Date of Award
Doctor of Philosophy
Mechanical Engineering; Biorenewable Resources and Technology
Co-pyrolysis of biomass with plastic is a promising pathway to produce pyrolysis oil with improved quantity and quality. The technology can also provide guidance for processing Municipal Solid Waste consisting of plastic and organic wastes. However, the reaction pathway and chemistry behind co-pyrolysis of biomass and plastics are very complex and unclear. Research in this dissertation focuses on unravelling the cross-reactions between biomass and plastics during co-pyrolysis, and enhancement of these reaction for optimizing the yields of valuable chemicals and hydrocarbons.
First, co-pyrolysis of high density polyethylene and red oak was conducted in a bench-scale continuous fluidized bed reactor. Problems encountered previously including reactor clogging and defluidization were overcome by increasing the pyrolysis temperature over 525 ÃÂ°C. It was found that pyrolysis oil from co-pyrolysis had a significantly higher HHV compared to that from red oak pyrolysis. Synergetic effects were observed in terms of increased yields of furan, acids from read oak, and inhibited char yield.
Second, the co-conversions of polyethylene and cellulose, xylan, lignin were studied in a tandem micro-pyrolyzer. When co-pyolyzed with PE, cellulose and xylan were found to produce more anhydrosugars and light oxygenated compounds, and lignin with higher yield of phenolic monomers. Biomass also facilitated the depolymerization of polyethylene by increasing smaller hydrocarbon molecules. By changing the pyrolysis and catalyst bed temperatures, it was found both thermal synergy and catalytic synergy contribute to the synergetic effects between biomass and polyethylene.
Third, acid pretreated corn stover and polyethylene were co-pyrolyzed to investigate the possibility of boosting the quality of pyrolysis products through synergistic effects. It was discovered that acid infusion strongly catalyzes the cross-reaction between corn stover and polyethylene to improve the sugar yields (during non-catalytic pyrolysis) and hydrocarbon yields (during catalytic pyrolysis) due to enhanced hydrogen transfer from the plastic to biomass. Co-pyrolysis of the acid infused corn stover and polyethylene also demonstrated a potential for overcoming char agglomeration associated with pyrolysis of the acid infused corn stover.
Lastly, a systematic investigation of how carrier gases and feedstock-catalyst contact mode affecting the pyrolysis of different plastics was conducted. The product distribution from catalytic pyrolysis of plastics were highly dependent on the arrangements of feedstock and catalyst (in-situ VS. ex-situ). Pyrolysis of hydrogen deficient plastics (PS and PET) benefited from hydrogen as carrier gas in terms of reduced solid residue and increased selectivity of mono-ring aromatic.
Xue, Yuan, "Thermochemical conversion of organic and plastic waste materials through pyrolysis" (2017). Graduate Theses and Dissertations. 16242.