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Plastic wastes coming from a waste packaging separation and classification plant have been pyrolysed in a semibatch nonstirred autoclave, swept by a continuous flow of N 2 . The plastic waste contains 39.5% PE, 34.2% PP, 16.2% PS and EPS, and some other minor materials. Temperatures in the range 400–600 °C have been explored, and it has been found that over 460 °C total thermal decomposition of the waste plastics takes place. Three catalysts have been tested: HZSM-5, red mud and AlCl 3 . Solid yields about 5–7%, liquid yields in the range 40–70% and gas yields in the range 12–24% were obtained. The liquid products were a mixture of C 5 –C 20 compounds with a very high proportion of aromatics (>70%). Such liquids contain significant amounts of valuable chemicals such as styrene (20–40%), toluene (9–15%) and ethylbenzene (7–16%) and have rather high GCV (40–43 MJ kg −1 ). Thermal pyrolysis oils were a wax-like product which solidified at room temperature, whereas the oils obtained with any of the catalysts were less viscous and maintained in liquid state at room temperature. HZSM-5 favoured gas production and, increased the aromaticity and decreased the carbon number of the oils. AlCl 3 did not modify pyrolysis yields but gave rise to lighter liquids. Red mud produced higher liquid yields and the liquids were less viscous, but it was not observed a clear effect on the carbon number of the oils. |
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