**3.2 Pyrolysis products**

The products formed in the MAP process of these plastic materials were liquid, gas, and char. In all cases, the liquid was the most important fraction both in quantity and commercial value. The characterization of this fraction for the most significant tests is reported below; the chemical–physical properties are shown in **Table 5**. Physical characteristics of liquids from MAP of PS were not affected by the variation of the MW power. The density recorded in all samples was almost the same and in a very narrow range among 0.92–0.95 g/cm3 . Furthermore, close values of ultimate analyses and the molar C/H ratios suggested that all the liquid samples had a similar composition, even if different process parameters have been employed. The C/H molar ratio in a range between 0.94 and 1.0 wt% confirmed the prevailing presence of the aryl compounds in liquids from PS pyrolysis.

The lower calorific value (LHV) of the liquids from MAP of PS also showed the same trend as the C/H molar ratio, with values close to styrene, benzene, and ethylbenzene (LHV of 39.6, 40.0, and 39.1 MJ/kg, respectively for PS1, PS2, and PS5). As foreseen from the literature and in agreement with the tests carried out both in the laboratory and on the pre-industrial prototype, the main products of PS pyrolysis are aromatic hydrocarbons such as benzene, toluene, ethylbenzene, styrene, and α-methylstyrene (**Table 6**).

Styrene is always the predominant compound in each liquid sample. From the analysis of data reported in **Table 7** it is possible to show how the amount of styrene (evaluated by chromatographic area of the GC/MS spectra) is correlated with the
