Pyrolysis of high density polyethylene (HDPE) in the open system
was studied. A plastic bag for food packing was used as a source of HDPE.
Pyrolysis was performed at temperatures of 400, 450 and 500 °C, which were
chosen based on thermogravimetric analysis. The HDPE pyrolysis yielded
liquid, gaseous and solid products. Temperature rise resulted in the increase of
conversion of HDPE into liquid and gaseous products. The main constituents
of liquid pyrolysates are 1-n-alkenes, n-alkanes and terminal n-dienes. The
composition of liquid products indicates that the performed pyrolysis of HDPE
could not serve as a standalone operation for the production of gasoline or
diesel, but preferably as a pre-treatment to yield a product to be blended into a
refinery or petrochemical feed stream. The advantage of a liquid pyrolysate in
comparison to crude oil is the extremely low content of aromatic hydrocarbons
and the absence of polar compounds. The gaseous products have desirable
composition and consist mainly of methane and ethene. The solid residues do
not produce ash by combustion and have high calorific values. Co-pyrolysis of
HDPE with mineral-rich lignite indicated positive synergetic effect at 450 and
500 °C, which is reflected through the increased experimental yields of liquid
and gaseous products in comparison to theoretical ones.