Influence of time and temperature on pyrolysis of plastic wastes in a semi-batch reactor

The objective of this work is the study of the influence of temperature and time in the products obtained in the pyrolysis of plastic wastes. The thermal behaviour of a mixture, which resembles municipal plastic wastes has been studied both in a thermogravimetric analyser and in a 3.5 dm3 semi-batch reactor at atmospheric pressure in order to establish the most appropriate time–temperature combination for plastic waste pyrolysis. It has been proved by the authors that temperature has a strong effect in the characteristics of pyrolysis liquids and to a lesser extent in gas and solid properties. At the lowest temperature tested (460 °C), a great proportion of extremely viscous liquids with high content of long hydrocarbon chains are obtained, while at the highest temperature tested (600 °C) low proportion of liquids with a high content of aromatics is produced. The effect of time is not as strong as that of temperature except for very short reaction times (0–15 min). 15–30 min was established as the optimum reaction time range, since total conversion is achieved and longer reaction times do not produce any effect neither in conversion nor in products characteristics. 500 °C has been found to be the most appropriate temperature for the pyrolysis of such plastic waste in terms of both conversion and quality of the products.

► Pyrolysis transforms plastic wastes into valuable liquids and gases.
► Temperature has a significant influence in the properties and proportions of pyrolysis products.
► The influence of time in a semi-batch reactor is only noticeable for low reaction times.
► 500 °C and 30 min are the most appropriate conditions for plastic wastes pyrolysis.