Nitrogen transfer mechanism research on the co- pyrolysis macroalgae with polyethylene

Abstract

This study unveiled the effect of co-pyrolysis and nitrogen transformation characteristics of macroalgae (Enteromorpha prolifera (EP)) and waste plastics (polyethylene) by using Py-GC/MS experiment and density functional theory (DFT). The possible reaction pathways were designed by using composition and pyrolysis intermediates of EP including amino acids and cyclic acylamide as model compounds, respectively. Subsequently, the mechanism of nitrogen transformation during the pyrolysis of EP and the synergistic mechanism of co-pyrolysis with polyethylene (PE) were revealed by DFT. Py-GC/MS results showed that the nitrogen-containing products of EP pyrolysis were mainly Sarcosine, Imidazole, and (2E)-3-(2-Amino-1H-imidazol-5-yl) acrylic acid, and the co-pyrolysis products were urea and cadaverine. Co-pyrolysis is beneficial to decreased the species and quantities of N-containing compounds, and the relative content of nitrogen-containing compounds decreased from 7.91% to 3.53%. The DFT results also verified the rationality of each possible pathway using the quantum chemistry calculation and through analysis of the activation energy (ΔG*), the reaction heat (ΔG) and the reaction enthalpy change (ΔH). This study confirmed that there is a synergistic effect in the co-pyrolysis process of EP and PE in which the hydrogen radicals provided by PE can reduce the reaction energy barrier and then promote the mechanism of nitrogen during the pyrolysis process.