Production of liquid fuels from waste plastics

Exploratory work was carried out to develop a process for conversion of mix ed plastic wastes into liquid transportation fuels or petrochemicals. The c oncept used is based on thermal depolymerization of the polymers in a suita ble solvent followed by catalytic conversion of the resulting polymeric fra gments into hydrocarbons with boiling points below 525 degrees C. The proce ss is carried out batch-wise over a zeolite catalyst at temperatures from 3 50 degrees C to 450 degrees C and at atmospheric pressure. No hydrogen is u sed and volatile products formed are continuously removed from the reactor. Tests were carried out on polyethylene and polypropylene alone, and on mix tures of the two. Finally, a synthetic mixture of four different plastics w as tested. From 90% to 98% of the plastic was converted to gases or distill able hydrocarbons. Of this yield, from 20% to 55% was gas, primarily propyl enes and butylenes, and from 32% to 70% was a light hydrocarbon oil. Very l ittle non-distillable coke or residue was formed. The use of mixtures did n ot affect the high conversions obtained, but the results could only be appr oximately predicted based on a pro-rating of results for the individual com ponents.