(533e) Effects of Acid-Pretreatment on Co-Pyrolysis of Biomass and Plastic

Authors: 
Xue, Y., Iowa State University
Bai, X., Iowa State University
Over 521 million pounds of agricultural plastics are annually used in US farm field to protect plants and improve crop yield. Due to the non-biodegradability of the plastics, disposal of the used plastics is problematic. The agricultural waste plastics are mostly burned in farm land, buried or sent to landfill, which cause many environmental problems and health hazards. Since waste plastics and crop residues are often present together in the farm field, co-pyrolyzing the two streams of materials could be an attractive solution to address the environmental issue while promoting energy recovery from waste plastics. In the present study, the methods for improving the co-pyrolysis efficiency of biomass and plastic are explored. It is known that the inorganic impurities presenting in cellulosic biomass favor undesired ring opening and charring reactions to reduce bio-oil yield. Acid washing and acid infusion of biomass prior to pyrolysis are known as effective methods to overcome the detrimental effect of inorganic impurities to increase bio-oil yield. The effect of acid pretreatment on co-pyrolysis of biomass and plastic is studied. Corn stover biomass pretreated with sulfuric acid (both acid washed and acid infused) were co-pyrolyzed with polyethylene in a tandem micropyrolyzer with and without zeolite catalyst. During non-catalytic pyrolysis, levoglucosan yield increased from 0.5wt% with non-treated corn stover to 9.5wt% in acid treated biomass, which is expected. It was found that co-pyrolysis of acid-treated corn stover with PE can further increase the yield of levoglucosan, as well as the yields of phenolic monomers due to synergistic effect. The stronger synergistic effects were also observed when the acid treated corn stover and PE were co-pyrolyzed using HZSM-5 zeolite catalyst in comparison to co-pyrolyzing non-treated corn stover and PE using same catalyst. Due to the synergistic effects, the amount of total aromatic hydrocarbons and the selectivity of mono-ring aromatic hydrocarbons both increased significantly.