Recovery of carbon fibres and production of high quality fuel gas from the chemical recycling of carbon fibre reinforced plastic wastes

Abstract

A solvolysis process to depolymerize the resin fraction of carbon fibre reinforced plastic waste to recover carbon fibre, followed by hydrothermal gasification of the liquid residual product to produce fuel gas was investigated using batch reactors. The depolymerisation reactions were carried out in ethylene glycol and ethylene glycol/water mixtures at near-critical conditions of the two solvents. With ethylene glycol alone the highest resin removal of 92.1% was achieved at 400 °C. The addition of water to ethylene glycol led to higher resin removals compared to ethylene glycol alone. With an ethylene glycol /water ratio of 5, at 400 °C, resin removal was 97.6 %, whereas it was 95.2 % when this ratio was 3, at the same temperature. The mechanical properties of the recovered carbon fibre were tested and showed minimal difference in strength compared to the virgin carbon fibre. The product liquid, containing organic resin degradation products was then subjected to catalytic supercritical water gasification at 500 °C and 24 MPa in the presence of NaOH and Ru/Al 2 O 3 as catalysts, respectively. Up to 60 mol.% of H 2 gas was produced with NaOH as catalyst, and 53.7 mol.% CH 4 gas was produced in the presence of Ru/Al 2 O 3 .

Impact of Solvolysis Process on Both Depolymerization Kinetics of Nylon 6 and Recycling Carbon Fibers from Waste Composite

“…Platform molecules such as phenol and aniline which represent a potential monomer recovery were significantly recovered. Moreover, the decomposition of polybenzoxazine resin in ethylene glycol/water revealed the presence of aniline, methylaniline, quinolone and phenyloxazine at 400 °C [21]. They were also interested in the degradation of this liquid phase into gaseous molecule by supercritical water gasification.…”

Chemical Recycling of Printed Circuit Board Waste by Depolymerization in Sub- and Supercritical Solvents

“…The solid residue was dried to a constant weight in an oven at 105 °C to determine its weight. A portion of the liquid effluent was extracted with diethyl ether based on the method applied in our previous work and analysed on a Varian 380 GC fitted with a Saturn 2200 ion trap MS/MS according to the analytical procedure previously reported by Blanco et al [19,20]. The remaining aqueous phase was also analysed for the bromine content by ion chromatography.…”

Evaluating the mechanical properties of reinforced LDPE composites made with carbon fibres recovered via solvothermal processing

“…The elemental (CHNSO) composition of the CFRP was; 80.3% carbon, 2.05% hydrogen, 5.9% oxygen, 4.15% nitrogen and 1.65% sulphur. The procedure for the recovery of the CF from the waste CFRP has been previously described [15]. Briefly, 10 g of the CFRP sample was loaded into a 500 ml capacity hydrothermal reactor, along with 50 ml ethylene glycol and 10 ml distilled water.…”

“…Pyrolysis involves heating the waste material to elevated temperature (400-600°C) in the absence of air/oxygen, while gasification (T ≥ 800 °C) can be used to convert the organic components of waste into CO and H 2 in the presence of a limited amount of steam and air/oxygen [4,[11][12][13]. Under hydrothermal processing, water is used as a solvent [14][15][16][17][18]. The properties of water under hydrothermal conditions are distinct from those of ambient water.…”

“…Sometimes, the solvating ability of water under these conditions can be improved by the addition of organic co-solvents such as alcohols. Liquid products of thermal processes contain a variety of organic compounds depending on the polymer type and the reaction conditions and can be used as raw material for chemical synthesis and as feedstock in refinery for petrochemicals or upgraded to fuels [15].…”