Co-pyrolysis of waste office paper and high-density polyethylene: product distribution, kinetics and reaction mechanism

This study investigated the thermal behaviors and kinetics of waste office paper (WP) and high-density polyethylene (HDPE) during co-pyrolysis. The co-pyrolysis of HDPE and WP exhibited significant synergistic effects, characterized by reduced activation energy, optimized product distribution, and increased yield of aliphatic hydrocarbons. Specifically, the activation energy for co-pyrolysis was reduced by up to 20.2 % at a HDPE-to-WP mass ratio of 1:2, in comparison with that of individual pyrolysis. Acid and alkali pretreatments of WP further improved the co-pyrolysis product distribution, where acid pretreatment effectively removed hemicellulose and lignin and promoted the formation of short-chain aliphatic hydrocarbons (C <= 10). In comparison, the alkali pretreatment facilitated the generation of long-chain aliphatic hydrocarbons (C > 20). The plausible reaction mechanism for co-pyrolysis transformation of WP with HDPE was also proposed in detail. This study provides theoretical support and technical guidance for the co-disposal of waste office paper and HDPE, and offers insights for the industrial application of co-pyrolysis transformation of biomass with waste plastics.