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

Abstract

The feasibility of catalytic and non-catalytic pyrolytic conversion of low value post-consumer high density polyethylene (HPDE) 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.