Fe-, Ti-, Zr- and Al-pillared clays for efficient catalytic pyrolysis of mixed plastics

Catalytic pyrolysis of mixed plastics including high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and PET (polyethylene terephthalate) has been performed in presence of a series of modified pillared clays (PILC) and Al-PILC. The catalysts were well characterized by BET, FTIR of pyridine adsorption, XRD, SEM, TEM/EDX. The effect of different catalysts on the composition and amount of pyrolysis products including gas, liquid, and char residue was evaluated. With the introduction of Fe-PILC, the yields of oil product were enhanced, suggesting that secondary over-cracking of primary pyrolytic intermediate species was reduced in the presence of the catalyst. A high oil yield of 79.3 wt.% with excellent selectivity for diesel fraction (80.5%) and high yield of H2 gas (47.7 vol%) were obtained in the case of Fe-PILC. The superior catalytic performance of Fe-PILC is probably attributed to its moderate total acidity, relatively high BET surface area, and uniformly dispersed iron oxide particles on montmorillonite support. Accordingly, with the clay catalyst, an efficient and environmentally friendly process can be developed to produce valuable products (e.g. diesel, hydrogen) through pyrolysis of plastic waste.