Thermal and catalytic decomposition of mixed plastics

Abstract The decomposition of a polymer mixture containing 24 wt.% HDPE, 39 wt.% LDPE, 21.5 wt.% IPP, 10 wt.% PS, 4 wt.% ABS and 1.5 wt.% PET (composition close to that frequently met in municipal plastic waste without PVC), over HZSM-5 and orthophosphoric acid modified (PZSM-5) zeolite catalysts has been comparatively studied. The reaction products were analyzed by chromatographic, IR and 1 H-NMR spectroscopic methods as well as by standard methods, which are frequently used in the petrochemical laboratories. Catalytic decomposition increased the amount of gaseous products, lowered the condensate, and changed their composition with respect to the non-catalytic at the same pyrolysis temperature. The gaseous products contained a large C 3 fraction, while the liquid products contained mainly aromatic hydrocarbons. PZSM-5 catalyst promoted the formation of α-alkyl substituted and condensed ring aromatics hydrocarbons while HZSM-5 produced more isomeric compounds. The global yields of the reaction products from the catalytic decomposition at 400–450°C over both catalysts were close to that obtained by non-catalytic decomposition at 600–700°C temperature range. The composition of all products was dependent on the catalyst activity and acidity.