Catalytic hydrothermal degradation of carbon reinforced plastic wastes for carbon fibre and chemical feedstock recovery

Recovery of carbon fibre and chemical feedstock via catalytic hydrothermal degradation of waste carbon fibre reinforced plastic (CFRP) sample was investigated in a stainless steel batch reactor between 400 and 420 °C and pressures of 20 and 25 MPa, respectively. Sodium hydroxide and potassium hydroxide were used as catalysts/additives. Using supercritical water alone, a maximum of 54.5 wt% of resin was removed from the CFRP at 420 °C, but with high recovery of phenol in the liquid residual. The presence of NaOH or KOH alone in water led to up to 81 wt% resin removal, even at short reaction times. Extracts from the liquid residual contained phenol and aniline as the major components; thus representing a potential for monomer recovery. For instance, the use of KOH alone gave phenol yield of 377 mg/(g resin) and aniline yield of 112 mg/(g resin). In addition, the presence of the alkalis led to the recovery of carbon fibres with very good mechanical properties.