(631c) Catalytic Co-Hydropyrolysis of Biomass and Plastics for Improved Product Quality
Yuan Xuea, Xianglan Baia
a Department of Mechanical Engineering, Iowa State University
Every year, a tremendous amount of Municipal Solid Waste (MSW) is generated in the US. In 2013, Americans produced 254 million tons of trash and only recycled 1/3 of it. The environmental pollution and land usage from the improper disposal of MSW has become an increasingly urgent issue. Among MSW, the major compositions of waste plastics are polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET), which are petroleum-derived synthetic polymers, rich in carbon and hydrogen. In the present work, catalytic co-pyrolysis of the plastics and biomass is investigated by co-pyrolyzing red oak with PE, PP, PS or PS using HZSM-5 zeolite catalysts. The work is conducted in a tandem micropyrolysis both in-situ and ex-situ under a helium and hydrogen environment. It was found that in-situ catalytic co-hydropyrolysis significantly improved the product distribution for all cases compared to the helium environment, by dramatically increasing the yield of aromatic hydrocarbons and reducing the formation of solid residues. The yield of alkanes also increased at the expense of the decreasing yield of alkenes for co-hydropyrolysis of red oak with PE and PP. For the co-pyrolysis of red oak with PS and PET, the yield of CO increased, whereas the yield of CO2 decreased in hydropyrolysis compared to pyrolysis under a helium environment. For the ex-situ catalytic co-pyrolysis, hydropyrolysis was less effective as there were fewer changes in the product distribution compared to pyrolysis under a helium environment. The study suggests that the external hydrogen plays an important role in promoting a series of reactions involving the biomass and plastics over the zeolite catalyst, which include cracking, deoxygenation and aromatization.