(633h) Determining the Effect of Pyrolysis Operating Conditions on the Catalytic Co-Pyrolysis of Ldpe and PET with Zeolite Catalysts

The pyrolysis of low-density polyethylene (LDPE), as well as other polyolefins, is researched often as a way to convert plastic waste into valuable fuels and chemicals. The utilization of zeolite catalysts during polyolefin pyrolysis helps to decrease pyrolysis temperature as well as increase the yield of target products. The catalytic pyrolysis of polyethylene terephthalate (PET) plastic is not researched as often, as while it can result in high yields of benzene, it also forms high yields of catalytic coke. Polyolefins and PET can be found together in unsorted plastic waste and are inherently mixed in multilayer packaging. Researching the catalytic co-pyrolysis of these two types of plastic is vital for the push towards a circular economy. In previous works it was shown that interactions occur between polyolefins and PET during their catalytic co-pyrolysis with zeolite catalysts. These lead to an increase in alkylated benzenes and polyaromatic hydrocarbons, and a decrease in benzene and C3-C6 paraffins and olefins. What is not understood, is the effect of pyrolysis operating conditions on these interactions that were observed.

To investigate, we conducted the catalytic pyrolysis and co-pyrolysis of LDPE and PET with zeolite catalysts using a tandem micro-reactor connected to a two-dimensional gas chromatography system with flame ionization detector and time-of-flight mass spectrometer. Over 190 chemical products were identified with match factor above 800, and quantified using the effective carbon number approach. Thermogravimetric analysis was used to determine the solid residual yield. Operating conditions such as temperature, catalyst contact mode, and pyrolysis time were varied. Increasing the temperature from 380°C to 500°C contributed to higher levels of interactions which increased toluene yield and decreased benzene yield from what was expected. Further insights into the impact of other operating conditions will help to determine optimal conditions for the catalytic co-pyrolysis of PET with polyolefins.