Pyrolytic kinetics, products and reaction mechanisms of invasive plant and high-density polyethylene: TG, Py-GC/MS and DFT analysis

Abstract

In this study, the devolatilization properties and reaction mechanisms of the mixture of spartina alterniflora Loisel. (SA, an invasive plant) and high-density polyethylene (HDPE) were investigated via thermogravimetric analysis (TGA). The reaction difficulty and the residual mass were decreased upon adding HDPE to the feedstock. The synergism between SA and HDPE was determined by calculating the deviation (△W) between the experimental and theoretical TG values, and the optimum SA to HDPE mass ratio was found to be 3:1. A further decrease of △W could be observed as introducing HZSM-5 to the sample. Flynne-Walle-Ozawa and Kissinger-Akahira-Sunose methods were used to calculate the activation energy (E) to determine the kinetic characteristics during the pyrolysis process. The findings suggested that blending 25% HDPE with SA could significantly reduce the E value, and a lower E value was required when the HZSM-5 was added to the mixture. Pyrolysis-gas chromatography/mass spectrometry was used to analyze the distribution of the co-pyrolysis products, and the presence of HDPE and HZSM-5 promoted the formation of hydrocarbons. Furthermore, on the basis of DFT analysis by Gaussian 09 suites, potential hydrodeoxygenation reaction pathways of guaiacol and furfural were inferred. Guaiacol and furfural would be converted to benzene and pentane, respectively, under the attack of hydrogen radicals.