Methods of depolymerizing polyolefin-based material into useful petrochemical products using supported metal oxides and heat are described. The supported metal oxides improve the depolymerization reaction by decreasing the half time for the depolymerization, which results in a higher depolymerization rate and a shorter residence time in the depolymerization unit, allowing for a predictable depolymerization reaction, and decreasing the branching or aromatic formations in the product.