Viability of Glycolysis for the Chemical Recycling of Highly Coloured and Multi-Layered Actual PET Wastes.

The chemical recycling of poly(ethylene terephthalate) -PET- fractions, derived from actual household packaging waste streams, using solvolysis, was investigated. This recycling strategy was applied after a previous on-line automatic identification, by near-infrared spectroscopy -NIR-, and a subsequent selective sorting of the different PET materials that were present in the packaging wastes. Using this technology, it was possible to classify fractions exclusively including PET, virtually avoiding the presence of both other plastics and materials, such as paper, cardboard and wood, that are present in the packaging wastes, as they were efficiently recognised and differentiated. The simple PET fractions, including clear and monolayered materials, were adequate to be recycled by mechanical means meanwhile the complex PET fractions, containing highly coloured and multi-layered materials, were suitable candidates to be recycled by chemical routes. The depolymerisation capacity of the catalytic glycolysis, when applied to those complex PET wastes, was studied by evaluating the effect of the process parameters on the resulting formation and recovery of the monomer bis(2-hydroxyethyl) terephthalate -BHET- and the achieved quality of this reaction product. Comparable and reasonable results, in terms of monomer yield and its characteristics, were obtained independently of the type of complex PET waste that was chemically recycled.

Compositional insights and valorization pathways for carbonaceous material deposited during bio-oil thermal treatment.

This work analyses the composition, morphology, and thermal behavior of the carbonaceous materials deposited during the thermal treatment of bio-oil (thermal pyrolytic lignin-TPL). The bio-oil was obtained by flash pyrolysis of lignocellulosic biomass (pine sawdust), and the TPLs were obtained in the 400-700 °C range. The TPLs were characterized by performing elemental analysis; (13)C NMR, Raman, FTIR, and X-ray photoelectron spectroscopy; SEM; and temperature-programmed oxidation analyzed by differential thermogravimetry and differential scanning calorimetry. The results are compared to a commercial lignin (CL). The TPLs have lower oxygen and hydrogen contents and a greater aromaticity and structural order than the CL material. Based on these features, different valorization routes are proposed: the TPL obtained at 500 °C is suitable for use as a fuel, and the TPL obtained at 700 °C has a suitable morphology and composition for use as an adsorbent or catalyst support.