Textural development and hydrogen adsorption of carbon materials from PET waste

Polyethyleneterephthalate, PET, has become one of the major post-consumer plastic wastes. PET products present a problem of considerable concern due to the huge amount of solid waste produced. The disposal of this waste, together with its low bioand photo-degradability represents a serious challenge for industrial countries all over the world. Pyrolysis could provide an alternative and economically viable route for processing PET waste due to the potential uses of different by-products: energy from the pyrolysis gases (58% yield in this work), recovery of terephthalic acid and other subproducts (20%), and a solid residue (22%), which has shown a high textural development after activation. The pyrolysis of PET waste was performed in a quartz reactor (i.d. 35 mm) under an inert atmosphere. Further activation was carried out at a temperature of 925 oC, with a flow rate of 10 mL min of CO2. A series of carbon materials with different burn-off degrees was obtained. Textural characterisation of the samples was carried out by performing N2 adsorption isotherms at –196 oC. Changes in the morphological and structural properties of chars were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The carbons obtained were isotropic and highly microporous materials with apparent BET surface areas of up to 2500 mg. The suitability of the samples for hydrogen storage was studied by performing H2 adsorption measurements in the 0-1 bar pressure range. Adsorption-desorption experiments showed that reversible physisorption takes place in all the samples. The hydrogen adsorption capacities of the activated PET waste compare favourably well with those attained with high-value carbon materials.