(241a) Fast Pyrolysis of Polyolefins in a Fluidized Bed Reactor: A Route for Waste Plastic Recycling

According to the EPA, 35,370 U.S. tons of plastic was produced in 2017 in the United States alone. Of that, 2,960 U.S. tons were recycled. The remaining 91 percent have the potential to be transformed into fuels and chemicals, turning this waste into a valuable hydrocarbon feedstock. Research Triangle Institute’s (RTI) extensive resources and expertise in the field of biomass pyrolysis were leveraged to begin addressing the issue of plastic waste. The product composition of polyolefin pyrolysis was assessed using our tandem micropyrolyzer GC-MS/FID, elucidating the impact varying the thermal condition has on polyethylene, polypropylene, and polystyrene. Our laboratory-scale fluidized bed reactor (FBR) system, which has been fully described in literature, was used to pyrolyze these three plastics in an inert nitrogen atmosphere at temperatures between 500 and 700 ^oC, using conditions influenced by the microscale studies. The raw plastic material was milled to less than 1 mm and pneumatically conveyed into a fluidized bed of inert quartz sand, externally heated by an electric furnace. The pyrolytic vapors were then collected in a condensation train. The oil and wax were analyzed via GC-FID, GC-MS, and elemental analysis. Micro-GC and GC-FID instruments were used to identify and quantify the non-condensed vapors. The FBR was shown to yield over 90% valuable oil, wax, and fuel gas from the pyrolysis of these polyolefins, confirming the data gathered by the micropyrolyzer. The effect of an acid catalyst, as well as the interactions which occurred during the co-pyrolysis of mixed plastic streams were also examined on the lab-scale reactor. The process parameter’s effect on the product’s carbon number distribution and composition, as well as the fractionation of the products, will be discussed and compared to literature.