Catalytic compositions for depolymerizing polyolefin-based waste material into useful petrochemical products and methods of use are described. The compositions are a composite of at least one zeolite catalyst with one or more co-catalyst(s) that is a solid inorganic material. These composite catalysts, along with heat, are used to both increase the depolymerization reaction rate of the feed streams and suppress poisoning effects of non-polyolefin polymers that may be present. This results in a shorter residence time in the depolymerization unit and more efficient process.