Conversion of Marine Plastic Litter into Chemicals and Fuels through Catalytic Pyrolysis Using Commercial and Coal Fly Ash- Synthesized Zeolites

A marine plastic litter (MPL) sample, collected during a beach cleanup campaign, underwent thermal , catalytic pyrolyses to demonstrate that valuable hydrocarbon oil and gas can be produced from heterogeneous plastic waste, partly aged and not mechanically recyclable. A low-cost H-X zeolite lab synthesized from coal fly ash (CFA) was tested and compared with two commercial zeolites (H-USY and H-ZSM-5) commonly used in the industrial cracking field. MPL characterization revealed it is mainly composed of polyethylene and polypropylene (52 and 45 wt %, respectively) , it has ideal physicochemical properties as feed for pyrolysis processes. Thermogravimetric analyses demon-strated that catalysts can reduce the degradation temperature of MPL from 472 to 425 degrees C and from 450 to 421, 342, and 380 degrees C for H-ZSM-5, H-X/CFA, and H-USY, respectively. These results were confirmed by thermal and catalytic pyrolyses tests performed in a bench-scale reactor. All the catalytic tests were carried out at 450 degrees C with a liquid phase contact mode. In particular, H-X/CFA, avoiding tar and wax formation, produced up to 87 wt % of light oil with a high content of short chain aliphatic hydrocarbons, obtaining results very similar to those gained with the expensive commercial H-USY. For all the catalytic pyrolysis tests, the produced gases proved to be more than sufficient to sustain the process heat requirement.

Automated summary

Valuable hydrocarbon oil and gas can be produced from marine plastic litter (MPL) through thermal, catalytic pyrolysis. The low-cost H-X zeolite synthesized from coal fly ash showed better degradation performance compared to the two commercial zeolites commonly used in the industrial cracking field.