Plastic depolymerization using silica based catalysts

A process for depolymerizing plastics, comprising:

• a) providing a plastic waste feed stock comprising recycled polypropylene and polyethylene, and melting the waste feed stock to form a melt product;
• b) subjecting the melt product obtained in (a) to a temperature ranging from 280° C. to 600° C. in a first depolymerization reactor which is an agitated vessel, thereby obtaining a depolymerization product, wherein the depolymerization product comprises a gaseous stream which is sent to a condensation unit;
• wherein the melt product is contacted with a catalyst comprising a support and a heteropolyacid, wherein the catalyst is a supported heteropolyacid, wherein the heteropolyacid comprises a transition metal portion containing one or more transition metals selected from the group consisting of W, Mo, and V and a non-metal portion containing one or more non-metal elements selected from the group consisting of Si, P, and As
• c) at least partially condensing the gaseous stream to form a condensed product, wherein the condensed product contains an oily condensed depolymerized product made from hydrocarbons;
• d) subjecting the condensed product to a second depolymerization reactor carried out in the presence of the catalyst thereby producing a first liquid depolymerization product and a gaseous depolymerization product;
• e) recycling the catalyst and part of the first liquid depolymerization product back to the first depolymerization reactor, and discharging a solid residue from the first depolymerization reactor;
• and
• f) condensing a gaseous effluent coming from the second depolymerization reactor thereby obtaining a second liquid depolymerization product.