A significant amount of research has been conducted
on the catalytic liquefaction of plastic. Excellent results
have been obtained from liquefaction of individual
polymers (polyethylene (PE), polypropylene (PPE), polystyrene
(PS), etc.) and relatively clean mixed plastic
using solid acid catalysts and metal-promoted solid acid
catalysts.6-14 For example, Venkatesh et al.13 and
Shabtai et al.14 have obtained high yields of liquids that
consist predominantly of isoalkanes in the gasoline
boiling range from HDPE, PPE, and PS at relatively
low temperatures (300-375 °C) using Pt-promoted ZrO2/
SO4 or ZrO2/WO3 catalysts. However, true post-consumer
plastic (PCP) contains heteroatoms (principally
chlorine, but also nitrogen and some sulfur), paper, dirt,
and inorganic matter that can render such catalysts
ineffective.