Co-pyrolysis of xylan and high-density polyethylene: Product distribution and synergistic effects

Abstract

The thermal weight-loss characteristics and product distribution of the co-pyrolysis between xylan from corn cob (XC) and high-density polyethylene (HP) were investigated by thermogravimetry coupled with fourier transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS) and pyrolysis gas chromatography/mass spectroscopy (Py-GC/MS). Moreover, the synergistic effects in the co-pyrolysis process were explored. The co-pyrolysis of XC and HP occurs in two stages. The first stage (220–350 °C) was the decomposition of XC, and the second stage (440–525 °C) was mainly attributed to the decomposition of HP. Co-pyrolysis caused the blends to decompose more easily. The synergistic effect was confirmed during the co-pyrolysis process. The co-pyrolysis process promoted the release of hydrocarbons (CH4, C2H2, C2H6, C3H6, and C3H8) and aldehyde derivatives (CH3CHO and CHO+) and decreased the production of H2 and H2O. Moreover, co-pyrolysis suppressed the generation of CO2 only when the content of HP was 75%. The Py-GC/MS results showed that the yield of oxygen-containing compounds decreased, and the yield of alkenes and alkanes increased. The increase in alkenes was greatest when the ratio of XC to HP was 1:3. This phenomenon could be attributed to the release of hydrogen radicals from mono-molecular and bi-molecular dehydrogenation reactions during the decomposition of HP. Thus, HP could be a hydrogen donor, providing hydrogen for xylan-derived oxygenates, which served as acceptors. A reaction mechanism for the co-pyrolysis of XC and HP was also proposed.