High-temperature pyrolysis of low-density polyethylene for hydrogen production and carbon capture

Utilizing low-density polyethylene (LDPE) as a feedstock, non-catalytic thermal pyrolysis represents a promising technology for large-scale hydrogen generation and carbon capture. Furthermore, the use of the solid carbon byproduct generated during the process, enhances the operation’s economic feasibility. This work uses the model compound to reveal the potential of LDPE pyrolysis for producing hydrogen and capturing carbon. A laboratory-scale high-temperature fixed bed reactor is operated in the temperature ranging from 700 °C to 1600 °C, with LDPE pellets of 5 mm in diameter. Despite a decrease in gas yield to 13.7 wt% as the temperature increases, the hydrogen yield significantly increased up to 11.0 wt% from 900 °C to 1600 °C. Approximately two-thirds of the hydrogen present in the polymer was identified as molecular hydrogen in the product gas. At 1600 °C, a purity of 98.5 mol% was achieved for the hydrogen produced, while the product gas at temperatures ranging from 700 °C to 900 °C predominantly contained methane and ethylene. The analysis of the influence of temperature on the condensable product phase demonstrated an increase in the yields of aliphatic and polycyclic aromatic hydrocarbons (PAHs) species up to a temperature of 1000 °C. The decrease in yield of Aliphatic and PAHs from 1000 °C onwards could be attributed to the gradual decarbonization of the gas phase through the formation of solid carbon. Additionally, the produced solid carbon was analyzed using various techniques, including TEM, SEM, DLS, TGA, XRD, and Raman spectroscopy. The results demonstrated its potential as a sustainable industrial carbon material.