Catalytic and thermal depolymerization of low value post-consumer high density polyethylene plastic

Authors: KUNWAR, BIDHYA - University Of Illinois; CHANDRASAKARAN, SRIRAM - University Of Illinois; Moser, Bryan; RAJAGOPALAN, NANDAKISHORE - University Of Illinois; SHARMA, BRAJENDRA - University Of Illinois

Submitted to: Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2016
Publication Date: 6/5/2016
Publication URL: http://handle.nal.usda.gov/10113/5642475
Citation: Kunwar, B., Moser, B.R., Chandrasakaran, S.R., Rajagopalan, N., Sharma, B.K. 2016. Catalytic and thermal depolymerization of low value post-consumer high density polyethylene plastic. Energy. 111:884-892.

Interpretive Summary: This research revealed that post-consumer high density polyethylene waste plastics are suitable as pyrolysis feedstocks for production of alternative fuels. Pyrolysis is defined as decomposition of material at elevated temperatures (above 570 deg F) in the absence of oxygen. The principal benefit of pyrolysis is conversion of low energy density substrates into higher density liquid and solid fractions. In the case of waste plastics, the liquid fraction was suitable as diesel fuel, as determined by comparing its fuel properties to those of conventional petroleum diesel as well as internationally accepted diesel fuel standards. Waste plastics were studied as feedstocks because of their proliferation in the environment and accumulation in municipal landfills. The objective of the current study was to explore their utility as a feedstock for production of liquid transportation fuels, thus reducing their impact on the environment while simultaneously reducing American dependence on foreign sources of petroleum oil. These results will be important to the alternative fuels industry, municipalities with landfills and litter issues, petroleum companies, plastics manufacturers, environmental organizations, and consumers. This research may ultimately improve market penetration, availability, and public perception of domestically produced alternative diesel fuels, thus affording greater independence from imported petroleum-based fuels while simultaneously enhancing economic opportunities across America.

Technical Abstract: The feasibility of catalytic and non-catalytic pyrolytic conversion of low value post-consumer high density polyethylene (HDPE) plastic into crude oil and subsequent distillation was explored. Translation of optimized conditions for catalytic and non-catalytic pyrolysis from TGA to a bench-scale system was validated using another kind of plastic (HDPE). The properties of the plastic crude (PC) oil and residue were studied for boiling point distribution; molecular weight distribution; elemental composition; and thermal degradation. The plastic crude oils had properties similar to conventional crude oil. The resulting PC oils were distilled into motor gasoline, diesel #1, diesel #2, and vacuum gas oil fractions. An increase in gasoline and diesel-range fractions was observed with Y-zeolite and MgCO3 catalysts, respectively. Diesel and vacuum gas oil fractions were the major products in the absence of catalyst. The distillate fraction was characterized for fuel properties, elemental composition, boiling point, and molecular weight distribution. The fuel properties of the diesel-range distillate (diesel fraction) were comparable to those of ultra-low sulfur diesel (ULSD) fuel. Market demand, growth, and value of end products will dictate which process, non-catalytic or catalytic (Y-Zeolite/MgCO3), is best suited for providing the product portfolio for a particular scenario.