ReaxFF reactive molecular dynamic simulation and density functional theory calculation of pyrolysis mechanism and electronic characteristic of lignin with the addition of plastics

The pyrolysis mechanism of lignin dimers with the addition of low-density polyethylene and the electronic characteristics of lignin dimers were studied using ReaxFF reactive molecular dynamic simulation and density functional theory calculation. The effects of temperature and the lignin dimer type on the lignin and LDPE co-pyrolysis were analyzed, the electronic properties and reactivities of lignin dimers were explored. The results showed that the oxygen-containing intermediate products generated from the pyrolysis of lignin promote the degradation of LDPE, thereby increasing the yield of hydrocarbon products. Meanwhile, the radicals released by LDPE interact with the pyrolysis products of lignin, further accelerating the pyrolysis of lignin. The reactivities of three lignin dimers were order as: α-ether type>β-aryl type>β-ether type. The oxygen atoms of hydroxyl in lignin dimer molecules exhibited strong negative charges and became electrophilic attack targets during the co-pyrolysis process.