribution and quality of the products obtained from the degradation of medium density polyethylene (MDPE). The activity of these catalysts was evaluated with and without a hydrogen donor solvent (tetralin), under high hydrogen pressure (5.5 MPa) and moderate temperatures (653-723 K). It was found that the production of oils from the conversion of MDPE correlated with the Bronsted acidity and not with the total acidity of the catalysts. The presence of the hydrogen donor solvent inhibited the activity of the catalysts and lead to an increase in the molecular weight of the oils.