Degradation of pure and waste polyolefins and PVC in the presence of modified porous catalysts

摘要

The catalytic degradation of pure and mixed polyolefin polymers such as polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly-(vinylchloride) (PVC) was followed by thermal analytical method (TA) and was performed in a laboratory batch system (LBS) using modified ZSM-5, MCM41 and hydrotalcites based catalysts. In degradation of PE, the acidic H-ZSM-5 resulted in less liquid products and more gaseous components than the other, transition metal containing catalysts. For PP degradation, the non-acidic Ti-MCM41 and the Fe-ZSM-5 samples produced liquid hydrocarbons with yields about 90%. Similar results have been obtained for PS degradation, however, the activity of the catalyst with small pore sizes (ZSM-5) have had lower activity (no reaction observed below 350 °C). The degradation of PVC takes place in two steps, the first is the release of HC1 at about 300 °C followed by formation of aromatic hydrocarbons. Minimal residue could be obtained over Fe,Mg,Al- and Ca,MgAl-mixed oxide catalyst. From the results obtained it can be concluded that not only the catalyst structure but also the polymer structure determines the activity of a micro- or mesoporous material in the catalytic degradation of plastics or plastic wastes. Therefore, different optimal conditions (catalyst and reaction temperature) can be applied for each plastics studied (pure, mixed and waste) in thermal treatment.