Oxidation reactivity and structure of LDPE-derived solid carbons: A temperature-programmed oxidation study

A wide set of solid carbons obtained by low-density polyethylene (LDPE) pyrolysis has been extensively analyzed by temperature programmed oxidation (TPO) technique. These samples showed different TPO behavior depending on pyrolysis conditions employed, having a wide range of TPO profiles, from one predominant peak to several overlapping curves. The evolution of the oxygen reactivity of LDPE-derived solid carbons heat treated to 1300, 2000, 2300, and 2600 C was also examined by TPO. The deconvolution of TPO curves of starting and heat-treated carbons allowed the identification of six different peaks consistently occurring in different samples, which was related to groups of carbon domains with equivalent reactivity. Four of them mainly appeared in the starting carbons and were related with more reactive and less ordered carbon domains. The heat-treatment of the carbons allowed the study of the evolution of carbon domain groups from higher to lower oxygen reactivity. A TPO parameter, T_max has been defined as a weight peak temperature oxidation and compared to other characterization techniques (X-ray diffraction (XRD), Raman spectroscopy, elemental analysis) in an attempt to correlate TPO reactivity and structural parameters. The TPO technique showed a high sensibility to analyze carbon structure.