(183e) Targeting Fuel-Ranged Aromatics through Co-Pyrolysis of Polystyrene and Polyethylene with H-ZSM5

The objective of this work is to upcycle low-density polyethylene (LDPE, resin code 4) and polystyrene (PS, resin code 6), which are currently unrecycled, for producing gasoline ranged aromatics. Common plastics for LDPE and PS are grocery bags and packaging foam, respectively. Typically, both plastics are either combusted along with other municipal waste inside power plant or transported to be landfilled. Due to environmental concerns resulted from current treatments, chemical upcycling could be promising since it could achieve almost total conversion of both plastics to fuel. In this study, fluid catalytic cracking catalyst H-ZSM5 were adopted for the catalytic co-pyrolysis of LDPE and PS. Hydrogen-rich LDPE could supplement the pyrolysis of PS to increase the yield of alkyl-benzene. In addition, the products from LDPE could diversify the aromatics from PS pyrolysis.

Experiments were carried out with the three independent variables: the presence of catalyst, catalyst acidity and catalyst ratio. H-ZSM5 used in this work varied in three silica to alumina ratios, 30, 80 and 280, corresponding to the acidities of each catalyst. PS and PE were tested individually and as a mixture (1:1 mass ratio) with and without the presence of H-ZSM5. Simulated cracking using thermogravimetric analysis (TGA) showed that the catalytic cracking had reduced the required temperature from 490 °C of non-catalytic cracking to 340 °C, for almost total conversion. Online Fourier-transform infrared spectroscopy (FTIR) of the flue gas from TG furnace showed that production of aromatics increased with the addition of PS in PE. For the products PS and mixed plastic samples, in the FTIR spectra, a peak at 700 cm^-1, attributing to benzene and derivatives, was found. This particular peak was absent in the PE products. The mass spectroscopy analysis of fixed bed reactor showed a more diversified aromatics produced from co-upcycling of PE and PS.