Recycling of polyethene and polypropene in a novel bench-scale rotating cone reactor by high-temperature pyrolysis

The high-temperature pyrolysis of polyethene (PE), polypropene (PP), and mixtures of these polymers was studied in a novel bench-scale rotating cone reactor (RCR). Experiments showed that the effect of the sand or reactor temperature on the product spectrum obtained is large compared to the effect of other parameters (for instance, residence time). In general, it can be concluded that the amount of polymer converted, into propene and butene decreases with higher cracking severity (higher temperatures or longer residence times), while the fraction methane increases. About 80 wt % of the polymer is converted into gas at a reactor temperature of 898 K, while 20 wt % is converted into intermediate waxlike compounds or aromatics in the case of PE. The gas yield increases slightly with the reactor and/or sand temperature to 88 wt % at higher temperatures. The total amount of alkenes decreases with increasing cracking intensity, which suggests that the reactor should be operated at the lowest possible temperature. Our results indicate that the reactor offers a few significant advantages compared to other reactors (no fluidization gas necessary, good solid-polymer mixing, no cyclones necessary) and a competitive product spectrum. However, significant improvements are still possible to make the reactor concept technically and economically more attractive.